Allied Engineering MG50, MG75, MG100, MG125, MG150 Installation Manual

INSTALLATION AND SERVICE MANUAL

MG & SG SERIES BOILERS

FOR MODELS MG-50 TO MG-150 AND SG-135 TO SG-270

SEE REAR COVER FOR INDEX

This manual must only be used by a qualified
heating installer, service technician or gas supplier.

See Section 3.10 for Installer’s Checklist

See Section 4.3 for Service Checklist

Manufactured by

Allied Engineering Company

Manufacturers of Gas and Electric Boilers, Stainless Steel Tanks, Heat Exchangers and Electric Boosters.

94 Riverside Drive, North Vancouver, B.C. V7H 2M6 • Telephone [phone] • FAX [phone]

PN2152451 Price $10

Division of E-Z-Rect Manufacturing Ltd.

Branches: Calgary • Edmonton • Toronto

A

A

MG SERIES BOILERS

DIMENSIONS AND SPECIFICATIONS

Standard Model Includes:

• Zone Control Board with Transformer

• Stainless Steel Burners

• Combination Gas Valve

• Dual Safety High-Limit Aquastat

• Temperature / Pressure Gauge

• A.S.M.E. Pressure Relief Valve

• Drain Valve

• Draft Hood

• Blocked Vent Safety Switch

• Flame Roll-out Safety Switch

• Automatic Vent Damper

“PS” Packaged Models Include
Standard Model Parts plus:

• Circulating Pump

• Custom Cast Iron Pump Adapter

• Expansion Tank

• Air Purger

• Combination Fill / Regulator Valve

• Automatic Air Vent

llow 18” (457 mm) minimum in front for servicing.

Minimum clearances to combustible material: Top 24” (610 mm), Sides 2” (51 mm), Rear 2” (51 mm), Flue 6" (153 mm)

PPROVED FOR COMBUSTIBLE FLOORS & CLOSET INSTALLATION.

The Super Hot product improvement program may result in changes to the design and / or specifications being made without notice.

MODEL

NUMBER

MG50 50 14.7 42.4 12.4 11.5 29.2 5.25 13.3 4.0 10.2 39.2 99.6 4.5 11.4 125 57

MG75 75 22.0 63.5 18.6 14.5 36.8 5.25 13.3 5.0 12.7 39.5 100.3 4.5 11.4 150 68

MG100 100 29.3 84.6 24.8 17.5 44.5 5.25 13.3 5.0 12.7 39.5 100.3 4.5 11.4 175 80

MG125 125 36.6 105.5 30.9 20.5 52.1 6.50 16.5 6.0 15.2 40.5 102.9 4.5 11.4 200 91

MG150 150 44.0 126.5 37.1 23.5 59.7 6.50 16.5 6.0 15.2 40.5 102.9 4.5 11.4 225 102

* For altitudes above 2,000 feet, refer to Section 3.6 to determine the appropriate Input derate or contact the factory.
** Output based on boilers equipped with electronic ignition.

INPUT* OUTPUT** DIM A DIM B DIM C DIM D DIM E

MBH kW MBH kW in cm in cm in cm in cm in cm lb kg

SHIPPING
WEIGHT

Options:

• Natural Gas add suffix "N" - Propane models add suffix “P”

• Electronic Ignition add suffix “E” - Hot Surface Ignition add suffix “HS”

• Add 35 pounds weight (16 kg) for packaged boilers - add suffix “PS”

2

A

A

SG SERIES BOILERS

DIMENSIONS AND SPECIFICATIONS

Standard Model Includes:

• Zone Control Board with Transformer

• Stainless Steel Burners

• Combination Gas Valve

• Dual Safety High-Limit Aquastat

• Temperature / Pressure Gauge

• A.S.M.E. Pressure Relief Valve

• Drain Valve

• Draft Hood

• Blocked Vent Safety Switch

• Flame Roll-out Safety Switch

• Automatic Vent Damper

“PS” Packaged Models Include
Standard Model Parts plus:

• Circulating Pump

• Custom Cast Iron Pump Adapter

• Expansion Tank

• Air Purger

• Combination Fill / Regulator Valve

• Automatic Air Vent

llow 24” (609 mm) minimum in front for servicing.

Minimum clearances to combustible material: Top 24” (610 mm), Sides 2" (51 mm), Rear 2" (51 mm), Flue 6" (153 mm)

PPROVED FOR COMBUSTIBLE FLOORS & CLOSET INSTALLATION.

The Super Hot product improvement program may result in changes to the design and / or specifications being made without notice.

MODEL

NUMBER

SG135 135 39.6 112 32.8 14.7 37.3 9.5 24.1 6.0 15.2 45.3 115 4.5 13.9 0.50” 191 87

SG180 180 52.8 150 44.0 17.7 45.0 9.5 24.1 6.0 15.2 45.3 115 4.5 13.9 0.50” 222 101

SG225 225 65.9 188 55.1 20.7 52.6 9.5 24.1 7.0 17.8 46.5 118 6.5 16.5 0.75” 253 115

SG270 270 79.1 225 65.9 23.7 60.2 9.5 24.1 8.0 20.3 47.6 121 7.5 19.0 0.75” 284 129

* For altitudes above 2,000 feet, refer to Section 3.6 to determine the appropriate Input derate or contact the factory.
** Output based on boilers equipped with electronic ignition.

INPUT* OUTPUT** DIM A DIM B DIM C DIM D DIM E

MBH kW MBH kW in cm in cm in cm in cm in cm NPT lb kg

GAS

CONN. F

SHIPPING
WEIGHT

Options:

• Natural Gas add suffix "N" - Propane models add suffix “P”

• Electronic Ignition add suffix “E” - Hot Surface Ignition add suffix “HS”

• High/Low fire add suffix “M” - Consult Factory for Availability

• Add 45 pounds weight (20 kg) for packaged boilers - add suffix “PS”

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MG & SG Series Boilers – Installation and Service Manual

ABOUT OUR MANUALS

Your Super Hot boiler has been provided with two manuals:

• User's Information Manual - This manual is intended for the owner or user of the boiler and provides
information on routine operation and maintenance, and emergency shutdown.

• Installation and Service Manual - This manual must only be used by a qualified heating installer,
service technician or gas supplier. Installation or service by anyone unqualified to do so may

result in severe personal injury, death or substantial property damage.

Both manuals should be kept in the envelope provided and affixed adjacent to the boiler so that they are
readily available for future reference.

Lighting Instructions Section 1

1.1 SAFETY INSTRUCTIONS

WARNING

If you do not follow these instructions exactly, a fire or explosion may result causing property
damage, personal injury or loss of life.

A. BEFORE LIGHTING smell all around the

boiler area for gas. Be sure to smell next to
the floor because some gas is heavier than
air and will settle on the floor.

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 call your gas supplier from a

neighbor's phone. Follow the gas
supplier's instructions.

• If you cannot reach your gas supplier,

call the fire department.

B. Use only your hand to push in or turn the gas

control knob. Never use tools. If the knob will
not push in or turn by hand, don't try to repair
it, call a qualified service technician. Force or
attempted repair may result in a fire or
explosion.

C. Do not use this boiler if any part has been

under water. Immediately call a qualified
service technician to inspect the appliance
and to replace any part of the control system
and any gas control which has been under
water.

1.2 LIGHTING INSTRUCTIONS

Determine the ignition system that applies from the list below and go to the applicable lighting instruction
section.

