Garland MCO-GS-10E, MCO-GS-10M, MCO-GD-10E, MCO-GD-10M User Manual

GARLAND

BUILT TO LEAD... BUILT TO LAST

A WELBILT COMPANY

SERVICE MANUAL

THE “MASTER”

GAS CONVECTION

OVENS

Models covered in this manual are:

MCO-GS-10M:

ASTER CONVECTION

ASTER CONVECTION OVEN

ASTER CONVECTION

185 East South Street  Freeland, Pennsylvania 18224

DIRECT “ON-SITE” SERVICE 1-800-451-1165

Oven - GAS S

- GAS S

Oven - GAS D

GARLAND Commercial Industries, Inc.

TANDARD DEPTH

MCO-GS-10E:

TANDARD DEPTH

MCO-GD-10M:

EEP DEPTH

MCO-GD-10E:

EEP DEPTH



GENERAL INFORMATION 1-800-424-2411

-(10)S

-(10)Single D

-(10)S

INGLE DECK

INGLE DECK ELECTRONIC CONTROL

INGLE DECK

ECK ELECTRONIC CONTROL

Manual C

ONTROL

FORM #GCI-MCOVN PRINTED IN THE U.S.A.

This service manual is designed to answer questions related to model operational requirements, troubleshooting and disassembly/assembly procedures. It contains electronic ignition operation, trouble-

shooting and electronic control operations that include diagnostic codes, ladder diagrams, wire diagrams and troubleshooting. It also includes BTU ratings, orifice size and gas pressure technical data for each model.

For example; if you need to know information on manual controls (manual controls - controls the oven with hydraulic thermostat, electric mechanical timer.) refer to SECTION 2: OVERVIEW OF OPERATIONAL SEQUENCES,

Sequence of Operation. This book is broken down into sections, each section will list the applicable topics. Use the Table of Contents to locate the topic and function that you are attempting to trouble-shoot.

Table of Contents

SECTION 1: SPECIFICATION & DIMENSIONS............................................................................3

GAS CONVECTION OVEN "GAS SPECIFICATIONS”...............................................................................................4

DIMENSIONS & SPECIFICATIONS ............................................................................................................................4

SECTION 2: OVERVIEW OF OPERATIONAL SEQUENCES.......................................................4

MANUAL CONTROLS - "M” .......................................................................................................................................5

Sequence of Operation.............................................................................................................................................5

Manual Ladder Diagram...........................................................................................................................................5

CALIBRATION OF THERMOSTAT .............................................................................................................................5

Instrumentation.........................................................................................................................................................5

Weighting..................................................................................................................................................................6

Thermostat Operation...............................................................................................................................................7

ELECTRONIC CONTROLS - “E”................................................................................................................................8

Sequence of Operation (With the Oven Doors Closed) ...........................................................................................8

Electonic Ladder Wire Diagram................................................................................................................................8

ELECTRONIC CONTROL FAILURE CODES .............................................................................................................9

CHART FOR INTERNAL OVEN TEMPERATURE SENSOR......................................................................................9

ROBERTSHAW COM6000 CONTROLLER................................................................................................................9

USER PREFERENCE OFFSET FOR THE ELECTRONIC CONTROLLERS ...........................................................10

COM6000 UPO MODE...........................................................................................................................................11

COM6700 UPO MODE...........................................................................................................................................11

ELECTRONIC PILOT & MAIN BURNER IGNITION SEQUENCE ............................................................................12

FIRST STAGE - TRIAL FOR PILOT IGNITION .....................................................................................................12

SECOND STAGE - MAIN BURNER OPERATION ................................................................................................12

SAFETY LOCKOUT TIME......................................................................................................................................12

SERVICE ....................................................................................................................................................................13

PRELIMINARY CHECK..........................................................................................................................................13

SYSTEM TROUBLE SHOOTING...........................................................................................................................13

S86 CHECKOUT AND TROUBLE SHOOTING.....................................................................................................14

CHECK SPARK IGNITION CIRCUIT .....................................................................................................................15

CONTROL MODULE FLAME SENSOR CIRCUIT.................................................................................................15

SECTION 3: COMPONENT ACCESS OF FUNCTIONAL COMPONENTS..................................16

DOOR GASKET REPLACEMENT............................................................................................................................17

TO REMOVE DOORS FROM THE OVEN................................................................................................................ 18

INSTALLATION OF OVEN DOORS.........................................................................................................................19

INSTALLING AND ADJUSTMENT OF THE DOOR CHAIN.....................................................................................19

DISASSEMBLY OF THE LEFT DOOR..................................................................................................................... 19

