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LDAP-IOM (01-22) 207733-A
Measure and Adjust Manifold Gas Pressure—Elevation >2,000 Feet (>610 Meters)
For installations at high elevations, measure and adjust the manifold (outlet) gas pressure as follows:
1 . If installation is at elevation >6,000 feet (1,830 meters), replace pressure switch in accordance with
section .
⚠ WARNING ⚠
Manifold gas pressure must never exceed 3.5 IN WC for natural gas or 10 IN WC for propane.
2 . Determine correct outlet pressure (refer to
) for elevation of installation . If unsure of elevation, contact
local gas supplier .
3 . Turn knob or switch on top of valve to OFF to prevent flow to gas valve .
NOTE: A manometer (fluid-filled gauge) is recommended rather than a spring-type gauge due to
the difficulty of maintaining the calibration of a spring-type gauge. Use a water column manometer
that is readable to the nearest tenth of an inch.
4 . Connect manometer to 1/8-inch output pressure tap on valve (see
) .
⚠ CAUTION ⚠
DO NOT bottom out the gas valve regulator screw. This can result in excessive overfire and heat
exchanger failure due to unregulated manifold pressure.
5 . For single-stage or two-stage high fire valve:
a . Turn knob or switch on top of valve to ON .
b . Remove cap from regulator screw (see
) and adjust pressure in accordance with
by turning
regulator screw IN (clockwise) to increase pressure or OUT (counterclockwise) to decrease pressure .
6 . For two-stage low fire valve:
a . Disconnect wire from HI terminal on gas valve .
b . Remove cap from low-fire regulator screw (see
) and adjust pressure in accordance with
by
turning regulator screw IN (clockwise) to increase pressure or OUT (counterclockwise) to decrease pressure .
c . Reconnect wire to Hi terminal on gas valve .
7 . Turn up thermostat .
8 . Cycle burner once or twice to properly seat adjustment spring in valve and recheck outlet pressure . When pressure
corresponds to
, disconnect manometer and install cap on regulator screw .
9 . Check for leakage at 1/8-inch outlet pressure tap fitting . Correct as necessary .
10 . Connect manometer to inlet pressure tap (see
) . While heater is operating, measure inlet pressure,
which should be between 5 and 13 .5 IN WC for natural gas or between 10 and 13 .5 IN WC for propane .
11 . If inlet pressure is not between 5 and 13 .5 IN WC for natural gas or between 10 and 13 .5 IN WC for propane,
inlet pressure must be corrected by adjusting manifold (outlet) pressure in accordance with steps 3 through 6 .
NOTE: The inputs and capacity of the heater varies depending on elevation.
12 . Refer to
for input and capacity values for elevation of installation .
a . Use permanent marker to fill in appropriate input and capacity values on high-elevation adjustment label from
literature bag provided with unit .
b . Select location for label on outside of heater access panel that will be conspicuous to anyone operating or
servicing unit .
c . Ensure that surface is clean and dry and affix label .
13 . Observe heater operation for at least one complete cycle to check for safe and proper operation .