• Standing pilot with combination gas valve (Section 1.3)

• Intermittent electronic & hot surface ignition with combination gas valve (Section 1.4)

If you are unsure which type of gas valve or ignition system your boiler is equipped with, check the
lighting instructions sticker on the boiler or contact the factory.

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MG & SG Series Boilers – Installation and Service Manual

1.3 LIGHTING INSTRUCTIONS FOR STANDING PILOT WITH COMBINATION

GAS VALVE.

1 This boiler has a pilot which must be lighted

by hand. When lighting the pilot, follow these
instructions exactly. Ensure gas supply to
boiler is turned on.

2 STOP! Read the safety instructions in

Section 1.1.

3 Set the room thermostat to lowest setting.
4 Turn off all electrical power to the boiler.
5 Remove control access panel if necessary.
6 Push in gas control knob slightly and turn

clockwise

NOTE: Knob cannot be turned from "PILOT"

to "OFF" unless knob is pushed in slightly.
Do not force.

7. Wait five (5) minutes to clear out any gas.
Then smell for gas, including near the floor.
If you smell gas, STOP! Follow "A" in the
safety instructions in Section 1.1. If you don't
smell gas, go to step 8.

 to "OFF".

8. Find pilot burner - follow
aluminum tube from gas valve.
The pilot is on the far left side
of the burner tray.

9. Depress gas control knob and
turn counterclockwise

"PILOT".

10. Push in control knob all the way and hold in.
Immediately light the pilot with a match.
Continue to hold the control knob in for about
(1) minute after the pilot is lit. Release knob
and it will pop back up. Pilot should remain lit.
If it goes out, repeat steps 6 through 10.

• If the knob does not pop up when

released, stop and immediately call your
service technician or gas supplier.

• If the pilot will not stay lit after several

tries, turn the gas knob clockwise
"OFF" and call your service technician or
gas supplier.

11. Turn gas control knob counterclockwise
"ON".

12. Replace control access panel if necessary.

13. Turn on all electrical power to the boiler.

14. Set room thermostat to desired setting.

To turn off gas to boiler or emergency shut-off

Follow Section 1.5.

 to

PILOT
BURNER

THERMO­COUPLE

 to

 to

1.4 LIGHTING INSTRUCTIONS FOR INTERMITTENT ELECTRONIC &
HOT SURFACE IGNITION WITH COMBINATION GAS VALVE.

1. This boiler is equipped with an ignition device
which automatically lights the pilot. Do not
to light the pilot by hand. Ensure gas supply
to the boiler is turned on.

2. STOP! Read the safety instructions in
Section 1.1.

3. Set the room thermostat to lowest setting.

4. Turn off all electrical power to the appliance.

5. Remove control access panel if necessary.

6. Push in gas control knob slightly and turn
clockwise

NOTE: On some gas valves the knob cannot

 to "OFF".

try

be turned to "OFF" or “ON” position unless
knob is pushed in slightly. Do not force.

7. Wait five (5) minutes to clear out any gas.
Then smell for gas, including near the floor. If
you smell gas, STOP! Follow "A" in the safety
instructions in Section 1.1. If you don't smell
gas, go to the next step.

8. Turn gas control knob counterclockwise

 to "ON".

9. Replace control access panel if necessary.

10. Turn on all electrical power to the Boiler.

11. Set room thermostat to desired setting.

12. If the appliance will not operate, follow the
instructions "To Turn Off Gas To Boiler" in
Section 1.5 and call your service technician or
gas supplier.

To turn off gas to boiler or emergency shut-off

Follow Section 1.5.

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MG & SG Series Boilers – Installation and Service Manual

1.5 TO TURN OFF GAS TO THE BOILER OR EMERGENCY SHUT-OFF.

WARNING

Should boiler overheat, or the gas supply fail to shut off, do not turn off or disconnect the
electrical supply to the circulating pump. Instead, shut off the gas supply at a location external
to the boiler.

1. Set the thermostat to the lowest setting.

2. Turn all electrical power to the boiler off.

3. Remove control access panel on the boiler if necessary.

4. Push in gas control knob slightly and turn clockwise

5. Replace control access panel if necessary.

 to "OFF". Do not force it.

Installation Instructions Section 2

2.1 RECEIVING

INSPECT SHIPMENT FOR POSSIBLE DAMAGE. All goods are carefully manufactured, inspected,

checked and packed by experienced workers. The manufacturer's responsibility ceases upon delivery of
goods to the carrier in good condition. Any claims for damage, shortage in shipment or non-delivery must
be filed immediately against the carrier by the consignee.

Use care when receiving and unpacking the boiler. Dropping the boiler may cause damage and prevent
safe and proper operation.

2.2 INSTALLATION CODES AND REQUIREMENTS

All applicable national, provincial/state, and local codes, laws, regulations, and ordinances must be
followed. They expand on and take precedence over any recommendations in this booklet. Authorities
having jurisdiction shall be consulted before installations are made.

In Canada, the installation must conform to the requirements of the authority having jurisdiction or, in the
absence of such requirements, to the CAN/CSA B149 Installation Codes (current edition). All electrical
wiring must be in accordance with the Canadian Electrical Code, CSA C22.1 Part 1 (current edition) and
applicable local codes.

In the United States of America, the installation must conform to the requirements of the authority
having jurisdiction or, in the absence of such requirements, to the National Fuel Gas Code, ANSI Z223.1
(current edition). All electrical wiring must be in accordance with the National Electrical Code, ANSI/NFPA
70 (current edition) and applicable local codes.

Where required by the authority having jurisdiction, follow the Standard for Controls and Safety Devices
for Automatically Fired Boilers, ANSI/ASME CSD-1 (current edition).

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MG & SG Series Boilers – Installation and Service Manual

2.3 LOCATION

MG and SG boilers are intended for indoor installation only. Observe the following minimum clearances
from the boiler to combustible materials:

Minimum Clearances to Combustible Materials

Model

MG

SG

• Minimum clearance from the boiler front to combustible materials for SG and MG is 6 in (153 mm);
however, a front clearance of 18" (457 mm) for MG boilers and 24” (609 mm) for SG boilers is
recommended for servicing.

• Maintain a clearance of 6" (152 mm) from draft hood and the flue pipe in any direction.

• Allow ample space for boiler inlet and outlet connections, and gas connection.

• Boiler must be installed on a stable and level foundation.

• MG & SG Series boilers can be installed on a combustible floor but must not be installed directly on

carpeting.

• A hot water boiler installed above radiation level must be provided with a low water cutoff
device at the time of boiler installation.

• This boiler must be installed such that gas ignition system components are protected from water
(dripping, spraying, rain, etc.) during appliance operation and service.

Sides Rear Top Front (service)

in. mm in. mm in. mm in. mm

2 51 2 51 24 610 18 457

2 51 2 51 24 610 24 610

2.4 GAS SERVICE PIPING

The boiler and its gas connection must be leak tested before placing the boiler in operation. The gas
controls furnished are suitable for a maximum operating gas pressure of 1/2 psi (14 inches water
column).

The boiler and its individual shutoff valve must be disconnected from the gas supply piping system during
any pressure testing of that system at test pressures in excess

The boiler must be isolated from the gas supply piping system by closing its individual manual shutoff
valve during any pressure testing at test pressures equal to or less than
column).

A manual main shut-off valve should be installed in the gas line outside the boiler jacket and as required
in Section 2.2. The valve should be readily accessible for turning on and off.

A drip pocket or sediment trap should be installed in the gas supply line upstream of the gas controls and
as close to the boiler as possible (example shown in Figure 3 in Section 6).

