Midco MPG 1.5G Service Manual

BURNER MODEL

BILL OF MAT'L
NUMBER

SERIAL NUMBER #

WIRING DIAGRAM

FOR SERVICE CONTACT:

Name

Address

Phone

Date of Installation

Installation and Service Instructions

909

8471 51

Unipower

MPG Series

Gas Burners

S A F E T Y I N F O R M A T I O N T E R M S : The following terms are used to identify hazards, safety precaution of special

notations and have standard meanings throughout this manual. They are printed in all capital letters using a bold type face
as shown below, and preceded by the exclamation mark symbol. When you see the safety alert symbol and one of the
safety information terms as shown below, be aware of the hazard potential.

DANGER: Identifies the most serious hazards which will result in severe personal injury or death.
WARNING: Signifies a hazard that could result in personal injury or death.
CAUTION: Identifies unsafe practices which would result in minor personal injury or product and property damage.

Midco International Inc.

4140 West Victoria St. - Chicago, Illinois 60646
tel [phone] fax [phone]

web www.midcointernational.com e-mail [e-mail]

Quality Designed for Proven Performance

WARNING: If the information in these instructions
is not followed exactly, a fire or explosion may result,
causing property damage, personal injury or death.

Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any
other appliance.

WHAT TO DO IF YOU SMELL GAS:

 Do not try to light any appliance.


Do not touch any electrical switch; do not use any

phone in your building.

 Immediately phone your gas supplier from another

building. Follow the gas supplier’s instructions. If
you cannot reach your gas supplier call the fire
department.

Installation and service must be performed by a

qualified installer, service agency or the gas supplier.

In the United States, installation must conform with local codes or in
the absence of local codes, with the National Fuel Gas Code, ANSI
Z223.1-latest edition available from American National Standard

Institute. Further reference should be made to the recommendation of
your fuel supplier.
In Canada, installation must conform with local codes or in the
absence of local codes, with Installation Codes for Gas Burning

Appliances and Equipment, CGA Standard CAN/CGA 1-B-149.1
or 2.

WARNING: Additions, changes, conversions and service
must be performed by an authorized Midco representative,
service agency or the fuel supplier. Use only MIDCO specified
and approved parts.

INSTALLER: Inform and demonstrate to the user the correct
operation and maintenance of the gas utilization equipment.
Inform the user of the hazards of storing flammable liquids and
vapors in the vicinity of this gas utilization equipment and
remove such hazards. Affix this manual and associated
literature to the burner.

CODE COMPLIANCE IS THE SOLE RESPONSIBILITY OF THE
INSTALLER.

USER: Retain this manual for future reference. If other than
routine service or maintenance as described in this manual and
associated literature is required, contact a qualified service
agency. DO NOT ATTEMPT REPAIRS. An inadvertent service
error could result in a dangerous condition.

Part 1 Installation

Specifications

1

___________________________

CAUTION: MPG-Series are not intended for outdoor installation and must be protected

from excessive moisture. Provide adequate clearance for service and proper operation.



 Open basements will generally allow sufficient air infiltration, so special provisions will seldom

be required. If the heating plant is located in a separate furnace room or in an unusually tight
basement, permanent means must be provided to supply an ample volume of fresh air for
combustion and boiler room ventilation. A direct opening to the outside air should be provided
sized on the basis of 1/2 square foot of free opening for each 1,000,000 BTU of burner rating
when the vent connector is equipped with a barometric draft control, 11/2 square feet when
equipped with a draft hood. If the ventilation opening is screened, it should be of 11/4" mesh.

Part 1

Installation

2

I Ventilation

The Midco power gas burner, MPG Series, is designed for firing natural gas or propane
gas in most applications. The burner is a self-contained unit including a blower housing
assembly, a burner gas manifold assembly, a burner cartridge, a flame safeguard, and a
main and pilot gas train. The burner is easy to install, it includes mounting the burner to the
gas utilization equipment, piping the main and pilot gas train and connecting the power
supply. Before shipment every burner is operationally fire tested at the factory, for
unassembled valve trains the pilot solenoid and ignition system is tested.

Burner Style Power Type Sensing
Pilot Type Intermittent; Flame Rod Sensing, Spark Ignition(Standard)

Intermittent; UV Sensing, Spark Ignition (Optional)
Interrupted; Flame Rod Sensing, UV Flame Scanner (Optional)

Pilot Safety Instantaneous Electronic Flame Safeguard

Voltage Standard

Controls 120/1/60
Motor 115/1/60

230/1/60

(Optional)

U.L. Listed -U.L.C. Listed
Non UL 220V / 50HZ - Contact Factory

MPG 1.5G **

MPG 2.5G **

1500

2500

325

540

4" W.C.

4

4" W.C.

4" W.C.

4

4" W.C.

Natural Propane

Maximum

Input

1

MBH/HR.*

Maximum

Air

SCFM

3

Models

Inlet Gas Pressure

Required

2

MPG 1.5G

MPG 2.5G

1

/2

3

/4

0.13 - 1.20" W.C.

0.09 - 0.80" W.C.

0.08 - 0.70" W.C.

0.06 - 0.50" W.C.

Natural

Propane

Motor HP

(3450 RPM)

See Table 3

See Table 3

Recommended

Combustion

Chamber

Size

Models

Burner Manifold Pressure

1

*1 MBH=1,000 BTU/HR
** High Turn Down Models available - contact factory

1. Values given based on 0" W.C. firebox pressure, altitudes to 2,000 feet. Derate burner
for altitudes over 2,000 feet by 4% for each 1,000 feet over sea level.

