Middleby Marshall PS570, PS360 User Manual

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technical service

manual

This Technical Service Manual includes information

for the following oven models:

 PS200/220/224 Series  PS310/360 Series  PS555/570 Series

P/N 47829  Rev. C  V1  4/02

Middleby is proud to support the

Commercial Food Equipment Service Association (CFESA).

We recognize and applaud CFESAs ongoing efforts

to improve the quality of technical service in the industry.

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  (847) 741-3300  FAX (847) 741-4406  24-Hour Service Hotline (800) 238-8444

W ARNING

Improper installation, adjustment, alteration, service or maintenance can cause

property damage, injury or death. Read the installation, operating and maintenance

instructions thoroughly before installing or servicing this equipment.

W ARNING

DISCONNECT THE OVEN FROM ITS ELECTRICAL

POWER SUPPLY

During the warranty period, ALL parts replacement and servicing should be performed by your

Middleby Marshall Authorized Service Agent. Service that is performed by parties other than

your Middleby Marshall Authorized Service Agent may void your warranty.

Using any parts other than genuine Middleby Marshall factory manufactured parts relieves the

manufacturer of all warranty and liability.

Middleby Marshall reserves the right to change specifications at any time.

BEFORE SERVICING.

NOTICE

TABLE OF CONTENTS

Section 1 - Sequence of Operation .................................................... 4

I. Gas Oven Sequence of Operation ............................................. 4

II. Electric Oven Sequence of Operation ....................................... 6

Section 2 - Air Flow and Heat Transfer ............................................. 7

I. Types of Heat Transfer ............................................................... 7

II. Blowers and Blower Speed ....................................................... 7

A. PS200-series ovens ............................................................ 7

B. PS360-series ovens ............................................................ 8

C. PS555/570-series ovens .................................................... 8

III. Air Fingers ................................................................................... 8

A. Description and Function .................................................... 8

B. Configuration and Alignment ............................................... 9

C. Performing a Test Bake ....................................................... 9

D. PS300/350 Air Finger Shutter Adjustment ......................... 10

IV. Oven Capacity ............................................................................12

A. Conveyor Speed and Bake Time ....................................... 12

B. Belt Time ..............................................................................12

C. Time of Delivery (TOD)....................................................... 12

Section 3 - Troubleshooting and Servicing Components

I. Conveyor Speed Controller and Drive Motor.............................13

A. Part Number Reference - Speed Controllers .................... 13

B. Part Number Reference - Pickup Assemblies ...................14

C. Preparing to Service the Speed Controller ........................ 14

D. Controller/Motor Failure ......................................................15

E. Basic Troubleshooting Flowcharts ................................... 16

 If the Conveyor Runs at Full Speed ......................... 16

 If the Conveyor Will Not Run at All .......................... 17

F. Initial Troubleshooting ......................................................... 18

G. Conveyor Control Pickup Test............................................ 19

H. Conveyor Motor Test ..........................................................19

I. Replacing the Magnetic Pickup .......................................... 19

J. Unshielded Pickup Wires on Early PS360-series Ovens . 19

K. Appendices .........................................................................20

 Conveyor sensor wiring changes for PS360-series

and PS570S, 10/95 .................................................... 20

 Service Bulletin MM-133B - Installation Instructions

for Conveyor Speed Controller Kit with Thumbwheel,

P/N 42810-0133, 4/95 ................................................ 21

 Instructions for Service Kit 42810-0133- Conveyor

Speed Controller Kit with Thumbwheel, 4/95 ..........23

 Service Bulletin MM-177 - Introduction and Compat-

ibility of Conveyor Speed Controller with Digital

Display, P/N 37337, 8/00........................................... 27

 Instructions for Service Kit 44756 - Conveyor Speed

Controller Kit for PS200R68-series Ovens, 2/02 ...28

 Service Bulletin MM-189 - New Conveyor Gear

Motors, Brushes, and Pickup Clamps, 8/01............29

 DIP switch settings for Conveyor Speed Controller

with Digital Display (P/N 37337), 4/02 .....................30

II. Temperature Controller ............................................................... 30

A. Part Number Reference - Temperature Controllers ..........31

B. Description ..........................................................................32

C. High Limit/Cooldown Functions..........................................32

D. Troubleshooting .................................................................. 32

E. Appendices.........................................................................32

 Temperature Controller Terminal

Cross-Reference, 4/02 .............................................. 32

 Instructions for Service Kit 47321 - Digital

Temperature Controller Kit, 2/02 .............................. 33

 Service Bulletin MM-136 - Electrical Noise Filter

Capacitor Assembly on Temperature Controllers,

9/93 ............................................................................. 43

TABLE OF CONTENTS (continued)

III. Hig h L i mit Control Module ...........................................................45

A. Part Number Reference - High Limit Control Modules ...... 45

B. Location ..............................................................................45

C. Troubleshooting ..................................................................45

D. Appendices ......................................................................... 46

 Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310,

350 & 360 Ovens, 5/99 ..............................................46

IV. Thermocouples ........................................................................... 54

A. Part Number Reference - Thermocouples ........................ 54

B. Thermocouple Functions ....................................................54

C. Troubleshooting ..................................................................54

D. Appendices ......................................................................... 56

 Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01 ................................. 56

V. B lo wer s ....................................................................................68

A. PS200-series ovens...........................................................68

B. PS360-series ovens...........................................................74

C. PS555/570-series ovens ................................................... 76

VI. Blower Motor Centrifugal Safety Switch (PS360-series) .......80

A. Part Number Reference - Blower Centrifugal Switch ......80

B. Troubleshooting .................................................................. 80

VII. Burner Blower Motor Centrifugal Safety Switch (PS200-

series gas, PS310, PS314, PS360, PS360WB, PS570S) .........80

VIII. Ai r Pr essure Safety Switch (PS200-series, PS555/570-

series, PS360EWB, PS360WB70) .............................................81

A. Part Number Reference - Air Switches ............................81

B. Troubleshooting .................................................................. 82

C. Appendices ......................................................................... 83

 Instructions for Service Kits 35624 and 35625 -

Air Pressure Switch Replacement Kits, 1/97 ..........83

 Instructions to Replace an Alternate Air Switch

P/N 36194 with Service Kit P/N 35624, 3/97 ...........85

IX. PS570/570S Flame Gate............................................................. 87

A. Part Number Reference - Flame Gate ...............................87

B. Flame Gate Orientation .......................................................87

X. Gas Train and Burner System ...................................................88

A. Part Number Reference - Gas Train Components............88

B. Part Number Reference - Gas Orifices and Gas

Conversion Kits ..................................................................91

C. Component Identification ....................................................92

D. Pilot/Ignitor Assembly .......................................................... 93

E. Burner Blower Motor .......................................................... 95

F. Air Shutter...........................................................................95

G. Burner Transformer ...........................................................96

H. Burner Motor Relay ............................................................ 96

I. High Flame Solenoid Valve ................................................. 96

J. Bypass (Low Flame) Orifice .............................................96

K. Modulating Gas Valve ......................................................... 97

L. Amplifier Board ................................................................... 97

M. Combination Gas Control Valve .........................................98

N. Ignition Module .................................................................... 99

O. Gas Conversion Kits ....................................................... 100

P. Burner and Gas Train Troubleshooting .......................... 100

Q. Checking the Gas Pressures .......................................... 102

R. Troubleshooting Flowcharts ........................................... 103

 Intermittent Pilot System Troubleshooting Table 103

 No Spark, System Does Not Work........................ 104

 Spark is Present, Pilot Will Not Light ................... 105

 Pilot Lights, Main Valve Will Not Come On ......... 106

S. Appendices ...................................................................... 107

 Instructions for Service Kit 42810-0117 -

Pilot/Ignitor Kit, 7/91 ............................................... 107

 Instructions for Service Kit 30185 - Pilot Tee, 3/94 . 108  Instructions for Service Kit 42810-0121 -

Combination Gas Valve, 1/92 ................................ 112

 Instructions for Service Kit 42810-0114 -

Ignition Module, 11/90 ............................................. 116

 Position of Combination Gas Valve Components

during Burner Operation, 4/02 ................................ 118

 Instructions for All Gas Conversion Kits

for Ovens with Wayne Burner, Natural Gas to

Propane, 8/00 ........................................................... 119

 Instructions for All Gas Conversion Kits

for Ovens with Wayne Burner, Propane to

Natural Gas, 8/00 ................................................... 125

 Instructions for Service Kit 36856 - Gas

Conversion Kit for PS360EWB/WB70 with

Midco Burner, Natural Gas to Propane, 1/98 ....... 131

 Instructions for Service Kit 36863 - Gas

Conversion Kit for PS360EWB/WB70 with

Midco Burner, Propane to Natural Gas, 1/98 ....... 135

 Equivalent Orifice Sizes at High Altitudes, 4/02 . 139

XI. Electric Oven Heating System ................................................ 140

A. PS200-series ovens ........................................................ 140

B. PS310/360-series ovens ................................................ 142

C. PS555 ovens .................................................................... 144

D. Electric Oven Mercury Contactor Replacement ............ 146

Section 4 - Electrical Wiring Diagrams ............................................ 149

I. Component Wiring.................................................................... 149

A. Temperature Controllers .................................................. 149

B. Ignition Modules ............................................................... 150

II. PS200-series Ovens ............................................................... 151

III. PS310/360-series Ovens ........................................................ 160

IV. PS555/570-series Ovens ........................................................ 166

Section 5 - Reference ..................................................................... 172

 25-point preventative maintenance checklist ....................... 172

 Fractional inches to decimal and millimeter equivalents ... 173

 Decimal equivalents of drill sizes ......................................... 173

 General conversion factors ................................................... 174

 Pressure conversions ............................................................ 174

 Pressure conversion chart ..................................................... 175

 Ohms Law equation wheel .................................................... 175

 Common electrical wiring diagram symbols ........................ 176

SECTION 1 - SEQUENCE OF OPERATION

SEQUENCE OF OPERATION

SECTION 1

I. GAS OVEN SEQUENCE OF OPERATION

A. Electrical Supply

Gas heated ovens operate on 208/240V, single phase. Standard incoming power configurations are:

1. 4-wire system (PS200 series, PS310/360 series, PS570, PS570S) - 2 single phase 208/240V supply (hot) lines, 1 neutral and 1 ground.

2. 3-wire system (PS360WB70, PS360EWB, PS555, PS570G, PS536) - 2 single phase 208/240V supply (hot) lines and 1 ground.

For all wiring configurations, the voltage when measured from either hot line to neutral should never exceed 130V.

B. Door Switch

Closing the control cabinet door (or machinery compartment door, as appropriate for the oven model) will close the door switch and allow the oven to operate.

Note that the electrical systems will still be live if the switch is open, although the oven cannot operate.

The door switch has a bypass position to enable service operation with the door opened. When the door is open, grasp the switch actuator and pull it out as far as possible. This will close the door switch and permit troubleshooting. Closing the control cabinet door will reset the switch.

1. Closing the door switch permits a circuit to go through a fuse (or circuit breaker, as appropriate for the oven model) to one side of the conveyor switch, blower motor switch, cooldown relay and heat switch.

2. Closing the door switch permits a circuit to go through the motor fuse (two 9A or 15A fuses per motor).

C. Conveyor Switch

Closing the conveyor switch permits a circuit to go to the Conveyor Speed Control Module, which:

1. Sends power to the gear motor (conveyor drive motor). The 120VAC signal to the Conveyor Speed Control Module is rectified to a 90VDC signal which is then sent to the gear motor.

2. Allows regulation of conveyor speed. Adjusting the thumbwheel (or digital pushbutton display unit, as appropriate) to the desired conveyor belt speed instructs the Conveyor Speed Control Module to regulate the output to the gear motor. This increases or decreases the conveyor speed as necessary to match the speed setting shown on the thumbwheel or display unit.

D. Blower Switch

Closing the blower switch energizes:

1. The cooling (axial) fan(s).

2. The blower motor contactor (s).

Closing this contactor starts the blower motor(s). When both blower motors are up to speed, centrifugal switches located inside the blower motors (or air switches detecting blower operation, as appropriate for the oven model) will close, setting up the heat circuit.

3. The Temperature Controller.

E. Heat Switch

Closing the heat switch completes a circuit:

1. Through the heat switch.

2. Through the blower motor centrifugal switches (or air switches, as appropriate for the oven model).

3. Through the high limit switch.

4. One circuit then goes to the:

a. Burner (L1).

b. Transformer (110V to 24V).

c. Motor relay coil. On a cold start the heater on

this relay takes about 30 seconds to warm up before the relay will energize. This gives an additional prepurge. The relay is not used on ovens with 208/240V burner blower motors.

d. Burner blower motor. As the motor reaches full

operating speed, the centrifugal switch (or air flow switch, as appropriate for the oven model) closes and applies voltage to the burner control. This energizes the ignitor control spark transformer and the pilot valve. The spark then lights the pilot. The flame sensor proves the presence of the pilot flame, and the ignitor control then shuts off the spark. At the same time, the main burner valve is opened. The main burner is then ignited.

If the pilot does not light within approximately 90 seconds, the oven will shut down.

The pilot and main gas valve will stay on (open) as long as the heat switch is ON and the flame is proven. If the flame goes out for any reason, the pilot will try to light for 90 seconds, and then go into automatic lockout. To relight the pilot after it has gone into automatic lockout, the burner and then turned ON again.

must be turned OFF for 5 minutes

SECTION 1 - SEQUENCE OF OPERATION

e. For ovens with an On-Off gas regulation sys-

tem (with solenoid valve): Temperature Controller terminals 4 & 5 (power for the primary relay contacts for the high flame solenoid valve).

For PS360EWB ovens with a modulating gas system and Temperature Controller P/N 32571: Temperature Controller terminals 4 & 5 (input signal to amplifier board).

For all other ovens with a modulating gas system: Temperature Controller terminals 15 & 16 (input signal to amplifier board).

In all ovens, the temperature-sensing thermocouple(s) send a millivolt signal to the temperature controller. As long as the temperature inside the oven is below the set point of the Temperature Controller, the Controller will do the following:

1. For ovens with an On-Off gas regulation system: If the temperature sensed by the thermocouple(s) is below the set point on the Temperature Controller, the Controller energizes the high flame solenoid. When the solenoid is energized, the solenoid valve permits 100% gas flow. Power to the solenoid is cut when the temperature reaches the set point, which closes the valve. This permits on-off gas flow to the burner.

When power is cut to the high flame solenoid, the burner will remain ON in the low flame mode. When the temperature drops a few degrees, the Temperature Controller will again energize the high flame solenoid, which opens the valve and restores gas flow to 100%.

An indicator on the Temperature Controller will show whether the high flame solenoid is energized (or whether the burner is activated, which is effectively the same). This indicator varies by Temperature Controller model. Refer to the instructions for the appropriate Temperature Controller for an illustration and description of this indicator.

2. For ovens with a modulating gas system: In response to the signal from the thermocouple(s), the Temperature Controller sends a 4-20mA signal to the amplifier board. The amplifier board converts this to a 0-20VDC signal which is sent to the modulating gas valve. The valve opens or closes in proportion to the signal from the amplifier board, allowing the gas flow to be regulated as required from 0-100%.

An indicator on the Temperature Controller will show whether the burner is activated. This indicator varies by Temperature Controller model. Refer to the instructions for the appropriate Temperature Controller for an illustration and description of this indicator.

F. High Limit

NOTE: Most PS200-Series and PS360-series gas ovens use the high limit feature of the Temperature Controller. All other oven models use a separate High Limit Control Module. Refer to the wiring diagram for the appropriate oven model to check whether a separate High Limit Control Module is used.

The high limit relay will shut the oven burner OFF:

1. If the high limit thermocouple senses an oven temperature above 650°F.

2. If the signal from the high limit thermocouple is lost.

An indicator on the Temperature Controller will show a high limit condition. This indicator varies by Temperature Controller model. Refer to the instructions for the appropriate Temperature Controller for an illustration and description of this indicator.

G. Cooldown

NOTE: PS200VL-series ovens do not include a cooldown feature.

When the heat and blower Switches are turned OFF the cooldown relay will allow the blowers to remain ON until the oven temperature falls to 200°F (93°C).

During cooldown, the Temperature Controller will continue to show the oven temperature.

SECTION 1 - SEQUENCE OF OPERATION

ll. ELECTRIC OVEN SEQUENCE OF OPERATION

A. Electrical Supply

Most electrically heated ovens operate on a 208/230/ 380/440V, 3 phase, 4 wire system. The fourth wire is for a 120 V neutral ground. This 120 V neutral ground eliminates the need for a control transformer. Where a neutral is not available, a 240/110V transformer is supplied.

B. Door Switch

Closing the control cabinet door (or machinery compartment door, as appropriate for the oven model) will close the door switch and allow the oven to operate.

Note that the electrical systems will still be live if the switch is open, although the oven cannot operate.

Closing the door switch permits a circuit to go through a fuse (or circuit breaker, as appropriate for the oven model) to one side of the conveyor switch, blower motor switch and to the heat switch.

C. Conveyor Switch

Closing the conveyor switch permits a circuit to go to the Conveyor Speed Control Module, which:

1. Sends power to the gear motor (conveyor drive motor). The 120VAC signal to the Conveyor Speed Control Module is rectified to a 90VDC signal which is then sent to the gear motor.

D. Blower Switch

Closing the blower switch energizes:

1. The cooling (axial) fan(s).

2. The blower motor contactor (s).

Closing this contactor starts the blower motor(s). When both blower motors are up to speed, centrifugal switch(es) located inside the rear end of the motor(s) (or air flow switch[es], as appropriate for the oven model) will close, setting up the heat circuit.

3. The Temperature Controller.

E. Heat Switch

Closing the heat switch completes a circuit:

1. Through the heat switch.

2. Through the blower motor centrifugal switch.

3. Through the high limit switch.

4. For ovens with on On-Off heater activation mode: To the primary relay contacts of the Temperature Controller (terminals 4 and 5 for digital controllers, terminals 5 and 6 for analog controllers).

When the temperature-sensing thermocouple(s) indicate that the oven temperature is below the set point on the Temperature Controller, the Temperature Controller will energize the contactor(s) which in turn energize the heaters.

When the oven temperature reaches the set point of the Temperature Controller, the Temperature Controller will cut power to the heaters. When the temperature drops a few degrees, the Temperature Controller will again energize the heaters.

An indicator on the Temperature Controller will show whether the Controller is calling for heat. This indicator varies by Temperature Controller model. Refer to the instructions for the appropriate Temperature Controller for an illustration and description of this indicator.

5. For ovens with a Variable Pulse heater activation system: To terminals 15 and 16 on the temperature controller. In response to the signal from the thermocouple(s), Terminals 15 and 16 send a 420mA signal to a controller module that contains an amplifier board and two solid state relays. The relays activate the heating elements at 100% power on a fixed cycle time, for a length of time proportional to the signal from the temperature controller.

A HEAT ON indicator on the Temperature Controller will light to show whether the Controller is calling for heat.

F. High Limit

NOTE: Electric oven models use a separate High Limit Control Module.

The High Limit relay will shut the oven burner OFF:

1. If the high limit thermocouple senses an oven temperature above 650°F.

2. If the signal from the high limit thermocouple is lost.

G. Cooldown

When the heat and blower switches are turned OFF the cooldown relay will allow the blowers to remain ON until the oven temperature falls to 200°F (93°C).

During cooldown, the Temperature Controller will continue to show the oven temperature.

SECTION 2 - AIR FLOW AND HEAT TRANSFER

SECTION 2

AIR FLOW AND HEAT TRANSFER

I. TYPES OF HEAT TRANSFER

Heat constantly moves from a warm object to a cold object. Heat moves in three different ways: thorough conduction, through radiation, and through convection. Middleby Marshall conveyor ovens use all three of these paths to cook the product.

 Conduction - Heat is transferred through surface con-

tact (such as pizza dough in contact with a pan).

 Radiation - Heat is transferred from light-colored ob-

jects to dark-colored objects. The darker the color of an object, the greater the amount of heat that it absorbs. The lighter the color of an object, the greater the amount of heat that it reflects. Middleby ovens use light-colored interiors (aluminized or stainless steel, depending on the oven model) to reflect as much heat as possible to the product.

 Convection - Heated air will transfer heat to objects

with which it comes into contact. Unless the air flow is controlled, hot air will rise and be replaced by cooler air. Middleby Marshall ovens use blowers (one or two large fans, depending on the oven model) to force air through adjustable air fingers onto the product.

The intensity of the heat at the point at which it is sensed is called temperature. The difference in temperature between the food product and the heat source - that is, the pan, oven interior, or heated air, as described above - determines the speed at which the heat flows. The greater the difference in temperature, the faster the heat flows to the product.

In Middleby Marshall conveyor ovens, the heat transfer from conduction is greatly dependent on the customers product and cooking surface (pans, etc.). Likewise, the heat transfer from radiation is effectively constant, because the color of the oven interior cannot be changed. For these reasons, the best way to optimize heat transfer is by regulating the convection air. This can be done in two ways:

 Adjusting the

quantity and velocity of air delivered onto the product.

 Adjusting the air finger configuration to change the pat-

tern in which the vertical columns of air are delivered to the product.

II. BLOWERS AND BLOWER SPEED

A. PS200-series ovens

PS200-series ovens have a single blower motor mounted inside the machinery compartment, with a pulley on the end of the motor shaft. A belt connects this pulley to another on the shaft of the blower fan. The air velocity can be changed by using a larger or smaller pulley on the motor shaft, and changing the length of the belt to match the new pulley. See Figure 1.

However, note that there are only two approved belt/ pulley combinations for PS200-series ovens; one for 60Hz ovens, and one for 50Hz ovens. Field modifications to these approved combinations are not permitted unless under the specific directions of the Middleby Technical Service Department. Any changes to convection air delivery MUST be made using the air fingers.

blowers and blower speed to change the

PS200-series

PS360-series PS555/570-series

Blower

Wheel

Orientation

Figure 1

Blowers, belts and pulleys

Early

(PS570)

Current

(PS570S,

PS570G, all

PS555)

Blower Wheel

Orientation

SECTION 2 - AIR FLOW AND HEAT TRANSFER

B. PS360-series ovens

PS360-series ovens feature two blower motors. A blower wheel is fastened onto the end of the motor shaft. In order to adjust the amount and speed of heated air that is directed by the blower wheels, it is necessary to change the size of the wheels and/or change the speed of the motor. See Figure 1.

Each PS360-series oven model has a specific combination of blower motor and blower wheel. Field modifications to these approved combinations are not permitted unless under the specific directions of the Middleby Technical Service Department. Any changes to convection air delivery MUST be made using the air fingers.

C. PS555/570-series ovens

PS555/570-series ovens have one blower motor mounted inside each of the end compartments of the oven, with a pulley on the end of the motor shaft. The oven has two blower wheels; a belt connects each motor pulley to a pulley on the end of one of the blower wheel shafts. The air velocity can be changed by using a larger or smaller pulley on the motor shaft, and changing the length of the belt to match the new pulley. See Figure 1.

Some customers have a specific belt/pulley combination approved by Middleby Marshall, while others use a standard configuration. Field modifications to these approved combinations are not permitted unless under the specific directions of the Middleby Technical Service Department.

III. AIR FINGERS

A. Description and Function

Air fingers direct the heated air from the blowers into vertical jets that are directed at the top and bottom of the conveyor belt. Each air finger configuration has been tested to optimally cook a specific customers product. As a rule, air finger configurations should NOT be changed from customer specifications without direct instructions from the Middleby Technical Services Department.

Middleby uses two main types of air fingers:

 PS300/350 and early PS310/360 ovens used a shut-

ter-type air finger assembly. The finger is assembled from a manifold, inner plate and outer plate. The inner plate is assembled from two separate plates, each with a series of holes, that are riveted together. The plates can be repositioned relative to each other to restrict the air flow through the holes as necessary. These fingers are no longer in general use, but may still be found in older ovens in the field. See Figure 3.

 All current ovens use an air finger which is com-

posed of a manifold, inner plate, and outer plate. No adjustments are necessary or possible to these fingers, but a wide variety of styles is available to meet different customers baking needs. See Figure 4.

Figure 3

PS300/350 air finger with shutter plate

Outer plate

Lower air fingers have wire

rack as shown to prevent

conveyor belt from rubbing

on outer plate.

Hot air flow

from blower

wheel(s)

Vertical

columns of

high-velocity

hot air

Figure 2

Air finger operation

Rivets

Inner plate

Shutter

Manifold

Figure 4

Current standard air finger (all oven models)

Outer plate

Width and hole

configuration varies.