The pipe compound used should be resistant to the action of liquefied petroleum gases. Check for gas
leaks in piping before placing the boiler in operation by using a soap and water solution. DO NOT USE

AN OPEN FLAME.

INSTALLER MUST IDENTIFY EMERGENCY SHUT-OFF DEVICES.

All piping and fittings must be installed as per codes in Section 2.2.

of 1/2 psig (14 inches water column).

1/2 psig (14 inches water

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MG & SG Series Boilers – Installation and Service Manual

2.5 AIR SUPPLY FOR COMBUSTION AND VENTILATION

A sufficient air supply MUST be provided to this boiler. Air openings to the boiler room provide the air for
combustion, flue gas dilution and ventilation and are always required, regardless whether the air is taken
from inside or outside. The air opening size and location (as well as other air supply and venting
considerations) must conform to Section 2.2.

The boiler room must never be under a negative pressure. Always provide air openings sized not only to
the dimensions required for the total input of all fuel-fired appliances in the boiler space, but also to
handle the air movement rate of any exhaust fans or air movers using air from the building or space.

The venting terminations must always be kept clear of obstructions (i.e. snow, ice, etc.). Louvers and
grilles used in the air supply and ventilation system should be kept clear of any dust, dirt, or debris which
will block proper air flow.

2.6 CORROSIVE ATMOSPHERES

If a gas boiler is to be installed near a corrosive or potentially corrosive air supply, the boiler should be
isolated from it and outside air should be supplied as recommended in Section 2.5.

Chemical vapors from products containing chlorine or fluorine must be avoided. Even though these
chemicals may be safe to breathe, corrosive substances can become liberated when passed through a
gas flame. Even at low concentrations, these chemicals can significantly contaminate the air supply and
shorten the life of any gas burning appliance. The following is a list of some of the products which should
be avoided:

• bleaches and chlorinated cleaning products

• paints and sprays

• water softeners (calcium or sodium chloride)

• leaking refrigeration equipment

• freon from common aerosol dispensers

These chemicals are especially commons near swimming pools, beauty shops, dry cleaning
establishments, laundry areas, workshops, and garages. The warranty is void when failure is due to

corrosion.

2.7 VENTING

The responsibility of providing a suitable vent of adequate draft capacity and in good usable condition is
that of the gas fitter/installer. Interference with the air supply for the boiler shall be prohibited.

Vent installation and type of gas vent or vent connector MUST follow all applicable national,
provincial/state, and local codes, laws, regulations, and ordinances as described in Section 2.2.

For boilers for connection to gas vents or chimneys, vent installations shall be in accordance with Part 7,
Venting of Equipment, of the National Fuel Gas Code, ANSI Z223.1 or Section 7, Venting Systems and
Air Supply for Appliances, of the CAN/CGA B149, Installation Codes, or applicable provisions of the local
building codes.

The venting shall be supported as required by applicable code(s). Horizontal runs shall slope upward not
less than ¼ inch per foot (21 mm/m) from the boiler to the vent terminal.

This unit must be installed with the factory supplied draft hood in place. The draft hood is a safety device
designed to control chimney drafts that might affect combustion or blow out the pilot. The draft hood
supplied with the boiler must not be altered. The minimum skirt height as indicated on the draft hood
must be maintained.

Vent connectors serving the boiler must not be connected into any portion of mechanical draft systems
operating under positive pressure.

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MG & SG Series Boilers – Installation and Service Manual

Vent Terminal Information

The minimum distance from the termination of a vent terminal to adjacent public walkways, adjacent
buildings, openable windows and building openings shall be not less than those values specified in the
National Fuel Gas Code, ANSI Z223.1 and/or CAN/CGA Installation Codes.

For proper operation, the vent terminal must be kept free of snow and other debris at all times.

To prevent discoloration and degradation of building materials by flue gases and flue gas condensation,
ensure that the vent terminal is installed clear of nearby obstacles. In all cases, installation shall be in
accordance with code.

Maintain a minimum clearance of 4 feet (1.22 m) horizontally, and in no case above or below, unless a 4
foot (1.22 m) clearance is maintained from electric meters, gas meters, regulators and relief equipment.

Removal of an Existing Boiler

When an existing boiler is removed from a common venting system, the common venting system is likely
to be too large for proper venting of the appliances connected to it.

At the time of removal of an existing boiler, the following steps shall be followed with each appliance
remaining connected to the common venting system placed in operation, while the other appliances
remaining connected to the common venting system are not in operation.

a) Seal any unused openings in the common venting system.

b) Visually inspect the venting system for proper size and horizontal pitch and determine there is no

blockage or restriction, leakage, corrosion and other deficiencies which could cause an unsafe
condition.

c) Insofar as is practical, close all building doors and windows and all doors between the space in which

the appliances remaining connected to the common venting system are located and other spaces of
the building. Turn on clothes dryers and any appliance not connected to the common venting
system. Turn on any exhaust fans, such as range hoods and bathroom exhausts, so they will
operate at maximum speed. Do not operate a summer exhaust fan. Close fireplace dampers.

d) Place in operation the boiler being inspected. Follow the lighting instructions. Adjust the thermostat

so the boiler will operate continuously.

e) Test for spillage at the draft hood relief opening after 5 minutes of main burner operation. Use the

flame of a match or candle, or smoke from a cigarette, cigar or pipe.

f) After it has been determined that each appliance remaining connected to the common venting system

properly vents when tested as outlined above, return doors, windows, exhaust fans, fireplace
dampers and any other gas burning appliance to their previous conditions of use.

g) Any improper operation of the common venting system should be corrected so the installation

conforms with the National Fuel Gas Code, ANSI Z223.1 and/or CAN/CGA Installation Codes. When
re-sizing any portion of the common venting system, the common venting system should be resized
to approach the minimum size as determined using the appropriate tables in Part 11 of the National
Fuel Gas Code, ANSI Z223.1 and/or CAN/CGA Installation Codes.

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MG & SG Series Boilers – Installation and Service Manual

2.8 AUTOMATIC VENT DAMPER

This boiler is supplied with an automatic vent damper. The following instructions must be observed:

• The automatic vent damper should be installed at the top of the factory supplied draft hood (Figure 1 ­Alternate 3). No modifications to the automatic vent damper are permitted.

• The venting system must be arranged so that only the boiler is served by the automatic vent damper
with which it was supplied.

• Connect the wiring harness from the boiler to the automatic vent damper as indicated on the supplied
wiring drawings.

• The automatic vent damper position indicator should be clearly visible after installation.

• A minimum clearance of not less than 6 inches (153 mm) must be maintained between the automatic

vent damper device and combustible construction. Provision must be made for service access to the
automatic vent damper.

• The automatic vent damper must be in the open position when the boiler's main burner is operating.

• For orientation other than vertical, refer to automatic vent damper installation instructions

2.9 BLOCKED VENT AND FLAME ROLL-OUT SAFETY SWITCHES

All boilers with an input of 300,000 Btu/h and under are equipped with blocked vent and flame roll out
safety switches. The blocked vent safety switch is installed in the clip provided on the draft hood (Figure
1 - Alternate 1) or is mounted with screws (Figure 1 - Alternate 2). The blocked vent safety switch is pre­wired at the factory either directly to the boiler controls (Figure 1 - Alternate 1 & 2), or through a wiring
harness for a boiler with an automatic vent damper (Figure 1- Alternate 3). If the vent becomes blocked a
boiler shut down will occur. Ensure that the vent is free of obstructions.

The flame roll out safety switch will cause a boiler shutdown if the heat exchanger becomes blocked with
soot or corrosion.

