Reznor UDBS Unit Installation Manual - Manual (Page 14)

Form I-UDB, P/N 202658 R14, Page 14
Instructions
NOTE: If operating at high altitude, outlet pressure requires adjustment. Follow the
instructions in Paragraph 6.1.3 below.
1) Locate the 1/8” output pressure tap on the valve (See FIGURE 10). With the
manual valve turned off to prevent flow to the gas valve, connect a manometer
to the 1/8” pipe outlet pressure tap in the valve. NOTE: A manometer (fluid-filled
gauge) is recommended rather than a spring type gauge due to the difficulty of
maintaining calibration of a spring type gauge.
Check Valve Outlet
Pressure (can only
be done after heater
is operating)
6.1.3 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.
Valve Outlet Pressure Settings by Elevation
This adjustment
can only be done
after the heater is in
operation. High altitude
adjustment is included
in the startup Steps.
NOTE: If elevation is
above 6000 ft (1830M),
a high altitude pressure
switch is required; see
Paragraph 3.2.1.
Manifold Pressure Settings by Altitude for the UNITED STATES
Altitude Natural Gas (inches w.c.) Propane Gas (inches w.c.)
Feet Meters
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
Single-Stage and
Two-Stage High Fire
Two-Stage
Low Fire
0-2000 0-610 3.5 1.8 10.0 5.0
2001-3000 611-915 3.1 1.6 8.8 4.4
3001-4000 916-1220 3.0 1.5 8.5 4.2
4001-5000 1221-1525 2.8 1.5 8.1 4.1
5001-6000 1526-1830 2.7 1.4 7.7 3.9
6001-7000 1831-2135 2.6 1.3 7.4 3.7
7001-8000 2136-2440 2.5 1.3 7.1 3.5
8001-9000 2441-2745 2.4 1.2 6.7 3.4
9001-10000 2746-3045 2.3 1.2 6.7 3.4
2) Open the manual valve and operate the heater. (NOTE: On Model UDBS, depress
and hold the door safety switch.) Measure the outlet pressure of the gas valve. To
measure low-stage pressure on a unit equipped with a two-stage valve, disconnect
the wire from the “HI” terminal on the valve. (Be sure to reconnect the wire.)
Normally when operating 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 pres-
sure to correct settings by turning the regulator screw IN (clockwise) to increase
pressure. Turn regulator screw OUT (counterclockwise) to decrease pressure.
6.1 Gas Piping
and Pressures
(cont’d)
6.0 Mechanical
(cont’d) 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.
6.1.2 Valve Outlet or Orifice Pressure Setting (cont’d)
CAUTION: DO NOT
bottom out the gas valve
regulator adjusting
screw. This can result
in unregulated manifold
pressure causing
excess overfire and heat
exchanger failure.
FIGURE 10 - Top View of Valves showing Outlet Pressure Tap and Adjustment Locations
Single-Stage
Valve
(two styles)
Two-Stage Valve
Adjust High
Fire Outlet
Pressure
Adjust Low
Fire Outlet
Pressure
Inlet
Pressure
Tap 1/8” Outlet
Pressure Tap
1/8” Outlet
Pressure Tap Inlet Pressure Tap
Adjust Outlet Pressure
1/8” Outlet
Pressure Tap
Adjust Outlet
Pressure
Inlet
Pressure Tap