Inner plate

Width and hole

configuration varies.

May have inner dam.

Manifold

Width varies to match inner

and outer plates. Baffle may

be solid, perforated, partially

perforated, or absent.

Several special shapes are

available to meet specific

customer needs.

SECTION 2 - AIR FLOW AND HEAT TRANSFER

B. Configuration and Alignment

To ensure proper baking of the product, the air flow MUST be properly aligned as it exits the air fingers.

Because air finger configurations are tested at the factory for a specific customers product, severe bake problems related to the air fingers are rare. If you encounter a problem, check the following:

1. Check that the air fingers are properly assembled, cleaned and free of obstructions. For the standard air fingers shown in Figure 4, a variety of styles are available for each of the three components. It is often possible to assemble these components incorrectly, as they are designed to be modular. This will affect the quality of the bake.

If you need information on the correct air finger configuration of the oven, check the following:

 3D air finger label or card. Many current ov-

ens will have a three-dimensional drawing on the front panel of the oven that shows the correct air finger configuration, as shown in Figure 5. Other ovens may have this information on a laminated card attached to the oven.

 Internal air finger chart. All Middleby ovens

have a chart similar to the one shown in Figure 6 attached inside the machinery compartment door. Note that if the air finger configuration has been updated since the oven was installed, this chart may no longer be correct.

 If there is no label present on the oven, and the

chart inside the machinery compartment is incorrect, contact Middleby Technical Service for assistance.

Figure 5

3D air finger label (if present)

2. Check that the bake time and temperature settings of the oven match the customers specifications. Most customers have an acceptable range for bake time and temperature to allow for local variations in altitude, humidity, etc.

3. If these checks fail to correct the problem, you should perform a test bake to pinpoint the type of baking problem that is present.

C. Performing a Test Bake

Before you attempt to correct any problem, please CONFIRM THAT THERE IS ACTUALLY A PROBLEM. It is extremely difficult to tell if an oven is baking unevenly by simply looking at a pizza with ingredients, especially if the pizza is a large combination-type. Often, the ingredients and toppings themselves can cause an uneven bake.

The best way to check for an uneven bake is to make a test bake with a consistent, predictable product and then read it. We recommend using the customers dough (for a pizza product) OR a commercially-available pancake mix (for customers with a variety of products). The pancake mix is generally more sensitive to variations in temperature and thus provides more accurate results than the dough test.

When interpreting the results of the test, consistently uneven baking on the top of the product may indicate a problem with the upper air fingers. Likewise, consistently uneven baking on the bottom of the product may indicate a problem with the lower air fingers.

The most common bake problem is a front-to-back bake issue. This problem occurs when the front of the conveyor belt (towards the window) receives more heat than the rear, or vice-versa. This results in uneven baking for the product based on where it is placed on the conveyor.

Figure 6

Internal air finger chart

NOTE: Labels of this type are not

used on all ovens. Label placement

and design will vary based on

customer preference.

NOTE: All ovens use a chart of this

type inside the machinery compartment.

Changes to the air finger configuration

after oven installation MAY NOT BE

INDICATED.

SECTION 2 - AIR FLOW AND HEAT TRANSFER

To perform the test bake:

1. Select identical pans for the test. Choose the pans based on the width of the conveyor; you should space the pans in line completely across the conveyor without having them touch each other. For instance, for a 32 /813mm-wide conveyor, you could use three 10/ 254mm pans or two 15/381mm pans.

You will need enough pans to have three complete rows. This eliminates the possibility of a single row distorting the results. If necessary, the test can be run with only 1 row of pans, but the results are not as reliable.

2. For a pancake batter test, mix the pancake batter as instructed by the manufacturer. Pour the batter EVENLY into the test pans to a depth of 1/4 (6mm). You may use any type of pancake mix that is available, AS LONG AS YOU USE THE SAME TYPE THROUGHOUT THE TEST.

For a dough test, have the customer make up a thin crust dough in each pan. The dough should be of a consistent thickness in each pan and should be no thicker than 1/4 (6mm). Thicker doughs will provide too great a cushion and will distort the test results.

3. Place the pans side-by-side on the conveyor. The front and rear edges of the pans should be aligned so that it is easier to see if there is a front-to-back bake problem. DO NOT stagger the rows of pans diagonally. Also, check that the pans do not touch each other; this can transfer heat to the test product and distort the results.

4. Run the products through the conveyor at the customers normal bake time and temperature settings.

5. Read the results of the test. Each pan of product should have the same coloration.

If you used pancake batter, the sugar in the mix will brown very rapidly if over-baked. This highlights an outof-balance oven.

If the product lightens or darkens slightly from front-toback in only one row, there is probably not a significant front-to-back bake problem. If the product is noticeably lighter or darker at the front or back in ALL of the rows of pans, there is a front-to-back bake problem. See Figure 7.

Also, remember that

consistently uneven baking on the top of the product may indicate a problem with the upper air fingers. Likewise, consistently uneven baking on the bottom of the product may indicate a problem with the lower air fingers.

 If the oven has the current standard air finger type,

you should contact Middleby Technical Services for assistance.

 If the oven has the PS300/350-style air fingers with

a shutter plate, it is possible to adjust the positions of the air shutters to correct a front-to-back bake problem. Proceed to Step D, PS300/350 Air

Figure 7

Front-to-back uneven bake

NOTE: In this example,

the front of the product

is darker than the rear.

The opposite condition

is also possible.

Finger Shutter Adjustment.

D. PS300/350 Air Finger Shutter Adjustment

Before attempting to properly balance a Middleby Marshall oven equipped with shutter fingers, you should understand the principles of operation of this type of finger.

The oven moves approximately 2000 ft.³ of air per minute. When this large amount of air is moved through the plenum and fingers it rushes through the plenum and to the end of the air finger. This creates a back pressure of air inside the finger and tends to deliver more air onto the product at the front of the air finger.

The inner plate has a separate shutter plate riveted to it at a slight angle. Since there is more pressure at the end of the fingers (front of the oven) than at the plenum (rear of the oven), the shutter plate is angled to restrict the air flow near the front of the oven. This creates a proper balance permitting an even amount of air to exit out of the holes across the width of the conveyor. See Figure 8.

Before adjusting the shutters, it is necessary to determine if the finger is providing a balanced air delivery across the width of the conveyor. This is the purpose

SECTION 2 - AIR FLOW AND HEAT TRANSFER

of making a test to read the bake.

1. Remove all upper air fingers from the oven.

NOTE: As the air fingers are removed, use a felt pen to mark all parts of the fingers. This includes the manifold, inner plate and outer plate. If a blank or choke plate is used, mark that plate also. Fingers are marked in the order shown below, as viewed from the front of the oven. If there are upper and lower oven cavities, you should mark the fingers for the upper oven with a U and those for the lower oven with a L.

VERY IMPORTANT: When the ovens were shipped from the factory, all of the shutters were pre-adjusted for their location within the oven. AII parts of the fingers must be marked as explained above and reassembled into their original position.

2. Check the size of the openings at the front of the shut-

ter plates by inserting a drill into the opening. The factory setting is a #46 drill (0.081/2.06mm).

3. Drill out the four 1/8 pop rivets that are located toward

the front of the fingers. See Figure 8.

NOTE: DO NOT drill out the rivet at the back of the air finger. This is the pivot for the shutter.

4. If the product is lighter at the front of the oven, increase

the opening by 1/16/1.59mm. If the product is darker at the front of the oven, decrease the opening by 1/16/

1.59mm.

The best way to check the size of the openings is to use numbered drills as a gauge. An orifice drill set is ideal for making this adjustment. For example, to increase the opening by 1/16, you would use a #30 drill (0.1285/3.26mm), which is approximately 1/16 larger than the original setting measured with the #46 drill (0.081/2.06mm).

Be sure that the measurement is taken at the largest

point of the opening. See Figure 8.

5. While holding the new adjustment, clamp the two shutter plates together (two pairs of vice grip pliers are ideal) and drill holes for new pop rivets.

NOTE: Most of the old rivet holes can be reused if the old hole is simply elongated. However, if the hole is not properly elongated, the new rivets may pull the plates out of adjustment when they are installed.

IMPORTANT: Aluminum 1/8 pop rivets are ideal for use here. They are much easier to drill out than stainless steel rivets.

6. Repeat these steps to adjust all upper air fingers. Then, reinstall the fingers into the oven.

7. Perform another test bake.

lMPORTANT: This test bake must be an exact duplicate of the first test bake. If you change any of the conditions you will change the results.

 If the test indicates an even bake, your adjustment

is complete.

 If the test indicates that the bake is still uneven,

you will need to repeat the adjustment procedure until an even bake is obtained. By keeping the tests identical, you should be able to determine how much more the shutter plates should be opened or closed to achieve a balanced bake without removing the fingers for a third time.

VERY IMPORTANT: After attaining a proper adjustment of the fingers, each air finger should be marked with a metal stamp showing its position inside the oven. This will eliminate future problems of operators mixing the adjusted fingers when cleaning the oven.

Figure 8

PS300/350-style air finger with adjustable shutter plate

Pivot

DO NOT

drill out

Vise grip

pliers

Higher pressure at the

front of the fingers is

regulated by the

shutter openings

Drill out

rivets

Insert drill bit

to check size

of opening

SECTION 2 - AIR FLOW AND HEAT TRANSFER

IV. OVEN CAPACITY

Oven capacity is generally not a service issue. However, when reporting a service problem, customers may use terms relating to capacity, such as bake time, belt time, time of delivery, etc. This information is provided as a reference for understanding these terms.

A. Conveyor Speed and Bake Time

Middleby Marshall conveyor ovens display the Conveyor Speed on the Thumbwheel (or on the display of the Digital Speed Controller, as appropriate for the oven model). Conveyor Speed is also called Bake Time.

Conveyor Speed (Bake Time) is a leading edge to lead- ing edge measurement. That is, it is the elapsed time from the leading edge of the product entering the bake chamber to the leading edge of the product leaving the bake chamber. See Figure 9.

Figure 9 - Conveyor Speed (Bake Time)

Conveyor Speed

(Bake TIme)

B. Belt Time

Belt Time is a measurement used by several customers. It is a trailing edge to trailing edge measurement. That is, it is the elapsed time from the trailing edge of the product entering the bake chamber to the trailing edge of the product leaving the bake chamber. See Figure 10.

Note that belt time is equal in length to conveyor speed (bake time), although the time is measured during a different period of the baking process.

C. Time of Delivery (TOD)

Time of delivery (TOD) is a leading edge to trailing edge measurement. That is, it is the elapsed time from when the leading edge of the product enters the bake chamber to when the trailing edge of the product leaves the bake chamber. See Figure 11.

Figure 10 - Belt Time

Belt Time

Direction of

Conveyor Travel

Leading edge

of product

Trailing edge

of product

Figure 11 - Time of Delivery

Time of Delivery

Direction of

Conveyor Travel

Leading edge

of product

D. Formulas for Determining Time of Delivery (TOD) and Oven Capacity per Hour

1. Time of Delivery (TOD)

Time of Delivery (TOD) = x (Bake Chamber Length + Product Diameter)

Conveyor Speed

Bake Chamber Length

Example: PS570S Oven, 7:00 Bake Time, 16 Product Diameter = x (70 + 16) = 8.6 mins. (8:36)

Trailing edge of

product

7 mins.

70

Direction of

Conveyor Travel

2. Oven Capacity/Hour

Oven Capacity/Hour = x

Example: PS570S Oven, 7:00 Bake Time, 16 Product Diameter = x 6.98 = 75 pizzas/hr.

(Bake Chamber Length + Product Diameter) x Bake Chamber Depth

Product Diameter²

(70 + 16) x 32

256 in.²

60 min./hr.

TOD

SECTION 3 - SERVICING COMPONENTS

SECTION 3

SERVICING COMPONENTS

I. CONVEYOR SPEED CONTROLLER AND DRIVE

MOTOR

The Conveyor Speed Controller is used to set and monitor the speed of the conveyor. The Controller consists of three components:

 Control Module

Early units used a module which featured a microcomputer that was unique to each oven model. Using this control module required verifying that the correct microcomputer was installed.

Later units use DIP switches to set up the controller for a particular oven model. This later model was initially available with a thumbwheel unit (either 4 or 8 DIP switches). Current models feature a digital display with keypad (8 DIP switches).

 Thumbwheel Unit (or Digital Display with Keypad)

This module displays the conveyor speed and allows it to be adjusted by the operator. It is connected to the control module by a ribbon cable.

 Pickup Assembly

The pickup assembly consists of a magnetic wheel on the end of the gear motor (conveyor drive motor) shaft, and a Hall Device sensor that provides feedback to the control module.

As the magnetic wheel turns, the revolutions of the magnet are monitored by the Hall Device sensor. The signals are sent to the control module, which compares the motor speed with the speed shown on the thumbwheel or digital display. The control module increases or decreases the voltage to the gear motor (conveyor drive motor) depending on the signal.

A. Part Number Reference - Speed Controllers

1. Original-style speed controller with interchangeable microcomputer and thumbwheel. This unit is no longer

available and part numbers are provided for reference only. Servicing this unit is beyond the scope of this manual. If this controller is in need of service, we recommend simply installing a current unit (see below).

P/N Description

28174-0004 PS360 controller, yellow (12A) microcomputer 28074-0006 PS360 microcomputer, yellow (12A) 27170-0232 PS360 microcomputer w/emulator, yellow (12A) 28074-0007 PS314 controller, orange (13A) microcomputer 28074-0008 PS314 microcomputer, orange (13A) 27170-0233 PS314 microcomputer w/emulator, orange (13A) 28074-0013 PS200 microcomputer, pink (15A)

2. Current-style speed controller with either 4 or 8 DIP switch settings and thumbwheel. This unit is no longer available

from the factory, but may still be stocked by service agencies.

P/N Description

42810-0133 Controller assembly with thumbwheel 42810-0118 Thumbwheel only

3. Current-style speed controller with 8 DIP switch settings and digital display/keypad. Note that the two types

of controllers ARE NOT compatible - the controller and display unit MUST be of the same type.

P/N Description

37337 Controller assembly with digital display/keypad,

NCC (8/00-current) 37503 Digital display/keypad unit only, NCC 45133 Controller assembly with digital display/keypad,

Danaher (2/02-current)

Figure 12

Original-style speed controller

Produced with thumbwheel only.

Interchangeable microcomputer selects oven model.

THIS CONTROLLER IS OBSOLETE AND NO

LONGER AVAILABLE.

Control module

Microcomputer

Thumbwheel

Produced with Thumbwheel or digital display.

DIP switches may

be on control

module or digital

display, depending

on the controller

model.

Figure 13

Current-style speed controller

4 or 8 DIP switches select oven model.

Cover plate shows DIP

switch settings

Thumbwheel

or digital

display

Control module

SECTION 3 - SERVICING COMPONENTS

B. Part Number Reference - Pickup Assemblies

1. PS350-style pickup assembly or old-style pickup assembly (see Figures 14-15). These parts use the same

part number. They are no longer available from the factory, but may still be stocked by some service agencies.

P/N Description

28074-0005 Pickup assembly, PS350-style or old-style

2. Current-style pickup assembly (see Figures 16-17)

P/N Description

27170-0263 Pickup assembly, current

C. Preparing to Service the Speed Controller

NOTE: To properly service this equipment, you must use a digital meter. An analog meter will not work.

1. Before troubleshooting the conveyor speed controller, check the following:

a. Conveyor belt is tight.

b. Drive chain is tight and aligned.

c. Set screws on drive sprockets are tight.

d. Axial fan(s) are running and clean of dust and de-

bris.

e. Motor and pickup wires are secure at the Conveyor

Terminal Block (location of the block varies by oven model).

f. Wire connections on conveyor speed control mod-

ule (including the ribbon cable to the thumbwheel/ display unit) are secure.

2. Check the pickup for the following (see Figures 14-17):

a. Pickup is secure.

b. Magnet is not cracked or chipped.

c. Magnet is not rubbing on plastic housing.

d. Mounting bolt is not worn or bent.

e. Pickup bearing in good condition.

f. On PS350-style pickup (Fig. 14), gap between

magnet and Hall Device is spaced approximately 1/64-1/32 (0.4-0.8mm, or a business card thickness).

Figure 14

PS350-style pickup assembly

(used on early PS360)

Figure 15

Old-style pickup assembly

SECTION 3 - SERVICING COMPONENTS

Figure 16

Current pickup assembly - side view

D. Controller/Motor Failure

When the conveyor speed controller fails, it is very possible that a shorted conveyor motor caused the problem. Unless the motor is changed, the installation of another conveyor speed controller will simply burn up the new controller.

You are STRONGLY ADVISED to bypass the speed controller and install the tester unit shown in Figure 18 before replacing any speed controller that has burned out. This will identify the source of the problem - the speed controller or the motor. It is much less expensive to burn out the tester than another speed controller.

The components for this tester can be purchased at any electrical supply store. The tester is not as accurate or sensitive as the speed controller, and so should NOT be left in place on the oven after servicing!

Figure 17

Current pickup assembly -

end view

Components needed for the field tester:

 Full-wave AC-DC bridge, 400V, 4A  Light dimmer switch, 5A  In-line 5A AC fuse enclosed in plastic case  2 alligator clips

CAUTION: DO NOT turn the conveyor switch ON while the field tester is connected!

1. Disconnect the motor lead wires and attach to the field tester as shown in Figure 18. Depending on the oven model, you can simply use the black and red gear motor leads, or the remote leads at the terminal block connection.

To reverse the conveyor motor direction, simply interchange the black and red leads.

2. To start the test, the dimmer switch should be turned until the motor begins to operate. The switch can then be turned down to the desired motor speed.

Figure 18

Field Tester for Conveyor Drive Motor

or circuit breaker

SECTION 3 - SERVICING COMPONENTS

E. Basic Troubleshooting Flowcharts

1. IF THE GEAR MOTOR RUNS AT FULL SPEED:

NOTE:

Middleby no longer stocks parts for the original speed controller with interchangeable microcomputer. If it is necessary to replace this version of

the controller or the microcomputer, and the

service agent does not have the parts in stock, it

will be necessary to replace the entire speed

controller with a current model.

2. IF THE GEAR MOTOR WILL NOT RUN AT ALL:

SECTION 3 - SERVICING COMPONENTS

NOTE:

Middleby no longer stocks parts for the

original speed controller with inter-

changeable microcomputer. If it is necessary to replace this version of the controller or the microcomputer, and the service agent does not have

the parts in stock, it will be necessary

to replace the entire speed controller

with a current model.

SECTION 3 - SERVICING COMPONENTS

F. Initial Troubleshooting

NOTE: When changing the conveyor speed on a controller with a thumbwheel, it is advisable to turn the conveyor switch OFF before adjusting the thumbwheel. Note that this cannot be done on a digital keypad, as switching the conveyor switch OFF will also turn off the display.

1. Check all connections at the terminals on the conveyor speed control module to ensure that they are correct and tight. Connections are shown in the drawing.

Correct the connections if necessary.

Connections are

reversed if

conveyor direc-

tion is reversed.

120VAC supply.

Wire colors vary

by oven model.

2. Ensure that there is power to the controller. Use a digital multimeter to read the voltage between the terminals marked AC. The voltage should read between 110-120VAC.

If the power is not present or of an incorrect voltage, check the power source.

3. With the AC power on, check the DC voltage to the conveyor motor. Match the measured voltage with those shown on the chart below. If the voltage reading is more than ±5VDC of that shown on the chart, complete the Motor Test on the next page.

Thumbwheel/ DC Motor Voltage

Display PS200, PS310, 360,

Setting 570, 360WB70 360WB, 360EWB

3 mins. 84VDC 67VDC 4 mins. 63VDC 50VDC 5 mins. 51VDC 40VDC 6 mins. 43VDC 34VDC 7 mins. 37VDC 28VDC 8 mins. 32VDC 25VDC 9 mins. 29VDC 22VDC

10 mins. 27VDC 20VDC 11 mins. 24VDC 18VDC 12 mins. 22VDC 17VDC 13 mins. 19VDC 14VDC 15 mins. 18VDC 13VDC

4. Check the magnetic pickup on the motor.

If the pickup is in good condition, check that the conveyor is running and then check the voltage between the COM and ±5VDC terminals on the controller. On controllers with thumbwheels, the voltage should read 5VDC, ±0.3VDC. Digital controllers should read 5VDC , ±1.0VDC.

Next, check the voltage between the COM and COUNT terminals. The reading should stay between 2 and 3VDC.

If EITHER of these two readings are incorrect, perform the Conveyor Control Pickup Test on the next page.

SECTION 3 - SERVICING COMPONENTS

G. Conveyor Control Pickup Test

1. Visually check the pickup for the following:  The magnet is clean and the bearing is in good

condition.  There are no chips or cracks on the magnet.  If using a PS350-style pickup (see Figure 14), there

is a 1/64 to 1/32 (0-4-0.8mm, or a business card

thickness) gap between magnet and hall device.

2 Set the multimeter to the VDC scale, then connect the

meter probes as shown in Figure 19. The black (-common) probe should connect to the COM terminal on the speed control board, while the red (+VW) probe connects to the +5V terminal. +5VDC should be present at all times when the conveyor is operating.

 If +5VDC is present, proceed to Step 3.  If +5VDC is not present, disconnect the three pickup

wires (connected to the COM, SIGNAL, and +5V

terminals) and again check for +5VDC.

- If +5VDC is present with the pickup disconnected, replace the pickup assembly.

- If +5VDC is still not present, replace the conveyor speed controller.

3. Connect the multimeters red (+) lead to the SIGNAL terminal; then, disconnect the motor wires from the ARM and +ARM terminals. Using a 5/16 open-end wrench, very slowly rotate the motor pickup shaft while observing the multimeter. Two (2) changes from +5VDC to 0VDC should occur for each motor revolution.

 lf the signal is always at 0VDC, go to Step 4.  lf the signal is always at 5VDC, OR if the signal

changes more than 2 times per revolution, replace the pickup assembly.

4. Disconnect the pickup signal wire from the speed controller and check for +5VDC at the SIGNAL terminal of the controller.

 If +5VDC is present, replace the pickup assembly.  If 0VDC is present, replace speed control.

Figure 19

Connections for pickup test

H. Conveyor Motor Test

1. Disconnect the gear motor wires from the Speed Controller terminals (-ARM and +ARM).

2. Remove the brush retainer caps from the gear motor. DO NOT remove the brushes.

3. Set the multimeter to the lowest Ohm scale. Then, place one meter probe on each brush retaining plate. BE SURE THAT NEITHER PROBE TOUCHES THE MOTOR CASING.

4. Using a 5/16 open-end wrench, very slowly rotate the motor pickup shaft while observing the multimeter. During a 1/2 rotation:

 The Ohm reading should stay betweeen 3-5W.  There should NEVER be a complete short.  There should never be a high Ohm reading. If the motor fails any of these tests, replace the motor.

I. Replacing the Magnetic Pickup

If you need to replace the magnetic pickup on a gear motor shaft:

1. Apply Loctite Removable #242 (or equivalent) sparingly to the threads.

2. Turn the mounting screw until it is finger tight, then turn it an additional 1/4 turn with a wrench.

J. Unshielded Pickup Wires on Early PS360-series ovens

The conveyor speed controller can be affected by electrical noise transmitted by other electrical components or wiring. Early PS360-series ovens used an unshielded connection between the pickup assembly and the control module. On these ovens, the unshielded wiring can pick up the noise and transmit it to the control module. The problem is most easily seen when the conveyor fails during burner spark ignition.

There are two remedies for this problem:

1. Turn the conveyor switch to the OFF position, and then back to the ON position, after the burner has ignited. The controller should reset and allow normal operation. This should be used as a stop-gap measure ONLY to allow the oven to continue operation.

2. Replace the pickup wiring between the control module and the terminal block with a new shielded cable (P/N 42400-0334). When installing the shielded cable, follow the color code change shown here:

Old Wiring Shielded Cable

Br own Black

Orange Red

Yellow White

Wiring diagrams are also provided in Figures 20 and 21 on the next page.

There is a fourth lead on one end of the shielded cable. This is a ground lead which is attached to the black wire of the cable. The ground lead should be connected to the terminal block inside the motor compartment.

Current PS360-series ovens have the shielded cable installed at the factory and do not require this retrofit.