WARNING

Shut down of the boiler by either the “Blocked Vent” or the “Flame Roll-out” safety switch is an
indication that carbon monoxide may be improperly venting into the premises and the boiler
must be serviced by a qualified person who is capable of determining the cause of the shut
down and can take corrective action. Carbon monoxide is a lethal, colorless and odorless gas.

ALTERNATE 1 ALTERNATE 2

ALTE RNAT E 3

FIGURE 1 - MOUNTING LOCATION OF BLOCKED VENT SAFETY SWITCH AND WIRE ROUTING

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MG & SG Series Boilers – Installation and Service Manual

2.10 BOILER PIPING SYSTEM

The boiler piping system of a hot water boiler connected to heating coils located in air handling units
where they may be exposed to refrigerated air circulation must be equipped with flow control valves or
other automatic means to prevent gravity circulation of the boiler water during the cooling cycle.

The boiler, when used in connection with a refrigeration system, must be installed so the chilled medium
is piped in parallel with the boiler with appropriate valves to prevent the chilled medium from entering the
boiler.

2.11 CORROSION PREVENTION (INTERNAL)

We strongly recommended the use of oxygen barrier tubing to protect the system and its components
from corrosion. Chemical inhibitors are not recommended, as their improper use or maintenance can
cause accelerated corrosion, resulting in premature failure of the boiler heat exchanger and/or system
components. Corrosion is a preventable condition and is not covered by the Super Hot product warranty.
Should your system include "non-oxygen-barrier-tubing" please contact the factory or your heating
professional for recommendations.

2.12 SYSTEM OPERATING REQUIREMENTS

WARNING

If you do not follow these instructions exactly, a fire or explosion may result causing property
damage, personal injury or loss of life.

Avoid unnecessary replenishment of system water. It can allow oxygen to enter the system and cause
serious corrosion problems. As well, minerals dissolved in the water supply will precipitate when heated;
minerals preferentially deposit in the heat exchanger. Do not draw water from the heating system for
cleaning, flushing, etc.

Super Hot MG and SG series boilers are designed for use in closed loop systems and are not intended
for open systems, as in heating pool water or systems where water is constantly replenished. Operating
the boiler in an open system will result in premature failure of the heat exchanger. Super Hot boilers
may be used to heat water in open systems indirectly by installing a heat exchanger, such as the Super
Hot C-Coil, to separate open and closed systems.

Heating systems with low temperature return water may cause flue gas moisture to condense on the
boiler heat transfer surfaces, causing corrosion and restricting flue gas flow. Also, low temperature return
water may overcool the flue gases, resulting in reduced vent suction. These are natural phenomena and
are independent of the boiler design. As a guide to avoiding such corrosion and draft problems, it is
imperative that the return water be not less than 135°F (57°C).

MG AND SG SERIES BOILERS MUST ALWAYS BE USED WITH FORCED SYSTEM CIRCULATION.

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MG & SG Series Boilers – Installation and Service Manual

2.13 PRESSURE RELIEF VALVE

A pressure relief valve is supplied as standard equipment. The pressure relief valve is extra protection
against damage that could be caused by malfunctioning controls or excessive water pressure. If a
pressure relief valve is not used, the warranty is void.

The pressure relief valve should be installed on the boiler outlet with its spindle vertical. The connection
between the boiler and the relief valve must have at least the area of the valve inlet.

A discharge pipe should be used. The discharge pipe outlet should be positioned over a suitable drain
and so arranged that there will be no danger of being scalded. The discharge pipe must pitch down from
the valve and should be no smaller than the outlet of the valve. The end of the discharge pipe should not
be concealed or threaded and should be protected from freezing. Extensive runs, traps or bends could
reduce the capacity of the pressure relief valve.

No valve of any type should be installed between the pressure relief valve and unit or in the discharge
pipe. The pressure relief valve is a code requirement. Field installation of the relief valve must be
consistent with the ANSI/ASME Boiler and Pressure Vessel Code, Section IV.

Avoid contact with the hot water discharged to prevent personal injury.

2.14 ELECTRICAL WIRING

All electrical wiring must conform with the requirements in Section 2.2.

Run a separate circuit from the electrical service panel through a fused disconnect switch to the boiler.
This boiler must be electrically bonded to ground in accordance with the requirements of the authority
having jurisdiction or, in the absence of such requirements, with the National Electrical Code, ANSI/NFPA
70 (current edition) and and/or the Canadian Electrical Code, CSA C22.1 Part 1 (current edition). Field
wiring shall conform to Section 2.2 and to the temperature limitations of Type T [63°F (35°C) rise] or
better.

Make connections as shown in the wiring diagrams provided. For details of electrical wiring for different
pilots and controls, refer to wiring diagrams included in this manual.

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MG & SG Series Boilers – Installation and Service Manual

Startup Instructions Section 4

3.1 PRE-STARTUP

a. Fill entire heating system with water and vent or purge air from system. Add water as needed to

reach boiler operating pressure. Water should be of suitable quality. Do not use water with high
hardness.

b. Check for and repair any leaks in water piping.
c. Check burners to see that they are not dislodged.
d. Check for proper installation of pressure relief valve, draft hood, and venting.
e. Check that the electrical wiring matches the wiring diagram in this manual or on the boiler.
f. Check if the flame roll out safety switch and blocked vent safety switch are properly located and

wired.

g. Use a soap solution to check for leaks in gas piping from meter to boiler pilot and manifold. Repair

and retest any leaks found.

h. Operate circulating pump and vent all radiation units and high points in system piping.

3.2 STARTUP

WARNING

The following instructions are intended as a guide for qualified persons. Before lighting the
boiler, the pre-startup instructions of Section 3.1 MUST be performed. If you do not follow these
instructions exactly, a fire or explosion may result causing property damage, personal injury or
loss of life.

WARNING

Should boiler overheat, or the gas supply fail to shut off, do not turn off or disconnect the
electrical supply to the circulating pump. Instead, shut off the gas supply at a location external
to the boiler.

a. Standing pilot

1) Make sure Gas Valve and all electrical power to the boiler are "OFF".

2) Connect a manometer at the pressure tapping on the downstream side of gas valve.

3) Supply gas as far as the pilot only, ignite as per lighting instructions in Section 1.3, and adjust the

4) Set the thermostat above room temperature. Open the gas valve to turn on main burner.

5) Assure that all other gas appliances are turned off, including their pilot flames.

6) Check manifold pressure reading on the manometer and make necessary adjustments. Check

7) Turn Gas Valve to "OFF" and listen for the audible click which signifies that the automatic safety

8) Before re-lighting, wait 5 minutes with the Gas Valve closed to allow all unburnt gas to vent.

9) Return thermostat and controls to normal operation settings.

pilot as described in "Pilot Flame" in Section 3.3.

burner input to match rating plate input.

valve has closed. This should occur within 90 seconds.

Then smell for gas, including near the floor. If you smell gas, STOP! Follow the safety
instructions provided in Section 1.1 under WHAT TO DO IF YOU SMELL GAS. Remember that
propane does not vent upward naturally.

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MG & SG Series Boilers – Installation and Service Manual

b. Intermittent pilot

This boiler does not have a continuous pilot flame. It is equipped with an ignition device which
automatically lights the pilot. Do not try to light the pilot by hand.

In the event of failure of any component, either the system will not operate or it will go into safety lockout.

1) Make sure the Gas Valve and all electrical power to the boiler are "OFF".

2) Set room thermostat to the lowest setting.

3) Connect a manometer at pressure tapping on downstream section of gas valve.