DISASSEMBLY OF THE RIGHT DOOR (W/O WINDOW).......................................................................................20

TO REPLACE OR ADJUST DOOR LATCH MECHANISM......................................................................................22

TO REPLACE CONVECTION OVEN MOTOR ASSEMBLY.................................................................................... 22

CONVECTION OVEN MOTOR ASSEMBLY............................................................................................................23

MAIN BURNER, PILOT BURNER & DOOR MICRO-SWITCH LOCATION ............................................................24

SECTION 4: COMMON WIRE DIAGRAMS.................................................................................25

SECTION 1: SPECIFICATION & DIMENSIONS

GAS CONVECTION OVEN "GAS SPECIFICATIONS”

TOTAL

MAIN

BURNER

ORIFICE

PILOT

ORIFICE

GAS

PRES. W/C

B.T.U.'S ORIFICE AMT. ORIFICE AMT. NAT PRO

NAT PRO

MCO

40,000

MCO

60,000

MCO

* - Gas pressure measured at burner manifold. ** - Gas pressure measured at redundant gas valve pressure tap.

All models (single deck ovens) amperage rating is 6.2 (each oven). Manifold size is ¾" N.P.T. (National Pipe Thread). NOTE: Two-speed motor, 1140 and 1725 R.P.M., 60 Hz, clock-wise motor rotation looking into oven cavity. NOTE: Each deck supplied with a 6 ft. power supply cord for 120-volt units.

DIMENSIONS & SPECIFICATIONS

1-1/2

[38mm]

[813mm]

57-1/2

[1461mm]

25-1/2

[648mm]

Single Deck

INTERIOR DIMENSIONS (per oven) EXTERIOR DIMENSIONS SHIP WEIGHT/DIM

Model # W H D W H (w/legs) D Lb./KG Cu. Ft.

MCO-GS-10 29”(736mm) 24”(610mm) 24”(610mm) 38”(965mm) 57½”(1460mm) 39”(991mm) 510/232 42 cu. ft. MCO-GS-20 29”(736mm) 24”(610mm) 24”(610mm) 38”(965mm) 70½”(1791mm) 39”(991mm) 1020/464 84 cu. ft. MCO-GD-10 29”(736mm) 24”(610mm) 28”(711mm) 38”(965mm) 57½”(1460mm) 43”(1092mm) 510/232 42 cu. ft. MCO-GD-20 29”(736mm) 24”(610mm) 28”(711mm) 38”(965mm) 70½”(1791mm) 43”(1092mm) 1020/464 84 cu. ft.

80,000

[965mm]

(Front View)

INPUT CHART - Natural or Propane Gas ELECTRICAL CHARACTERISTICS

Model #

MCO-GS-10 60,000 17.6 One @ ¾” NPT One @ 6.2 Amps One @ 3.1 Amps ½ HP MCO-GS-20 120,000 35.2 One @1” NPT Two @ 6.2 Amps Two @ 3.1 Amps ½ HP MCO-GD-10 60,000 17.6 One @ ¾” NPT One @ 6.2 Amps One @ 3.1 Amps ½ HP MCO-GD-20 120,000 35.2 One @ 1” NPT Two @ 6.2 Amps Two @ 3.1 Amps ½ HP

/64”

(.0781”)

/64”

(.0781”)

/64”

(.0781”)

1/2 N.P.T. [13mm] GAS INLET

54-9/16

[1386mm]

[965mm]

BTU/HR

#55

1-7/16

[37mm]

43-1/4 DEEP

[1099mm] DEEP

39-1/4 STD

[997mm] STD

17-3/4

[451mm]

Equiv.

7-3/4

[197mm]

2-3/8 x 5 [60mm x 127mm] FLUE

(Top View)

Gas Inlet

NAT PRO

.020" .012"

1-1/2

[38mm]

1-7/8

[48mm]

REAR GAS INLET

38-1/4

[972mm]

120V/1 Phase

70-1/2

[1791mm]

[813mm]

6-1/2

[165mm]

[965mm]

Double Deck

240V/1 Phase Motor

(Front View)

4.5"

5.0”

5.1”

5.5”

[813mm]

[483mm]

10.0"

3/4 N.P.T. [19mm] GAS INLET

35-9/16

[903mm]

SECTION 2: OVERVIEW OF OPERATIONAL SEQUENCES

Understanding the sequence of operation is necessary in properly trouble-shooting this appliance. In this section the sequence of operation will be covered first, as well as calibration and operation of components, and basic trouble shooting techniques for that specific model. Follow each sequence carefully, and get to understand its operation before moving on to trouble shooting.

