35
LDAP-IOM (01-22) 207733-A
NOTE: For unit sizes 800 and 1200, be sure to replace the pressure switch in each heat section
but do not replace the flue connection box pressure switch—it is the same for all elevations.
Measure and Adjust Manifold (Outlet) Gas Pressure
If the heater is being installed at an elevation
≤
2,000 feet (
≤
610 meters), adjust the manifold (outlet) gas pressure in
accordance with the
Measure and Adjust Manifold Gas Pressure—Elevation
section .
If the heater is being installed at an elevation >2,000 feet (>610 meters), adjust the manifold (outlet) gas pressure in
Measure and Adjust Manifold Gas Pressure—Elevation >2,000 Feet (>610 Meters)
section .
⚠ WARNING ⚠
Valve outlet gas pressure must never exceed 3.5 IN WC for natural gas or 10 IN WC for propane.
The maximum inlet supply pressure for natural gas or propane is 14 IN WC. Maximum gas pressure
can never be exceded either during operation or when unit is static (with lock-up regulator).
⚠ CAUTION ⚠
Before attempting to measure or adjust valve outlet gas pressure, the inlet supply pressure must
be within the specified range, both when the heater is in operation and when it is 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.
NOTES:
• Measuring outlet pressure cannot be done until the heater is in operation.
• During normal operation at sea level, adjustment to factory-setting should not be necessary.
• Unit size 400 has one gas valve, unit size 800 has two gas valves, and unit size 1200 has three
gas valves. Adjust both/all gas valves on unit sizes 800 and 1200.
• 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 or high fire of a two-stage valve is regulated
to 3.5 IN WC. Low fire on a two-stage valve (unit size 400 only) is set to 1.8 IN WC. Inlet supply
pressure to the valve for natural gas must be a minimum of 5 IN WC or as noted on the rating
plate and a maximum of 14 IN WC.
• For propane: when the heater leaves the factory, the combination gas valve is set so that the
valve outlet gas pressure for a single-stage valve or high fire of a two-stage valve is regulated
to 10 IN WC. Low fire on a two-stage valve (unit size 400 only) is set to 5.0 IN WC. Inlet supply
pressure to the valve for propane must be a minimum of 11 IN WC and a maximum of 14 IN WC.
• Gas conversion kits are available for changing from propane to natural gas or natural gas to
propane. A factory-authorized conversion kit MUST be used.
Measure and Adjust Manifold Gas Pressure—Elevation
≤
2,000 Feet (
≤
610 Meters)
For installations at normal elevations, measure and adjust the manifold (outlet) gas pressure as follows:
1 . 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.
2 . Connect manometer to 1/8-inch output pressure tap on valve (see
) .
3 . Open manual valve and operate heater .
4 . Observe manometer gauge to measure outlet pressure of gas valve . To measure low-stage pressure on unit size
400 equipped with two-stage valve, disconnect wire from the HI terminal on valve . Be sure to reconnect wire .