4) Wait five minutes to clear out any gas. If you smell gas, STOP! Follow the safety instructions

provided in Section 1.1 under WHAT TO DO IF YOU SMELL GAS. Remember that propane does
not vent upward naturally.

5) Check the ignition control module as follows:

a) Set thermostat above room temperature to call for heat and turn power on for the boiler.
b) Watch for spark at pilot burner on units equipped with spark ignition. All models will

automatically lockout if no pilot flame is detected within 15 seconds. Automatic retry will
occur in 5 minutes.

6) Turn Gas Valve to ON. Pilot burner should ignite, followed by main burners. Check main and

pilot burners and adjust pilot, if necessary, as described in Section 3.3.

7) Assure that all other gas appliances are turned off, including their pilot flames.

8) Check manifold pressure reading on the manometer and make necessary adjustments. Check

burner input to match rating plate input.

9) Return thermostat and controls to normal operation settings.

c. Hot Surface Ignition

This boiler does not have a continuous pilot flame. It is equipped with an ignition device which
automatically lights the pilot. Do not try to light the pilot by hand.

1) Make sure the Gas Valve and all electrical power to the boiler are "OFF".

2) Set room thermostat to the lowest setting.

3) Connect a manometer at pressure tapping on downstream section of gas valve.

4) Wait five minutes to clear out any gas. If you smell gas, STOP! Follow the safety instructions

provided in Section 1.1 under WHAT TO DO IF YOU SMELL GAS. Remember that propane
does not vent upward naturally.

5) Set room thermostat to call for heat.

6) Turn on the gas valve.

7) Turn on all electrical power to the boiler. The hot surface element should glow bright orange and

ignite the pilot, followed by the main burners. Check main and pilot burners and adjust pilot, if
necessary, as described in Section 3.3.

8) Assure that all other gas appliances are turned off, including their pilot flames.

9) Check manifold pressure reading on the manometer and make necessary adjustments. Check

burner input to match rating plate input.

10) Return thermostat and controls to normal operation settings.

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MG & SG Series Boilers – Installation and Service Manual

3.3 CHECK BURNER SYSTEM

To maintain safe and efficient operation, examine the burner system regularly through the inspection hole
near the pilot tube.

Check condition of burner system

It is possible for parts of the burners system to
become plugged, cracked, eroded and/or
dislodged resulting in unsafe operation.

Pilot Flame

Remove cap screw
cover on gas valve,
then adjust gas flow to
the point where the
thermocouple tip or
sensor rod is
completely enveloped
by the flame (Figure 2),
but not necessarily
glowing red. Replace
and tighten cap.

Check for lifting

FIGURE 2 - PILOT FLAME

ADJUSTMENT

Flames should not lift excessively from the

Check ignition and extinction

Ignition should flow quickly and smoothly across
all the burners. Popping noises or explosions
from the burners during ignition, extinction or
normal burner operation indicates the need for
service.

Check flame color

An extremely yellow flame, as seen on a burning
candle or match, is an indication of incomplete
combustion and is usually accompanied by the
formation of soot and carbon monoxide (carbon
monoxide is a lethal, colorless and odorless
gas). If soot is allowed to accumulate, it will
partially restrict free passage of products of
combustion to the flue. Under typically
operating conditions, the flame should have a
distinct bright blue inner cone and a blue/orange
outer cone.

burner ports. The flames may lift slightly during
ignition or when the burners are cold.

If any of the above problems are observed or the burner system does not operate properly,
immediately take corrective measures.

3.4 AQUASTAT ADJUSTMENT

The factory mounted aquastat controls main burner firing by sensing outlet water temperature. To set the
temperature of this control, adjust the dial until indicator points to the temperature (setpoint) at which the
gas valve will close. The gas valve will open at setpoint less the differential. The automatic reset safety
high-limit aquastat is either fixed or, if adjustable, should be set a minimum of 20°F (10°C) above the
setting of the aquastat.

3.5 GAS MANIFOLD PRESSURE

The designated manifold pressures are as shown in the table below. A 1/8” NPT tapping is provided on
the manifold or gas valve for connecting a manometer to check this pressure. Both natural gas and
propane models are furnished with gas valves which have a built in gas pressure regulator. If necessary,
adjust to the proper value by removing cap and turning adjusting screw clockwise to increase manifold
pressure or counterclockwise to decrease manifold pressure.

Model Natural Gas Propane

MG

SG

3.5” W.C. 11.0” W.C.

3.5” W.C. 10.0” W.C.

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MG & SG Series Boilers – Installation and Service Manual

3.6 CHECK INPUT & ORIFICES

For safety, the input shown on rating plate must not be exceeded. Check with the table below that

the orifice size and input rate shown on your boiler rating plate match your application, i.e. boiler model,
fuel type, and altitude. See MG & SG Specifications to find a boiler model's input rate.

FOR CANADA

Model

MG

SG

NOTE: For elevations above 4,500 feet reduce high altitude input 4% for each additional 1000 feet.
Reference Natural Gas and Propane Installation Code B149.1, 3.22 High Altitude Installations

0 to 2,000 feet 2,000 to 4,500 feet 0 to 2,000 feet 2,000 to 4,500 feet

#51 orifice
standard input

#43 orifice
standard input

Example of High Altitude Derate
Boiler: SG-270
Altitude: 5,500 feet
Standard Input (0 to 2,000 ft) = 270,000 Btu/h (from page 3)
High Altitude Input (2,000 to 4,500 ft) = Derate Standard Input by 10% (see above

table)
= 270,000 Btu/h x (1 - 0.10)
= 270,000 Btu/h x 0.90
= 243,000 Btu/h

% Reduction for additional 1000 ft = 4% x 1 = 4%
Input at 5,500 ft = Derate High Altitude Input by 4%

= 243,000 Btu/h x (1 – 0.04)
= 243,000 Btu/h x 0.96
= 233,280 Btu/h

Model

MG

SG

*Reference National Fuel Gas Code ANSI Z223.1, 8.1.2 High Altitude.

0 to 2,000 feet Over 2,000 feet 0 to 2,000 feet Over 2,000 feet

#51 orifice
standard input

#43 orifice
standard input

Natural Gas Propane

#51 orifice
standard input

#44 orifice
10% derate input

FOR UNITED STATES

Natural Gas Propane

Input must be reduced
4% for each 1000 feet
above sea level. *

#60 orifice
standard input

#54 orifice
standard input

#60 orifice
standard input

#54 orifice
standard input

#61 orifice
10% derate input

#55 orifice
10% derate input

Input must be reduced
4% for each 1000 feet
above sea level. *

Example of High Altitude Derate
Boiler: MG-100
Altitude: 5,000 feet
Standard Input (0 to 2,000 ft) = 100,000 Btu/h (from page 2)
% Reduction for 5,000 ft = 4% x 5 = 20%
Input at 5,000 ft = Derate Standard Input by 20%

= 100,000 Btu/h x (1 - 0.20)
= 100,000 Btu/h x 0.80
= 80,000 Btu/h

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MG & SG Series Boilers – Installation and Service Manual

Small adjustments to the input rate can be made by varying the manifold pressure. Normally it should be
adjusted no more than 0.2 inch w.c. for natural gas or 0.5 inch w.c. for propane from the manifold
pressure specified on the rating plate.

WARNING

Exceeding the allowable input rate can produce dangerous concentrations of carbon monoxide,
and cause the boiler to overheat resulting in severe personal injury, death or substantial
property damage. Carbon monoxide is a lethal, colorless and odorless gas.