2. Maximum inlet pressure both gases: 14" W.C. Refer to Section VI Piping for high pressure.

3. SCFM=Standard Cubic Feet/Minute

4. Requires special valve train - contact factory

Table 1: Burner Specifications

*1 MBH=1,000 BTU/HR. See Table 6 for gas pressure and air shutter settings

Models

MPG 1.5G

MPG 2.5G

500

850

1500

2500

1500

2500

1400

2450

1.0

1.0

1200

2000

Maximum Capacity in MBH at

Combustion Chamber-

Back Pressure

0" W.C. .25" W.C. .50" W.C.

Minimum

Firing

Rate

MBH*

Maximum

Back
Pressure
in " W.C.

Maximum

MBH* at

Maximum

Back Pressure

Table 2: Maximum Capacity at Specified Back Pressures

500

850

Minimum

Input

1

MBH/HR.*

The opening should be located at least six feet above ground level to prevent accidental
obstruction. If a direct opening to the outside air is not available, an amply sized air duct can be
run to the nearest outside air source or if practical, open stairwells or building corridors
connecting to an outside wall having a ventilating opening can be used for this purpose, provided
that no possibility of accidental closure exists.



 While the spark ignition pilot system performs successfully under moderate or momentary

back draft conditions, it is not intended for operation under sustained reverse draft, for example,
in a building with large ventilating fans but with insufficient make-up air. Even if burner operation
is successful under these conditions, they must be corrected to prevent the hazard of drawing
flue gases into the building. Consult your local gas company when doubt exists concerning boiler
room ventilation.

___________________________



 The heating system, both the gas utilization equipment and the distribution system, should be

in good operating conditions and sufficient to properly heat the building. It should be determined if
any serious faults are present that would cause excessive fuel consumption, unsafe operation or
improper heating, and measures taken to correct them.



 Firing door catches should be filed off or otherwise arranged so that the door will open easily

to relieve pressure. No positive catches should be used. The use of a spring-type door holder is
recommended.

___________________________



 Mount the burner to the gas utilization equipment. A tight seal between the mounting flange

and the front plate should be accomplished using the supplied high temperature rope. When
installing the gas burner the distance from the flange to the blast tube edge should be the same
as the gas utilization equipment wall thickness plus the flange gasket or rope thickness. That
means the burner blast tube will be flush with the inner chamber wall after the burner has been
installed. If the blast tube is extended into the combustion chamber possible damage to the
burner may happen. See Figure 1 & 2 for reference.

3

Part 1 Installation

II Preparation of

the Gas Utilization

Equipment

III Combustion

Chamber

Figure 1: Dry Base Boiler with Combustion

Chamber Liner (Warm Air Furnace

Construction is Similar)

Figure 2: Wet Base Boiler with Unlined

Combustion Chamber

Figure 3: Scotch Marine Boiler

Figure 4: Warm Air Furnaces

I Ventilation

Continued



 The MPG gas burner is designed for "in-shot" firing. It can be fired into the ash pit of a boiler

designed for solid fuels, or it can be fired into the primary heat exchanger of a boiler designed for
liquid or gaseous fuels. The ash pit installation requires a refractory lining.



 The combustion chamber serves to contain and promote combustion and to protect non-heat

exchange surfaces from direct flame contact. Built-up combustion chambers should be made of
2600° insulating firebrick. As an alternative, a monolithic floor can be cast in place, using a high
temperature (2400°) light weight insulating refractory. Check with your supplier to determine the
thickness which will yield equivalent insulating qualities.



 The combustion chamber sizes given in Table 3 are based on the maximum rated burner

capacity. If the input is to be permanently set at a reduced rate the combustion chamber floor
area can be reduced proportionately to the proposed input, with the length as closely
proportioned to twice the width as possible.



 Where recommended size combustion chambers (225,000 BTU/sq. ft.) can be

accommodated, the type of construction shown in Figure 1 should be used. If lack of space
prohibits use of this construction, higher BTU values per square foot can be allowed for by using
the constructions shown in Figures 2 and 3.



 The back wall of the combustion chamber should be carried 2 or 3 courses higher and

overhung to deflect the flames from direct impingement on the rear heat exchanger surface. Hard
firebrick should be used to prevent erosion of the brick by high velocity gases.



 The burner is equipped with a mounting flange for direct attachment to the boiler front. The

burner nozzle must not extend into the combustion chamber. It should be sealed into the opening
as shown in Figures 1 - 4.



 The refractory lined combustion chamber can be omitted in "Scotch Marine" and "Steam

Generator" boilers or warm air furnaces that do not include ash pits. The burner is fired directly
into the heat exchanger, requiring no refractory unless the combustion chamber is so short that
flame would impinge excessively on the rear heat exchanger wall (this is particularly important in
a warm air furnace). Refractory protection is recommended if the length of the primary chamber
is less than 20% larger than the length given in Table 3. In any case, the burner entry wall must
be refractory lined if it is not a heat exchanger surface.

___________________________

WARNING: The chimney shall be inspected for unsafe conditions such as
deteriorated masonry and excessive soot or other blockage or potential blockage.
Installation must conform with local codes or in the absence of local codes with NFPA,
ANSI Z223.1-latest edition.