MANUAL CONTROLS - "M" Sequence of Operation (Starting with the oven doors in closed position.)

1. Turn the Mode Switch to the “Cook” position. This sends line voltage to the timer. And with the doors closed, line voltage is sent via the door switch to the thermostat and the Hi/Lo Fan switch.

2. Select Hi or Lo speed, the motor will now be operational.

O F F

COOK

COOL DOWN

POWER

TIMER

HIGH

LOW

3. Rotate the temperature dial to desired temperature. The thermostat will now call for heat sending line voltage to the 24 volt transformer. With the motor operating, the centrifugal switch is closed, completing the neutral circuit to the transformer.

4. The 24v transformer now sends 24 volts to the ignition module.

TEMP

5. The *ignition sequence starts and oven temperature begins to rise.

*See “Ignition Sequence” later in this manual. Below is a simplified power diagram:

Hi/Lo Sw.

Door Sw. Mode Sw.

Line

Light Sw.

CALIBRATION OF THERMOSTAT INSTRUMENTATION

Hi/Lo Sw.

Timer

Thermostat

Hi Speed

Lo Speed

24 Volt

Transformer

Ign. Module

Neutral

Motor

Centrif. Sw.

A thermocouple type test instrument is preferred for measuring oven temperatures accurately. Mercury thermometers are acceptable providing they can be proven accurate.

Regardless of the type instrument used, it is most desirable to double-check it just before making an oven temperature check. This can be done simply and quickly by placing the thermocouple tip (or immersing the entire mercury thermometer) in boiling water. Note: Mercury oven thermometers should be the "total immersion type." The resulting reading should be within several degrees of 212°, -depending on the altitude.

Generally, a mercury thermometer can drop in excess of 25° when the doors are opened to check oven tem perature. This condition makes it extremely difficult to get a true temperature reading.

Almost all ranges today have oven burners which cycle "on and off." The high and low points of the resulting temperature "swing" (differential) in the oven must be measured-and averaged-to determine the true operating temperature. A thermocouple type test instrument is best suited to measure these temperature changes quickly and accurately, and without opening the oven door.

With an accurate, thermocouple test instrument or mercury thermometer, it is still difficult to measure these changing oven temperatures and then, average them correctly. This is why we recommend that the thermocouple tip or the bulb of the thermometer be "weighted." Weighting (adding mass) to the test instrument compensates for oven temperature changes by making the test instrument less sensitive to these constant changes in temperature. Note: How this weighting can be done is discussed later.

Measuring these changing high and low temperatures points in an oven is possible with either type of test device without weighting but is subject to possible inaccuracies. This is most true at low temperature setting because, in this area, the function of "time" becomes a factor. The simple averaging of temperatures, then, may not produce the true operating temperature. "Weighting" provides the compensation for both time and temperature that is necessary. We produced (next page) test curves showing actual results in the low temperature area showing the difference in results when using an unweighted and a weighted thermocouple or thermometer. Tests were made with the same control, same oven and dial at 170° mark (not move d).

Chart No.1

260 240 220 200 180 160 140 120 100

Unweighted Thermocouple dial setting 170 F

260 240 220 200 180 160 140 120 100

Weighted Thermocouple Dial Setting 170F

Chart No.2

From the above, it can be seen that an error of 15° is possible. Chart #1, unweighted thermocouple indicates an erroneous average oven temperature of 185°. Chart #2, weighted thermocouple indicates the "average" or true temperature to be 170°.



WEIGHTING



A thermocouple can be weighted by clamping the tip between two one-inch squares of 1/16" thick aluminum. The thermocouple can also be weighted (just as successfully) by using a letter-size sheet of aluminum foil. Fold the foil

five times doubling the thickness with each fold. After the fifth fold, place the thermocouple tip in the center of the aluminum piece and fold once more. Finally, fold in the sides so that the foil clings to the thermocouple tip.

A mercury thermometer can be weighted in much the same way by wrapping several layers of aluminum foil around the bulb end thus creating the necessary mass. This procedure is a must if you open an oven door to check temperature.

THERMOSTAT OPERATION It is normal for a hydraulic thermostat cycling with a temperature swing of 45° to 50°. When checking calibration first;

allow the thermostat to cycle a minimum of four (4) times, second; place your temperature sensor in the geometric center of the empty oven. Once the oven has been allowed to preheat record the temperature at which the burners cycle "ON and OFF". Average the two readings, that average should be +-20° of the set point temperatu re.

