Installation manual
7.1.3 Valve Outlet or Orice Pressure Setting
Measuring valve outlet gas pressure cannot be done until the heater is in opera-
tion. It is included in the steps of the “Check-Test-Start” procedure in Paragraph
11. The following warnings and instructions apply.
WARNING
Valve outlet gas pressure must never exceed 3.5” w.c.
for natural gas and 10” w.c. for propane gas.
For Natural Gas: When the heater leaves the factory, the combination
gas valve is set so that the valve outlet gas pressure for a single-stage
valve is regulated to 3.5” w.c. Inlet supply pressure to the valve for natural
gas must be a minimum of 5” w.c. or as noted on the rating plate and a
maximum of 14” w.c.
For Propane: The heater is shipped factory equipped for use with natural gas. A
propane conversion kit is included. Follow the instructions in Paragraph 7.1.4 to
convert for use with propane.
At startup, measure the valve outlet pressure. Refer to the pressure chart on page
11 for correct outlet pressure.
When using propane, the inlet supply pressure to the valve must be a minimum of
11” w.c. and a maximum of 14” w.c.
Before attempting to measure or adjust valve outlet gas pressure, the inlet supply
pressure must be within the specied range both when the heater is in operation
and on standby. Incorrect inlet pressure could cause excessive valve outlet gas
pressure immediately or at some future time. If natural gas supply pressure is too
high, install a regulator in the supply line before it reaches the heater. If natural gas
supply pressure is too low, contact your gas supplier.
NOTE: A gas conversion kit for
changing from natural gas to
propane is included with each
heater. See Paragraph 7.1.4 for
conversion instructions.
7.0 Mechanical
(cont’d)
7.1 Gas Piping and
Pressure (cont’d)
Instructions
1) Locate the 1/8” output pressure tap on the valve (See FIGURE 6, page 11).
With the manual valve turned off to prevent ow to the gas valve, connect
a manometer to the 1/8” pipe outlet pressure tap in the valve. NOTE: A
manometer (uid-lled gauge) is recommended rather than a spring type
gauge due to the difculty of maintaining calibration of a spring type gauge.
2) Open the manual valve and operate the heater. Depress and hold the door
safety switch. Cycle the burner once or twice to properly seat the adjustment
spring in the valve. Measure the outlet pressure of the gas valve.
Normally when operating on natural gas at sea level, adjustments should
not be necessary to the factory setting. (For high altitude settings, see next
paragraph.)
If adjustment is necessary, remove the cap from the adjustment screw(s). Set
pressure to correct settings by turning the regulator screw IN (clockwise) to
increase pressure. Turn regulator screw OUT (counterclockwise) to decrease
pressure.
CAUTION: DO NOT bottom out the gas valve regulator
adjusting screw. This can result in unregulated manifold
pressure causing excess overre and heat exchanger
failure.
Check Valve Outlet
Pressure (can only be
done after heater is
operating)
NOTE: If operating at high alti-
tude, outlet pressure requires
adjustment. Follow instructions
below.
Derate by Valve Outlet
Pressure Adjustment for
High Altitude Operation
Instructions for High Altitude Derate
1. Determine the required valve outlet pressure for the elevation where the
heater will be operating. If unsure of the elevation, contact the local gas
supplier.
Form I-UEAS, Page 10