WARNING: No movable vent connector damper is permitted on any power gas burner
installation. The chimney should be inspected for unsafe conditions such as deteriorated
masonry and excessive soot or other blockage or potential blockage. Check your local
authorities for regulations covering barometric draft regulators on gas equipment.

WARNING: The vent connector shall not be connected to a chimney already venting
solid fuel burning equipment, an incinerator or an open fire place.



 The MPG burner does not depend on chimney draft. Combustion air is supplied by the forced

air blower, which is sufficient to supply adequate air for any normal application. This reduces the
function of the chimney to remove of flue products from the boiler. A chimney height of 15' above
the boiler flue outlet will generally prove ample if the recommended or larger vent connector and
chimney diameters are used. The chimney must of course, extend several feet over the roof of
the building, or adjacent buildings. Vent connector material should be 24 gauge or heavier steel,
galvanized to resist corrosion. The horizontal run of vent connector should be pitched upward
from the appliance flue outlet at least 1/4" to the foot. Avoid excess elbows or other constructional
features that would create excessive resistance to flow of flue products. Fasten joints with sheet
metal screws to prevent sagging. The vent connector should be maintained at least 6" from
combustible building materials; more if it is uninsulated. Where it passes through partitions
constructed of combustible materials a ventilated thimble should be used. Refer to your local
building codes. The vent connector should be firmly cemented into the chimney but must not

4

Part 1 Installation

IV Chimney, Vent

Connector and

Draft Control

Gas Input,

MBH/Hr Width/Height " Length "

500 12" 26"
1000 15" 34"
1500 18" 42"
2000 21" 50"
2500 24" 58"

Table 3: Recommended Combustion

Chamber Minimum Required Dimensions

Max Input, Flue Pipe
MBH/Hr Diameter "

700 9"

950 10"
1400 12"
1950 14"
2500 16"

Table 4: Recommended Size of Flue
Pipe and Chimney - Based on Maximum
Height of 15’ and Lateral Run of 15’

OTE: For actual
vent diameter
information refer to
the ational Fuel
Gas Code Handbook

- Latest Edition

III Combustion

Chamber

Continued

extend beyond the inner face.
Where two or more appliances
use the same chimney, be sure
not to enter the chimney with
both flue pipes at the same level.



 Do not arbitrarily reduce the

vent connector size, since a back
pressure can build up, leading to
possible leakage of flue products
into the room.



 Chimney construction can be

either of brick, preferably tile
lined, or of steel. Joints in the
chimney should be smooth and
leak free to prevent
uncontrollable air infiltration. They
should be made so that
condensation if any, will not
collect in the joints or leak to the
outside.



 If the vent connector must be

extra long, the area of the pipe
and chimney should be increased
or the chimney height must be
increased, or both. Never allow
the horizontal length of the vent
connector to exceed the height of the chimney.



 Two kinds of draft control are acceptable; an A.G.A. type draft hood as illustrated in Figure 5,

or a barometric damper as shown in Figure 6. Use of a draft hood is usually limited to burners
with lower range capacities, while a barometric draft control is suitable for all capacities.
Application should depend on the requirements of the installation.



 If a draft hood is used, it should be of the same size as the vent connector and is free

swinging without interference from surrounding objects so that the velocity pressure of the flue
gases does not interfere with its operation. See Figure 5 for proper installation.



 When any vent connector passes through a partition the draft control must be located in the

same room as the heating appliance. A device which will automatically shut off gas to the burner
in the event of sustained backdraft is recommended if such backdraft might adversely affect
burner operation or if flue gas spillage might introduce a hazard. If such a device is used, it shall

5

Part 1 Installation

Figure 5: Recommended Locations for Draft Hoods

Note:
Figures 3 and 4 :
Copyright by
American Gas
Association.
Used by
permission of the
copyright holder.

Figure 6: Location for Barometric Draft Regulators

Note: Figures 3 and 4 :

Copyright by American Gas Association.

Used by permission of the copyright holder.

IV Chimney, Vent

Connector and

Draft Control

Continued

6

be of the listed type and installed and adjusted by a qualified service technician in accordance
with the manufacturer's instructions.

___________________________



 Electrical installation must be made in accordance with the United States to National Electric

Code, ANSI/NFPA No.70-latest edition or Canadian Electrical Code, Part 1, CSA Standard
C22.1. and applicable local code. If the burner is a part of a gas utilization equipment system,
check the wiring diagram as supplied by the manufacturer.



 The burner when installed, must be wired and grounded in accordance with local codes or in

the absence of local codes, with the National Electric Code ANSI/NFPA No. 70-latest edition.
In Canada, refer to CSA Standard C22.1, "Canadian Electrical Code Part 1".

CAUTION: Refer to the separate wiring diagram included with each burner.



 When wiring, be sure that the electrical power take-off is connected to a permanently live

circuit and use multiple 14 gage copper wire conductors. Provide a fused disconnect switch in the
burner circuit. Each installation must include a limit control to guard against excess temperature
or steam pressure. Steam or vapor systems will require a low water cut-off.

WARNING: Wiring shown is for standard burners. Consult the factory for specific

wiring and have the Bill of Material Number ready when calling.

___________________________

Part 1 Installation

V Electrical

Figure 7A: Wiring Diagram for MPG 1.5G - 120 V

Figure 7B: Wiring Diagram for MPG 2.5G - 120V

7



 Piping must comply with national and local codes.