SECTION 3 - SERVICING COMPONENTS

Figure 20

Wiring for PS360 Shielded

Pickup Cable - early terminal

block design

Figure 21

Wiring for PS360 Shielded

Pickup Cable - late terminal

block design

K. Appendices

Appendix - Conveyor sensor wiring changes for PS360-series and PS570S, 10/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-133B - Installation Instructions for Conveyor

Speed Controller Kit with Thumbwheel, P/N 42810-0133, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-133B - Installation Instructions for Conveyor

Speed Controller Kit with Thumbwheel, P/N 42810-0133, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 42810-0133-

Conveyor Speed Controller Kit with Thumbwheel, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 42810-0133-

Conveyor Speed Controller Kit with Thumbwheel, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 42810-0133-

Conveyor Speed Controller Kit with Thumbwheel, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 42810-0133-

Conveyor Speed Controller Kit with Thumbwheel, 4/95

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-177 - Introduction and Compatibility of

Conveyor Speed Controller with Digital Display, P/N 37337, 8/00

Bulletin No. MM-177 Date: 8/18/00

Middleby Cooking Systems Group

1400 Toastmaster Drive  Elgin, IL 60120-9272 U. S. A.  Telephone: (847)741-3300  Service and Parts Fax: (847)741-4406

Service Bulletin

SUBJECT

Availability of Conveyor Speed Controller Kits

GENERAL

Middleby Marshall is changing is standard Conveyor Speed Controller from the familiar thumbwheel control to a unit that features a digital display with pushbutton speed selectors. The part numbers of these components are summarized here:

Speed Controller with Thumbwheel

 Kit (includes control module and thumbwheel): 42810-0133  Thumbwheel unit only: 42810-0118

Speed Controller with Digital Display

 Kit (includes control module and digital display): 37337  Digital selector/display unit only: 37503

Because of this change, supplies of the previous speed controller are VERY LIMITED, and the separate thumbwheel is no longer available. your remaining thumbwheel controls for use with the oven models that cannot use the new controller.

Immediately stock the new Speed Controller units and save

APPLICATION

 Service agents should immediately begin to stock P/Ns 37337 and 37503 to fulfill their normal

need for conveyor speed controllers. The new units can be used without modification on ALL OVENS EXCEPT THE PS200R68-SERIES.

 Your existing stock of P/Ns 42810-0133 and 42810-0118 should be used, whenever possible,

ONLY for PS200R68-series ovens.

 The new speed controller and digital display are already in use on Middleby Marshall PS555 ovens;

so, your Agency may already have some of these components in stock. Please check your existing stock of these components before placing addtional orders.

COMPATIBILITY

The Speed Controller with Digital Display is compatible with all Middleby Marshall ovens EXCEPT the PS200R68, PS220R68, and PS224R68.

AVAILABILITY

 P/Ns 37337 and 37503 are available for immediate shipment.

 P/N 42810-0133 is available in very limited quantities. Note that some future orders may not be

fulfilled.

 P/N 42810-0118 is no longer available.

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 44756 - Conveyor Speed Controller Kit

for PS200R68-series Ovens, 2/02

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  USA  (847) 741-3300  FAX (847) 741-4406

Instructions for Service Kit 44756

Conveyor Speed Controller Kit for PS200R68-series ovens

KIT COMPONENTS:

Qty. P/N Description

1 37337 Conveyor speed controller with digital display

1 44749 Cable assembly, PS200R68-series ovens

1 44757 Instructions, PS200R68-series oven conveyor speed controller kit

This Service Kit will update one Middleby Marshall PS200R68, PS220R68, or PS224R68 oven to operate using the current digital conveyor speed controller with keypad display (P/N 37337), instead of the previous controller with thumbwheel adjustment (P/N 42810-0133). If the oven is already equipped with controller P/N 37337, this Kit is not necessary; P/N 37337 may be used as a direct replacement for the existing controller.

WARNING

BEFORE PERFORMING ANY SERVICE WORK, THE ELECTRICAL POWER SUPPLY SUPPLY

MUST BE TURNED OFF.

AND THE GAS

1. Disconnect the oven from its electrical power supply at the circuit breaker/fused disconnect. For ga s o ve ns , shut off the gas supply to the oven.

2. Identify the 24-pin control cable (female at both ends) that connects the rear of the remote box (on top of the oven) to the rear of the machinery compartment (on the side of the oven).

3. Remove and discard the cable.

4. Open the machinery compartment door and locate the conveyor speed control module.

5. One at a time, disconnect the leads from the terminals on the existing speed control module and connect them to the corresponding terminals on the new control module.

6. Remove the ribbon cable plug from its socket on the old speed control module, and attach it to the corresponding socket on the new control module.

7. Remove and discard the old control module from the inside of the machinery compartment door.

8. Adjust the DIP switch settings on the new speed control module to the correct settings for the PS200-series oven with a 3-30 minute bake time range. These settings are

shown on the case of the controller and are also provided in Figure 1.

9. Install the new module in place. Close and fasten the machinery compartment door.

10. Temporarily remove the remote box from the top of the oven. Open the remote box.

11. Disconnect the thumbwheel units ribbon cable plug from its socket on the remote board. Then, remove and discard the thumbwheel unit.

12. Install the new digital display unit in place. Connect its ribbon cable plug into its socket on the remote board.

13. Close the remote box and reinstall it atop the oven.

14. Install the new kit-supplied control cable between the back of the remote box and the back of the machinery compartment.

15. Restore the electrical and gas utility supplies to the oven.

16. Test the operation of the new conveyor speed controller to make certain that it is operating properly. The oven is now ready for operation.

Figure 1

DIP Switch Settings

Middleby Cooking Systems Group

1400 Toastmaster Drive

Elgin, IL 60120

(847) 741-3300  FAX (847) 741-4406

Middleby Corporation Service

Hotline 1-800-238-8444

P/N 44757  Rev. C  V1  2/02

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-189 - New Conveyor Gear Motors,

Brushes, and Pickup Clamps, 8/01

Bulletin No. MM-189 Date: 8/24/01

Middleby Cooking Systems Group

1400 Toastmaster Drive  Elgin, IL 60120-9272 U. S. A.  Telephone: (847)741-3300  Service and Parts Fax: (847)741-4406

Service Bulletin

SUBJECT

New conveyor gear motors, brushes, and pickup clamps for Middleby Marshall ovens

GENERAL

The conveyor gear motors used on all Middleby Marshall ovens (except model PS536) have been redesigned by the vendor. Changes to the motors include:

 A smaller-diameter motor casing.

 New motor brushes.

- Old-style motors continue to use brush P/Ns 22450-0052 or 22450-0230 as shown in the table below. All of the new motors use brush P/N 46658.

 A shorter clamp to attach the pickup assembly. This accommodates the smaller diameter of the motor.

- The pickup assembly with the original clamp is still available as P/N 27170-0263. This kit is only available in limited quantities. existing clamp to attach a new pickup assembly to an old-style motor.

- The pickup assembly with the new, shorter clamp is available as P/N 46451.

- All of the new motors will be shipped in a kit that also includes the new clamp. This allows you to attach an existing pickup assembly to a new motor.

- In 7/01 and 8/01, some of the new motors were shipped under the part numbers of the old motors. These parts shipped without the new clamp. In most of these cases, you can tighten the existing clamp to fit the new motor. Some older clamps, however, cannot be tightened enough to fit. in all ovens, you should add the new clamp, P/N 46602, to your required parts stocking list, and carry a few spare clamps on each service vehicle.

Please be aware of these changes as you order your stocking parts. Some versions of the old motor, as well as the oldstyle pickup assembly, are still available in limited quantities. The brush for the old motor (P/N 22450-0052) will remain available in order to maintain motors already in the field.

Ratio Used on Motor Brush Pickup Motor* Brush Pickup Clamp

1400:1 PS310 27384-0008 22450-0052 27170-0263 46603 46658 46451 46602

PS314 PS360/360S PS360SS High Speed PS360T Tandem PS360WB PS360WB70 PS360EWB PS555 PS570/570S Single Belt

1350:1 PS200/220FS/224 27384-0011 22450-0230 27170-0263 46604 46658 46451 46602

PS200VL/220VL/224VL PS200R68/220R68/224R68 PS200T Tandem PS570/570S Split Belt (Standard)

600:1 PS314SBI 27384-0003 22450-0052 27170-0263 46605 46658 46451 46602

300:1 PS200/220FS/224 (High Speed) 27384-0014 22450-0230 27170-0263 46606 46658 46451 46602

PS570/570S Split Belt (High Speed)

* New Motor part numbers shown in this table are kits that include both the motor and the new pickup clamp.

After our stock of the old-style pickup assembly kit is exhausted, you will need to save the

To be sure that you can install the new motor

Old Old Old Ne w Ne w Ne w Ne w

SECTION 3 - SERVICING COMPONENTS

Appendix - DIP switch settings for Conveyor Speed Controller

with Digital Display (P/N 37337), 4/02

II. TEMPERATURE CONTROLLER

The Temperature Controller is used to set and control the oven temperature. Depending on the oven, model, the controller has several functions:

 On gas ovens with On-Off gas valve operation, the tem-

perature controller opens and closes the high flame solenoid. This allows 100% or 0% gas flow to the burner in response for the need for heat to maintain the set point temperature. The temperature controller has no effect on the low flame bypass or oven ignition.

For this operating mode, the temperature controller is set to the On-Off Mode as described in the Kit instructions.

 On gas ovens with modulated gas valve (PID) opera-

tion, the temperature controller sends a signal to the amplifier board which in turn controls the operation of the modulating valve. This allows a modulated gas flow of any necessary value from 0-100% in response for the need for heat to maintain the set point. The temperature controller has no effect on oven ignition.

For this operating mode, the temperature controller is set to the PID Mode as described in the Kit instructions.

 On electric ovens with On-Off heater activation (includ-

ing most PS200-series and PS360-series electric ovens), the temperature controller permits or cuts power to the heating elements as necessary to maintain the set point temperature.

For this operating mode, the temperature controller is set to the On-Off Mode as described in the Kit instructions.

 On electric ovens with variable pulse heater activation

(including PS555 electric ovens), the temperature controller sends its signal to a controller module that contains an amplifier board and two solid state relays. The relays activate the heating elements at 100% power on a fixed cycle time, for a length of time proportional to the signal from the temperature controller.

For this operating mode, the temperature controller is set to the PID Mode as described in the Kit instructions.

Note that temperature controller P/N 46837 (inc. with Service Kit 47321) includes a dedicated variable pulse mode intended for the PS536 electric oven. This special mode is NOT used on the PS555.

 The temperature controller regulates the cooldown func-

tion. NOTE: PS200VL-series ovens do not include a cooldown function.

 On most PS200-series and PS300-series gas ovens

(except the PS200VL), the temperature controller monitors the high limit. All other oven models use a High Limit Control Module that is independent of the temperature controller.

A. Part Number Reference - Temperature Controllers

Middleby Marshall ovens have used several different models of temperature controllers. The current Digital Temperature Controller (P/N 46837, included in Service Kit 47321) is the only model currently available. All other controllers

SECTION 3 - SERVICING COMPONENTS

shown are no longer available and part numbers are provided for reference only. Servicing these units is beyond the scope of this manual. If one of these controllers is in need of service, we recommend simply installing a current unit (P/N 46837, included in Kit P/N 47321).

 P/N 28071-0012 (A)

Analog Temperature Controller cooldown functions, 120V, on-off mode only.

 P/N 28071-0018 (A)

Analog Temperature Controller with high-limit and cooldown functions, 120V, on-off mode only.

 P/N 34983 (B)

Analog Temperature Controller without high-limit and cooldown functions, 120V, on-off mode only. Used on

PS200VL-series ovens only. PS200VL-series ovens equipped with this Temperature Controller do not have a cooldown feature and use a separate high limit control module.

 P/N 28071-0027 (C)

Digital Temperature Controller with blue plastic faceplate, 120V, on-off mode only.

 P/N 28071-0028 (D)

Digital Temperature Controller with gray rubber faceplate and buttons with text, 120V, on-off mode only.

 P/N 28071-0028 (E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, 120V, on-off mode only.

without high-limit and

 P/N 30871 (E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, 208-240V, on-off mode only. Used on early PS360WB70 and some CE oven

models.

 P/N 32571 (E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, 208-240V, PID mode only. Used on early PS360EWB.

 P/N 36021 (F)

Digital Temperature Controller with gray face plate (steel trim on edges), 120-240V, selectable on-off or PID modes.

 P/N 36056 (G) - Service Kit P/N 36939

Digital Temperature Controller with black plastic face plate, 120-240V, selectable on-off or PID modes.

 P/N 46837 (G) - Service Kit P/N 47321

Digital Temperature Controller with black plastic face plate, 120-240V, selectable on-off, PID and variable pulse modes.

Note that the dedicated variable pulse mode is used on the PS536 electric oven ONLY. Using this mode requires moving a jumper on one of the PC boards inside the controller. The PS555 variable pulse electric oven does NOT use this mode and should have the controller set to the PID mode as described in the Kit instructions.

Figure 22 - Temperature controllers

DEFG

SECTION 3 - SERVICING COMPONENTS

B. Description

The temperature controller consists of two main components: a sleeve or case (metal or plastic) with terminal connections on the back, and a plug-in chassis that includes the faceplate and circuitry. The sleeve is mounted to the panel or door of the oven, and the chassis is inserted into the front of the sleeve.

VERY IMPORTANT: When replacing a controller, you should ALWAYS replace the sleeve as well. Some controller models have sleeves of a similar size, but with DIFFERENT CONNECTIONS. Using an incorrect sleeve can damage the controller and cause the oven to function incorrectly. Exception: The sleeve used on Controllers 36056 and 46837 is identical except for the information label.

C. High Limit/Cooldown Functions Except where noted in Section A (Part Number Reference),

the temperaturecontroller incorporates circuitry for the high limit and cooldown functions.

1. The High Limit function (terminals 11 and 12) will shut off the burner/heating elements if the oven temperature sensed by the thermocouple(s) exceeds 650°F/343°C. This function is used on most PS200-series and PS360series gas ovens. All other oven models use a separate high limit control module.

If the high limit temperature is reached, an indicator on the controller will illuminate. The current controller (P/N 46837) has a lamp marked OVERTEMP to show this condition. Older controllers will have different indicators; you should refer to the operating instructions for the controller in question for assistance.

2. The Cooldown function allows the blowers to continue in operation after the operator switches off all operating switches on the control panel. The blowers will remain in operation until the cooldown switch opens (usually 180°F/82°C).

D. Troubleshooting

1. Troubleshooting the Temperature Controller and Thermocouple(s) using the Altek Thermocouple Source (Middleby P/N 27170-0192)

 Turn the heat switch OFF.  Disconnect the thermocouple leads from Terminals

7 and 8 on the temperature controller. Tape the ends to prevent shorting.

 Connect the white lead of the Thermocouple Source

to Terminal 8 (+). Connect the red lead of the Thermocouple Source to Terminal 7 (-).

 Set the Thermocouple Source as close as pos-

sible to the customers set point. Then, turn the BLOWER switch to the ON position.

The temperature controller should read close to the customers set point. Failure indicates a problem with the temperature controller. If the temperature controller is functioning properly, check the thermocouples. Refer to Section IV, Thermocouples.

2. Troubleshooting the High Limit Switch On ovens that use the high limit function of the tem-

perature controller (most PS200-series and PS360-series ovens), an intermittent high limit switch will cause intermittent operation of the burner. If you suspect that this is a problem, a good check is to place a 1A fuse in parallel around the switch contacts (terminals 11 and

12). If the switch is functioning properly, the fuse will never

carry a load. The only time the switch would open would be under a no-load condition.

If the switch is trying to open intermittently, however, the full current load of the blowers will be carried by the fuse. Regardless of the oven model, this load is far greater than 1A, and the fuse will blow.

E. Appendices

Appendix - Temperature controller terminal cross-reference, 4/02

Terminal for Terminal for

28071-0012 and Terminal for 36056 and Description

28071-0018 34983 46837

1 TC+ 8 + TC 2TC-7 - TC 5 COM 5 Input to Temperature Control Relay

6 NO 4 Output to High Flame Solenoid or Heater Contactors L2 L2 L2 Neutral L1 L1 L1 Power

GG Ground

13 -- 9 Input to Cooldown Relay 14 -- 10 Output from Cooldown Relay 15 -- 11 Input to High Limit Relay 16 -- 12 Output from High Limit Relay

-- -- 15 PID or Variable Pulse Output

-- -- 16 PID or Variable Pulse Output

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  USA  (847) 741-3300  FAX (847) 741-4406

Instructions for Service Kit 47321

Digital Temperature Controller

Installation, Programming and Troubleshooting Instructions

KIT COMPONENTS

Qty. P/N Description

1 46837 Digital Temperature Controller (On/Off Gas & Electric, PID Gas, and

Variable Pulse Electric operating modes), with mounting brackets

1 47322 Instructions

TABLE OF CONTENTS

Controller Types ............................................................................................... 2

Before You Begin ............................................................................................. 3

Installation ........................................................................................................ 3

Electrical Connections ..................................................................................... 4

Jumper Setting ................................................................................................. 6

Programming ................................................................................................... 6

Diagnostic Error Messages ............................................................................. 8

Operating Instructions (to be left with customer after installation) ...................... 9

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120

(847) 741-3300  FAX (847) 741-4406

Middleby Corporation Service Hotline 1-800-238-8444

Page 1 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Controller Types

This Kit includes one Digital Temperature Controller (P/N 46837) that can operate at 120-240V, and can be programmed to operate in on-off, PID, or variable pulse modes. The Controller is shown in Figure 1G, below. By following these instructions, the Controller can be installed into any Middleby Marshall oven equipped with the following Controllers.

 P/N 28071-0012 (Fig. 1A)

Analog Temperature Controller cooldown functions, operating at 120V, on-off mode only.

 P/N 28071-0018 (Fig. 1A)

Analog Temperature Controller cooldown functions, operating at 120V, on-off mode only.

 P/N 34983 (Fig. 1B)

Analog Temperature Controller cooldown functions, operating at 120V, on-off mode only.

Used on PS200VL models. As of 12/01, P/N 34983 is still available and should be used on these ovens if possible.

 P/N 28071-0027 (Fig. 1C)

Digital Temperature Controller with blue plastic faceplate, operating at 120V, on-off mode only.

 P/N 28071-0028 (Fig. 1D)

Digital Temperature Controller with gray rubber faceplate and buttons with text, operating at 120V, on-off mode only.

without high-limit and

with high-limit and

without high-limit and

 P/N 28071-0028 (Fig. 1E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, operating at 120V, onoff mode only.

 P/N 30871 (Fig. 1E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, operating at 208-240V, on-off mode only. Used on early PS360WB70 and some

CE oven models.

 P/N 32571 (Fig. 1E)

Digital Temperature Controller with gray rubber face plate and buttons with symbols, operating at 208-240V, PID mode only. Used on early PS360EWB.

 P/N 36021 (Fig. 1F)

Digital Temperature Controller with gray face plate (steel trim on edges), operating at 120-240V, selectable onoff or PID modes.

 P/N 36056 (Fig. 1G)

Digital Temperature Controller with black plastic face plate, operating at 120-240V, selectable on-off or PID modes.

Figure 1

EFG

This Kit CANNOT be installed in a PS536 oven equipped with the P/N 44783 (variable pulse electric) or P/N 44823 (PID gas) controller shown below.

Page 2 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

WARNING

BEFORE PERFORMING ANY SERVICE WORK, THE ELECTRICAL POWER SUPPLY AND THE GAS SUPPLY MUST BE TURNED OFF.

Before you Begin

1. This Temperature Controller requires a current-version thermocouple for proper operation. Check that the thermocouple(s) installed in the oven match the current three-lead, flanged versions BEFORE you begin to install the Temperature Controller. See Figure 2.

If the oven is not equipped with current thermocouples, you should replace them BEFORE you install the new Temperature Controller.

P/N 33984: Thermocouple kit for PS300-series, PS555 and PS570

P/N 33985: Thermocouple kit for PS200-series and PS536

Figure 2

flange

Cable

(3 leads)

Current thermocouple

Cable

(2 leads)

Obsolete 2-lead

thermocouple

clip

Installation

1. Check the ovens existing temperature controller, as shown on the previous page.

 IF THE EXISTING CONTROLLER IS P/N 36056 OR P/N 46837 (shown in Figure 1G), the new

controller can be installed directly into the existing sleeve as follows:

- Loosen the Phillips screw at the bottom center of the faceplate.

- Pull the old controller out of the sleeve.

- Skip ahead to the Jumper Setting section of these instructions on Page 6 to set up the new controller. After the jumper is configured, the new controller can be installed directly into the existing sleeve.

 IF THE EXISTING CONTROLLER IS OF ANY OTHER TYPE, the sleeve will have to be replaced

with the one included in this Kit. Continue on to Step 2 in this section.

2. Access the back of the existing temperature controller. Tag each wire that connects to the controller with its terminal number. These numbers will be used later to wire the new controller.

3. Disconnect all wires from the terminals on the temperature controller. that are removed.

4. Remove the controller and sleeve from the oven as follows:  For analog controllers P/Ns 28071-0012 and 28071-0018 (Fig. 1A), remove the two bracket

screws on the back of the control. Then, remove the bracket. Pull the controller and sleeve out through the front of the oven panel.

 For all other controllers, remove the two screws and brackets that hold the controller in place.

Then, pull the controller and sleeve out through the front of the panel.

Page 3 of 10

Be sure to retain any jumpers

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

5. Check that the new controller is mounted into its sleeve. Then, slide the assembly into the opening in the panel from the outside. Check that the controller is upright, with the display on top and the keypad on the bottom.

6. Locate the rectangular holes on the top and bottom of the new controllers sleeve. Attach the two kitsupplied mounting brackets against the inside panel of the oven, and into the holes in the sleeve, as shown in Figure 3. Check that the heads of the screws point to the rear of the controller.

7. Tighten the two screws evenly until the lip of the sleeve is seated tightly against the panel.

8. If there is a protective clear plastic strip on top of the display, remove it at this time.

Figure 3

Temperature controller is

pre-installed into sleeve

and is upright

Control

panel

Bracket clips and

screw heads point to

REAR of controller

Electrical Connections

1. Wire the new controller as follows:

 If you are replacing an Analog Temperature Controller, P/Ns 28071-0012 or 28071-0018 (see

Fig. 1A), refer to Figure 4A for a listing of the new terminal numbers.

 If you are replacing an Analog Temperature Controller P/N 34983 (Fig. 1B - PS200VL models

only), refer to Figure 4B for a listing of the new terminal numbers.

 If you are replacing any Digital Temperature Controller, simply reconnect ALL of the original

wires and jumpers to the same terminals, as all terminals are numbered the same.

EXCEPTION: Controller P/N 32571(Fig. 1E - used on early PS360EWB ovens only) uses Terminals 4 & 5 for the mA output to the amplifier board. The current controller uses Terminals 15 & 16 for these connections, as shown in Figure 5A.

Page 4 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Figure 4a

Analog temperature controller (P/Ns

28071-0012 and 28071-0018) terminals

New temperature

controller terminals

Not used on

Not used

pulse output (electric ovens with variable pulse system). Neither of these systems were available with ovens equipped with these controllers.

Terminal for

28071-0012 and Terminal for Terminal for Description

28071-0018 34983 46837

1TC+8 + TC 2TC-7 - TC 5 COM 5 Input to Temperature Control Relay

6 NO 4 Output to High Flame Solenoid or Heater Contactors L2 L2 L2 Neutral L1 L1 L1 Power

GG Ground 13 - - 9 Input to Cooldown Relay 14 - - 10 Output from Cooldown Relay 15 - - 11 Input to High Limit Relay 16 - - 12 Output from High Limit Relay

-- -- 15 PID or Variable Pulse Output

-- -- 16 PID or Variable Pulse Output

some gas and electric ovens

Not used

Not used. These terminals provide PID output (gas ovens with modulating valve) or variable

Not used

Analog temperature controller

(P/N 34983) terminals

New temperature

controller terminals

Figure 4b

Not used. PS200VL ovens have a separate high limit module and do not include a cooldown feature.

Not used

Not used. PS200VL ovens do not include a modulating gas system.

Figure 5a

Modulated Gas Output System

4-20mA

input

NOTE: Controller P/N 32571 used Terminals 4 & 5

for the 4-20mA input to the amplifier board.

These connections must be moved to Terminals

15 & 16 on the new controller as shown.

Amplifier board

24VAC

input

Figure 5b

Variable Pulse Output System

Modulating

valve

Relay

20VDC pulsed output

0-24VDC

output

NOTE: Safety switches may be placed between

the temperature controller

and the relay on some

oven models.

Page 5 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Jumper Setting

Loosen the Phillips screw at the bottom center of the faceplate. Then, pull the controller out of its sleeve. Next, access the jumper shown in Figure 6. This jumper affects the signal that is output from Terminals

15 and 16.

