MODU-FIRE® Forced Draft Gas-Fired Boiler
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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 provided 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 resistance at high
fire. The following chart details the minimum gas pressure required based on the static pressure at the boiler flue
gas outlet.
For Natural Gas:
Stack pressure:
Min. gas pressure required:
Less than 1” W.C.
4.5” W.C.
More than 1” W.C.
7.0” W.C.
For Propane, a minimum of 7 inches W.C. inlet gas pressure is required.
All threaded connections must be made using a pipe compound that is
certified resistant to the action of liquefied petroleum gases. Do not use Teflon tape on gas line
threads.
NOTICE! Piping must be installed such that no piping stresses are transmitted to the boiler. The boi-
ler 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 before being
placed into service. Test with compressed air or inert gas if possible. The boiler must be disconnected at the
boiler manual 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