 Provide a sediment trap, manual safety shut-off valve and union in piping close to burner as

shown in Figure 8:



 To obtain the maximum firing rate of the burner, the fuel gas supply piping must be sized to

provide a minimum of 5" w.c. pressure to the inlet of the combination valve when the burner and
all other gas appliances are on based on valve train size.



 For the usual low pressure gas supply system, 5" to 14" W.C. NATURAL (11" to 14" W.C.

PROPANE) use Table 5 to find the recommended gas supply line size.



 Piping follows normal practices and should be connected to the burner in the manner shown

in Figure 8. If the piping must be rearranged because of space limitations be sure to carry out the
sequence of components illustrated. While the pilot regulator can be mounted in any position, the
main regulator should be mounted upright and in a horizontal run of pipe.



 Run full size pipe or tubing from regulator vent openings to outside of building. Provide no

traps in the vent lines and terminate away from all doors and windows; also make provisions for
keeping rain and foreign objects from entering the vent piping.



 When high supply gas pressure is encountered, as in the case in many industrial plants, the

gas line size can be reduced to allow for a greater pressure drop; however, the size must be
sufficient to deliver the necessary burner gas inlet pressure.

CAUTION: High gas pressure supply lines require the proper pressure reducing
regulators. Install two separate high pressure regulators, of the Tight Shut-Off type
upstream of the low pressure regulators. One sized for main gas input, and one suitable
for the minimum flow regulating capacity of the pilot.





The high pressure regulators may be substituted for the low pressure regulators. If high pressure
regulators are used as substitutes, they must be adjustable down to a minimum of 2"
W.C. outlet pressure for the pilot and 5" W.C. for the main gas. They must be adjustable down to the
maximum burner inlet pressure rating (14" W.C.).

DANGER: Explosion hazard.
Do not use oxygen for pressure testing. An
explosion could occur during initial start-up.



 When the gas supply line is about to be put into service it must be tested to insure that it is gas

tight. Use air or inert gas under pressure and test with soap and water or other liquids to locate
leaks.

CAUTION: Because it is difficult to accurately control pressure, disconnect all low
pressure (14" W.C. max.) components (main and pilot) during supply pipe leak testing.
Exposing low pressure regulators and valves to a pressure over 1/2 PSIG (14" W.C.) will
damage components and void their warranties.

Part 1 Installation

VI Piping

Figure 8: Standard Piping Diagram MPG Burner

Pilot components and manual valves are shipped loose

CAUTION: Do not exceed maximum rated capacity of burner model-See Tables 1 & 2.



 Before gas is introduced to the system, a check must be made to see that there are no open

fittings and to make sure the burner main and pilot manual valves are closed. After checking
above, purge the gas line up to the burner inlet. Purging the air from the gas supply line at this
step will expedite the first light-off.

CAUTION: Purge outside the building. Do not purge into the gas utilization equipment
combustion chamber.

___________________________

Burners are approved for use with NATURAL gas or PROPANE gas and should be used only
with the gas specified on the rating plate.
 The gas input should be set at the heating rate determined by the building heat loss and/or
heating plant survey, but not exceeding the rated maximum input of the gas utilization equipment.

8

Part 1 Installation

VII Main Gas

Input Selection

VI Piping

Continued

20

730
1150
1100
1730
2100
2500
2500
2500
2500
2500

60
400
630
610
960

1150
1800
1850
2500
2500
2500

100
300
480
460
725

870
1370
1400
2200
2500
2500

40
500
785
760

1200
1450
2280
2300
2500
2500
2500

Pipe
Size

1 1/4
1 1/4
1 1/2
1 1/2

2

2
2 1/2
2 1/2

3

3

Natural

Propane

Natural

Propane

Natural

Propane

Natural

Propane

Natural

Propane

200

330
320
500
610
960

980
1550
1700
2500

Approximate Capacity -MBH

Pipe Length

Type

of Gas

Capacities shown are for a
total pressure drop of

0.3"W.C. For 0.5"W.C.
pressure drop, multiply
capacity shown by 1.3 .
Propane capacities shown
are for a total pressure drop
of 0.5” W.C. For higher
permissible pressure drops,
consult your gas supplier.
Source: Gas Engineers
Handbook - 1974

Table 5: Schedule 40

PT Pipe-Capacity Chart

MPG 1.5 (On-Off) Gas Flow & Air Shutter Setting

Firing Rate (MBH/Hr)* 500 700 800 900 1000 1100 1200 1300 1400 1500
Natural gas

manifold pressure 0.13 0.26 0.34 0.43 0.53 0.65 0.77 0.90 1.05 1.20
" W.C. **
Propane gas

manifold pressure 0.08 0.15 0.20 0.25 0.31 0.38 0.45 0.53 0.61 0.70
" W.C. **
Air shutter

position 0.0 0.0 0.2 0.3 0.5 0.8 1.4 2.3 4.0 6.8

MPG 2.5 (On-Off) Gas Flow & Air Shutter Setting

Firing Rate (MBH/Hr)* 850 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500
Natural gas

manifold pressure 0.09 0.29 0.33 0.37 0.41 0.46 0.51 0.56 0.62 0.68 0.74 0.80
" W.C. **
Propane gas

manifold pressure 0.06 0.18 0.20 0.23 0.26 0.29 0.32 0.35 0.39 0.42 0.46 .050
" W.C. **
Air shutter

position 0.0 0.7 0.9 1.1 1.3 1.6 1.8 2.0 2.2 2.5 2.9 3.5

* 1 MBH=1,000 BTU/HR
** Based on zero chamber pressure at sea level (Chamber pressure can be measured at pilot gas pressure tap with pilot gas off

Table 6: Manifold Gas Pressure and Air Shutter Settings

___________________________

1) Check the gas piping for leaks. If a leak is detected it should be located with a
soap suds test and repaired.

