Hydronic Heating Boilers and Domestic Water Heaters Installation and Service Manual

9. If gas pressure is out of range, contact your gas utility, gas
supplier, qualified installer or service agency to determine
the necessary steps to provide proper gas pressure to the
control.
10. If gas supply pressure is within normal range, remove the
gas manometer and replace the pressure tap fittings in the
gas control as indicated in the following steps.
11. Turn the power switch to the “OFF” position.
12. Turn gas valve knob to the “OFF” position.
13. Shut off gas supply at the manual gas cock in the gas
piping to the unit. If fuel supply is L.P. gas, shut off gas
supply at the tank.
14. Remove the manometer and related fittings from the
“inlet” side of the gas valve, replace 1/8" hex plug in the
gas valve and tighten.
15. Turn on the gas supply at the manual valve, turn on L.P.
gas at the tank if required.
16. Turn the power switch to the “ON” position.
17. Turn the gas valve knob to the “ON” position.
18. Set the electronic temperature control or thermostat to call
for heat.
 WARNING: After completing any testing
on the gas system, leak test all gas connections.
Apply a soap/water solution to all gas
connections while main burners are operating.
Bubbles forming indicate a leak. Repair all leaks
at once. Do not operate this unit with a leak in the
gas train, valves or related piping.
Check burner performance by cycling the system while you
observe burner response. Burners should ignite promptly.
Flame pattern should be stable, see Burner Flames, page 40.
Turn the system off and allow burners to cool, then cycle
burners again to ensure proper ignition and flame
characteristics.
Figure 20 - Measuring Gas Supply Pressure at
Combination Gas Valve
Gas Manifold Pressure Adjustment
IMPORTANT: The gas valves are referenced to
the fan pressurized chamber by a hose
connected from the vent of the gas valve
regulator to the chamber pressure tap located on
the front inside portion of the jacket. Reference
the drawings in this section for component and
connection points for pressure measurement.
The referenced chamber pressure must be
subtracted from the manifold pressure to obtain
actual net manifold pressure for normal
operation. A manometer or magnahelic gauge
legible in 0.1" increments up to 10 inches w.c. is
required to check and adjust the manifold
pressure. The regulator cover screw on the gas
valve must be in place and tight for the unit to
operate properly.
1. Remove screws that fasten the control panel access door
and remove the door.
Installation and
Service Manual
19
INLET
OUTLET
MANOMETER
1/8" HEX INLET
PRESSURE TAP
4
3
2
1
0
1
2
3
4
GAS
VALVE
CONTROL
KNOB