Input Rate Test

Consult gas company to determine the heating value of the gas supplied in Btu per cubic feet. Operate
boiler for 15 minutes starting with all parts at room temperature and check input by clocking gas meter
with all other gas appliances turned off, including their pilot flames. Use the following formula:

INPUT (Btu/h) =

To ensure accuracy for rating, clock enough cubic feet of gas so that there is at least one revolution of the
test dial and the clocked time is at least 60 seconds.

Two Stage Gas Valve

When a two stage gas valve is used, it must be checked for correct input at both "High" and "Low" fire
settings. The clocked input rate MUST be within the "Minimum Input" and the "Input" as specified on the
boiler's rating plate. To force the boiler to low fire, unplug the blue wire from the "HI" (or "W-2") port of the
two stage gas valve. Perform the Input Rate Test described above and adjust manifold pressure of High
and Low settings as necessary. For altitudes above 2000 feet, DO NOT derate the "Minimum Input" rate.

Clocked Seconds

Timed) FeetCubic of (Number x Gas) of Value(Heating(3600) ×

3.7 CHECK FOR DRAFT HOOD SPILLAGE

WARNING

Continuous spillage at the draft hood relief opening may result in severe personal injury, death
or substantial property damage.

After the main burners have operated for 5 minutes, check to see that combustion products are going up
the chimney or gas vent properly by passing a lighted match (or smoke from a cigar, cigarette, or pipe)
around the edge of the relief opening of the draft hood. If the chimney or gas vent is drawing properly,
the match flame or smoke will be drawn into the draft hood. If not, the combustion products will tend to
extinguish this flame. While performing this test, make sure all exhaust fans, air movers, and gas
appliances are operating and doors and windows are closed. If the combustion products are escaping
from the relief opening of the draft hood, IMMEDIATELY shutdown the boiler and make proper
adjustments or repairs.

3.8 CHECK OF CONTROLS

After the unit has been operated for awhile, lower the aquastat setting below the setpoint and burner
should shut off. Rotate the aquastat higher than setpoint and the main burner should ignite. Return the
aquastat to its original setpoint and make sure boiler cycles normally. Repeat this type of check on the
safety high-limit aquastat, thermostat and other system controls to ensure all work satisfactorily. If any of
the safety or controls do not function, necessary corrections should be made immediately.

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MG & SG Series Boilers – Installation and Service Manual

3.9 CHECK FOR GAS LEAKS

To identify gas leaks, smell for gas around boiler area and gas piping connections (See Section 1.1). To
check a specific area for leakage, spray a mixture of soap and water onto the suspected area – active
bubbling indicates a gas leak. DO NOT TEST FOR LEAKS WITH AN OPEN FLAME. Gas leaks must be
repaired immediately.

3.10 INSTALLER'S CHECKLIST

Reference

The information printed on the boiler rating plate matches the application (i.e.

ο

altitude and fuel type).

All applicable electrical codes have been met.

ο

Gas piping has been purged and checked for leaks with a soap solution.

ο

System is filled with water and all air has been purged. Only oxygen barrier

ο

tubing has been used.

A manometer has been used to check the manifold pressure and gas supply

ο

pressure against requirements printed on boiler rating plate.

Bypass or mixing valve has been used to prevent return water less than

ο

135°F.

All applicable venting codes have been met. Air openings sized to provide
adequate supply air for combustion, flue gas dilution and ventilation and will

ο

not be blocked off.

Check for spillage at draft hood and other areas susceptible to spillage.

ο

Operate the boiler for 15 minutes, then clock and calculate Btu/h input rate.
The input rate must not exceed that specified on the boiler rating plate.

ο

Clocked BTU/H Input Rate: ______________

Perform check of temperature controls: aquastat, high limit aquastat, and

ο

thermostat.

Test any other controls as specified by the manufacturer.

ο

Visually inspect main burners and pilot to ensure proper flame operating

ο

characteristics and ignition/extinction is ok.

Allow the boiler to cycle a few times to ensure functions are operating

ο

correctly.

Close main shut-off valve and check that burners and pilot flame extinguish.

ο

Clearly identify emergency shut-off devices and make the user or owner

ο

aware of their location and method of operation.

Fill in the contact information on the cover of the User's Information Manual

ο

and leave both manuals in the envelope adjacent to the boiler.

Section

3.5

2.2, 2.14

2.2, 2.4, 2.9

2.11, 2.12

3.2, 3.5

2.12

2.2, 2.5, 2.6, 2.7

3.7

3.6

3.4, 3.8

3.3

NOTE: INSTALLER'S RESPONSIBILITY

"Before leaving installations, installers shall ensure that an appliance, accessory, component, or
equipment installed by them comply with the Code requirements, and the person initially activating the
appliance shall ensure that the appliance is in safe working order."

CSA B149.1-00 Natural Gas and Propane Installation Code

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MG & SG Series Boilers – Installation and Service Manual

Service & Maintenance Instructions Section 4

4.1 SERVICE & MAINTENANCE INSTRUCTIONS

WARNING

Label all wires prior to disconnection when servicing controls. Wiring errors can cause
improper and dangerous operation.

If any part of this boiler has been under water, inspect the boiler and replace any part of the
control system and any gas control which has been under water.

This boiler has been designed to provide years of trouble-free performance in normal installations. The
owner or user should conduct a general external examination covering all items on the "User Checklist" at
the beginning of each heating season and in mid-heating. In addition, the owner or user will have the
boiler inspected by qualified service technician or gas supplier’s service person at least once every year
at the beginning of the heating season for continued safe operation. Note that some operating conditions
may require more frequent inspections.

The qualified service technician or gas supplier's service person should follow the "Service Checklist".
The "Service Checklist" must only be used by a qualified service technician or gas supplier's service
person.

WARNING

Verify proper operation after servicing.

4.2 CLEANING PROCEDURE

1. Shutdown the boiler as described in the lighting instructions in Section 1.5.

2. Inspect flue gas passages and burners for the presence of soot, rust or scale.

3. If necessary, use a wire brush and vacuum to clean and remove any blockages. Plugged burner

ports must be cleared.

4. Replace any parts which have severely corroded.

5. Reassemble parts removed during cleaning as they were before, ensuring air tightness of flue gas

passages.

6. Corrosion can be caused by low return water temperature or a contaminated air supply. Sooting

can be caused by improper burner adjustment. Check and adjust as necessary.

7. Return boiler to operation following lighting instructions in Section 1.5.

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MG & SG Series Boilers – Installation and Service Manual

4.3 SERVICE CHECKLIST

Do not store anything against the boiler or allow dirt or debris to accumulate in the
area immediately surrounding the boiler. The flow of supply and exhaust air must

ο

not be obstructed.
Check air openings are not restricted and complies with applicable code(s).

ο

Adequate supply air is necessary for combustion, flue gas dilution and ventilation.
When the boiler has operated for several minutes, check for spillage at draft hood,

ο

venting ducts, and other areas susceptible to spillage.
Check externally the draft hood and vent system for soot, rust scale or corrosion.

ο

Check for dislodged venting or possible leaks in venting ducts.
Remove the draft hood from the boiler and inspect the flueways for the presence of

soot or rust scale. Inspect the draft hood and smoke pipe connecting the draft hood to

ο

the flue for rust or corrosion before replacing the draft hood. The presence of soot,
rust scale or corrosion indicates misadjustment.