2) Make sure that the burner main and pilot gas lines are both completely purged of air.
Don’t purge into the combustion chamber. Purge outside the building.

3) Make sure the burner power switch is off, manual valves of main gas and pilot gas
are closed, and motor is free to rotate.

4) Make the proper settings on all limit controls and set controller to call for heat.

5) Set air shutter to the correct position according to Table 6 and tighten in place.

6) Energize Power On-Off switch, and allow motor to run through the pre-purge of 30
seconds and the pilot ignition cycle. Check the blower wheel for proper rotation.
Viewing from blower inlet side, rotation should be counter-clockwise. With no pilot
gas, the flame safeguard will lock out, stopping the motor.

7) Wait one minute, reset the flame safeguard and open the pilot manual valve with
main manual valve still closed. When pre-purge period of 30 seconds has been
completed the pilot solenoid valve and spark generator will be energized. The pilot
should light and the flame rod senses pilot flame. Adjust the pilot gas pressure to
reach a strong and stable pilot flame according to Table 8. Test for ignition and
stability of pilot several times.

8) Turn off Power On-Off switch. Open Main Manual Shut-off Valve half way.

9) Find the required main gas manifold pressure from the Table 6. Use a Digital Gas
Manometer to measure the main gas manifold pressure.

10) Turn on Power On-Off switch. The burner will start and go through the 30 second
pre-purge period and you should have pilot ignition and then the Main flame should
light

11) Slowly open the Main Manual Shut-off Valve and adjust the gas pressure regulator on
the Main Gas Combination Valve, until the main gas manifold pressure reaches the
required value as shown in Table 6 and the Main Manual Shut-off Valve is wide open.

12) Check the emissions in the flue with a Gas Analyzer, adjust the Air Shutter until
the O

2

level of flue gas is approximately 3.5-4.5 %.

13) Cycle the burner on and off several times and check for Pilot ignition, Main gas
ignition, main gas manifold pressure and O

2

, CO2, and CO readings.

For Hi-Low and Full Mod startup instructions see section XVI

Part 1 Installation

9

VIII Initial Start-

up /Adjustment

On-Off Burners

MPG 1.5 (2 Stage and Full Modulation) Gas Flow & Air Shutter Setting

Firing Rate (MBH/Hr)* 500 600 700 800 900 1000 1100 1200 1300 1400 1500
Natural gas pressure drop

between 2nd valve and main 0.06 0.09 0.12 0.16 0.20 0.24 0.30 0.35 0.41 0.48 0.55
gas flow control valve, " W.C. *
Propane gas pressure drop
between 2nd valve and main 0.03 0.05 0.07 0.09 0.11 0.13 0.16 0.19 0.23 0.26 0.30
gas flow control valve, " W.C. *

Air shutter position 0.0 0.0 0.0 0.2 0.3 0.5 0.8 1.4 2.3 4.0 6.8

MPG 2.5 (2 Stage and Full Modulation) Gas Flow & Air Shutter Setting

Firing Rate (MBH/Hr)* 850 900 1100 1300 1500 1700 1900 2100 2300 2500
Natural gas pressure drop

between 2nd valve and main 0.06 0.06 0.10 0.14 0.18 0.23 0.29 0.35 0.42 0.50
gas flow control valve, " W.C. *
Propane gas pressure drop
between 2nd valve and main 0.03 0.04 0.05 0.06 0.10 0.13 0.16 0.20 0.24 0.28
gas flow control valve, " W.C. *

Air shutter position 0.0 0.0 0.2 0.4 0.7 1.1 1.6 2.0 2.5 3.5

* 1 MBH=1,000 BTU/HR

** Based on zero chamber pressure at sea level (Chamber pressure can be measured at pilot gas pressure tap with pilot gas off

Table 7: Manifold Gas Pressure and Air Shutter Settings

___________________________



 The blower functions to supply a constant and positive supply of air for complete combustion.

Air volume is controlled by an adjustable shutter in the blower inlet.



 No routine service is necessary on the blower other than occasionally cleaning the blower

wheel. If the blower wheel must be replaced, be sure to check the replacement for proper
rotation. The concave sides of the blades must face the blower outlet, and rotation of the wheel
must be toward the outlet. Motor sizes and specifications are given in Table 1. All motors contain
integral motor overload protection, usually manual, occasionally automatic reset.



 Proof of blower operation is

provided by the diaphragm air
switch, which must close its contacts
and maintain them closed when the
blower is running. In case of
malfunction, the diaphragm air
switch must be replaced.

___________________________

A combination integrated redundant main gas valve with an integrated gas pressure regulator is
used on the standard MPG burner.



 The gas pressure regulator is used to automatically reduce and maintain constant gas

pressure to the burner. To vary the outlet pressure, remove the seal cap for access to the
adjusting screw. Turning the screw clockwise will increase outlet pressure, counter-clockwise will
decrease outlet pressure.



 Maximum and minimum allowable gas pressures are shown in Table 1.