CAUTION

If the jumper is incorrectly set, the oven will be unable to properly maintain temperature. In addition, DAMAGE MAY OCCUR TO THE CONTROLLER AND OTHER OVEN COMPONENTS. Always make sure that the jumper is correctly set BEFORE restoring power to the oven!

 For gas ovens equipped with the modulating gas system, the jumper must be set to the

W1 position.

This instructs the controller to send a variable-current 4-20 mA signal from Terminals 15 and 16 to the amplifier board. The board converts this to a 0-24VDC signal which is sent to the modulating valve. The valve regulates the gas flow according to the need for heat to maintain the set point.

For gas ovens, you should always check inside the machinery compartment to see whether a modulating valve is present in the unit before setting this jumper.

 For electric ovens equipped with the variable pulse system, the jumper must be set to the

W2 position.

This instructs the controller to send a constant-current, pulsed 20VDC signal to the relay. Once per second, the signal pulses on proportional to the need for heat to maintain the set point.

As of 1/02, only the PS536 Electric oven uses the variable pulse system. Other oven models equipped with this system will be announced by Middleby as they become available.

 For all other ovens - gas or electric - that use the on-off system, the jumper may be set to

either position.

After the jumper has been properly set, replace the controller into its sleeve and tighten the screw.

The jumper MUST be set to the correct position for proper operation of the controller.

Figure 6

Jumper is set to the W1

position for gas ovens with

modulating gas system

Jumper is set to the W2

position for electric ovens

with variable pulse system

Programming

1. Restore electrical power to the oven.

2. Refer to Figure 7. Set the following options, according to the customers preferences:

 Set Point locked or unlocked  Degrees Fahrenheit or Celsius  Set Point or Actual Temperature display

3. Set the controller to PID or On-Off operating mode. Choose the PID mode for BOTH gas ovens with the modulating system AND for electric ovens with the variable pulse system.

4. Adjust the Set Point according to the customers specifications.

5. If the PID operating mode was chosen, perform an Auto-Tune calibration as per the instructions in Figure 7.

6. Check that the customer is familiar with the operation of the controller. The last page of these instructions includes an operating guide for the controller. Remove this page and leave it with the customer for future reference.

Page 6 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Figure 7

Temperature Controller Service Instructions

Page 7 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Diagnostic Error Messages

The controller runs background tests during normal operation. If any problems occur during the tests, an error message flashes in the display. A listing of these diagnostic error messages is shown below.

1. Turn the Blower Switch (HEAT Switch for PS536 ovens with the twoswitch configuration) OFF for 2 minutes.

2. Turn the Blower Switch (or HEAT Switch, as per Step 1) ON.

Flashes on the display (alternating with the temperature) indicating that the internal diagnostic test has failed.

The oven temperature has not reached 200°F/93°C within 15 minutes of startup. On gas ovens, this is usually a result of the burner not lighting.

3. If necessary, repeat Steps 1 and 2 up to two additional times.

4. If the problem does not clear after 3 attempts, replace the controller.

1. Turn the Blower Switch (HEAT Switch for PS536 ovens with the twoswitch configuration) OFF for 2 minutes.

2. Turn the Blower Switch (or HEAT Switch, as per Step 1) ON.

3. If the problem does not clear, contact the Middleby Technical Service Department for assistance.

Caused by an open in the thermocouple circuit.

Polarity of the thermocouple leads is reversed.

1. Check that the thermocouple leads are properly connected to Terminals 7 & 8 of the temperature controller.

2. Check the continuity of the thermocouple at room temperature. You should measure 9-20 Ohms of resistance.

3. If the reading was outside the correct range, the thermocouple has an open. Remove and replace the thermocouple.

If the reading was inside the correct range, contact the Middleby Technical Service Department for assistance.

1. Check the polarity of the thermocouple leads. The red wire (-) should be attached to Terminal 7 on the temperature controller. The white wire (+) should be attached to Terminal 8.

2. If the polarity connections are incorrect, connect the thermocouple properly.

If the polarity connections are correct, replace the thermocouple.

Page 8 of 10

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Digital Temperature Controller

P/N 46837

Operating Instructions

"SP LOCK" Light

Lights when the set point is locked out from changes. This setting can only be changed by service personnel.

OVERTEMP Light

Lights when the oven temperature is greater than 650°F (343°C).

Temperature Key

Press this key once to view the Actual Temperature in the Display.

Display

Shows the Set Point or the Actual Temperature in degrees Fahrenheit (F) or Celsius (C).

"HEAT ON" Light

Lights when the burner or heating elements, as appropriate for the oven model, are in operation.

"SET PT" (setpoint) Light

Lights when the set point is shown in the display.

"ACTUAL TEMP" Light

Lights when the Actual Temperature is shown in the display.

Service Key

For use by service personnel only.

Unlock Key

Press this key together with the Set Point Key to allow the Set Point to be changed. Changes can only be made for 60 seconds.

Up Arrow and Down Arrow Keys

Press these keys to adjust the Set Point up or down. If the Set Point will not change, refer to Key and Unlock Key.

Set Point

Set Point Key

Press this key together with the Unlock Key to allow the Set Point to be changed. Changes can only be made for 60 seconds.

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 47321 - Digital Temperature Controller Kit, 2/02

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120

(847) 741-3300  FAX (847) 741-4406

Middleby Corporation Service Hotline 1-800-238-8444

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-136 - Electrical Noise

Filter Capacitor Assembly on Temperature Controllers, 9/93

SECTION 3 - SERVICING COMPONENTS

Appendix - Service Bulletin MM-136 - Electrical Noise

Filter Capacitor Assembly on Temperature Controllers, 9/93

SECTION 3 - SERVICING COMPONENTS

III. HIGH LIMIT CONTROL MODULE

On most PS200-series and PS300-series gas ovens, the temperature controller monitors the high limit. All other oven models use a High Limit Control Module that is independent of the temperature controller.

Middleby ovens have used several different types of high limit control modules. See Figure 23.

 The United Electric Type 54 control was used for high

limit functions only. Ovens equipped with this control did not have a cooldown feature. The control was used on early PS310 and PS360 electric ovens.

 The United Electric Type 55 control included both high

limit and cooldown functions, and was used on PS310 and PS360 electric ovens.

 The Watlow high limit control module is the only ver-

sion still in use by Middleby. The module includes high limit functions only. The cooldown function is controlled by the ovens temperature controller, except on PS200VL-series ovens, which do not include a cooldown feature.

The Watlow high limit control module is used on PS200series, PS360-series, and PS555/570-series ovens.

Service information in this Manual is limited to the current Watlow high limit control module. The United Electric units are no longer available. Service Kit P/N 39733 can be used to upgrade either of the two previous controllers to the Watlow version.

A. Part Number Reference - High Limit Control Mod-

ules

P/N Description

28071-0002 United Electric Type 54 high limit control module

No longer available - upgrade to current model 34982 using Service Kit 39733

28071-0014 United Electric Type 55 high limit/cooldown con-

trol module

No longer available - upgrade to current model 34982 using Service Kit 39733

34982 Watlow high limit control module, 115V

For use on ovens with 120V control circuits

33983 Watlow high limit control module, 240V

For use on ovens with 208-240V control circuits

30693 Illuminated reset button (green) for Watlow con-

trol (all voltages)

39733 High Limit Conversion Kit for PS300, PS310,

PS350, and PS360 ovens

Replaces P/Ns 28071-0002 or 28071-0014 with P/N 34982

B. Location

On ovens that include the separate high limit control module, it is located:

 PS200-series - Inside the machinery compartment.  PS360-series - Inside the control compartment.  Early PS555 ovens - Inside the left blower motor com-

partment.

 Current PS555 and all PS570 ovens - Inside the

machinery compartment.

C. Operation and Troubleshooting

Refer to the wiring diagrams at the back of this manual for high limit wiring connections.

The Watlow high limit control module generally uses a dedicated high limit thermocouple. Some older ovens use a dual-function, four-lead thermocouple that sends a signal to both the temperature controller and the high limit control module. Refer to Thermocouples on Page 54 for details.

If the temperature sensed by the high limit thermocouple exceeds 650°F/343°C, the high limit control module will shut down the oven and illuminate the green reset button. The module will need to be reset (by pressing the reset button) before the oven can be operated. The reset button is located inside the machinery compartment to ensure that it is reset by an authorized service agent. The agent should determine and correct the cause of the high limit condition before returning the oven to service.

An open high limit thermocouple will trigger the high limit control module to shut down the burner. The high limit control will need to be reset after the open is corrected (as per the procedure described above) before the oven can return to operation.

Figure 23 - High limit control modules

(Shown in PS360-series oven)

United Electric Type 54

high limit control module

United Electric Type 55

high limit/cooldown

control module

Watlow high limit

control module

Reset button

SECTION 3 - SERVICING COMPONENTS

D. Appendices

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  USA  (847) 741-3300  FAX (847) 741-4406

Instructions for Service Kit 39733

High Limit Conversion Kit for PS300, 310, 350, & 360 Ovens

KIT COMPONENTS -

Qty. P/N Description

TOOLS REQUIRED

 Drill with 3/16 drill bit  Middleby Marshall Thermocouple Signal Source

 Wire cutters/strippers

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

Check that the kit includes ALL of these parts BEFORE you begin!

Qty. P/N Description

1 39732 Instructions 1 34982 Watlow high limit control module 1 30693 Reset switch w/ lighted pushbutton 1 35634 Mounting bracket, reset switch 1 35691 Wire set, reset switch (includes 4

wires and 3 1/4/25mm connectors)

1 33812-1 Thermocouple, type J, 6/152.4mm 1 39690 Mounting sleeve, thermocouple

Generator (P/N 27170-0192)

2 ft./610mm 27152-0050 Wire, #18 AWG, brown 2 ft./610mm 27152-0053 Wire, #18 AWG, white 2 ft./610mm 27152-0054 Wire, #18 AWG, purple

8 1455A8750 1 3002693 Wire tie, nylon 2 2000076 Screw, 6-32 X 1-5/8 2 1421B8803 Screw, 6-32 X 1/4 4 2001327 Nut, 6-32

Wire connector, 1/4/6.4mm

Figure 1

United Electric Type 54

High Limit Control

A. OVERVIEW

This Service Kit is used to replace two different types of United Electric high limit/cooldown controllers with a Watlow high limit controller for PS300, 310, 350, and 360 Ovens. See Figure 1.

 The early (Type 54) United Electric control was ONLY

equipped with a high limit circuit. Ovens equipped with this control did NOT have a cooldown circuit. This control was used on the following models:

- PS300/350 Gas (early)

- PS300/310/350/360 Electric (early - all voltages)

For these ovens, the kit directly replaces the Type 54 high limit control with the Watlow high limit control.

 The later (Type 55) United Electric control was

equipped with BOTH high limit and cooldown circuits, and was used on the following models:

- PS300/310/350/360 Electric (late), 208/240V and 480V UL versions ONLY

For these ovens, the kit replaces the Type 55 control with the Watlow high limit control, and uses the ovens temperature controller to provide the cooldown circuit.

United Electric Type 55

High Limit/Cooldown

Control

Lighted Reset

Switch

Watlow High Limit Control

Page 1 of 8

P/N 39732

Rev. B  V1  5/99

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

B. INSTALLATION

WARNING

BEFORE PERFORMING ANY SERVICE WORK, THE GAS SUPPLY (IF SO EQUIPPED) THE ELECTRICAL SUPPLY TO THE OVEN

1. Open the machinery compartment and control compartment access panels.

2. Locate the high limit thermo bulb/capillary assembly. Its location is shown in Figure 2. Loosen the set screw that holds the assembly in place. Remove the thermo bulb/capillary assembly from the mounting tube.

3. Disconnect the wires (2 for the Type 54 control, 4 for the Type 55 control) from the terminals of the United Electric control. Bundle the loose wires together, and allow them to hang loose for later reconnection.

4. Remove the mounting screws that hold the United Electric high limit control in place. Then, remove and discard the high limit control and its mounting screws.

5. Position the new high limit control in place on the left wall of the control compartment, as shown in Figure 3. When positioning the control:

 Ensure that the control is positioned AT LEAST 1 (25mm) back into the compartment to allow the

compartment door to close.

 Ensure that additional space is left underneath the control for the reset switch.

NOTE: Instead of holding the high limit control in place, you may use the dimensions provided in Figure 4 to determine the location of the control and its mounting holes.

MUST BE TURNED OFF.

AND

6. Mark the locations of the two mounting holes for the high limit control. Then, drill the holes using a 3/16 drill bit.

7. Secure the high limit control in place using the kit-supplied 6-32 x 1-5/8 screws and 6-32 nuts.

8. Position the bracket for the reset switch on the left wall of the control compartment, as shown in Figure

3. Note that the face of the bracket with the large, circular switch-mounting hole should face YOU. Also, the bracket should be positioned AT LEAST 3 (75mm) back into the compartment to allow the door to close.

9. While holding the bracket in place, mark the locations of the two mounting holes. Then, remove the bracket and drill the holes using a 3/16 drill bit.

10. Secure the bracket to the panel using the kit-supplied 6-32 x 1/4 screws and 6-32 nuts. DO NOT INSTALL THE RESET SWITCH INTO THE BRACKET AT THIS TIME.

11. Insert the kit-supplied thermocouple into its mounting sleeve. Position the sleeve so that the mounting hole is at the base of the thermocouple, not the tip. See Figure 5.

12. Insert the thermocouple and mounting sleeve into the original mounting tube. The set screw opening in the sleeve should align with the set screw hole on the side of the mounting tube.

Push the thermocouple into the opening until its base seats firmly on the mount. See Figure 6.

13. Insert the thermocouples set screw into the hole on the side of the mounting tube. Tighten the set screw to hold the thermocouple and sleeve in place.

14. Thread the thermocouples shielded cable into the electrical compartment. Coil the free end of the cable and fasten it with the kit-supplied nylon wire tie. Be sure to leave enough free cable to reach the new high limit control.

Page 2 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

High limit thermocouple location -

lower oven

Figure 3 Figure 4

Figure 2

High limit thermocouple location -

upper oven

NOT TO SCALE

Base

Figure 5

Thermocouple

Hole in sleeve is

base of

next to

thermocouple

Figure 6

Sleeve

Page 3 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

C. WIRING

For the various wiring connections listed below, cut the kit-supplied #18 AWG wires to length. Refer to Figures 7 and 8 (on pages 6 and 7) for diagrams of the wiring connections.

Lighted Reset Switch Wiring and Installation

14. Using the kit-supplied 1/4 wire connectors, connect the following kit-supplied wires:

- Red wires ................. connect one wire to each RESET terminal on the high limit control

- Black wire ................. connect to terminal NC on the high limit control

- White wire ................. connect to terminal L2 on the ovens temperature controller

15. Slip the free ends of these four wires through the circular hole in the reset switch mounting bracket, so that they hang down in front of the control compartment.

16. Use the kit-supplied 1/4 wire connectors to connect these four wires to the terminals on the lighted reset switch.

- Terminals 1 and 3 ..... Red wires (these connections are interchangeable)

- Terminal 2 ................ Black wire

- Terminal 4 ................ White wire (kit-supplied)

17. Push the lighted reset switch through the mounting hole in the center of the bracket until it snaps into place. Be sure to avoid pinching the wires against the sides of the mounting hole.

Cooldown circuit wiring

NOTE: Perform steps 18 and 19 ONLY if you are replacing a UE Type 55 controller. If you are replacing a UE Type 54 controller (which has no cooldown circuit), skip ahead to Step 20.

18. Attach the ovens troller, as shown in Figures 7 and 8.

For Ovens with a Digital Temperature Controller:

a. Terminal 9 ................ Black wire (from blower switch)

b. Terminal 10 .............. Brown wire (from blower switch)

For Ovens with an Analog Temperature Controller:

a. Terminal 13 .............. Black wire (from blower switch)

b. Terminal 14 .............. Brown wire (from blower switch)

19. Attach a brown kit-supplied wire between the following terminals on the Temperature Controller:

Digital Controller ............. Terminals 10 and L1

Analog Controller............ Terminals 13 and L1

High Limit Control wiring

20. Using the kit-supplied 1/4 wire connectors, wire the high limit control terminals as follows:

a. Terminal NO ........... Purple wire (originally to UE control)

c. Terminal TC + ........ White wire (to thermocouple) - DO NOT CUT THIS WIRE TO LENGTH.

d. Terminal TC - ......... Red wire (to thermocouple) - DO NOT CUT THIS WIRE TO LENGTH.

f. Terminal L2 ............ White wire (kit-supplied; to neutral on the ovens terminal block)

h. Terminal COM........ Orange wire (originally to UE control)

existing cooldown wiring to the following terminals on the ovens Temperature Con-

21. Using a 1/4 wire connector, attach a brown kit-supplied wire to the L1 terminal on the high limit control. Attach the free end of the wire to the L1 terminal on the temperature controller.

Page 4 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

D. TESTING THE INSTALLATION

22. Remove the thermocouple wires from the TC + and TC - terminals on the high limit control.

23. Attach a Middleby Marshall Thermocouple Source (P/N 27170-0263) to the TC + and TC - terminals on the high limit control, in place of the thermocouple wires. Note that it may be necessary to attach a pair of terminal connectors to the leads of the Thermocouple Source to allow them to connect to the high limit controls terminals.

24. Restore the gas supply (if so equipped) and the electrical supply to the oven. Because the control compartment door is still open, pull the door safety switch out into the service position.

25. Test the operation of the high limit control as follows:

a. Set the Thermocouple Source to a normal operating temperature, between 200°-600°F (93°-315°C).

b. Turn the oven on, and allow it to heat to 600°F (315°C).

c. After the oven has reached the setpoint temperature, set the Thermocouple Source to 700°F (371°C).

The high limit control is set to open at any temperature in excess of 650°F (343°C). This will shut down the ovens heat circuit and illuminate the Reset Switch lamp.

26. Set the Thermocouple Source to a temperature setting below 600°F (316°C), and depress the Reset Switch. This should turn off the Reset Switch lamp and restore heat circuit operation.

27. Turn the oven off.

28. If you replaced a UE type 55 controller (with a cooldown circuit), you must set the Thermocouple Source to a temperature setting below 200°F (93°C). Then, wait for the blowers to turn off.

29. Press the door safety switch in to reset it to normal.

30. Remove the Thermocouple Source from the oven.

31. Reattach the thermocouple wires to the high limit controls terminals as follows:

White wire ................ TC +

Red wire ................... TC -

32. Close the machinery compartment and control compartment access panels, and fasten them in place. The oven is now ready for normal operation.

Page 5 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

KEY

Figure 7 - United Electric Model 55 replacement: ovens with a cooldown feature

Page 6 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

KEY

Figure 8 - United Electric Model 54 replacement: ovens without a cooldown feature

Page 7 of 8

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kit 39733 -

High Limit Conversion Kit for PS300, 310, 350 & 360 Ovens, 5/99

A MIDDLEBY COMPANY

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  USA  (847) 741-3300  FAX (847) 741-4406

Middleby Corporation Service Hotline 1-800-238-8444

www.middleby.com

Page 8 of 8

SECTION 3 - SERVICING COMPONENTS

IV. THERMOCOUPLES

All temperature controller and high limit functions are based on input from thermocouples. When two wires composed of dissimilar metals are joined together and one of the ends is heated, a continuous current flow is generated. Middleby ovens use a Type J (iron constant) thermocouple. The iron wire increases the number of dissimilar metal junctions in the circuit.

Middleby has used several types of thermocouples. All can be replaced with the current version. Refer to Figure 24 for illustrations.

 A two-lead thermocouple with a small retaining clip.

Used for EITHER temperature-sensing OR high-limit functions. This type is no longer available.

 A four-lead thermocouple with a small retaining clip.

This is a dual-function unit that sends its signal to the temperature controller and to a separate high limit control module. This type is no longer available.

 A three-lead thermocouple with a separate ground lead,

a shielded cable and a large mounting flange. This is the only type of thermocouple available from Middleby at this time. If it is used to replace a four-lead dualfunction thermocouple, two complete and separate thermocouples will have to be installed.

Figure 24 - Thermocouples

Cable

flange

Current 3-lead

thermocouple

Obsolete 2-lead

or 4-lead

thermocouple

A. Part Number Reference - Thermocouples

Part numbers are provided ONLY for the current, 3-lead thermocouple kits. These thermocouples include instructions for replacing all previous thermocouple designs, in all oven models.

P/N Description

33984 Kit, thermocouple, PS360-series or PS555/570

series

33985 Kit, thermocouple, PS200-series or PS536

(3 leads)

Cable

(2 or 4 leads)

clip

B. Thermocouple Functions

1. Temperature-sensing thermocouple(s) All thermocouples monitor oven temperature. However,

Middleby uses the term temperature-sensing thermocouple in reference to thermocouples that send their signal to the temperature controller instead of to a separate high limit control module.

On ovens that do NOT include a separate high-limit control module (this includes most PS200-series and PS360-series gas ovens), this thermocouple signal is used to monitor the oven temperature for regulating the gas flow/heater activation, AND to activate the high limit warning in case of an overtemp condition.

Middleby ovens use from one to three temperature-sensing thermocouples, depending on the oven model.

Temperature-sensing thermocouples are used on all oven models and are connected to Terminals 7 and 8 on the temperature controller. Based on the signal from this thermocouple, the temperature controller:

 Calls for heat from the burner/heating elements to

maintain the set point (output from Terminals 4 & 5 for on-off electric and gas ovens; output from Terminals 15 & 16 for variable pulse electric and modulating gas ovens).

 Controls the cooldown feature if the HEAT switch

is turned off while the oven is above the cooldown temperature (output from Terminals 9 & 10).

 On ovens without a separate high limit control mod-

ule (most PS200-series and PS360-series gas and electric ovens), the oven temperature sensed by this thermocouple is also used to activate the high limit warning (output from Terminals 11 & 12).

2. High limit thermocouple Middleby uses the term high limit thermocouple in

reference to the thermocouple that sends its signal solely to the separate high limit control module.

If the oven does not have a separate high limit control module, there is no high limit thermocouple. On these ovens, the temperature-sensing thermocouple(s) control high limit activation.

C. Troubleshooting

1. Open thermocouple An open in a thermocouple will cause the temperature

controller to read the maximum temperature (usually 909°F/487°C). This causes the following:

 On ovens without a separate high limit control mod-

ule, an open thermocouple triggers the high limit alarm. This shuts down the burner. After the open has been corrected, the high limit will need to be reset to allow the oven to resume operation.

 On ovens with a separate high limit control mod-

ule, an open temperature-sensing thermocouple causes the temperature controller to stop calling for heat. This shuts down the burner.

 On ovens with a separate high limit control mod-

ule, an open high limit thermocouple will trigger the high limit control module to shut down the burner. Note that the high limit control will need to be reset after the open is corrected before the oven can return to operation.

SECTION 3 - SERVICING COMPONENTS

2. Checking the thermocouple with a DC millivolt meter It is possible to check that a thermocouple is reading

accurately by using a multimeter set to read DC millivolts. At 32°F/0°C the thermocouple should read 0 mVDC. This can be checked by inserting the ther-

mocouple into an ice bath for several minutes. At 72°F/ 22°C the reading should be 1.134mVDC.

You can use the chart below by checking the temperature at the thermocouples junction terminals. This is called the Junction Temperature.

Figure 24 - Thermocouple millivolt readings at various operating and junction temperatures

SECTION 3 - SERVICING COMPONENTS

D. Appendices

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  USA  (847) 741-3300  FAX (847) 741-4406

Instructions for Service Kits P/Ns 33984 and 33985

Oven Thermocouple Kit

This Service Kit provides the parts and instructions necessary to replace one temperature-sensing or high limit thermocouple in any of the following Middleby Marshall oven models:

 PS200 Series uses Kit P/N 33985  PS360 Series uses Kit P/N 33984

These instructions include replacement procedures for ovens built with the current flanged thermocouple, AND for ovens built with the obsolete thermocouple without a flange (P/N 28071-0001).

KIT CONTENTS - KIT P/N 33984

P/N Qty. Description

33812-1 1 Thermocouple, type J, 6 L

B301A8861 2 Screw, hex wshr hd #6 x 3/8 21292-0001 3 Screw, hex wshr hd #10-16 x 3/4 27276-0001 1 Cable clamp, nylon

41687 1 Attachment plate, PS360 rear thermocouple 34701 1 Instructions

IMPORTANT - READ THIS

The thermocouple in your Kit has three leads:  The red and white leads connect directly to the thermocouple terminals on the ovens temperature controller (or high

limit control module, as appropriate), or to a local terminal block that in turn is connected to one of these units.