Inspect and, if necessary, clean the pilot burner and main burner. Check burners to

ο

see that they are not cracked or dislodged.
Visually check the pilot and main burner flames. A yellow flame caused by improper

adjustment is always accompanied by formation of soot which, if allowed to continue,

ο

will partially restrict free passage of products of combustion to the flue.
Check that gas piping is secured. Smell for gas leaks around boiler and gas piping

connections. Gas leaks can also be checked for using a soap solution; do not use

ο

an open flame to check for leaks. Note: Propane is heavier than air and pools in a
low area in the event of a leak.

Inspect for leaks in the water piping and at water piping connections.

ο

Circulating pumps used with hot water heating systems should be inspected for

ο

water leaks.
Check for weeping at pressure relief valve outlet during normal operation.

ο

Listen for unusual audible sounds in the boiler. Any audible sounds in the boiler
system may be indications of scaling or lack of sufficient water flow and the system

ο

should be checked without delay. Scaling is due to improper maintenance. It is not
the fault of the boiler. Scale damage is not covered by warranty.

Check the temperature and pressure gauge and expansion tank pressure is within

ο

an acceptable range for the heating system.
Keep boiler area clear and free from combustible materials, gasoline and other

flammable vapors and liquids. Combustible materials, gasoline and other flammable

ο

vapors and liquids should not be stored in the area of the boiler.
Check should be made on ignition system, operation controls and safety shut-off

ο

valves for gas tightness.
If applicable, inspect low water cutoff for proper operation.

ο

Check for proper operation of the blocked vent and flame roll-out safety switches.

ο

The emergency shut-off devices are identified and the owner is aware of their

ο

location and method of operation.

Reference

Section

2.5

2.2, 2.5,

2.6, 2.7

3.7

4.2

3.3, 4.2

3.3

3.9

2.13

2.12

2.9

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MG & SG Series Boilers – Installation and Service Manual

4.4 CAUTION: WATER REPLENISHMENT

Avoid unnecessary replenishment of system water. It can allow oxygen to enter the system and cause
serious corrosion problems. As well, an excessive amount of minerals may be deposited in the heat
exchanger. Do not draw water from the heating system for cleaning, flushing, etc.

Any audible sounds in the boiler system may be indications of scaling or lack of sufficient water flow and
the system should be checked without delay. Scaling is due to improper maintenance. It is not the fault
of the boiler. Scale damage is not covered by warranty.

4.5 REFRACTORY HANDLING PROCEDURE

WARNING

The mineral block and fiberglass wool used in this product are RCFs (Refractory Ceramic
Fibers). RCFs pose a possible cancer hazard by inhalation and can cause respiratory, skin and
eye irritation.

After mineral block has been fired, it will produce increased levels of nuisance dust and poses
increased carcinogenic risk.

Follow the precautionary measures below before attempting service or access.

PRECAUTIONARY MEASURES:

• Avoid breathing fibers and contact with skin and eyes.

• Use a National Institute for Occupational Safety and Health (NIOSH) approved dust/mist

respirator.

• Wear long-sleeved, loose fitting clothing, gloves and eye protection.

• Wash work clothes separately from other clothing. Rinse washer thoroughly.

• Operations such as sawing, blowing, tearout and spraying may generate airborne fiber

concentration requiring additional protection.

• Use a vacuum with a HEPA filter for clean up.

• Dispose of all RCF scrap and dust in a closed airtight plastic bag.

FIRST AID MEASURES:

• Eye contact – Flush eyes with water to remove dust for at least 15 minutes. If irritation persists,

seek immediate medical attention.

• Skin contact – Wash affected area gently with soap and warm water after handling.

• Difficulty breathing – Move to an area of clean fresh air. Seek immediate medical attention if

difficulties persist.

• Ingestion – Do not induce vomiting. Drink plenty of water. Seek immediate medical attention.

Boiler Water Flow Data Section 5

Typical Water Flow Versus Pressure Drop Across Boiler

Model

Number

MG50 4.0 1.1 3.0 1.0

MG75 6.0 2.2 4.0 1.1
MG100 8.0 3.5 6.0 2.2
MG125 10.0 5.2 7.0 2.8
MG150 12.0 8.0 8.0 3.5

SG135 11.4 2.8 7.6 1.2
SG180 15.1
SG225 18.9 2.8 12.6 1.2
SG270 22.7 2.8 15.1 1.2

U.S. GPM P.D. FT. U.S. GPM P.D. FT.

20°F T.D. 30°F T.D.

2.8

10.1 1.2

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MG & SG Series Boilers – Installation and Service Manual

Replacement Parts Section 6

NOTE: To supply the correct part it is important that you state the boiler model number, serial number

and type of gas when applicable.

Any part returned for replacement under standard company warranties must be properly tagged with
Return Goods Authorization Form (R.G.A.), completely filled in with the boiler serial number, model
number, etc., and shipped to the Company freight prepaid.

If determined defective by the Company and within warranty, the part will be returned in kind or equal
substitution, freight collect. Credit will not be issued.

Refer to Figures 3 and 4 for replacement parts.

22

MG & SG Series Boilers – Installation and Service Manual

23

MG & SG Series Boilers – Installation and Service Manual

Wiring Diagrams Section 7

Simplified Wiring Instructions

IMPORTANT

• Disconnect power source to boiler before wiring zone control board.

• All wiring must comply with applicable codes, ordinances and regulations.

• The non-replaceable fuse on the board will be blown if 240 Vac is connected to the board or if the

24 Vac system is even momentarily shorted out.

A: Line Voltage Connections

Connect 120 Vac, 60 Hz, single phase power to terminals L1 (HOT) and L2 (NEUTRAL). Strip wire ends
to a maximum of 3/16" before inserting into terminal block. Tighten terminal screw clamps. Connect
ground wire to ground screw “G” on the boiler control panel.

B: Zones

Remove zone one plug-in terminal block. Connect 24 Vac thermostat leads to terminals TH1 and TH2 on
plug-in terminal block. Connect normally closed zone valve 24 Vac motor leads to terminals ZV1 and
ZV2. Connect zone valve “end switch” leads to terminals ES1 and ES2. Strip wire ends to a maximum of
3/16" before inserting into terminal block. Tighten terminal screw clamps. Re-insert plug-in terminal
block into mating connector on Zone Control Board. Repeat for zones 2, 3, and 4 as required.

C: Optional Second Pump

A second pump (120 Vac, 1/6 HP maximum) may be connected to terminals P1 (HOT) and P1C
(NEUTRAL).

D: Jumpers

Jumpers J1 and J2 are factory set for a multi-zone installation.

E: For Single zone Applications

Install jumper J2 and connect 24 Vac thermostat leads to terminals TH1 and TH2 on Zone 1 plug-in
terminal block.

Manufactured exclusively by

Allied Engineering Company

24

MG & SG Series Boilers – Installation and Service Manual

3.1.2.

25

MG & SG Series Boilers – Installation and Service Manual

3.1.2.

26

MG & SG Series Boilers – Installation and Service Manual

3.1.2.

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MG & SG Series Boilers – Installation and Service Manual

3.1.2.

28

MG & SG Series Boilers – Installation and Service Manual

•

•

•

y aq

•

•

•

Adj

Troubleshooting Guide Section 8

Problem Possible Cause Solution

Boiler will not fire.

Boiler goes on and off at
frequent intervals.

Boiler fires continuously.

Rumbling and moaning
sound in boiler.

Gas odor.

Flame roll out on ignition
or during operation.

Pilot outages with
standing pilot.

• No power.

• No gas supply to boiler. • Check gas source and pressure.

• Gas supply pipes are not purged of air. • Purge gas line.

• No heat demand. • Check if thermostat setting is above room

• Flame roll-out or blocked vent safety switch

is not reset.

