Form I-UDA, P/N 195673 Rev 13, Page 14
.
Locate the 1/8” output pressure tap on the valve (See
FIGURE 10
, page 13).
Turn
the knob on the top of the valve to “OFF”. Connect a manometer to the 1/8” pipe
outlet pressure tap in the valve. Use a water column manometer that is readable to
the nearest tenth of an inch.
3.
Single-Stage and Two-Stage High Fire
- Turn the knob on the top of the valve to
“ON”. Remove the cap from the pressure adjusting screw and adjust the gas train
pressure to the pressure selected from the table above. Adjust pressure by turning
the regulator screw IN (clockwise) to increase pressure or OUT (counterclockwise)
to decrease pressure.
Two-Stage Low Fire
- Disconnect the wire from the “HI” terminal on the gas valve
and check the low fire pressure. Turn the regulator screw to adjust the low fire outlet
pressure to the “Low Fire” pressure selected from the table. Re-connect the wire to
the gas valve.
4.
Turn up the thermostat. (
NOTE
: On Model UDAS, depress and hold the door
safety switch.) Cycle the burner once or twice to properly seat the adjustment
spring in the valve.
Re-check the pressure(s). When the outlet pressure is right for the installation,
remove the manometer and replace the cap.
Check for leak at the pressure tap fitting.
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
Manifold Pressure Settings by Altitude for CANADA
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
2001-4500
611-1373
2.8
1.5
8.1
4.1
6. Mechanical
(cont’d)
6.1 Gas Piping
and Pressures
(cont’d)
)
Open the manual valve and operate the heater. (NOTE: On Model UDAS, 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. 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.