Example: Thermostat set point at 300°, first cycl e Off at 325°. Cycle back ON at 291°. The average of 325° and 291° is 308°. This thermostat is with the +-20° to lerance. If the thermostat is cycling beyond the 20° tolerance and the appliance is under warranty recalibrate the thermostat or if not under warranty consult owner for proper action. If the thermostat is out of calibration more than fifty 50°, it will not likely hold an attempt of recalibration, we suggest that the thermostat be replaced.

"B" Dial Shaft

"A" Calibration Screw Head

1/4" Turn

Increase

Decrease

- CALIBRATION NOTES -

ELECTRONIC CONTROLS - “E” Sequence of Operation (With the Oven Doors Closed)

1. Line Voltage is supplied to the Mode Switch, Door Switch and the Momentary Light Switch.

2. Set Mode Switch to COOK and close the oven doors. Line Voltage is sent from Mode Switch to power up the Controller and to the AUX relay on the controller. With the oven doors closed Line Voltage is sent to the 24 volt transformer.

3. Set desired temperature. The controller’s relays now close.

4. The AUX relay sends Line Voltage to the motor relay coil, closing the circuit to the Hi/Lo Fan Switch. The motor now operational causes the centrifugal switch to close and send the Neutral Voltage to the 24 Volt Transformer.

5. The bake relay completes the circuit from the 24 volt transformer to the ignition module and *ignition occurs, heating the oven.

Below is a simplified power diagram:

24 Volt

Transformer

Motor

Centrifugal Switch

COOK

O F F

COOL

DOWN

+- - +

START TIMER

TIMER

0-12 HOUR

HEAT

HIGH

LOW

CANCEL

TIMER

TEMP

140-500F

Door Sw.

Mode Sw.

24 V

Thermostat

Ign. Module

Hi Speed

Motor Relay

Lo Speed

Neutral

AUX

COM6000

Light Sw.

ELECTRONIC CONTROL FAILURE CODES

The GARLAND digital control has a self-diagnostic program. If a problem occurs within the digital controller, you may see one of the "F" codes.

Below is a listing of the "F" codes with explanations:

-F1- Relay output is enabled when not cooking. If this failure code appears in the display, the cook relay may be on even if the control is not cooking. The control should be replaced.

-F2- Over temperature alarm. If this failure code appears in the display the control is sensing an oven temperature 50° or more above the maximum set temperature (500°). This failure may be caused by a faulty sensor.

Check the sensor connection for loose wires. Replace the sensor and check for proper operation. If failure continues replace the control.

-F3- Open sensor circuit. If this failure appears in the display, the control is sensing an open circuit at the sensor input. This failure is most often caused by a poor connection or broken sensor.

Check sensor connection and leads for broken wires of loose connections. Replace sensor and check for

proper operation. If failure continues replace control.

-F4- Shorted sensor circuit. If this failure appears in the display, the control is sensing a short circuit at the sensor input. This failure is most often caused by loose wires at the connection of shorted sensor leads.

Check sensor connection and leads for loose wires. Replace sensor and check for proper operation. If failure

continues replace control.

-F5- Relay outputs not enabled when cooking. If this failure appears in the display the control cannot turn the relays on even when cooking. The control should be replaced.

-F6- No 60 Hz input. The control does not sense the input power. This failure mode is most often the result of a failed component in the control. However, this failure may also be the result of a very noisy power line. Look for any large electrical noise producing machinery (such as mixers, compressors, dishwashers etc.). If possible, turn these machines off. Reapply power to the oven. If the failure repeats, replace the control. If the failure does not repeat, an electronic control may not work in this application because of noise. You must

-F7- The control has detected that calculated EEPROM check sum is not the same as the expected check sum

RESISTANCE vs. TEMPERATURE CHART FOR INTERNAL OVEN TEMPERATURE SENSOR

The chart below will provide the Ohms at various temperatures. This will enable you to determine if the temperature probe is operable.

The chart is in Degrees Fahrenheit. How to use chart, for 350°, read down to 300 then across to 50, answer is 1654Ohms of resistance.

isolate the supply circuit.

retrieved from the EEPROM. When the control detects this error code, it will disable outputs before the alarm sounds.

TEMP 0° 10° 20° 30° 40° 50° 60° 70° 80° 90°

0° 100° 200° 300° 400° 500°

ROBERTSHAW COM6000 CONTROLLER

932 953 974 995 1016 1038 1059 1080 1101 1122 1143 1163 1184 1205 1226 1247 1267 1288 1309 1329 1350 1370 1391 1411 1432 1452 1472 1493 1513 1533 1553 1574 1594 1614 1634 1654 1674 1694 1714 1733 1753 1773 1793 1813 1832 1852 1871 1981 1911 1930 1949 1969 1988 2008 2027 2046 2065 2085 2104 2123

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