• Flow switch or low water cut off. • Check pump capacity & flow direction.

• Gas valve failure (closed position). • Check gas valve and replace if necessary.

• Thermocouple failure. • Check thermocouple and replace if

• Faulty wiring. • Check wiring of aquastats, zone valves, and

• Faulty aquastat, thermostat, or zone valve.

• Pilot not lit. • Relight standing pilot. (For electronic

• Poor flow in boiler or circulator failure. • Check pump for proper capacity & flow

• Thermostat, heat anticipator, or aquastat

set too low.

• Boiler oversized or insufficient radiation. • Check and adjust if necessary.

• Wrong type of thermostat or controller. • Check and replace if necessary.

• Gas valve failure (open position).

• Faulty wiring. • Check wiring of aquastats, zone valves, and

• Fault

• Boiler is overheated and safety high limit

aquastat fails to cut out.

• Improper wiring. • Check and correct.

• Foreign matter in heat exchanger. • Flush heat exchanger if necessary.

• Poor circulation. • Check pump for correct flow.

• Air trapped in heating system. • Purge air.

• Negative draft.

• Insufficient combustion air to boiler. • Check combustion and ventilation air

• Leak in gas system. • See “What to do if you smell gas” on cover.

• Carbon build up on the heat exchanger,

caused by improper venting, ventilation air or
low return water temperature.

• Negative draft. • Check venting.

• Improper pilot flame.

• Thermocouple lead to gas valve is loose. • Check and tighten lead.

• Thermocouple is defective. • Replace thermocouple.

uastat, zone valve or thermostat.

Check power switches and wiring.

temperature and aquastat setting is above
boiler water temperature.

• Push reset and diagnose cause.

Check for correct water levels and air locks.

necessary.

thermostats for loose or broken wires and
repair.

Check and replace if necessary.

ignition, see "Pilot flame will not light on
electronic ignition".)

direction. Replace if necessary.

• Check and adjust.

Check gas valve, replace if necessary.

thermostats for short circuits or incorrect
wiring.

Check and replace if necessary.

• Check aquastats and adjust or replace if
necessary.

Incorrect vent size or blocked vent.

opening in boiler room meets installation code
requirements, and combustion air flow
openings in the boiler base and burner tray are
not blocked.

Have gas fitter test system and repair leaks.

• Have a qualified service technician inspect
and clean the heat exchanger and check and
adjust the system.

ust pilot flame.

29

MG & SG Series Boilers – Installation and Service Manual

Problem Possible Cause Solution

Pilot flame will not light on
electronic ignition.

Pilot lights but flame
failure after trial for
ignition.

Burner starts but flame
will not stay established.

Boiler carbonizes (forms
soot) quickly.

Boiler overheats and
system remains cold.

Boiler and heating system
overheat.

• No spark. • High voltage wiring is loose, broken or

• Ignition electrodes are damaged. • Replace electrodes.

• Ignition electrodes improperly adjusted. • Correct adjustment of electrode.

• Faulty electronic ignition controller. • Replace controller.

• No gas. • Confirm supply of gas to pilot and repair if

• Gas supply pipes not purged of air. • Purge gas line.

• Low pilot gas pressure. • Adjust pressure.

• Dirt or foreign material in pilot. • Clean.

• Incorrect pilot flame pressure. • Set pilot pressure to correct pressure.

• Poor connections in wiring to flame sensor. • Repair wiring.

• Electrodes are damaged. • Replace electrodes.

• Ignition electrodes improperly adjusted. • Correct adjustment of electrodes.

• Ignition electrodes are wet, dirty or

improperly adjusted (for electronic ignition
only).

• Poor connections in wiring to flame sensor. • Repair wiring.

• Incorrect orifice sizing. • Check orifice and replace if necessary.

• Inadequate combustion and ventilation air. • Check and adjust.

• Dusty environment. • Clean.

• Low return water temperature. • Adjust system.

• Manifold pressure too high. • Adjust manifold pressure.

• Insufficient circulation. • Check pump, clean and replace if necessary.

• Air trapped in piping. • Purge system.

• Improper system wiring. • Test and correct.

• Faulty thermostat or controller. • Check, adjust, and replace if necessary.

• Faulty aquastat and/or safety high limit

aquastat.

• Faulty wiring. • Check wiring for short circuits and repair.

grounded. Repair wiring.

necessary.

• Check, clean, change and/or adjust the
electrodes.

• Check, adjust, and replace if necessary.

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MG & SG Series Boilers – Installation and Service Manual

NOTES Section 10

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MG & SG Series Boilers – Installation and Service Manual

INDEX Section 10

Section Page

Dimensions and Specifications – MG Series Boilers.................................................................................... 2

Dimensions and Specifications – SG Series Boilers ....................................................................................3

About Our Manuals ....................................................................................................................................... 4

1 Lighting Instructions......................................................................................................................... 4

1.1 Safety Instructions............................................................................................................................... 4

1.2 Lighting Instructions ............................................................................................................................ 4

1.3 Lighting Instructions for Standing Pilot with Combination Gas Valve ................................................. 5

1.4 Lighting Instructions for Intermittent Electronic & Hot Surface Ignition with Combination Gas Valve 5

1.5 To Turn off Gas to the Boiler or Emergency Shut-Off.........................................................................6

2 Installation Instructions.................................................................................................................... 6

2.1 Receiving............................................................................................................................................. 6

2.2 Installation Codes and Requirements ................................................................................................. 6

2.3 Location............................................................................................................................................... 7

2.4 Gas Service Piping.............................................................................................................................. 7

2.5 Air Supply for Combustion and Ventilation ......................................................................................... 8

2.6 Corrosive Atmospheres....................................................................................................................... 8

2.7 Venting ................................................................................................................................................8

2.8 Automatic Vent Damper .................................................................................................................... 10

2.9 Blocked Vent and Flame Roll-out Safety Switches........................................................................... 10

2.10 Boiler Piping System ......................................................................................................................... 11

2.11 Corrosion Prevention (Internal) ......................................................................................................... 11

2.12 System Operating Requirements ...................................................................................................... 11

2.13 Pressure Relief Valve........................................................................................................................ 12

2.14 Electrical Wiring................................................................................................................................. 12

3 Startup Instructions ........................................................................................................................ 13

3.1 Pre-startup................................................................................................................

3.2 Startup............................................................................................................................................... 13

3.3 Check Burner System ....................................................................................................................... 15

3.4 Aquastat Adjustment ......................................................................................................................... 15

3.5 Gas Manifold Pressure...................................................................................................................... 15

3.6 Check Input & Orifices....................................................................................................................... 16

3.7 Check for Draft Hood Spillage........................................................................................................... 17

3.8 Check of Controls.............................................................................................................................. 17

3.9 Check for Gas Leaks......................................................................................................................... 18

3.10 Installer’s Checklist............................................................................................................................ 18

4 Service & Maintenance Instructions ............................................................................................. 19

4.1 Service & Maintenance Instructions.................................................................................................. 19

4.2 Cleaning Procedure........................................................................................................................... 19

4.3 Service Checklist ............................................................................................................................... 20

4.4 Caution: Water Replenishment .........................................................................................................21

4.5 Refractory Handling Procedure......................................................................................................... 21

5 Boiler Water Flow Data ................................................................................................................... 21

6 Replacement Parts .......................................................................................................................... 22

7 Wiring Diagrams.............................................................................................................................. 24

8 Troubleshooting Guide................................................................................................................... 29

9 Notes................................................................................................................................................. 31

10 Index ................................................................................................................................................. 32

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