 The uninsulated lead is a ground wire for the thermocouples protective sheath. The ground connection helps to drain

any radio-frequency disturbances from the thermocouple before the signal enters the temperature controller or high limit control module. For a temperature-sensing thermocouple, the ground lead MUST be connected to the ground terminal on the temperature controller. For a high limit thermocouple, the ground lead should be connected to a chassis ground or to the mounting screw for the high limit control module.

Some early thermocouples may have either two or four leads:  The two-lead thermocouple is simply an earlier version of the current model, without the ground lead. When replacing

a two-lead thermocouple, it will be necessary to connect the new ground lead.

 The four-lead thermocouple is actually a dual-function unit which sends its signal to both the temperature controller

and the high limit control module. Current ovens use separate thermocouples for these functions. When replacing a four-lead thermocouple, it will be necessary to use a SECOND KIT to install the high limit thermocouple. In addition, any oven equipped with these early thermocouples should have all of its thermocouples updated at the same time. For a PS570 or PS570S oven, this will require THREE THERMOCOUPLE KITS - two for the existing thermocouples, and one for the new, separate high limit.

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

 PS536 uses Kit P/N 33985  PS555 uses Kit P/N 33984

KIT CONTENTS - KIT P/N 33985

P/N Qty. Description

33812-2 1 Thermocouple, type J, 13-3/8 L

B301A8861 1 Screw, hex wshr hd #6 x 3/8

34701 1 Instructions

BEFORE YOU BEGIN!

 PS570 uses Kit P/N 33984

Oven Model Page

PS200 Series - before 2/96, serial numbers before ASH-0001 ........... 2

PS200 Series - 2/96 or later, serial numbers after ASH-0001 ............. 2

PS360 Series rear wall thermocouples - before 2/96, serial

numbers before ASH-0001 .................................................................3

PS360 Series rear wall thermocouples - 2/96 or later, serial

numbers after ASH-0001 .................................................................... 3

PS360 Series front-mounted thermocouples inside the

machinery compartment...................................................................... 4

PS536 ................................................................................................5

WARNING

BEFORE PERFORMING ANY SERVICE WORK, THE ELECTRICAL POWER SUPPLY

Oven Model Page

PS555 Gas - rear wall thermocouples with screw terminal

connections (no terminal blocks) .........................................................8

PS555 Electric and PS555E............................................................... 9

PS570 (X01-X05 name plate ID numbers) and PS570S (early) with side-mounted thermocouples inside

the blower motor compartments ........................................................ 10

PS570S (late) - rear wall thermocouples with left-side AND

right-side terminal block connections ................................................. 12

PS555G and PS570G - rear wall thermocouples with

left-side terminal block connections.................................................... 14

AND THE GAS SUPPLY MUST BE TURNED OFF.

P/N 34701  Rev. C  V1  11/01

or outside

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS200 Series - before 2/96, serial numbers before ASH-0001

Thermocouples on these ovens are located inside the machinery compartment. They are secured in place by a set screw in the mounting tube, inside the plenum chamber.

This Kit eliminates the set screw. The new thermocouple is held in place by the head of the screw that is already used to attach the mounting tube.

NOTE FOR HIGH LIMIT THERMOCOUPLES:

CE ovens and PS200VL models have two thermocouples, one mounted above the other. In these ovens, the upper thermocouple senses the oven temperature and is connected to the temperature controller. The lower thermocouple is connected to the high limit control module. Either thermocouple can be replaced using this Kit.

1. Remove the lower end plug from the control end of the oven. Then, remove 1 or 2 lower air fingers as necessary to access the thermocouple mounting tube.

2. Refer to Figure 1. REMOVE AND DISCARD the set screw and pull the thermocouple out of the mounting tube. Disconnect the thermocouple wiring from the temperature controller or high limit module, as appropriate.

3. Remove AND RETAIN the #10-16 screw that fastens the flange of the thermocouple mounting tube to the plenum wall. Leave the mounting tube in place.

4. Install the new thermocouple so that its flange fits firmly against the mounting tube flange.

5. Replace the #10-16 screw that you removed in Step 3. Check that the head of the screw holds the thermocouple flange securely in place, as shown in Figure 1.

6. Route the thermocouple leads away from the ignition cable. Connect the leads as shown in Figure 2.

PS200 Series - 2/96 or later, serial numbers after ASH-0001

Thermocouples on these ovens are located in the same position as the earlier PS200 models described above. However, these ovens feature a flanged thermocouple identical to the new thermocouple provided in this Kit.

The thermocouple SHOULD be held in place by the screw that attaches the thermocouple mounting tube, as per the replacement procedure above. For these ovens, simply disconnect the thermocouple wiring from the temperature controller and follow Steps 3-6 of the procedure shown above to remove and replace the thermocouple.

On some of these ovens, the thermocouple flange rests ON TOP of the retaining screw for the mounting tube, as shown in the INCORRECT inset of Figure 1. These thermocouples are held in place by the set screw on the mounting tube, inside the plenum chamber. For these ovens, you should remove and replace the thermocouple by following Steps 1-6 of the preceding section.

Thermocouple Installation - PS200 Series

Thermocouple

Set screw

(not used with new

thermocouple)

CORRECT

Thermocouple flange sits firmly on

mounting tube flange; tube

mounting screw holds thermo-

couple in place.

Thermocouple Wiring - PS200 Series

White

Red

Shielded

ground lead

Analog

Temperature

Controller

Red White

Shielded

ground lead

SECTION 3 - SERVICING COMPONENTS

Figure 1

Thermocouple

Tube

flange

shown.

Digital

Controller

Shielded

ground lead

Control Module

Mounting

tube

screw

flange

Mounting

tube

Figure 2

Oven

wall

INCORRECT

Thermocouple flange sits on top of

screw head, leaving a gap as

Temperature

RedWhite

High Limit

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS360 Series rear wall thermocouples before 2/96, serial numbers before ASH-0001

Thermocouples on these ovens are located on the rear wall of the baking chamber. They are secured in place by a clamp on the outside of the oven.

This Kit eliminates the clamp. The flange of the new thermocouple is held to the back wall of the oven by a retaining plate, as shown in Figure 3.

1. Loosen the retaining clamp and pull the thermocouple straight out. Disconnect the thermocouple leads. Carefully thread the wiring out of the oven and discard the thermocouple.

2. Remove and discard the cable clamp.

3. Slide the new thermocouple into the mounting tube until the flange is seated firmly on the back wall of the oven.

4. Install the kit-supplied retaining plate (P/N 41687) as shown in Figure 3.

5. Fasten the attachment plate to the back wall of the oven using the two kit-supplied #10-16 x 3/4 self-tapping screws. Ensure that the thermocouple flange is securely trapped between the plate and the rear wall of the oven.

6. Route the wiring through the grommet hole and into the machinery compartment. Check that the leads are clear of all components, PARTICULARLY THE BLOWER MOTOR, by using the existing wiring bundles.

7. Connect the leads as shown in Figure 4.

8. Attach the kit-supplied nylon clamp and #10-16 x 3/4 screw to the rear of the oven. The clamp should be positioned to support the thermocouple leads away from the flue pipes and vent openings.

Thermocouple

Plenum

wall

tube

Figure 3

Clamp (remove

and discard if

present)

thermocouple

Figure 4

Thermocouple

flange

New

Retaining

plate

Thermocouple Installation - PS360 Series

Mounting

(welded to

plenum)

Oven

wall

Thermocouple Wiring - PS360 Series

Digital Temperature Controller

White

Red

#10-16 x 3/4

mounting

screws (2)

PS360 Series rear-wall thermocouples - 2/96 or later, serial numbers after ASH-0001

Thermocouples on these ovens are mounted directly to the back wall of the oven using a single retaining screw. It should be possible to simply replace the existing thermocouple using the original mounting hardware.

To replace the thermocouple:

1. Remove AND RETAIN the screw that holds the thermocouple in place on the rear wall.

2. Disconnect the thermocouple leads. Carefully thread the wiring out of the oven and discard the thermocouple.

3. Slide the new thermocouple into the mounting tube until the flange is seated firmly on the back wall of the oven.

4. Fasten the thermocouple to the back wall of the oven using the original mounting screw. Then, perform Steps 6-8 of the preceding section to wire the thermocouple.

Shielded

ground lead

Analog Temperature Controller

Shielded

RedWhite

ground lead

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS360 Series front-mounted thermocouple inside the machinery compartment

These thermocouples are mounted in a tube that extends diagonally up and into the plenum chamber. They are secured in place by a set screw located on the mounting tube, and by a bead of high-temperature silicone around the end of the shaft.

The new thermocouple will be held in place in the same manner, except that the silicone should be applied so that it wraps around the edges of the thermocouples mounting flange.

Thermocouple

SECTION 3 - SERVICING COMPONENTS

Thermocouple Installation - PS360 Series

Machinery Compartment

Figure 5

Set

screw

High-temperature

silicone wraps around

thermocouple flange

and onto mounting

tube

NOTE FOR HIGH LIMIT THERMOCOUPLES:

PS310/360 electric ovens have two thermocouples inside the machinery compartment. One thermocouple is connected to the temperature controller, while the other is connected to the high limit control module.

The thermocouple supplied in this Kit is incompatible with the early United Electric Type 54 and Type 55 high limit control modules used on these ovens. If the oven is equipped with one of these control modules, it will be necessary to upgrade the control unit to the current Watlow model (shown in Figure 6) before the thermocouple can be replaced. Service Kit 39733 includes all parts and instructions needed for the conversion. Refer to Service Bulletin MM-168 (5/7/99) for details.

1. Remove the silicone seal around the end of the thermocouple. Loosen the set screw.

2. Pull the thermocouple out of its mounting tube. Carefully thread the wiring out of the oven and discard the thermocouple.

3. Check that the silicone has been removed completely from the end of the mounting tube. Any remaining silicone can interfere with the correct placement of the new thermocouple.

4. Insert the new thermocouple until its flange is seated on the end of the mounting tube. See Figure 5.

5. Tighten the set screw until the thermocouple is secure inside the tube. AVOID OVERTIGHTENING THE SET SCREW TO PREVENT DAMAGE TO THE THERMOCOUPLE.

6. Use high-temperature silicone to seal the flange to the mounting tube, as shown in Figure 5. Check that all holes and spaces are filled by the silicone. This not only helps to hold the thermocouple in place, but prevents heat from entering the machinery compartment.

7. Route the wiring for the new thermocouple through the hole in the side of the electrical control box by using the existing wiring bundle. Check that the leads are clear of the ignition cable and all components.

8. Connect the leads as shown in Figure 6.

White

Red

Shielded

ground lead

Shielded

ground lead

Plenum

wall

Mounting

tube

Thermocouple Wiring - PS360 Series

Figure 6

RedWhite

Analog

Temperature

Controller

Red White

Digital

Temperature

Controller

Shielded

ground lead

High Limit

Control Module

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS536

Thermocouples on these ovens are located inside the machinery compartment. They are secured in place by a sheet metal screw that traps the thermocouple flange against the wall of the compartment. See Figure 7.

NOTE FOR HIGH LIMIT THERMOCOUPLES:

PS536 ovens have two thermocouples, one mounted above the other. The upper thermocouple senses the oven temperature and is connected to the temperature controller. The lower thermocouple is connected to the high limit control module. Either thermocouple can be replaced using this Kit.

Thermocouple

Thermocouple Installation - PS536

Figure 7

Plenum

wall

Sheet metal screw

Thermocouple

flange

Machinery

compartment

wall

1. Loosen the sheet metal screw that holds the thermocouple flange to the wall of the machinery compartment.

2. Pull the thermocouple out of the machinery compartment. Disconnect the thermocouple leads.

3. Install the new thermocouple so that its flange fits firmly against the wall of the machinery compartment. Tighten the sheet metal screw so that its head holds the thermocouple flange securely in place.

NOTE: PS536 ovens do not use a thermocouple mounting tube, so it is CRITICAL that the thermocouple flange is securely fastened to the wall of the machinery compartment.

4. Route the thermocouple leads away from the ignition cable. Connect the leads as shown in Figure 8.

Temperature-

sensing

thermocouple

High limit

thermocouple

Figure 8

Thermocouple Wiring - PS536

Digital Temperature Controller

White

Red

Screw head holds thermocouple

flange in place

Shielded

ground lead

High Limit Control Module

Red White

Shielded

ground lead

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS555 Gas - thermocouples with screw terminal connections (no terminal blocks)

Thermocouples on these ovens are located on the rear wall. They are secured in place by two screws that are inserted through the holes in the thermocouple flange. These ovens are equipped with a three-lead, flanged thermocouple identical to the one in this Kit.

NOTE FOR HIGH LIMIT THERMOCOUPLES:

These ovens have a high limit thermocouple installed in the last mounting hole at the exit end of the oven.

The thermocouple supplied in this Kit can be used to replace ANY of the temperature-sensing or high limit thermocouples on the oven.

1. Remove the rear shrouds and blower motor covers. This allows access to the thermocouples (on the rear wall) and screw terminals (inside the blower motor compartments).

2. Remove the screws that hold the thermocouple to the wall. Slide the thermocouple out of its mounting hole.

3. Disconnect the thermocouple leads. Refer to Figure 9.

 High limit thermocouples are wired directly to the

high limit control module. The thermocouples ground wire is connected to the mounting screw for the high limit control module.

 The red and white leads from ALL temperature-sens-

ing thermocouples are joined at capped screw terminals, located inside the left blower motor compartment. Leads from these screw terminals connect to the temperature controller at the front of the oven.

The ground leads for temperature-sensing thermocouples are connected to the chassis ground lug inside the left blower motor compartment.

4. Remove and discard the thermocouple.

5. Install the new thermocouple into the original mounting hole. Fasten it in place with the supplied #6 x 3/8 screws.

6. Wire the thermocouple as shown in Figure 9.

6. Use the kit-supplied nylon clamp and #10-16 x 3/4 screw to secure the thermocouple leads so that they will clear the shrouds, blower belts, and pulleys.

7. Close the machinery compartment door. Replace all shrouds onto the oven.

Cap

Screw terminals:

1 for red leads

1 for white leads

2 total

Temperature-sensing

thermocouple leads

(red or white)

1 lead to temperature

controller

Thermocouple Wiring - PS555

Temperature-sensing thermocouple ground

leads attach to

ground lug

Shielded

ground lead

High limit

thermocouple leads

attach directly to high

limit control module

Figure 9

Red White

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS555 Electric and PS555E

Temperature-sensing thermocouples on these ovens are located on the rear wall. High limit thermocouples are located inside the machinery compartment. All thermocouples are secured in place by two screws that are inserted through the holes in the thermocouple flange. These ovens are equipped with a three-lead, flanged thermocouple identical to the one in this Kit.

NOTE FOR HIGH LIMIT THERMOCOUPLES:

PS555E electric ovens are equipped with a high limit thermocouple at the front of the oven, inside the machinery compartment. All other PS555E, PS555G and PS570G ovens have a high limit thermocouple installed into the rear wall in the last mounting hole at the exit end of the oven.

The thermocouple supplied in this Kit can be used to replace ANY of the temperature-sensing or high limit thermocouples on the oven.

1. If you will be replacing the high limit thermocouple, open the machinery compartment door.

To replace any other thermocouple, first remove the rear shrouds. Then, remove the cover over the left blower motor. This allows access to the thermocouples on the rear wall, and to the terminal block inside the blower motor compartment.

Note that all of the rear wall thermocouples are connected to the terminal block inside the left blower motor compartment. It is not necessary to access the right blower motor compartment.

2. Remove the screws that hold the thermocouple to the wall. Slide the thermocouple out of its mounting hole.

3. Disconnect the thermocouple leads. Rear wall thermocouples are connected to the terminal block inside the left blower motor compartment. High limit thermocouples are connected directly to the high limit control module.

4. Remove and discard the thermocouple.

5. Install the new thermocouple into its mounting hole. Fasten it in place with the supplied #6 x 3/8 screws.

6. Wire the thermocouple as shown in Figure 10.

7. If you replaced a rear wall thermocouple, use the kitsupplied nylon clamp and #10-16 x 3/4 screw to secure the thermocouple leads so that they will clear the shrouds, blower belts, and pulleys.

8. Replace all shrouds onto the oven. Close the machinery compartment door.

Temperature-sensing

thermocouple leads

Ground

leads

WhiteRed

To temperature

controller

To ground

terminal on temp

controller

Thermocouple Wiring - PS555 Electric and PS555E

Figure 10

Temperature-sensing

thermocouple leads

Shielded

ground lead

Left

Terminal

Block

High Limit

Control Module

Red White

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS570 (X01-X05 name plate ID numbers) and PS570S (early) with side-mounted thermocouples inside

or outside the blower motor

compartments

These ovens are equipped with two thermocouples, one on each end wall of the oven. The thermocouples may be mounted either inside or outside of the blower motor compartments.

 The thermocouple on the right side of the oven has two

leads and sends its signal to the temperature controller.

 The thermocouple on the left side of the oven is a dual-

function unit. It has FOUR LEADS and sends individual signals to the temperature controller and the high limit control module.

Installing this Kit will replace BOTH thermocouples with current three-lead versions located on the back wall of the oven. The Kit also requires the installation of a THIRD thermocouple to act as a high limit sensor. Because of this,

you will need three separate thermocouple kits for these ovens.

If the oven has already been updated with the rear-wall thermocouple configuration, you can simply replace the affected thermocouple. Follow the instructions for PS570S (late) rear wall thermocouples on Page 10.

1. If the thermocouples are located outside the blower motor compartments, remove and retain the thermocouple covers.

2. Remove the end plugs from the oven. Then, remove 1 or 2 air fingers from each end of the oven as necessary to access the thermocouple mounting tubes.

3. Remove the rear shrouds. Open the blower motor compartment doors.

4. Remove the cooling fans from both blower motors. Then, remove the blower belts.

5. For each thermocouple:

 Disconnect the thermocouple leads from the ter-

minal block inside the blower motor compartment.

 Remove and discard the screws that hold the ther-

mocouple mounting tube to the plenum wall. Remove and discard the thermocouple and tube.

 Plug the internal and external openings left by the

tubes using a high-temperature silicone sealant.

6. If the thermocouples were located outside the blower motor compartments, replace the thermocouple covers.

7. Refer to Figure 11. Measure and scribe marks in the rear wall of the oven for drilling the thermocouple mounting holes. Make sure that your measurements begin at the edges of the rear panels, and NOT at the outer edges of the oven!

Note that there are two different thermocouple placement locations: one for Pizza Hut (and Pizza Hut International, or Tricon) ovens, and one for all other ovens.

8. Drill the new thermocouple mounting holes using an 11/32 (8.73mm) D x 8 (203mm) L bit. Make sure that you drill through all three walls of the oven.

9. Drill the two screw mounting holes for each thermocouple using a 7/64 (2.78mm) bit. Tap the holes using a #6-32 tap.

10. If necessary, remove air fingers from the oven to access the areas around the new thermocouple mounting holes.

11. Vacuum out ALL drill shavings. If the oven is equipped with a screen over the openings for the lower air fingers, use a flexible hose extension on the vacuum to reach the shavings through the upper air finger openings.

12. Reinstall the air fingers and end plugs onto the oven.

13. Install the three new thermocouples into the back wall of the oven. Check that the thermocouple flanges are flush with the back wall.

14. Secure each thermocouple in place with the two kitsupplied #6 x 3/8 screws.

15. Wire the thermocouples as shown in Figure 12. The thermocouples should be wired to the terminal block inside the blower motor compartment closest to the thermocouple.

IMPORTANT

As you wire the thermocouples, be sure to connect a single chassis ground wire to the mounting screw for the terminal block. See Figure 12.

A good ground connection for the thermocouples uninsulated lead is REQUIRED for proper operation!

16. If you will be replacing additional thermocouples, repeat Steps 7-15 as necessary.

17. Using the kit-supplied nylon clamps and #10-16 x 3/4 screws, secure the thermocouple leads to the back wall of the oven so that they will clear the shrouds, blower belts, and pulleys.

18. Replace the blower belts and cooling fans.

19. Close the blower motor compartment doors. Replace all shrouds onto the oven.

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

Location of New Thermocouple Mounting Holes - PS570, PS570S

Figure 11

High limit thermocouple

position for ovens with

LEFT-TO-RIGHT conveyors

Thermocouple positions

for non-Pizza Hut/Tricon ovens

High limit thermocouple

position for ovens with

RIGHT-TO-LEFT conveyors

Thermocouple positions

for Pizza Hut/Tricon ovens

Thermocouple Wiring - PS570 and PS570S (early) after thermocouple update - Left to Right Conveyor

Left

Terminal

Ground

lead

White

(temp)

Red

(temp)

Figure 12a

(temp)

Red

White

(temp)

Ground

leads (all)

Red

(hi lim)

White

(hi lim)

Block

Right

Terminal

Block

To temperature

controller

ground wire

To temperature

controller

To high limit

control module

New chassis

Figure 12b

Thermocouple Wiring - PS570 and PS570S (early) after thermocouple update - Right to Left Conveyor

Left

Terminal

Block

White

(hi lim)

To high limit

control module

Red

(hi lim)

Ground

leads (all)

To temperature

controller

White

(temp)

Red

(temp)

New chassis

ground wire

Red

(temp)

To temperature

controller

White

(temp)

Ground

lead

Right

Terminal

Block

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS570S (late) - rear wall thermocouples with left-side AND right-side terminal block connections

Thermocouples on these ovens are located on the rear wall and are secured in place by two screws that are inserted through the holes in the thermocouple flange.

Most of these ovens have either three or four thermocouples, all installed in the back wall of the oven. The thermocouple at the extreme exit end of the oven is the high limit thermocouple, while all other thermocouples send their signals to the digital temperature controller. The thermocouple supplied in this Kit can be used to replace ANY of the thermocouples on these ovens.

Some PS570S ovens are equipped with only two thermocouples. In these ovens:

 The thermocouple on the right side of the oven has two

leads and sends its signal to the temperature controller.

 The thermocouple on the left side of the oven is a dual-

function unit. It has FOUR LEADS and sends individual signals to the temperature controller and the high limit control module.

 Installing this Kit will replace BOTH thermocouples with

current three-lead versions located on the back wall of the oven. The Kit also requires the installation of a THIRD thermocouple to act as a high limit sensor. Because of this, you will need three separate thermo-

couple kits for these ovens.

1. Remove the rear shrouds and open the blower motor compartment doors. This allows access to the thermocouples (on the rear wall) and terminal blocks (inside the blower motor compartments).

2. Remove the screws that hold the thermocouple to the wall. Slide the thermocouple out of its mounting hole.

3. Disconnect the thermocouple leads. Remove and discard the thermocouple.

4. Perform Step 4 ONLY if you are installing a high limit thermocouple and no mounting hole is present. This would be the case if the oven formerly used a four-lead thermocouple to send a signal to the high limit control module.

Temperature-sensing thermocouples for these ovens should be installed in the two existing thermocouple mounting holes.

 Refer to Figure 13. Measure and scribe marks in

the rear wall of the oven for drilling the high limit thermocouple mounting hole. Make sure that your measurements begin at the edges of the rear panels, and NOT and the outer edges of the oven!

 Drill the new high limit thermocouple mounting hole

using an 11/32 (8.73mm) D x 8 (203mm) L bit. Be sure to drill through all three walls of the oven.

 Drill the two screw mounting holes for the high limit

thermocouple using a 7/64 (2.78mm) bit. Tap the holes using a #6-32 tap.

 If necessary, remove the end plugs and air fingers

from the oven to access the areas around the new high limit thermocouple mounting hole.

 Vacuum out ALL drill shavings. If the oven is

equipped with a screen over the openings for the lower air fingers, use a flexible hose extension on the vacuum to reach the shavings through the upper air finger openings.

 Reinstall the air fingers and end plugs onto the oven.

Location of High Limit Thermocouple Mounting Hole - PS570S

High limit thermocouple

position for ovens with

LEFT-TO-RIGHT conveyors

Figure 13

High limit thermocouple

position for ovens with

RIGHT-TO-LEFT conveyors

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

Thermocouple Wiring - PS570S (Late) - Left to Right Conveyor

Left

Terminal

NOTE: This configuration shows leads for three temperature-sensing thermocouples - two on the left side, and one on the right. Ovens with only two temperature-sensing thermocouples will have a single set of leads on the left terminal block, instead of the two sets that are shown.