___________________________

Note: All burners are equipped with dual valves. Burner construction for special codes and/or
insurance requirements such as Factory Mutual or Industrial Risk Insurers (GAP) may require
alternate construction. (Refer to Section XV Special Equipment.)

10

Part 1 Installation

XIII Main Automatic

Valves

XII Gas Pressure

Regulator

XI Blower and

Motor

Drawer Assembly with Flame Rod

Drawer Assembly with UV Scanner

Figure 9: Drawer Assembly MPG Burner

VIII Initial Start-

up /Adjustment

On-Off Burners

Continued

Orifice Orifice Drill Pilot Gas

Model Type Size " Size Pressure

On-Off A 0.11" #35 2.0"-3.5"

Low Fire Start B 0.076" #48 2.0"-3.5"
(Full Mod and
2-Stage)

Table 8: Pilot Gas Pressure Orifice Size

Open to 7/64" Gap

11



 The Honeywell diaphragm valve supplied on standard burners is of the slow opening, fast

closing type. Closing force combines a gas pressure differential, diaphragm weight and spring.



 When the controller is not calling for heat, the coil is de-energized. The plunger of the three

way actuator is in the down position, so that the bleed is closed and the supply port is open. Gas
flows to the top diaphragm, causing the gas pressure and spring to hold the valve closed.



 With a call for heat, the flame safeguard energizes the coil. This pulls the plunger to the up

position, opening the bleed valve and closing the supply port. The gas then bleeds off the top of
the diaphragm, allowing the gas pressure below to lift the diaphragm, and open the valve. When
all the gas has bled off the top of the diaphragm, the valve is fully opened. In the event of a
power failure during operation, the valve will close. Normal operation will resume upon restoration
of power.



 For general service, tests for gas tightness and proper operation will suffice. If leakage is

observed, replace valve. If the valve will not open, make sure that normal gas pressure is
available at the valve, the bleed line is unobstructed and power is available at the terminals.



 If the valve fails to close, make sure power is off at the terminals and gas flow is in the

direction of the arrow on the valve body. When a malfunction is found to be caused by the valve
operator head, the entire valve must be replaced.



 If the valve will not open, make sure normal gas pressure is available at the valve, the bleed

line is unobstructed, and power is available at the terminals.

___________________________



 Motorized Main On-Off Valves are available on special order burners.



 When the actuator is energized, hydraulic fluid is pumped from a reservoir to a metal bellows.

The bellows transfers the resulting pressure through the drive stem to open the valve.

___________________________



 MPG burners may feature a redundant solenoid gas safety valve. This valve is an On-Off (2

position) valve.



 When the valve operator is electrically energized, a plunger lifts the valve disk off the valve

seat, allowing gas to flow. When the current is broken the valve closes. It will normally require no
service. If the operator malfunctions or the valve leaks replace the entire valve. After replacement
check for leakage.

___________________________

WARNING: Explosion hazard. Do not use this device if it gets wet. It can malfunction

and cause serious injury or death. Replace any device that has been wet.



 Standard MPG burners are equipped with a Honeywell RM7895 microprocessor based burner

control, employing a flame rectification system of flame detection. Burner construction for special
codes and/or insurance requirements such as Factory Mutual or Industrial Risk Insurers (GAP)
may require alternate controls. Refer to Section XV Special Equipment. A safe start and run
control sequence is provided with instantaneous response to presence or loss of flame signal.
Flame failure response time is 3 seconds. Pilot Flame Establishing Period (PFEP) is field
selectable from 4 or 10-seconds. The RM7895 features a pre-purge time (30-seconds for On-Off,
90-seconds for 2-Step or Modulating burners) and a plug-in amplifier. An airflow circuit is also
field selectable to allow either lockout or recycle upon loss of airflow. Five LED's (light emitting
diodes) are provided to display sequence information. Refer to the Honeywell RM7895 literature
for detailed operating information, configuration requirements, testing and service.

INITIATE ("POWER" LED is lit).



 The RM7895 enters the INITIATE sequence when it is powered. The INITIATE sequence

lasts for ten seconds unless the voltage or frequency tolerances are not met (refer to Honeywell
RM7895 literature for criteria). When tolerances are met, the INITIATE sequence will restart. If
the condition is not corrected and the hold condition exists for four minutes, the RM7895 will
lock-out. Causes for hold conditions in the INITIATE sequence are in the Honeywell RM7895
literature.

STANDBY ("POWER" LED is lit).



 The RM7895 is idle in this state of sequencing. When the burner switch, limits, operating limit

controls and all microprocessor monitored circuits are in the correct state for the RM7895 to
continue, sequencing will advance to pre-purge.

1. Diaphragm Main
Automatic Valve

XIV Flame

Safeguard

3. Redundant
Solenoid Gas

Safety Valve

2. Motorized Main
Automatic Valve

Part 1 Installation

Part 1 Installation

PRE-PURGE ("POWER" LED is lit).



 The RM7895 in this application features a pre-purge time of 30-seconds for On-Off, 90-

seconds for 2-Step or Modulating burners.



 Once the STANDBY sequence has a "CALL FOR HEAT" input, normal start-up pre-purge will

be initiated.

A. The blower motor is powered to start the pre-purge sequence.
B. The airflow interlock switch must close in ten seconds of pre-purge or within the

specified purge card timing. Otherwise a recycle to the beginning of pre-purge or
lockout will occur, depending on how the airflow switch selectable jumper is
configured. Refer to Honeywell RM7895 literature for configuration requirements.

