Introduction
1-12
750-204
Profire D/LND
1.9.2 — Pilot Gas Train Components
1.9.3 — Operation
Metered gas flows through the main gas shutoff cock, through the pressure regulator to the automatic gas valves
and butterfly valve to the gas manifold.
The butterfly gas valve modulates flow to burner input demand. The butterfly valve is positioned through
mechanical linkage by the modulating motor. The air control damper is positioned simultaneously by the modu-
lating motor.
The automatic gas valve(s) cannot be energized unless the combustion air proving switch is closed. The low and
high gas pressure switches must be closed to prove proper gas pressure.
A normally open vent valve, if required, is located between the two automatic gas valves. This valve is shut when
the automatic gas valves are open. When the automatic valves are closed, the vent valve is open for venting gas
to the outside, should any be present.
Component Description
Gas Pilot Valve A solenoid valve that opens during the ignition period to admit fuel to the pilot. It
closes after main flame is established.
Gas Pressure Regulator Reduces gas pressure to that required by the pilot.
Gas Pilot Shutoff Cock For manually closing the pilot gas supply.
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