Block

terminal on temp

To ground

controller

Ground

leads

Figure 14a

White

Red

(temp)

To temperature

controller

Red

(temp)

To temperature

controller

White

Ground

(temp)

leads (all)

To ground

terminal on temp

controller

White

Red

(hi lim)

To mounting screw

for high limit

control module

Right

Terminal

Block

To high limit

control module

Thermocouple Wiring - PS570S (Late) - Right to Left Conveyor

Figure 14b

Left

Terminal

White

(hi lim)

Red

(hi lim)

Ground

leads (all)

Block

NOTE: This configuration shows leads for three temperature-sensing thermocouples - two on the right side, and one on the left. Ovens with only two temperature-sensing thermocouples will have a single set of leads on the right terminal block, instead of the two sets that are shown.

To high limit

control module

To mounting screw

for high limit

control module

To ground

terminal on temp

controller

5. Install the new thermocouple into its mounting hole. Fasten it in place with the supplied #6 x 3/8 screws.

6. Wire the thermocouple as shown in Figure 14. The thermocouples should be wired to the terminal block inside the blower motor compartment closest to the thermocouple.

IMPORTANT

As you wire the thermocouples, check that ground leads run from the terminal blocks inside the blower motor compartments to BOTH the temperature controller AND the high limit control module, as shown in Figure 14.

If the ground leads to the front compartment of the oven are NOT present - for example, on an oven that previously used the older-style 2-lead or 4-lead thermocouples

- it is acceptable to use a single chassis ground wire to the mounting screw for the terminal block. See Figure

15.

A good ground connection for the thermocouples uninsulated lead is REQUIRED for proper operation!

Red

White

(temp)

Red

(temp)

To temperature

controller

(temp)

To temperature

controller

(temp)

Ground

leads

To ground

terminal on temp

controller

7. If you will be replacing additional thermocouples, repeat Steps 2-6 as necessary.

8. Use the kit-supplied nylon clamp and #10-16 x 3/4 screw to secure the thermocouple leads so that they will clear the shrouds, blower belts, and pulleys.

9. Close the machinery compartment and blower motor compartment doors. Replace all shrouds onto the oven.

Red

Figure 15

Ground

leads (all)

White

(temp)

Red

(temp)

Use ONLY if ground leads to front compartment are not present.

Alternate ground lead wiring

White

(hi lim)

Right

Terminal

Block

New chassis

ground wire

To high limit

control module

To temperature

controller

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 33984 and 33985 -

Oven Thermocouple Kit, 11/01

PS555G and PS570G rear wall thermocouples with left-side terminal block connections

Thermocouples on these ovens are located on the rear wall. They are secured in place by two screws that are inserted through the holes in the thermocouple flange. The ovens are equipped with a three-lead, flanged thermocouple identical to the one in this Kit.

NOTE FOR HIGH LIMIT THERMOCOUPLES:

These ovens have a high limit thermocouple installed in the last mounting hole at the exit end of the oven.

The thermocouple supplied in this Kit can be used to replace ANY of the temperature-sensing or high limit thermocouples on the oven.

1. Remove the rear shrouds. Then, remove the cover over the left blower motor. This allows access to the thermocouples on the rear wall, and to the terminal block inside the blower motor compartment.

Note that the thermocouples on these ovens are all connected to the terminal block inside the left blower motor compartment. It is not necessary to access the right blower motor compartment.

Figure 16

Thermocouple Wiring - PS555G and PS570G

2. Remove the screws that hold the thermocouple to the wall. Slide the thermocouple out of its mounting hole.

3. Disconnect the thermocouple leads from the terminal block. Remove and discard the thermocouple.

4. Install the new thermocouple into its mounting hole. Fasten it in place with the supplied #6 x 3/8 screws.

5. Wire the thermocouple as shown in Figure 16. Note that the terminals are labeled - TC for temperaturesensing thermocouple leads, G for ground leads, and HL for high limit thermocouple leads.

6. Use the kit-supplied nylon clamp and #10-16 x 3/4 screw to secure the thermocouple leads so that they will clear the shrouds, blower belts, and pulleys.

7. Replace all shrouds onto the oven.

White

(temp)

Ground

leads (all)

Red

(temp)

To temperature

controller

Middleby Cooking Systems Group  1400 Toastmaster Drive  Elgin, IL 60120  (847) 741-3300  FAX (847) 741-4406

Middleby Corporation Service Hotline 1-800-238-8444

To ground

terminal on temp

controller

Red

(hi lim)

To mounting screw

for high limit

control module

(hi lim)

To high limit

control module

SECTION 3 - SERVICING COMPONENTS

V. BLOWERS

A. PS200-series ovens

All PS200 ovens are equipped with one 1/3hp blower motor. The motor indirectly drives a pulley on the shaft of the blower fan with a fan belt.

Two main designs exist for the PS200 indirect fan drive assembly:

 Early design, used through 6/90. This design used

1/2 (12.7mm) bore flange mount bearings and a 1/2 (12.7mm) diameter blower fan shaft. See Figure 25.

 Current design, used 7/90 and later. This design uses

5/8 (15.9mm) pillow block bearings and a 5/8 (15.9mm) diameter blower fan shaft. See Figure 26.

Blower motors on both versions are rated for 208-240V, single-phase, and are protected by:

 A built-in thermal overload protection device.

 Two 9A fuses on the inside of the machinery compart-

ment door. Fuse location is shown in Figure 27.

In addition, the blower fan is protected by an air pressure saftety switch that prevents the burner/heating elements from activating if the fan is not rotating. See Air Pressure Safety Switch on Page 81.

Figure 25

Early-style PS200 indirect drive assembly

Direction of rotation

(viewed from

rear of oven)

Figure 26

Current PS200 indirect drive assembly

1. Part number reference

Early version components

NOTE: If an early-version PS200-series oven has a failed fan shaft, upgrade the oven to the current drive assembly using Kit P/N 49810-0121.

Part Number Description

22230-0072 Pulley, 1/2 / 12.7mm bore

22071-0019 Bearing, 1/2 / 12.7mm bore, flange

mount

37900-0094 Fan shaft alignment tool (early)

27381-0066 Motor, 1/3 hp, 200-240V, 50/60Hz ,1 Ph

22181-0034 Fan belt

Current version components Part Number Description

35900-0232 Shaft, blower fan

22230-0073 Pulley, 5/8 / 15.9mm bore

22072-0025 Bearing, 5/8 / 15.9mm bore, pillow

block mount

27399-0003 Blower fan, 16 / 0.4m diameter

37900-0106 Fan shaft alignment tool (current)

49810-0121 Indirect drive upgrade kit (upgrades

early-style version to current version)

49810-0018 Fan shaft service kit (includes 2 bear-

ings, 1 shaft, and alignment tool )

27381-0066 Motor, 1/3 hp, 200-240V, 50/60Hz ,1 Ph

22181-0034 Fan belt

Direction of rotation

(viewed from

rear of oven)

Figure 27

Blower motor fuses

Blower

motor fuses

Control

fuse

SECTION 3 - SERVICING COMPONENTS

2. Blower balancing and direction of rotation

Proper blower rotation is extremely important. From the rear of the oven, the blower shaft pulley should turn in a clockwise direction. See Figures 25 and 26.

All blower fans are balanced at the factory. Any fan found to be out of balance should be replaced. Vibration from an out-of-balance fan can cause poor baking and premature bearing failure. Note that vibrations can also be caused by other sources, including defective motor or blower shaft bearings, loose bearings or motor mounting bolts, or an incorrectly tensioned fan belt.

3. Lubricating the blower fan shaft bearings

IMPORTANT: Middleby uses two different types of grease in blower shaft bearings:

 DuPont Krytox® grease is used in some

PS536 ovens. Refer to Service Bulletin MM192 (included in the Appendices section of this chapter) for details on identifying Krytox® bearings.

 All other ovens use the standard Middleby

high-temperature grease, P/N 17110-0015.

Mixing grease types within the bearing will cause the bearing to seize. For all PS200 ovens, be sure to use ONLY the standard Middleby grease.

Figure 28

Bearing lubrication

Grease fittings (1 per bearing,

2 total)

Figure 29

Blower belt tension

1 (25mm)

vertical

deflection

NOTE: Middleby recommends lubricating the blower fan shaft bearings every three months.

Use a grease gun to lubricate the main blower fan shaft bearings. See Figure 28. When lubricating the bearings:

 Use a high-quality NLGI #2, lithium soap grease with

petroleum oil, such as Middleby P/N 17110-0015.

 Add the grease slowly until a small bead of grease

is present at the seals. AVOID OVERGREASING. Excessive greasing may cause harm to the bearing.

Manually turn the blower shaft by pulling on the belt to purge the grease. Wipe off any excess grease. The oven cannot be operated until the rear shroud is replaced.

4. Blower belt tension

NOTE: Middleby recommends checking the blower belt condition and tension every three months.

Check the blower belt for at least 1" (25mm) deflection at the center, and for cracking or excessive wear. Overtightening the belt will cause premature bearing failure and possible vibrations. See Figure 29.

If necessary, adjust the tension of the belt by loosening the two motor mounting bolts as shown in Figure 30. Reposition the motor as neccessary until the correct deflection is reached, then tighten the bolts.

Figure 30

Repositioning the blower motor

Loosen bolts to

reposition motor

and adjust belt

tension

SECTION 3 - SERVICING COMPONENTS

5. Early-style PS200 bearing replacement and alignment

NOTE: This procedure is for early-style indirect fan shaft assemblies only, as shown in Figure 25. Bearing replacement procedures for the current-style indirect fan shaft assembly (Figure 26) are provided on Page

72.

IMPORTANT: Before attempting any repair on the early-style PS200 Indirect Fan Drive Assembly:

 If you need to perform any maintenance more

involved than replacing and aligning the shaft bearings, you should upgrade the fan shaft assembly to the current version.

 Check the front and rear brackets (Item 6 in Fig-

ure 32). If the brackets ARE NOT welded together, you should upgrade the fan shaft assembly to the current version.

In either of these cases, you can upgrade the fan shaft assembly using Service Kit P/N 49810-0121. See Part Number Reference on Page 68 for details.

The following procedures are necessary to align the fan shaft whenever service to the fan shaft or replacement of the bearings is required. REFER TO FIGURE 32 FOR ILLUSTRATIONS OF THE COMPONENTS DESCRIBED HERE.

1. Remove the entire back wall (Item 1) of oven to service the fan assembly.

2. Remove the blower fan (Item 13) and pulley (Item

8).

NOTE: If parts are to be replaced, you should replace them now.

3. When installing the Drive Bracket Assembly (Item

5) insert one 3/8 flat washer (Item 4) at the 4 outer holes and one 3/8 special flat washer (Item 14) at the 4 inner holes between bracket and back wall at mounting locations. Use eight 3/8-16 x 1 screws (Item 2) and assemble a 3/8 lockwasher (Item 3) and a 3/8 flat washer (Item 4) onto each screw. Insert a screw at all 8 locations, hand tighten only at this time.

4. Install front and rear fan shaft flange bearings (Item

10), if they were removed, to Indirect Drive Bracket (Item 6) using three 1/4-20 x 3/4 screws (Item 11) and three 1/4 lockwashers (Item12) on each bearing.

IMPORTANT: The bearings (10) must be mounted so the grease fitting faces up when the bracket assembly (Item 5) is mounted on the rear wall.

NOTE: Do not tighten flange bearing block screws until Step 10 has been completed.

9. Install the fan shaft as shown in Figure 32. Align bearing set screws with flats on shaft but do not tighten set screws at this time.

10. Insert fan shaft alignment tool (Item 15) into back wall as shown in Figure 31.

NOTE: The bracket assembly is designed for slight up and down and right to left movement to attain free shaft rotation when the shaft alignment tool is in place. Once free shaft rotation is achieved, tighten all eight bracket screws (Item 2).

11. Tighten rear flange bearing block screws (Item 11) then front flange bearing block screws.

12. Remove shaft alignment tool, then recheck fan shaft for free rotation.

13. Install pulley (Item 8) on fan shaft and position fan shaft per the dimensions shown in Figure 32. Align the two flats per bearing which are machined on fan shaft for the bearing set screws. Use High Temperature Loctite, RC 620 on bearing set screws and then tighten set screws. Recheck fan shaft for free rotation.

14. Apply anti-seize compound on fan shaft before installing fan blade (Item 13). Position fan blade per dimension shown in Figure 32.

15. Apply High Temperature Loctite Type RC 620 to fan blade set screws.

NOTE: Tighten the two set screws on fan blade per the following sequence when viewing fan blade from front: first, the screw at the 12:00 position, then the screw at the 3:00 position.

16. Recheck fan shaft rotation before installing back wall to oven cavity.

NOTE: Apply anti-seize compound (MM P/N 17110-

0017) to all 12 bolts before installing back wall assem-

bly to oven.

17. Install back wall on oven.

18. Install fan belt.

NOTE: Excessive fan belt tension will create overloading of rear bracket fan shaft bearing. Refer to Blower Belt Tension on Page 69.

Figure 31

Fan shaft alignment tool

SECTION 3 - SERVICING COMPONENTS

Figure 32

Bearing replacement and alignment - early-style PS200 fan shaft assembly

Item Qty. Part Number Description

11Not available Back Wall Assembly

2 8 21216-0001 Screw, Hex Cap SS 3/8-16x1

3 16 21422-0001 Lock Washer, Split 3/8

4 20 21416-0001 Flat Washer, SS 3/8

51Not available Indirect Fan Drive Bracket Assembly

61Not available Bracket, Indirect Drive

71Not available Shaft, Fan Drive

8 1 22230-0072 Pulley, 1/2 Bore

Item Qty. Part Number Description

9 1 21651-0008 Square Key 1/8

10 2 22071-0010 Flange Bearing, 5/8 Bore

11 6 21211-0004 Screw, Hex Cap 1/4-20 x 3/4

12 6 21421-0016 Lock Washer, Split 1/4

13 1 Not available Blower Fan, 16 Dia.

14 4 21419-0004 Flat Washer 3/8 SS Special

15 1 37900-0094 Fan Shaft Alignment Tool

IMPORTANT: If parts listed as Not Available require replacement, use Service Kit 49810-0121 to upgrade the fan shaft assembly to the current version.

SECTION 3 - SERVICING COMPONENTS

6. Current-style PS200 bearing replacement and alignment

NOTE: This procedure is for current-style indirect fan shaft assemblies only, as shown in Figure 26. Bearing replacement procedures for the early-style indirect fan shaft assembly (Figure 25) are provided on Page 70.

The following procedures are necessary to align the fan shaft whenver service to the fan shaft or replacement of the bearings is required. REFER TO FIGURE 34 FOR ILLUSTRATIONS OF THE COMPONENTS DESCRIBED HERE.

1. Remove the entire back wall (Item 1) of oven to service the fan assembly.

2. Remove the blower fan (Item 11) and pulley (Item

7).

3. Remove the indirect drive bracket assembly (Item

5) by removing eight (8) screws (Item 2). lf you are upgrading from the early-style assembly, save the hardware (Items 2, 3, 4, and 12) to be reused with the new style bracket (Item 5).

NOTE: If parts are to be replaced, you should replace them now.

4 Install front and rear fan shaft pillow block bearings

(Item 9), if they were removed, to indirect drive bracket (Item 5) using two (2) 3/8-16 X 1 screws (Item 2) and two 3/8 lockwashers (Item 10) on each bearing.

NOTE: Do not tighten the pillow block bearings until Step 7 has been completed.

5. Install the fan shaft (Item 6) as illustrated in Figure

34. Align bearing set screws with flats on shaft but do not tighten set screws at this time.

NOTE: Before proceeding to Step 6, it is advisable to position the rear wall assembly in an upright, vertical position using a block of wood under the fan ring.

6. When installing the drive bracket (Item 5) insert one 3/8 flat washer (Item 4) at the four outer holes and one 3/8 special flat washer (Item 12) at the 4 inner holes between the bracket and back wall at the mounting locations. Use eight 3/8-16 X 1 screws (Item 2) and assemble a 3/8 lockwasher (Item 3) and a 3/8 flat washer (Item 4) into each screw. Insert a screw at all 8 locations. Hand tighten only at this time.

7. Insert fan shaft alignment tool (Item 13) as shown into back wall.

8. Tighten rear pillow block bearing screws (Item 9) then front pillow block bearing screws.

9. Remove shaft alignment tool, then recheck fan shaft for free rotation.

10. Install pulley (Item 7) on fan shaft and position fan shaft per dimension shown in Figure 34. Align the flats machined on fan shaft with the bearing set screw holes. Apply High Temperature Loctite, type RC 620 on bearing set screws and then tighten set screws. Recheck fan shaft for free rotation.

11. Apply anti-seize compound on fan shaft before installing fan blade (Item 11). Position fan blade flush with 5/8 shoulder on shaft as called out in Figure

34.

NOTE: Fan blade hub has a 1/2 bore. The fan shaft is turned down from 5/8 to 1/2 to receive fan blade.

12. Apply High Temperature Loctite Type RC 620 to fan blade set screws.

NOTE: Tighten the two set screws on fan blade per the following sequence when viewing fan blade from front: first, the screw at the 12:00 position, then the screw at the 3:00 position.

13. Recheck fan shaft rotation before installing back wall to oven cavity. Be sure fan assembly has adequate clearance inside orifice ring and is not rubbing.

NOTE: Apply anti-seize compound (MM P/N 17110-

0017) to all 12 bolts before installing back wall assem-

bly to oven.

14. Install back wall on oven.

15. Check motor pulley and fan pulley alignment. See Figure 33.

16. Install fan belt.

NOTE: Excessive fan belt tension will create overloading of rear bracket fan shaft bearing. Refer to Blower Belt Tension on Page 69.

Figure 33 - Four-point alignment test for correct pulley alignment

Cord tied to shaft

Cord must touch sheaves at four points indicated by arrows

SECTION 3 - SERVICING COMPONENTS

Figure 34

Bearing replacement and alignment - current-style PS200 fan shaft assembly

Item Qty. Part Number Description

1 1 37900-0068 Back Wall Assembly

2 16 21216-0001 Screw, Hex Cap SS 3/8-16x1

3 16 21422-0001 Lock Washer, Split 3/8

4 12 21416-0001 Flat Washer, SS 3/8

5 1 37900-0101 Bracket, Indirect Drive

6 1 35900-0232 Shaft, Fan Drive

7 1 22230-0073 Pulley, 5/8 Bore

8 1 21651-0008 Square Key 3/16

9 2 22072-0025 Pillow Block Bearing, 5/8 Bore

10 4 21422-0001 Lock Washer, Split 1/4

Item Qty. Part Number Description

11 1 27399-0003 Blower Fan, 16 Dia.

12 4 21419-0004 Flat Washer 3/8 SS Special

13 1 37900-0106 Fan Shaft Alignment Tool

Also available:

-- -- 49810-0018 Fan Shaft Service Kit

Includes Qty. 2 of Item 9 and Qty. 1 ea. of Items 6 and 13.

-- -- 49810-0021 Fan Shaft Upgrade Kit

Includes parts and instructions to update early-style fan shaft assembly to the current version shown here.

SECTION 3 - SERVICING COMPONENTS

B. PS360-series ovens

All PS360-series ovens are equipped with two blower motors.  All gas ovens have motors rated at 230V, single-phase.  All electric ovens built before 8/02 have three-phase

motors.

 All electric ovens built 8/02 or later that operate on a

supply voltage of 208-240V have single-phase motors.

 All electric ovens built 8/02 or later that operate on supply

voltages above 240V have three-phase motors.

Blower motors are protected by:  A built-in thermal overload protection device.  For ovens with single-phase blower motors: Two 9A

fuses. Fuse location is shown in Figure 35.

 For ovens with three-phase blower motors: Three 5A

fuses. Fuse location is shown in Figure 36.

In addition, each motor contains a centrifugal safety switch that prevents the burner/heating elements from activating if either motor is not operating. See Blower Motor Centrifugal Safety Switch on Page 80.

The blower wheel is directly connected to the motor shaft. A heat slinger, also mounted on the motor shaft, helps to keep heat away from the motor bearings. If the motor is stopped when the temperature in the compartment is over 180°F/82°C, the bearings can be damaged.

1. Part number reference

Blower motors

Part Number Description

27381-0023 1 Ph, 1/3 hp (PS310, -314, -360, -360S)

27381-0024 3 Ph, 1/3 hp (PS310, -314, -360)

27381-0054 1 Ph, 1/4 hp (PS360Q)

27381-0075 1 Ph, 1/2 hp (PS360WB)

31432 1 Ph, 1 hp (PS360EWB, -WB70)

Blower wheels

Part Number Part Number

(clockwise) (counter-clockwise) Description

22523-0002 22523-0003 9-3/16 / 233mm dia. (PS310, -314,

-360, -360Q, -360S, -360WB)

35603 35604 9-1/8 / 232mm dia. (PS360EWB)

36014 36015 8-1/4 / 210mm dia. (PS360EWBQ)

31599 31600 9-7/8 dia. / 251mm (PS360WB70)

Other components

Part Number Description

27396-0005 Heat slinger

42400-0101 Blower wheel puller tool

Figure 35

Blower motor fuses - single-phase motors

Left motor

fuses - 9A

Right motor

fuses - 9A

Control

fuse - 5A

Figure 36

Blower motor fuses - three-phase motors

Left motor

fuses - 5A

Transformer fuses

(480V electric

ovens only)

Right motor

fuses - 5A

Control

fuse - 5A

2. Blower balancing

All blower wheels are balanced at the factory. Any blower wheel found to be out of balance should be replaced. Vibration from an out-of-balance wheel can cause poor baking and premature motor bearing failure. Note that vibrations can also be caused by other sources, including defective motor bearings and loose motor mounting bolts.

SECTION 3 - SERVICING COMPONENTS

3. Direction of blower rotation

Proper blower rotation is extremely important. Blower rotation is determined by viewing the motor and wheel from the REAR of the motor (or from the open end of the oven). See Figures 37-39.

Figure 37 - Clockwise blower wheel

Heat slinger

blades face motor

Note slant of blades

Direction

of rotation

(rear view)

Figure 38 - Counterclockwise blower wheel

Direction

of rotation

Heat slinger

blades face motor

4. Removing the blower wheels

To change a motor or blower wheel, the wheel must first be removed from inside the oven as follows:

 Remove the end plugs and conveyor assembly.

 From inside the oven cavity, reach into the blower

recess and remove the inlet rings. See Figure 40.

 Loosen the set screw on the blower wheel hub and

remove the blower wheel. A special wheel puller tool (P/N 42400-0101) is available for this purpose. See Figure 41.

IMPORTANT: Before installing the new wheel, apply an anti-seize lubricant (Middleby P/N 17110-

0017) to the motor shaft and the inside of the blower wheel hub.

Figure 40

Inlet ring

Note slant of blades

(rear view)

Figure 39 - Blower wheel placement

Shown from rear of oven

Clockwise

Upper right

Counter-

clockwise

Lower right

Figure 41

Blower wheel puller tool

Counter-

clockwise

Upper left

Clockwise Lower left

SECTION 3 - SERVICING COMPONENTS

A. PS555/570-series ovens

All PS555/570-series ovens are equipped with two 1hp blower motors. Each motor indirectly drives a pulley on the shaft of a blower wheel with a fan belt.

Two main designs exist for the PS555/570 blower fan system:

 PS570/570S design. In this version, the pillow block

bearings for the blower wheel shaft were mounted upright, on brackets that were parallel to the fan belts. See Figure 42.

 PS555/570G design. In this version, the pillow block

bearings are mounted with the grease fittings pointing in towards the center of the oven. See Figure 43.

Figure 42 - PS570/570S blower configuration

Blower

motor

Pulley

Belt

The two designs share many common parts, including blower wheels, motors, and bearings. From a service standpoint, the major difference is the size of the pulleys and the length of the belts.

Blower motors on all PS555/570-series ovens are rated for 208-240V, single-phase, and are protected by:

 A built-in thermal overload protection device.  Two 15A fuses or 15A circuit breakers. Refer to Figure

44 for the location of the fuses/breakers.

In addition, each blower fan is protected by an air pressure saftety switch that prevents the burner/heating elements from activating if the fan is not rotating. See Air Pressure Safety Switch on Page 81.

