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UEZ-IOM (07-23) 1034347-I
ADJUSTMENTS—CONTINUED
Measure and Adjust Manifold (Outlet) Gas Pressure—Continued
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 Pressure
Switch Replacement 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 Table 23) 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 combination gas valve.
NOTE: 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 Figure 30).
⚠ 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. Turn knob or switch on top of valve to ON.
6. Remove cap from regulator screw (see Figure 30) and adjust pressure in accordance with Table 23 by turning
regulator screw IN (clockwise) to increase pressure or OUT (counterclockwise) to decrease pressure.
7. Turn up thermostat. Depress and hold door safety switch.
8. Cycle burner once or twice to properly seat adjustment spring in valve and recheck outlet pressure. When
pressure corresponds to Table 23, 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 Figure 30). 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 Table 24 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. Depress and
hold safety door switch.
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