45
I-EEDU (02-21) 150492-A
1 . With manual valve on combination valve positioned to prevent flow to main burners, connect manometer to 1/8-
inch pipe outlet pressure tap (see
Figure 34. Combination Gas Valve Pressure Taps
2 . To measure low stage pressure on units equipped with two-stage valve, disconnect wire from HI terminal on valve .
3 . Open valve and operate heater and observe manometer reading .
NOTES:
• Natural gas units leave the factory with the combination valve set so that the outlet gas pressure
of a single-stage valve or high fire of a two-stage valve is regulated to 3.5 IN WC. Low fire on a
two-stage valve is set to 1.8 IN WC. Inlet supply pressure to the valve must be a minimum of 5 IN
WC or as noted on the rating plate and must be a maximum of 14 IN WC. Always check the rating
plate for the minimum gas supply pressure. Minimum supply pressure requirements vary based
on the size of the burner and the gas control option. Most units require a minimum of 5 IN WC,
but units with electronic modulation may require a minimum of 6 IN WC.
• Propane units leave the factory with the combination valve set so that the outlet gas pressure of
a single-stage valve or high fire of a two-stage valve is 10 IN WC. Low fire on a two-stage valve
is set to 5 IN WC. Inlet pressure to the valve must be a minimum of 11 IN WC and a maximum of
14 IN WC.
⚠ CAUTION ⚠
Do not bottom out the gas valve regulator adjusting screw. This can result in unregulated manifold
pressure, which may cause overfire and heat exchanger failure.
4 . Adjust pressure as necessary to required setting by turning regulator adjusting screw (see
)—IN
(clockwise) to increase pressure or OUT (counterclockwise) to decrease pressure .
5 . If wire from HI terminal on valve was disconnected in step 2, reconnect wire .
Burner Air Adjustment (Propane Units Only)
⚠ DANGER ⚠
Failure to install and/or adjust air shutters according to directions could cause property damage,
personal injury, and/or death.
NOTE: During regular service, check the main burner ports, the carryover assemblies, and the
orifices for cleanliness.
SINGLE-STAGE VALVE
1/8-INCH INLET
PRESSURE TAP
1/8-INCH OUTLET
PRESSURE TAP
1/8-INCH OUTLET
PRESSURE TAP
TWO-STAGE VALVE
1/8-INCH INLET
PRESSURE TAP
HIGH FIRE
REGULATOR
ADJUSTING
SCREW
LOW FIRE
REGULATOR
ADJUSTING
SCREW
REGULATOR
ADJUSTING
SCREW