Direction

of rotation

Blower

motor

Pulley

Bearing PulleyBlower

shaft

Blower wheel

(inside oven)

Figure 43 - PS555/570G blower configuration

Belt

Bearing PulleyBlower

shaft

Blower wheel

(inside oven)

Figure 44 - Fuse/circuit breaker locations

PS570/570S: 15A fuses located on left side of machinery

compartment

PS555 (early):

15A breakers located

inside left blower

motor compartment

PS555 (current),

PS570G: 15A

breakers located on

right side of machinery

compartment

SECTION 3 - SERVICING COMPONENTS

1. Part number reference

Part Number Description

27381-0069 Motor, 1 hp, 208-240V, 50/60 Hz, 1 Ph

22521-0005 Blower wheel, clockwise (right end of

PS570; left end of PS555, PS570S, PS570G)

22521-0006 Blower wheel, counterclockwise (left end

of PS570; right end of PS555, PS570S, PS570G)

Oven Blower Pulley Motor Pulley Belt Blower

Application model Hz Part No. Desc. Part No. Desc. Part No. Desc. RPM

Standard PS570 60 22230-0084 BK52 30476 BK47 22181-0037 -- --

PS570S 60 22230-0087 BK47H 30476 BK47 46744 BX55 1780 RPM

PS570S 50 22230-0087 BK47H 22230-0086 BK55 46745 BX56 1733 RPM

PS570G 60 39587 BK70 44977 BK70 46452 BX67 1780 RPM

PS555/ 60 39587 BK70 39586 BK80 44946 BX61 2080 RPM

555G/555E

Pizza Hut PS570S 60 22230-0087 BK47H 22230-0086 BK55 46745 BX56 1733 RPM

USA

PS570S 60 22230-0087 BK47H 39910 BK62 44963 BX58 2300 RPM

High Altitude

PS570G 60 39587 BK70 39586 BK80 46453 BX68 2057 RPM

PS570G 60 39587 BK70 46455 BK90 46454 BX70 2300 RPM

High Altitude

Pizza Hut PS570S 60 22230-0087 BK47H 22230-0086 BK55 46745 BX56 1733 RPM

Intl. (Tricon)

PS570G 60 39587 BK70 39586 BK80 46453 BX68 2057 RPM

PS555G 50 39587 BK70 42984 BK95H 47044 BX62 2020 RPM

PS555E 50 39587 BK70 39586 BK80 44946 BX61 1680 RPM

Dominos Q PS570S 60 22230-0087 BK47H 45796 BK45 46744 BX55 1692 RPM

PS570G 60 39587 BK70 47267 BK65 46452 BX67 1692 RPM

PS555G 60 39587 BK70 39910 BK62 44963 BX58 1580 RPM

Papa Johns PS555G 60 39587 BK70 39910 BK62 44963 BX58 1580 RPM

Part Number Description

22072-0026 Bearing, pillow block, 1 / 25.4mm bore

(PS570)

22072-0017 Bearing, pillow block, 1-7/16 / 36.5mm

bore (PS570S)

35210-0251 Blower shaft, 1 dia. (PS570)

35210-0506 Blower shaft, 1-7/16 dia. (PS570S)

41899 Blower shaft, 1-7/16 dia. (PS555 or

PS570G)

22031-0001 bushing

NOTE: If a particular customer/oven model combination is not listed (for example, Pizza Hut PS555G), use the Standard information.

SECTION 3 - SERVICING COMPONENTS

2. Blower balancing and direction of rotation

Proper blower rotation is extremely important. Proper blower rotation is shown in Figure 45.

Early PS570 blower wheels were positioned so that the open end of the wheel faced into the baking chamber. This was changed on the PS570S (and all later models) to improve airflow. Note that this also means that on early PS570 ovens the counterclockwise wheel is moved to the left side of the oven, and the clockwise wheel moved to the right side, so that the wheel blades point in the same direction. This is reflected in the Part Number Reference information on Page 77.

All blower wheels are balanced at the factory. Any blower wheel found to be out of balance should be replaced. Vibration from an out-of-balance wheel can cause poor baking and premature bearing failure. Note that vibrations can also be caused by other sources, including defective motor or blower shaft bearings, loose bearings or motor mounting bolts, or an incorrectly tensioned fan belt.

3. Lubricating the blower shaft bearings

Figure 45

PS500-series blower wheel orientation

Clockwise:

Right end

Counter-

clockwise:

Right end

Open end of wheel faces IN

PS570S, PS570G, PS555:

Open end of wheel faces OUT

PS570:

Counter-

clockwise:

Left end

Clockwise:

Left end

IMPORTANT: Middleby uses two different types of grease in blower shaft bearings:

 DuPont Krytox® grease is used in some

PS536 ovens. Refer to Service Bulletin MM192 (included in the Appendices section of this chapter) for details on identifying Krytox® bearings.

 All other ovens use the standard Middleby

high-temperature grease, P/N 17110-0015.

Mixing grease types within the bearing will cause the bearing to seize. For all PS555/570series ovens, be sure to use ONLY the standard Middleby grease.

NOTE: Middleby recommends lubricating the blower fan shaft bearings every three months.

Use a grease gun to lubricate the main blower fan shaft bearings. See Figure 46. When lubricating the bearings:

 Use a high-quality NLGI #2, lithium soap grease with

petroleum oil, such as Middleby P/N 17110-0015.

 Add the grease slowly until a small bead of grease

is present at the seals. AVOID OVERGREASING. Excessive greasing may cause harm to the bearing.

Manually turn the blower shaft by pulling on the belt to purge the grease. Wipe off any excess grease. The oven cannot be operated until the rear shroud is replaced.

Note slant of blades

Figure 46

Bearing lubrication

Grease fittings (1 per bearing,

4 total)

PS570,

PS570S

Grease fittings (1 per bearing,

4 total)

PS570G,

PS555

SECTION 3 - SERVICING COMPONENTS

4. Blower belt tension

NOTE: Middleby recommends checking the blower belt condition and tension every three months.

Check the blower belt for at least 1" / 25mm deflection at the center, and for cracking or excessive wear. Overtightening the belt will cause premature bearing failure and possible vibrations. See Figure 47.

If necessary, adjust the tension of the belt by loosening the two motor mounting bolts as shown in Figure 47. Reposition the motor as neccessary until the correct deflection is reached, then tighten the bolts.

5. Bearing replacement and alignment

Whenever service to the blower shaft or replacement of the bearings is required, the shaft will need to be aligned.

NOTE: Apply anti-seize compound (MM P/N 17110-

0017) to all bolts before installing back wall assembly to oven.

First, reassemble the back wall components, but DO NOT TIGHTEN THE HEX BOLTS that hold the bearings to their mounting brackets. Leaving the bearings loose allows the pulleys to be aligned.

Next, check the alignment of the pulleys using a cord as shown in Figure 48. Reposition the bearings as required to align the blower shaft, then tighten the hex bolts to hold the shaft in place.

Replace the belts and rear shrouds after the pulleys are properly aligned.

Figure 47

Blower belt tension and

repositioning the blower motor

PS570,

PS570S

1 (25mm)

vertical

deflection

PS570G,

PS555

Loosen bolts to

reposition motor

and adjust belt

tension

Figure 48 - Four-point alignment test for correct pulley alignment

Cord tied to shaft

Cord must touch sheaves at four points indicated by arrows

SECTION 3 - SERVICING COMPONENTS

VI. BLOWER MOTOR CENTRIFUGAL SAFETY SWITCH

(PS360-SERIES)

Middleby ovens have a safety feature that prevents the burner/heating elements from activating if the blower(s) are not in operation. On PS360-series ovens, this feature is controlled by a centrifugal switch mounted inside each blower motor. If either motor is not operating, the burner/ heating elements cannot activate.

The centrifugal switch is a normally-closed (NC) limit switch mounted inside the rear of each blower motor. See Figure

49. When the motor is not running, the centrifugal switch weight holds the switch open. As the motor reaches full speed, the weight moves away from the switch permitting the contacts to close. When the switch contacts of BOTH blower motors are closed, the heat circuit is completed, allowingthe burner/heating elements to activate.

If a blower motor is not operating, the switch will not close and the circuit remains open, preventing burner/heating element activation.

A. Part Number Reference - Blower Centrifugal Switch

On all PS360-series blower motors, the centrifugal switch can be replaced with switch P/N 27270-0144.

B. Troubleshooting

1. To access the switch, remove the rear motor wiring cover plates. See Figure 49.

2. When the switch is operating properly, both sides of the brown wires coming from the switch should be hot when the motor is at full RPM.

3. No adjustment can be made to the switch. If it is not operating properly, it must be replaced.

VII. BURNER BLOWER MOTOR CENTRIFUGAL SAFETY

SWITCH (PS200-SERIES GAS, PS310, PS314, PS360, PS360WB, PS570S)

Middleby gas ovens with a 120V burner blower motor have a centrifugal safety switch that prevents burner activation if the burner blower motor is not in operation. This includes:

 Most PS360-series ovens (except PS360WB70 and

PS360EWB);

 PS200-series gas ovens (except units produced with

the modulating gas system);

 All Model PS570S ovens.

Ovens with a 208/240V burner blower motor use a separate air pressure safety switch to prove motor operation. See Air Pressure Safety Switch on Page 81.

The centrifugal switch is a normally-closed (NC) limit switch mounted inside each blower motor. When the motor is not running, the centrifugal switch weight holds the switch open. As the motor reaches full speed, the weight moves away from the switch permitting the contacts to close. This completes the heat circuit, allowingthe burner to light.

If the burner blower motor is not operating, the switch will not close and the circuit remains open, preventing burner activation.

No adjustment can be made to the switch. If it is not operating properly, the burner blower motor must be replaced.

Figure 49 - PS360-series blower motor centrifugal safety switch

Switch

SECTION 3 - SERVICING COMPONENTS

VIII. AIR PRESSURE SAFETY SWITCH (PS200-SERIES,

PS555/570-SERIES, PS360EWB, PS360WB70)

Middleby ovens have a safety feature that prevents the burner/heating elements from activating if the blower(s) are not in operation. On PS200-series ovens and PS555/570series ovens, this feature is controlled by a separate air pressure switch that reads air flow from the blower. One switch is used for each blower (1 for the PS200-series, 2 for the PS555/570 series).

These ovens cannot use a centrifugal switch on the motor because they use an indirect, belted drive system. If a belt fails, it is possible for the motor to operate normally while the blower itself is stopped.

In addition, gas ovens with a line-voltage burner blower motor use an identical air switch to check that the burner blower motor is operating before burner activation. These ovens include the PS360EWB, PS360WB70, PS555, PS555G, and PS570G, as well as PS200-series ovens equipped with the modulating gas system. This additional air switch is not necessary on ovens with a 120V burner blower motor

Figure 50 - Air pressure safety switch models

because of the presence of a centrifugal air switch inside the motor housing (see Section VII, Burner Blower Motor Centrifugal Safety Switch, on the previous page).

The switch is an assembly that includes a normally-open microswitch and a diaphragm. When the blower is at speed, pressure is applied to the diaphragm which in turn closes the microswitch. This completes the heat circuit, allowing the burner/heating elements to activate.

If a blower is not operating, the microswitch receives no signal from the diaphragm and cannot close, preventing burner/heating element activation.

A. Part Number Reference - Air Switches

Middleby has used four different types of air switches for these applications. See Figure 50.

When replacing one of these switches, note that the current Yamatake-Honeywell air switch (#4 below) cannot be used as an upgrade for an older switch. If you are replacing Switches #1, #2 or #3 as shown in Figure 50, you should use the Service Kits described for Switch #2.

Original-style round air switch

Replace with #2

Positive

pressure

Adjustment

screw

Dungs square-case replacement air switch with screw adjustment

Replace with #2

Adjustment

screw

Dungs square-case air switch with dial adjustment

Replace with same

Adjustment dial

(in. W.C. or

mbar)

Positive

pressure

Negative

pressure

Yamatake-Honeywell air switch, non-adjustable

Replace with same

Positive

pressure

Negative

pressure

Adjustment

screw (fixed at proper setting - cannot

be adjusted)

Positive

pressure

Negative pressure

SECTION 3 - SERVICING COMPONENTS

1. Original-style round air switch with screw adjustment (P/N 28023-0005)

This was the standard switch used through 9/96 and is no longer available. If it must be replaced, use Kit P/N 35624 (for use in the USA) or 35625 (for export use). See #2 below for a description of these kits.

2. Dungs square-case air switch with dial adjustment

This was the standard switch used from 9/96 through 1/02. It cannot be upgraded to the current YamatakeHoneywell octagonal switch, and so should still be used as a service replacement. EXCEPTION: PS570G and all PS555 ovens have used the Yamatake-Honeywell switch throughout their production run (see #4 below).

Two different models were used; one for domestic ovens, and another for export ovens. The switches are identical except for the markings on the dial. The domestic unit measures pressure in water column inches (in. W.C.), while the export unit measures pressure in millibars (mbar).

 Domestic switch: Kit P/N 35624  Export switch: Kit P/N 35625.

3. Dungs square-case alternate air switch with threaded screw-type adjustment (P/N 36194)

This switch was used on a limited number of domestic production ovens in early 1997 to cover an availability problem with the standard switch (see #2 above). Markings were in water column inches (in. W.C.). An export version of this switch was never used.

This switch was never available as a service part. If it must be replaced, use Kit P/N 35624 (see #2 above).

4. Yamatake-Honeywell air switch, non-adjustable

This switch is the current standard for all new-production Middleby ovens. You may NOT use this switch as an upgrade on an oven equipped with an older switch.

Two different models are used; one for dometic and standard export ovens, and another for CE-approved ovens.

Figure 51

PS360WB70/EWB with Midco burner

 Domestic switch: P/N 39530  CE-version switch: P/N 37498

If this switch must be replaced, use an identical switch. Note that this is the ONLY time that you may use P/Ns 39530 and 37498 as service replacement parts.

B. Troubleshooting

1. Postive pressure vs. negative pressure All air switches except the original round version can

sense either positive air pressure or negative air pressure. The connection that is actually made to the switch depends on the application.

 If the switch is used to detect blower operation, the

tip of the pitot tube is located outside of the blower wheel. This means that the pressure applied to the end of the tube is positive. Because of this, the tube should be connected to the positive side of the switch.

 If the switch is used to detect burner blower opera-

tion,

check the type of burner used on the oven.

- The Midco burner, used ONLY on some PS360EWB and PS360WB70 ovens, has its pitot tube mounted inside the blower wheel. For correct operation, you should attach the tube to the NEGATIVE side of the switch.

Refer to Figure 51 for an illustration of the Midco burner.

- For ovens with the standard Wayne burner, the pitot tube is mounted outside the blower wheel. For correct operation, you should attach the tube to the POSITIVE side of the switch.

Note that some PS360EWB and PS360WB70 ovens use the Wayne burner. You should always check the type of burner installed into the oven before connecting the air tube. Refer to Figure 52 for an illustration of a typical PS360WB70/EWB gas train with the Wayne burner.

Figure 52

PS360WB70/EWB with Wayne burner

Connects to

negative pressure

side of air switch

Connects

to positive

pressure

side of air

switch

SECTION 3 - SERVICING COMPONENTS

C. Appendices

Appendix - Instructions for Service Kits 35624 and 35625 -

Air Pressure Switch Replacement Kits, 1/97

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions for Service Kits 35624 and 35625 -

Air Pressure Switch Replacement Kits, 1/97

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions to Replace an Alternate Air Switch

P/N 36194 with Service Kit P/N 35624, 3/97

SECTION 3 - SERVICING COMPONENTS

Appendix - Instructions to Replace an Alternate Air Switch

P/N 36194 with Service Kit P/N 35624, 3/97

SECTION 3 - SERVICING COMPONENTS

IX. PS570/570S FLAME GATE

All PS570/570S ovens produced for Pizza Hut USA through 8/00 were equipped with an adjustable flame gate at the end of the burner tube. The purpose of the flame gate was to direct heat towards the entrance end of the oven to better suit the customers cooking needs.

PS570S ovens produced 9/00 or later, as well as all PS570G ovens, are not equipped with the flame gate. The introduction of the modulating gas system to these ovens, as well as improvements to the customers air finger configuration and baking specs, make the flame gate unneccessary on these ovens.

A. Part Number Reference - Flame Gate

Part No. Description

35210-0555 Flame gate

35210-0511 Adjustment rod

35210-0510 Clamp

Figure 53

PS570/570S flame gate adjustment

LEFT-TO-RIGHT conveyor travel

(factory setting)

B. Flame Gate Orientation

To check the position of the flame gate, view it through the ovens window. See Figure 53. The gate must point towards the EXIT end of the oven. Note that this directs the flame from the burner tube towards the ENTRANCE end of the oven, as described above.

All ovens were originally shipped from Middleby Marshall with the gate pointing to the right. This is because all ovens were shipped with left-to-right conveyors. If the conveyor direction of one of these ovens is reversed in the field, the flame gate should be repostioned as follows:

 Loosen (do not remove) the two 7/16 hex bolts on

the clamps that hold the adjustment rod in place.

 Insert a #2 Phillips-head screwdriver into the hole

in the rod as shown in Figure 53. Swing the handle of the screwdriver to rotate the rod and move the flame gate. You should position the gate as far as possible towards the EXIT end of the conveyor as shown.

 Remove the screwdriver. Tighten the two screws

to hold the clamps in place.

RIGHT-TO-LEFT conveyor travel

(factory setting)

Gate points to

RIGHT (exit) end of oven

7/16 hex

bolts (2)

Rotate screwdriver handle to reposition

flame gate

Direction of

conveyor travel

Metal clamps

hold rod in

place

Direction of

conveyor travel

Gate points to

LEFT (exit)

end of oven

SECTION 3 - SERVICING COMPONENTS

X. GAS TRAIN AND BURNER SYSTEM

A. Part Number Reference -

Gas Train Components

OVENS WITH

MODULATING GAS

SYSTEM ONLY:

M420 modulating

valve, 1/2

41647

Combination gas

control valve, 1/2

45688

1/2 union

23051-0003

Manual shutoff

valve, 1/2

23115-0009

Figure 54

PS200-series gas train

Air shutter

42810-0087

Bypass line

(1/4 aluminum

tubing)

15125-0002

(per foot)

Pilot line

(1/4 aluminum

tubing)

15125-0002

(per foot)

Pilot

pressure

tap

30185

Burner blower and motor assy

OVENS WITH ON/OFF

GAS SYSTEM ONLY:

120V motor assy with centrifugal

safety switch 27170-0011

OVENS WITH MODULATING

GAS SYSTEM ONLY:

208/240V motor assy 27170-0287

OVENS WITH ON/OFF

GAS SYSTEM ONLY:

Junction box

Includes:

240Vp:120Vs

transformer 27170-0017

Relay 27170-0016

OVENS WITH ON/OFF GAS

SYSTEM ONLY:

Solenoid valve, 1/2

28091-0017

Manual shutoff

valve, 1/2

23115-0009

Figure 55

PS310, PS314, PS360 or PS360WB gas train

Burner blower and motor assy, 120V

with centrifugal safety switch

Solenoid valve, 1/2

Combination gas

control valve, 1/2

45688

1/2 union

23051-0003

27170-0011

Air shutter

42810-0087

28091-0017

Bypass line

(1/4 aluminum tubing)

15125-0002

(per foot)

pressure

30185

Pilot

tap

Junction box

Includes:

240Vp:120Vs

transformer

27170-0017

Relay

27170-0016

Pilot line

(1/4 aluminum

tubing)

15125-0002

(per foot)

SECTION 3 - SERVICING COMPONENTS

Figure 56

PS360EWB or PS360WB70 gas train with Midco burner

PS360WB70

ONLY:

Bypass line

(1/4 aluminum

tubing)

15125-0002

(per foot)

Manual shutoff

valve, 3/4

23115-0010

3/4 union

23051-0004

PS360WB70 ONLY:

Solenoid valve, 3/4

31500

PS360EWB ONLY:

M420 modulating

valve, 3/4

32570

Combination gas

control valve, 3/4

32569

Air tube

(silicone rubber)

22450-0297

(per foot)

TO NEGATIVE (-)

SIDE OF AIR

SWITCH

Pilot line

(1/4 aluminum tubing)

15125-0002

(per foot)

Air shutter

36830

Main orifice

See chart on

Page 69

Burner blower

motor,

208/240V

32195

Pilot

pressure

tap

Pilot orifice

See chart on

Page 69

PS360WB70 ONLY:

Bypass line

(1/4 aluminum tubing)

15125-0002

(per foot)

Manual shutoff

valve, 3/4

23115-0010

Figure 57

PS360EWB or PS360WB70 gas train with Wayne burner

PS360WB70 ONLY:

Solenoid valve, 3/4

31500

Air tube

PS360EWB ONLY:

M520 modulating

valve, 3/4

32570

Combination gas

control valve, 3/4

32569

3/4 union

23051-0004

(silicone rubber)

22450-0297

(per foot)

TO POSITIVE (+)

SIDE OF AIR

SWITCH

Air shutter

42810-0087

Burner blower

and motor assy,

208/240V

27170-0287

Pilot line

(1/4 aluminum

tubing)

15125-0002

(per foot)

Pilot

pressure

tap

30185

SECTION 3 - SERVICING COMPONENTS

1/2 union

23051-0003

Combination gas

control valve, 1/2

Manual shutoff

valve, 1/2

23115-0009

45688

(1/4 aluminum tubing)

Figure 58

PS570S gas train

OVENS RETROFITTED

WITH MODULATING GAS SYSTEM ONLY:

M420 modulating

valve, 1/2

Solenoid valve, 1/2

Bypass line

15125-0002

(per foot)

41647

28091-0017

Burner blower and

motor assy, 120V

with centrifugal

safety switch

27170-0011

Flexible air hose

22450-0255

Pilot line

(1/4 aluminum tubing)

15125-0002

(per foot)

Pilot

pressure

tap

30185

Air shutter

42810-0087

NOT SHOWN

(components are

installed on back wall

of machinery

compartment):

240Vp:120Vs blower

motor transformer

27170-0017

Relay

27170-0016

Combination gas

control valve, 1/2

45688

1/2 union

23051-0003

Manual shutoff

valve, 1/2

23115-0009

Figure 59

PS570G or PS555 gas train

M420 modulating

valve, 1/2

41647

Pilot pressure tap

30185

(1/4 aluminum tubing)

15125-0002

Pilot line

(per foot)

Air shutter

42810-0087

Flexible air hose

22450-0255

Burner blower

and motor assy,

208/240V

27170-0287

Air tube

(silicone rubber)

22450-0297

(per foot)

TO POSITIVE (+)

SIDE OF AIR

SWITCH

Pilot/ignitor

assembly

42810-0117

Pilot shield

27170-0204

SECTION 3 - SERVICING COMPONENTS

Figure 60 - Wayne burner - exploded view

Venturi

Wtih angled flame target:

27170-0223

With round flame target:

38127

Air shutter

42810-0087

Burner blower and motor assy

120V: 27170-0011

208/240V: 27170-0287

Pilot orifice

See chart below

Main orifice

See chart below

Pitot tube assembly

(for use with 208/

240V motors)

42400-0640

B. Part Number Reference - Gas Orifices and Gas Conversion Kits

PS200 PS220/224 PS310/314/360 PS360WB Midco burner Wayne burner PS555 PS570S/PS570G Description

42810-0125 42810-0126 42810-0120 42810-0127 36863 44664 43061 42810-0127 GAS CONVERSION KIT,

22176-0010 22176-0016 22176-0004 22176-0014 31821 22176-0014 43059 22176-0014 MAIN ORIFICE, NATURAL

0.204/5.18mm 0.182/4.62mm 0.219/5.56mm 0.250/6.35mm 0.234/5.94mm 0.250/6.35mm 0.228/5.79mm 0.250/6.35mm GAS

22174-0011 22174-0011 22174-0011 22174-0011 31818 22174-0011 22174-0011 22174-0011 PILOT ORIFICE, NATU-

0.028/0.71mm 0.028/0.71mm 0.028/0.71mm 0.028/0.71mm 0.032/0.81mm 0.028/0.71mm 0.028/0.71mm 0.028/0.71mm RAL GAS

22174-0006* 22174-0006* 22174-0006 22174-0006 22174-0006* 22174-0006* NONE* 22174-0006* BYPASS ORIFICE, NATU-

0.060/1.52mm/ 0.060/1.52mm/ 0.060/1.52mm/ 0.060/1.52mm/ 0.060/1.52mm/ 0.060/1.52mm/ 0.060/1.52mm/ RAL GAS

#53 drill #53 drill #53 drill #53 drill #53 drill #53 drill #53 drill

28092-0019 28092-0019 28092-0019 28092-0019 28092-0019 28092-0019 28092-0019 28092-0019 GAS VALVE SPRING KIT,

42810-0122 42810-0123 42810-0119 42810-0124 36856 44665 43062 42810-0124 GAS CONVERSION KIT,

22176-0007 22176-0017 22176-0003 22176-0015 31822 31980 43060 22176-0015 MAIN ORIFICE, PROPANE

0.1285/3.26mm 0.113/2.87mm 0.134/3.40mm 0.152/3.86mm 0.185/4.70mm 0.165/4.19mm 0.141/3.58mm 0.152/3.86mm

22174-0010 22174-0010 22174-0010 22174-0010 31819 22174-0010 22174-0010 22174-0010 PILOT ORIFICE, PROPANE

0.018/0.45mm 0.018/0.45mm 0.018/0.45mm 0.018/0.45mm 0.025/0.64mm 0.018/0.45mm 0.018/0.45mm 0.018/0.45mm

22174-0009* 22174-0009* 22174-0009 22174-0009 22174-0009* 22174-0009* NONE* 22174-0009* BYPASS ORIFICE, PRO-

0.038/0.97mm/ 0.038/0.97mm/ 0.038/0.97mm/ 0.038/0.97mm/ 0.038/0.97mm/ 0.038/0.97mm/ 0.038/0.97mm/ PANE

#62 drill #62 drill #62 drill #62 drill #62 drill #62 drill #62 drill

28092-0018 28092-0018 28092-0018 28092-0018 28092-0019 28092-0018 28092-0018 28092-0018 GAS VALVE SPRING KIT,

PS360WB70/EWB PS360WB70/EWB

PROPANE TO NATURAL

NATURAL GAS

NATURAL TO PROPANE

(same as PROPANE

natural gas)

*NOTE

Bypass orifices are used ONLY on ovens equipped with an on-off gas regulation system (with a solenoid valve). These ovens include:

 PS200-series

(through 3/02)

Ovens equipped with a PID modulated gas system (with a modulating valve) do not use a bypass orifice. These ovens include:  PS200-series

(4/02 or later)

 PS310  PS314

 PS360EWB  PS555

 PS360  PS360WB

 PS570S

(9/00 or later)

 PS360WB70  PS570S (through 8/00)

 PS570G

NOTE: Installations at higher altitudes have a lower ambient air pressure that disrupts the air-fuel mixture. To correct this problem, smaller gas orifices are required. A general rule is a 4% reduction for each 1000 ft. (305m) above sea level. Refer to the chart in the Appendices section (page 135) for a listing of orifice sizes showing this reduction.