IGNITION TRIAL

1. PILOT FLAME ESTABLISHING PERIOD (PFEP)
A. The pilot valve and spark generator are energized.
B. Flame must be proven by the end of the 4 or 10-second PFEP to allow the sequence to
continue. If flame is not proven by the end of PFEP, a safety shutdown occurs.

2. MAIN FLAME ESTABLISHING PERIOD (MFEP)



 After the ignition trials, and with the presence of flame, the main valve is energized.

("MAIN" LED will be lit.) If a flame-out occurs, the RM7895 will lockout or recycle within 3­seconds, depending on "jumper" configuration. Refer to Honeywell literature for proper
configuration.

RUN



 The RM7895 is now in RUN mode and will remain in run mode until the controller input opens,

indicating that the call for heat has been satisfied or a limit has opened. Once this occurs the
RM7895 will sequence back to the STANDBY mode.
Notes:1. During STANDBY and during RM7895 sequencing the "POWER" LED will blink

every four seconds. This is normal.

2. The "ALARM" LED will be lit in the event of any flame failure.

3. To maintain proper operation of this device it MUST be electrically grounded. Refer
to Honeywell RM7895 literature for grounding requirements.

___________________________



 Special equipment, either factory or field installed, can cause variations in the procedures and

descriptions given in this manual. Generally, any burner ordered with special factory installed
equipment will be supplied with the appropriate wiring diagram and related instruction manuals
from the special equipment manufacturer. Consult these manuals to identify any differences in
construction, operation and testing. Field installed special equipment is the responsibility of the
installing contractor.



 For example, when a high/low gas pressure switch is used, the high gas pressure setting must

be higher than the maximum manifold pressure during initial start-up and the low pressure setting
must be set below the normal minimum inlet pressure to prevent nuisance shutdowns during the
start-up procedure.



 After the burner is started, the low pressure setting should be raised until the burner shuts off.

Reduce the setting and set the low pressure switch to restart the burner. Reduce the high
pressure setting until the burner shuts off. Then raise the setting slightly and reset the high
pressure switch to restart the burner. Do not make the adjustments too close to trip points or
nuisance shut downs may occur. Anytime the burner gas supply is shut off with the main manual
valve, the low pressure switch will require resetting.



 If any doubt exists concerning burner operation when special equipment is involved, contact

the installing contractor or MIDCO INTERNATIONAL INC. (front cover).

___________________________

Note: These Instructions are designed for experienced combustion contractors/

technicians.

1) Check the gas piping for leaks. If a leak is detected, it should be repaired.

2) Make sure that the burner main and pilot gas lines are both completely purged of air.
Do not purge into the combustion chamber. Purge outside the building.

3) Make sure the burner power On-Off switch is OFF, manual main gas valve and manual
pilot gas valves are closed and the motor is free to rotate.

4) Make the proper settings on all limit controls and set the operating controller (by others)
to call for heat.

12

XVI Initial

Start Up

Instructions

2-Stage and Full

Modulating Burner

XV Special

Equipment

(OEM Versions)

XIV Flame

Safeguard

Continued

5) Loosen the linkage connecting rod at the ball joint (7/16” wrench) nearest to the
motorized actuator and the U clamp (5/16” deep socket) of the motorized actuator,
and set:

a. air shutter at minimum opening position
b. gas flow control valve at 2 O’clock
c. both crank arms at 7 O’clock

Note: Linkage connecting rod should be parallel to blower scroll housing face.

6) Turn the burner power On-Off switch to ON and allow the motor to run through the
pre-purge and ignition cycle. Check the blower wheel for proper rotation. Viewing from
the blower inlet screen, rotation should be counter-clockwise. After approximately 90
seconds, the flame safe guard will lock out, stopping the motor.

7) Open the pilot manual gas valve leaving the main manual gas valve closed. Reset the
flame safe guard. Motor will start. When the pre-purge period (90 seconds) has
completed, the flame safe guard will energize the pilot solenoid valve and the spark
generator. The pilot should be ignited and the flame rod or UV scanner senses the pilot
flame. Adjust the pilot gas pressure to reach the strongest and most stable pilot flame
signal. See Table 8 for preliminary pilot gas pressure settings. Test several times for
pilot ignition, stability and flame sensing signal.

8) Measure the main gas differential pressure by installing a digital manometer. One gas
pressure tap should be installed in the downstream port of the downstream automatic
main gas safety shutoff valve. The second gas pressure tap should be installed in the
manifold test tap that is located just upstream of the gas flow control valve. See Table
7 for initial differential manifold gas pressure & air shutter settings.

9) Slowly open the main manual gas valve with the main valves energized and watch
through the peep sight glass located on the back of the pilot drawer assembly to make
sure that the main flame ignites.

10) Check the flue gas readings with a combustion gas analyzer. Slowly and manually
adjust the gas flow control valve and/or air shutter to achieve the correct burner low fire
firing rate and proper preliminary flue gas readings (approximately 4 - 5% O

2

and

approximately 9 - 9 ½% CO

2

).

11) Slowly and manually adjust the gas flow control valve and/or air shutter to achieve the
correct burner high fire firing rate and proper preliminary flue gas readings
(approximately 4 - 5% O2and approximately 9 - 9 ½% CO2). Tighten the linkage
connecting rod at the ball joint (7/16” wrench) nearest to the motorized actuator.

