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MODU-FIRE® FORCED DRAFT
Gas-Fired Boiler Installation
3.7
GAS PIPING
Before making the gas hook-up, make sure the
boiler is being supplied with the type of fuel shown
on the boiler nameplate.
The boiler must be installed such that the gas system
components are protected from water (dripping,
spraying, rain, etc.) during appliance operation and
service (circulator replacement, control replacement,
etc.)
The boiler is factory fire-tested and adjusted for
proper combustion with a natural gas supply pres-
sure of 7 inches W.C. Typical supply gas pressure
is 7 inches W.C. for natural gas (11 inches W.C. for
propane). The gas train components are certified to
handle a maximum inlet pressure of 14 inches W.C.
(1/2 psig.). If the available gas pressure exceeds 14
inches W.C., a suitable additional intermediate gas
pressure regulator of the "lock up" type must be pro-
vided to reduce the pressure to less than 14 inches
W.C.
The minimum allowable gas pressure for proper
operation of the unit is dependent on the vent resis-
tance at high fire. The following chart details the
minimum gas pressure allowed based on the vent
frictional resistance.
For Natural Gas:
If: Then:
Vent <1” W.C. Min Gas Pressure = 4” W.C.
Vent >1” W.C. Min Gas Pressure = 5” W.C.
For Propane, a minimum of 7 inches W.C. inlet gas
pressure is required.
WARNING!
All threaded connections must be made using a
pipe compound that is certified resistant to the ac-
tion of liquefied petroleum gases. Do not use Tef-
lon tape on gas line threads.
Notice: Piping must be installed such that no piping
stresses are transmitted to the boiler. The boiler
shall not be used as a pipe anchor.
The boiler and all gas piping connections should be
pressure-tested and must be checked for leaks be-
fore being placed into service. Test with com-
pressed air or inert gas if possible.
The boiler must be disconnected at the boiler man-
ual shutoff valve (located at the end of the supplied
gas train) from the gas supply piping system during
any pressure testing of the system at pressures in
excess of 1/2 psig (14 inch W.C.).
Some leak test solutions, including soap and water,
may cause corrosion. These solutions should be
rinsed off with water after testing.
RECOMMENDED GAS PIPING INSTALLATION
Boiler Main Gas
Valve
Gas
Supply
Union
Drip Leg
Remote Gas
Shutoff
Meter
Field Gas Piping
Notice: A sediment trap (drip leg) and a union con-
nection should be installed upstream of the primary
manual shutoff valve on the boiler. Gas piping
should be installed in accordance with National Fuel
Gas Code, ANSI Z223.1, latest edition, and any
other local codes which may apply. In Canada,
please refer to CSA-B.149.
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