3Gas connections (continued)
Combination Gas Valves
Installation & Service Manual
PRESSURE REGULATOR ADJUSTMENT (UNDER CAP SCREW)
INLET PRESSURE TAP
OUTLET
PRESSURE TAP
PILOT OUTLET
Each unit has a combination gas valve(s) to control the gas supply to the burners. The 500,000 Btu/hr model has two combination gas valves to supply gas to the burners. The combination valve consists of a gas regulator and two valve seats to meet the requirements for redundant gas valves. The valve has a gas control knob that must remain in the open position at all times when the appliance is in service. Each gas valve has pressure taps located on the inlet and outlet sides. Manifold pressure is adjusted using the regulator located on the valve. The
RED RESET BUTTON |
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| GAS CONTROL KNOB |
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Figure 3-5_F1 Gas Valve, standing pilot
manifold pressure is preset at the factory and adjustment is not usually required. If the manifold pressure is to be adjusted, follow the “Gas Manifold Pressure Adjustment Procedure”, page 21 for proper adjustment.
Venting of Combination Gas Valves
PRESSURE REGULATOR |
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ADJUSTMENT (UNDER CAP SCREW) | WIRING TERMINALS |
INLET PRESSURE TAP
OUTLET
PRESSURE TAP
PILOT OUTLET
The combination gas valve regulator used on all models is equipped with an integral vent limiting orifice. The vent limiter ensures that the volume of gas emitted from the valve does not exceed the maximum safe leakage rate allowed by agency requirements. Combination gas valve/regulators equipped with integral vent limiters are not required to have vent or relief lines piped to the outdoors. A dust cap is provided at the vent termination point on the valve to prevent blockage of the vent limiter
GAS CONTROL KNOB
Figure 3-6_F9 Gas Valve, spark ignition
by foreign material. The combination gas valve regulator with an integral vent limiter complies with the safety code requirements of
Two Stage Burner Control System
The 315,000 through 399,999 Btu/hr boiler models (M9) will be equipped with a two stage gas valve to control high/low burner operation. The 500,000 Btu/hr boiler model achieves two stage burner firing by staging the operation of the two combination gas valves.
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