12) Check the flue gas readings with a combustion gas analyzer. Adjust the regulator of the
main gas combination valve or the independent main gas pressure regulator and/or the
air shutter to achieve the correct burner high fire firing rate and proper flue gas
readings (approximately 4 - 5% O

2

and approximately 9½ - 10% CO2).

NOTE: For a full modulating burner, check the burner combustion performance at mid
range firing rate and adjust as necessary.

13) Turn the burner power On-Off switch to OFF. Manually move the gas flow control
valve, connecting rod and air shutter to the low fire position. Tighten the U clamp of the
motorized actuator. Move the adjustable stop block of the motorized actuator to the
3 O’clock position and lock it in place. At the Midco control cabinet terminal strips,
disconnect the signal input wires from the remote temperature controller. Place a
temporary jumper from terminal M2 to M3 (this simulates a call for high fire heat).

Note: Circuit from terminal strip 5 to 6 must be closed in order for the burner to fire.

14) Turn the burner power On-Off switch to ON. The burner should start and
sequence as follows:

a. 10 second initiation
b. 90 second pre-purge period
c. Pilot ignition, flame proving
d. Main flame ignition, low fire start
e. Main flame, high fire operation

15) If the measured high fire firing rate is less (more) than the desired value, turn the
burner power On-Off switch to OFF, move the adjustable stop block of the motorized
actuator up (down) and try again until reaching the desired high fire firing rate.

13

XVI Initial

Start Up

Instructions

2-Stage and Full

Modulating Burner

Continued

Part 1 Installation

16) Cycle the burner several times and verify:
a. 10 second initiation period
b. 90 second purge period
c. pilot ignition
b. pilot flame sensing signal is strong and stable
c. main gas ignition
d. low fire firing rate
e. high fire firing rate
f. combustion gas analyzer readings

Adjust if necessary.

17) Turn the burner power On-Off switch to OFF and remove the temporary jumper that

was placed from terminal M2 to M3. Remove the digital monometer and connectors
and replace the plugs on the main gas valve and the main manifold test tap.
Reconnect the signal input wires from the remote temperature controller.

Make sure the thermostat and operating controls are calling for heat. Defective wiring or loose
connections can simulate the component defects outlined below. Check associated wiring before
replacing a component. ELECTRICAL AND FLAME CHECKS MUST BE MADE IN THE

ORDER LISTED.

___________________________

A. No power to flame safeguard
B. Flame safeguard locked out
C. Defective flame safeguard
D. Defective motor relay
E. Motor overload "out"

A. Motor overload "out"
B. Defective motor
C. Defective flame safeguard

A. Defective air switch
B. No air pressure at air switch
C. Defective purge timer
D. Defective flame safeguard

A. No pilot gas
B. Low pilot gas pressure
C. Defective pilot gas regulator
D. Mis-adjusted pilot regulator
E. Blocked pilot regulator vent
F. Defective pilot solenoid valve
G. Defective spark electrode
H. Mis-adjusted spark electrode
I. Defective spark cable
J. Defective spark generator
K. Clogged or incorrect pilot orifice
L. Air orifice missing
M. Clogged pilot air tube
N. Defective flame safeguard

14

IV Pilot Does

ot Light, Flame

Safeguard Locks Out

I Motor Fails

II Motor Fails to

Start, Flame,

Safeguard Energized

III Motor Runs

Continuously , o

Lighting Attempt

Trouble Chart

XVI Initial

Start Up

Instructions

2-Stage and Full

Modulating Burner

Continued

Part 2

Service

Part 1 Installation

A. Poor flame signal
B. Poor pilot flame
C. Misadjusted pilot regulator
D. Low gas pressure
E. Misadjusted air shutter
F. Defective flame rod wire
G. Defective or Mis-adjusted flame rod
H. Defective amplifier
I. Defective flame safeguard

A. Low gas pressure
B. Mis-adjusted main regulator
C. Blocked regulator vent
D. Defective main regulator
E. No power at main valve(s)
F. Blocked main valve bleed line (if equipped)
G. Defective main valve(s)
H. Closed test cock
I. Defective flame safeguard

A. Poor pilot
B. Pilot gas pressure drops severely when main gas valve opens
C. Mis-adjusted pilot regulator

A. Low gas pressure
B. Defective main regulator
C. Mis-adjusted main regulator
D. Too much air
E. Partially closed test cock

A. High gas pressure
B. Defective main regulator
C. Mis-adjusted main regulator
D. Too little air
E. Dirty blower wheel

A. Defective valve(s)
B. Defective valve actuator
C. Dirty valve seat

A. Low voltage
B. Defective motor
C. High ambient temperature
D. Dirty blower wheel

A. See IV above
B. See V above
C. See VI above

Note: Some of the probable causes listed above apply only to certain models as indicated,

therefore some may not apply to your particular case.

15

VI Pilot Lights,

o Lockout on

Flame Safeguard,

o Main Gas

VIII Short Main Flame

VII Main Flame

Lights, But Goes out,

Pilot Re-lights

XI Motor Overload

Frequently Trips Out

XI Flame Safeguard

eeds Frequent

Re-setting

X Main Valve(s) Fail

to Shut Off or Leaks

IX Long Hazy Flame

V Pilot Lights,

Flame safeguard

Locks Out

Midco International Inc. 4140 West Victoria Street * Chicago, Illinois 60646

tel [phone] fax [phone] web www.midcointernational.com email [e-mail]

909

8471 51

Part 2 Service