SECTION 3 - SERVICING COMPONENTS

C. Component Identification

1. Burner type

Middleby ovens are equipped with one of two main burner designs. Details of these burners are provided below.

1. Midco burner - see Figure 61. This burner was used on PS360WB70 and PS360EWB ovens only.

Late-production PS360EWB and PS360WB70 ovens used the Wayne burner shown in Figure 62. In addition, many PS360EWB ovens were retrofitted during 1998 to use the Wayne burner.

Servicing the Midco burner is beyond the scope of this manual. However, note that most gas train components EXCEPT FOR THE BURNER ITSELF are identical to the components used with the Wayne burner. If necessary, contact Middleby Technical Service for assistance.

2. Wayne burner - see Figure 62. Wayne burners are used on all Middleby oven models except earlyproduction PS360WB70 and PS360EWB models.

The Wayne burner configuration varies slightly between oven models and so may be slightly different from that shown in Figure 62. Refer to the drawings in Part Number Reference - Burner Com- ponents (pages 88-90) for illustrations of the burner configuration used on each oven model. Common variants include:

 Flexible air tube between the burner blower and

plenum. Used on all PS555/570 series ovens.

 120V burner blower motor. Used on PS200-

series (through 3/02), PS310, PS314, PS360, PS360WB and PS570S ovens.

 208/240V line voltage blower motor. Used on

PS200-series (4/02 or later), PS360WB70, PS360EWB, PS555, and PS570G ovens.

1. Solenoid valve vs. Modulating valve

Middleby ovens use one of the following systems for gas flow regulation:

 On-Off gas flow regulation. These ovens are

equipped with a high flame solenoid valve. The solenoid valve can only be positioned fully open (100% gas flow) or fully closed (0% gas flow) as necessary to maintain the set point. A bypass line supplies gas to maintain the flame when the valve is closed. On/off gas systems have a temperature swing of several degrees on either side of the set point.

On-Off gas flow regulation is used on the following Middleby oven models:

- PS200-series (through 3/02)

- PS310

- PS314

- PS360WB

- PS360WB70

- PS570S (through 8/00)

- PS360 Additional information on the solenoid valve is pro-

vided in Solenoid Valve on Page 96.

 Modulated gas regulation. These ovens are

equipped with a modulating gas valve. The modulating valve can open or close at any setting from 0100% gas flow in response to the need for heat to maintain the set point. Because of this flexibility, the temperature swing is eliminated.

The modulated gas system is used on the following Middleby oven models:

- PS200-series (4/02 or later)

- PS360EWB

- PS570S (9/00 or later)

- PS570G

- PS555

Additional information on the modulating valve is provided in Modulating Valve on Page 97.

Air

shutter

Main gas

line

Figure 61 - Midco burner

Burner blower

Pilot line

Burner blower

motor

Plenum

Figure 62 - Wayne burner

PS360EWB shown. For different oven models, refer

to the drawings on pages 88-90.

Plenum

Main gas

line

Pilot line

Burner

blower

Burner

blower

motor

Air shutter

SECTION 3 - SERVICING COMPONENTS

D. Pilot/Ignitor Assembly

The pilot assembly is attached to the end of the pilot line. It consists of an ignitor electrode/flame sensor, a pilot shield and the pilot burner. See Figure 63.

The pilot assembly includes a safety circuit. An electrical current is sent to the flame sensor probe to prove the presence of the pilot flame. When the spark ignites the pilot, a circuit is completed THROUGH THE FLAME from the flame sensor probe to the pilot burner, which is grounded. This safety circuit must be completed before the pilot will light.

1. Pilot Shield

The pilot shield is a plate located on the bottom of the pilot. It prevents drafts, etc. from blowing the pilot flame away from the sensing probe. See Figure 64.

2. Flame target

The flame target aids in distributing the flame from the end of the venturi. See Figure 65.

 PS310/360-series ovens built prior to 6/87 are not

equipped with a flame target. The burner on these ovens resembles the one shownin Figure 64.

 The angled flame target is used on:

- PS200-series ovens built through 3/02.

- PS310, PS314, PS360 and PS360WB ovens built 6/87 or later.

- PS570S ovens.

All of these ovens use a 120V burner blower motor. Most units equipped with the 120V burner blower motor also use the angled flame target.

 The round flame target is used on:

- PS200-series ovens built 4/02 or later.

- PS360EWB and PS360WB70 ovens equipped with the Wayne burner system.

- PS555 and PS570G ovens.

All of these ovens use a 208/240V burner blower motor. All ovens equipped with the line voltage burner blower motor use the round flame target.

Figure 63 - Pilot/ignitor assembly

Pilot

burner

Hood

Ignitor/sensor

probe

Figure 64

End of burner without flame target

showing pilot shield

Pilot

shield

Pilot line

connects here

Spark cable

connects here

Figure 65

Flame targets

Angled

target

Round

target

SECTION 3 - SERVICING COMPONENTS

3. Pilot and Proof of Pilot Flame Rectification

Figure 66

Flame structure

With standing pilots, heat is a necessary ingredient for proper thermocouple operation. But this is not the case with IIDS (Intermittent Ignition Device Systems) when flame conduction or rectification is used. To better understand the principles of flame conduction and rectification, we must first understand the structure of a gas flame. See Figure 66.

With the proper air-gas ratio to give a blue pilot flame, three zones exist.

Zone 1: An inner, fuel-rich cone that will not burn because excess fuel is present.

Zone 2: Around the inner, fuel-rich cone is a blue envelope. In this area is a mixture of vapor from the fuel-rich inner cone and the secondary, or surrounding, air. This is where combustion occurs.

Zone 3: Outside the blue envelope is a third zone that contains an excessive quantity of air and will not burn.

Of concern is the second, or combustion area. This is where the burning occurs and is the area that is of prime importance for good flame sensor location.

Flame Rectification

With flame rectification, two probes with different surface areas are exposed to a flame - in this case, the pilot flame. The probe with the larger surface area attracts more free electrons and, as a result, becomes the negative probe. Therefore, current is conducted through the flame from the positive probe to the negative probe. See Figure 67.

Note also that the AC voltage sine wave has not changed, but the negative portion of the current sine wave has been chopped off. This positive portion now represents a DC current. This is the phenomenon of flame rectification.

To apply this principle to an IID (Intermittent Ignition Device - in this case, the pilot/ignitor assembly), a pilot and flame sensor have been substituted for the two probes (See Figure 68). After the pilot is ignited, a DC current flow of 2.0mA (microamps) or more is conducted through the flame, from the flame sensor (the positive probe) to the pilot tip (the negative probe). The pilot tip, acting as the negative probe, completes the circuit to ground. The IID sensing circuit uses this DC current flow to energize a relay and open the main burner gas valve.

Figure 67 - Flame rectification

Figure 68 - Pilot and probe

THE FOLLOWING CONDITIONS WILL HAVE A DIRECT BEARING ON EVERY IID APPLICATION:

Voltage

The supply voltage to the ignition controls should be within the following ranges:

 120VAC controls  102 to 132VAC  24VAC controls  21 to 26.5VAC

24VAC systems should use transformers that will provide adequate power under maximum load conditions.

Gas Pressure

Inlet gas pressures

 Natural gas, Wayne burner - 6-12 W.C. (14.9-29.9 mbar)  Propane, Wayne burner - 11½-12 W.C. (28.7-29.9 mbar)  Midco burner (all gases) - 6-14 W.C. (14.9-34.9 mbar)

Regulated gas pressures

 Natural gas, Wayne burner - 3.5 W.C. (8.7 mbar)  Propane, Wayne burner - 10 W.C. (24.9 mbar)

 Midco burner (all gases) - 3-5 W.C. (7.5-12.5 mbar)

Pilot gas pressures

 Natural gas, Wayne burner - 3½-4 W.C. (8.71-9.95 mbar)  Propane, Wayne burner - 8-10 W.C. (19.9-24.9 mbar)  Midco burner (all gases) - 5-6 W.C. (12.5-14.9 mbar)

SECTION 3 - SERVICING COMPONENTS

Temperature

Ignition controls should not be exposed to temperatures exceeding 140°F (60°C) or less than -40°F (-40°C).

Pilot Application

The pilot and flame sensor application is the most critical aspect of the llD application.

The pilot flame must make contact with the pilot tip and surround the flame sensor probe. A multimeter or ampmeter set to read microamps (mA) is necessary to verify that the proper amount of current is being maintained through the pilot flame. The minimum value required is 2.0 mA. Rectification-based ignition systems respond in less than 0.8 of a second to a loss of flame. If the minimum signal is not being maintained at all times, OR if the pilot flame is briefly directed away from the flame sensor or pilot tip, the main gas valve may cycle rapidly (chattering) or the burner may be prevented from activating.

Other conditions that can cause the failure of the main burner to activate, OR chattering of the burner, are:

1. Pilot flame is too small.

2. Gas pressure is too low for proper pilot flame impingement on the flame sensor.

In these cases, the pilot may ignite, but the main burner gas valve will not be energized. It is also possible for drafts or unusual air currents to deflect the pilot flame away from the flame sensor. Deflection of the pilot flame may also be caused by main burner ignition concussion or roll-out of the main burner flame.

An additional point to be considered is the condition of the pilot flame. If the pilot flame is hard and blowing, the grounding area of the pilot is reduced to a point where the necessary current is not being maintained, and a shutdown of the system will result.

The positioning of the flame sensor is also critical in the pilot application. Positioning of the flame sensor should be such that it will be in contact with the second, or combustion area of the pilot flame. Passing the flame sensor through the inner cone of the pilot flame is not a recommended procedure. For this reason, a short flame sensor may provide a superior signal over a longer one. The final determination of the sensor location (length) is best determined by the use of a multimeter set to read microamps (mA).

E. Burner Blower Motor

The burner blower motor is located on the side or top of the burner housing. Some blowers use a flexible tube to connect the blower to the burner, depending on the available space inside the machinery compartment. The burner blower motor drives a blower wheel located in a housing attached to the end of the motor that is the primary air supply for combustion. The motor requires no lubrication.

Depending on the oven model, the burner motor operates on either 120V or 208/240V (line voltage). 120V motors have an internal centrifugal switch that controls the 24V power supply to the gas valve (see Burner Blower Motor Centrifugal Safety Switch on Page 80). 208/240V motors use a separate air pressure safety switch to sense blower operation (see Air Pressure Safety Switch on Page 81). This safety feature prevents burner operation in case of motor failure.

F. Air Shutter

The air shutter is a round metal plate located on the open end of the burner blower wheel. Adjusting the position of the shutter will increase or decrease the amount of air that is permitted into the plenum for combustion. Rotate the plate in a counterclockwise direction to increase the air supply, or in a clockwise direction to reduce the air supply.

You can insert a drill bit into the shutter gap to check the size of the opening. Refer to Figure 69 for the recommended opening sizes.

Early Midco burners use an adjustment screw on the front wall of the plenum to adjust the airflow. If it is not possible to adjust the air supply properly using the screw, a retrofit kit is available (P/N 36829) to install the external air shutter shown in Figure 69.

Figure 69

Air shutter adjustment

Wayne burner

Standard openings:  1/4/6.4mm for natural gas ovens  3/8/9.5mm for propane ovens

Clockwise -

less air

Standard opening 5/16/7.9mm (all gases)

Clockwise -

less air

Loosen hex

nut to adjust

shutter

Midco burner

Counterclockwise -

Loosen

screw to

adjust

shutter

Counter-

clockwise -

more air

SECTION 3 - SERVICING COMPONENTS

G. Burner Transformer

120V burner blower motors feature a transformer located in the electrical junction box on the burner. In PS570S ovens, AND all ovens with 208/240V burner blower motors, the transformer is located inside the machinery compartment.

The transformer supplies 24V to the burner motor relay (if present) and also to the 24V gas valve through the motors centrifugal switch (or air pressure safety switch).

H. Burner Motor Relay

120V burner blower motors feature a 24V time delay relay located in the electrical junction box on the burner. In PS570S ovens, the relay is located on the back wall of the machinery compartment.

Approximately 25 seconds after power is applied to the coil of the relay, the contacts will close and complete a circuit to the burner blower, allowing the motor to operate. This 15-30 second delay is a prepurge for a cold start. When the coil of the relay is warm, the delay is bypassed.

Ovens with 208/240V burner blower motors are not equipped with the burner motor relay, and do not have a prepurge for a cold start.

I. High Flame Solenoid Valve (if so equipped)

Ovens that use an on-off gas regulation system are equipped with a high flame solenoid valve. The valve is located between the combination gas control valve and the burner. The valve operates on 110-120V.

The valve opens when the ovens temperature falls 2 degrees Fahrenheit below the set point, and closes when the temperature rises to 2 degrees above the set point. Because of residual heat within the oven, however, the temperature swing after preheating is about 5 degrees Fahrenheit above and below the set point.

The solenoid valve can only be positioned fully open (100% gas flow) or fully closed (0% gas flow). While the valve is closed, gas is still supplied to the burner through the by-

pass line that goes around the solenoid valve. This allows the burner to operate in low flame mode while awaiting reactivation.

When the oven has been fully preheated and has maintained the set point for about an hour with a moderate product load, the low flame to high flame ratio should be approximately 1 to 1. That is, the oven will be calling for heat approximately half the time. To check this ratio, refer to the HEAT indicator on the temperature controller, which will only be active when the burner is on high flame.

EXCEPTION: Older PS310/314/360 ovens have a temperature-sensing thermocouple mounted at the front of the oven, inside the machinery compartment. On these ovens, the low flame to high flame ratio should be approximately 2 or 3 to 1 (oven calls for heat 1/3 or 1/4 of the time).

IMPORTANT: For proper functioning of the solenoid valve, the temperature controller MUST be set to the on-off operating mode. Refer to Tem- perature Controller on Page 31.

J. Bypass (Low Flame) Orifice (ovens with a high

flame solenoid valve only)

All ovens that use an on-off gas regulation system are equipped with an orifice in the low flame bypass line. See Figure 70.

When the oven is not calling for heat, the solenoid valve is closed, but gas is still supplied to the burner through the bypass line. This allows the burner to operate in low flame mode while awaiting re-activation.

The low flame orifice regulates the gas flow through the bypass line. If the orifice size is too large, the low flame will be too high. In some cases, this will prevent the oven from being able to maintain the set point.

Refer to the chart on Page 91 to determine the proper size for the bypass orifice.

Figure 70

Low Flame (Bypass) Orifice

Bypass line configuration varies depending on the oven model. Refer to the drawings on pages 88-90.

Low flame

(bypass)

orifice

Bypass

line

Solenoid

valve

SECTION 3 - SERVICING COMPONENTS

K. Modulating Gas Valve (if so equipped)

Ovens that use a PID (modulated) gas regulation system are equipped with a modulating gas valve instead of a solenoid valve. The valve is located between the combination gas control valve and the burner.

In response to the millivolt signal from the thermocouple, the Digital Temperature Controller sends a 4-20mA signal to an amplifer board. The board, in turn, passes on a 020VDC signal to the modulating valve itself. The valve opens or closes proportionally to the signal from the amplifier board, allowing any setting from 0-100% gas flow.

When the oven is switched on, gas demand is at its peak and the valve is fully open, permitting 100% gas flow. As the ovens temperature approaches the set point, the valve slowly begins to close, restricting gas flow to the 35-60% range. After the oven is fully preheated, the gas flow usually stabilizes at about 30%. The actual oven temperature can remain constant, with NO temperature swing, because the valve is adjusted constantly according to the demand.

Modulating valves are used on all PS360EWB, PS555, and PS570G gas ovens. They are also used on PS200 ovens produced 4/02 or later and PS570S ovens produced 9/00 or later.

The Model PS360EWB oven uses a Maxitrol M520 modulating valve with a 3/4 gas line, P/N 32570. All other Middleby oven models equipped with a modulating valve use the Maxitrol M420 valve with a 1/2 gas line, P/N 41647.

The modulating valve features a bypass adjustment screw, shown in Figure 71. For all ovens except the PS536, the screw should ALWAYS remain fully closed; no adjustment is necessary. The screw is pre-set to the fully-closed position from the factory. If the screw is adjusted to any setting other than fully-closed, the oven may not be able to maintain the set point temperature.

IMPORTANT: For proper functioning of the modulating valve, the temperature controller MUST be set to the PID operating mode. Refer to Tempera- ture Controller on Page 31.

L. Amplifier Board (ovens with a modulating gas

valve only)

Ovens equipped with a modulating gas valve have an amplifier board mounted inside the machinery compartment.

In response to the millivolt signal from the thermocouple, the Digital Temperature Controller sends a 4-20mA signal to the amplifer board. The board, in turn, passes on a 020VDC signal to the modulating valve. The valve opens or closes proportionally to the signal from the amplifier board, allowing any setting from 0-100% gas flow.

All Middleby oven models equipped with a modulating valve use amplifier board P/N 31651.

Modulating Valve

blue

blue/white

bypass adjustment

screw (under cap)

MUST BE FULLY

CLOSED

Figure 71 - Modulating Gas System

To transformer

24VAC input

orangeorange/white

To thermocouple

Amplifier Board

To amplifier board terminal 6

To amplifier board terminal 5

white +

red -

purple

purple/white

Digital Temperature

Controller

MUST BE SET TO PID

OPERATING MODE

purple/white

purple

PS360EWB

with Controller 32571

only

SECTION 3 - SERVICING COMPONENTS

M. Combination Gas Control Valve

1. Part Number Reference - Combination Gas Valve

 PS360WB70 and PS360EWB ovens are equipped with

a 3/4 (19.05mm) gas line. This requires the use of Combination Gas Valve P/N 32569. The valve has a tan plastic cover with a blue On/Off knob.

 All other oven models are equipped with a 1/2 (12.7mm)

gas line.

- Through 10/01 - these ovens used Valve P/N 28092-

0017. The valve operated on a 60 Hz supply, had a tan plastic cover and a blue On/Off knob.

- 11/01 and later - these ovens use Valve P/N 45688. The valve operates on a 50 or 60 Hz supply, has a grey plastic cover and a black On/Off knob. It is otherwise identical to the previous version, and may be used to replace it in all cases.

2. Valve Operation

When the ON-OFF knob on the valve is in the ON position, gas is allowed to enter the valve. Once 24VAC is supplied to the valve, gas is supplied to the pilot line.

When the pilot flame has been proved (see Pilot and Proof of Flame Rectification on Page 94), 24VAC is supplied to the combination valve by the ignition module, opening the main valve. Gas pressure from the inlet side of the valve is passed through the Pressure Regulator. The regulated pressure is supplied to a cavity below the main valve diaphragm. This pressure overcomes the spring force and moves the main valve to its open position. During operation, the main valve is opened and closed by the pressure regulator to keep a constant pressure at the outlet of the valve.

When power to the valve is cut, the cavity below the main valve diaphragm is depressurized and the valve spring closes the main valve rapidly to shut off the main burner.

When the 24VAC supply to the valve is cut, the valve stops gas flow to both the pilot and the main burner.

The combination valve includes taps to measure both the inlet pressure and the regulated pressure. To ensure accuracy, the regulated pressure should be measured when the oven is on low flame.

3. Servicing the Combination Valve

 Pilot pressure

One of the more common service issues with the combination valve occurs on ovens with the on/off gas regulating system (with a solenoid valve), when the oven is on low flame. During low flame, the servo can bounce inside the valve as it searches for the proper level. The bouncing line pressure can also cause surges in the pilot pressure. A properly adjusted pilot will tend to smooth out the surges.

The best way to check for a properly adjusted pilot is to check the pilot line pressure. This requires a pilot pressure tap in the pilot line. Ovens built 3/94 or later should have the tap installed in the line. The tap is also available as Service Kit P/N 30185 which includes installation instructions.

Recommended pilot gas pressures are:

- Wayne burner, natural gas - 3½-4 W.C. (8.71-9.95 mbar)

- Wayne burner, propane - 8-10 W.C. (19.9-24.9 mbar)

- Midco burner (all gases) - 5-6 W.C. (12.5-14.9 mbar)

 Burrs in pilot adjustment portal

Some combination valves have been shown to have shipped with small burrs in the pilot adjustment portal. Although this will not interfere with proper operation of the valve in any way, it does make it difficult to adjust the pilot pressure until the burr is removed.

Check for a burr by attaching a manometer to the pilot pressure tap. If the manometer does not detect any change in pilot pressure when the screw is tightened all the way down, there is probably a burr in the portal.

To remove a burr, perform the following procedure:

- Turn the adjustment screw all the way down.

- Apply more pressure to break through the burr.

- Back the screw out until the top of the screw is level with the top of the access hole.

- Turn the adjustment screw back down to adjust the pressure.

- Repeat these steps until the burr is cleared.

Figure 72 - Combination Gas Control Valve

Pressure regulator

adjustment

(under cap

screw)

Inlet

pressure

tap

On/Off knob (should

remain in ON position)

adjustment (under

Regulated

pressure

tap

Pilot line

connection

Pilot pressure

cap screw)

SECTION 3 - SERVICING COMPONENTS

N. Ignition Module

1. Part Number Reference - Ignition Module

 PS360WB70 and PS360EWB ovens equipped with the

Midco burner use Ignition Module P/N 31501.

 For all other oven models:

- Through 10/90 - these ovens used Ignition Module P/N 27161-0004. Some versions of this module included a separate, replaceable fuse. This module shared a common ground with the 24V transformer and the relay coil. See Figure 73.

- 11/90 or later - these ovens use Ignition Module P/N 27161-0005, included in Service Kit 42810-

0114. The module is internally grounded and the common ground with the transformer and relay coil has been eliminated. See Figure 74.

If you are replacing the obsolete module (P/N 27161-

0004) with the current version (P/N 27161-0005), BE SURE TO DISCONNECT THE MODULE FROM THE COMMON GROUND WITH THE TRANSFORMER AND RELAY. Double-grounding of the module creates a feedback voltage circuit that allows the module to operate without a signal from the burner/blower assembly. This procedure is explained in greater detail in the instructions for Kit 42810-0114, included in the Appendices section.

2. Module Operation

The ignition module delivers 24V to the pilot ignitor when the blower motor centrifugal switch (or air pressure safety switch) is closed.

When the module detects a current flow of at least 2.0 mA through the pilot flame, it supplies 24V to the combination gas control valve, allowing the valve to operate.

Figure 73

Wiring diagram of ignition and gas valve system (obsolete ignition module 27161-0004)

Figure 74

Wiring diagram of ignition and gas valve system (current ignition module 27161-0005)

Middleby Marshall PS570, PS360 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual