035-17468-001 Rev. A (801)
Unitary Products Group
27
ADJUSTMENT OF MANIFOLD GAS PRESSURE
Manifold gas pressure may be measured by two different pro-
cedures. It may be measured with the burner box cover in
place or it may be measured with the burner box cover
removed. Follow the appropriate section, 1a or 1b in the
instructions below.
1.
Read the inlet gas pressure using either of the two
methods below.
a.
Reading the gas pressure with the burner box
cover in place
- Disconnect the pressure reference
hose from the right side of the burner box. Using a
tee fitting and a short piece of hose, connect the
negative side of the manometer to the burner box
pressure reference port. Connect the positive side
of the manometer to the adapter previously installed
in the gas valve, See Figure 37 or 38.
b.
Reading the gas pressure with the burner box
cover removed
- Remove the screws securing the
burner box front cover plate. Remove the cover. It is
gasketed and may stick in place. Connect the posi-
tive side of the manometer to the adapter previously
installed in the gas valve as shown in Figure 37 or
38. There will be no second connection to the
manometer as it will reference atmospheric pres-
sure.
The regulated outlet pressures, both low and high, have been
calibrated at the factory. Additional pressure adjustment
should not be necessary. If adjustment is necessary, set to
the following specifications. After adjustment, check for gas
leakage.
High Outlet Pressure Adjustment
1.
Turn off all electrical power to the system at main fuse or
circuit breaker.
2.
Attach a manometer to the outlet pressure tap of the
valve.
3.
Turn on power and energize main and redundant (P.M.)
solenoids as well as the HI terminal.
4.
Remove high adjustment seal screw to expose the 3/32”
set screw (Refer to Figure 36).
5.
To increase outlet pressure, turn the 3/32” set screw
clockwise. To decrease outlet pressure, turn the set
screw counterclockwise. Adjust regulator until pressure
shown on manometer matches the pressure specified on
the appliance rating plate.
6.
Replace low adjustment seal screw and tighten securely.
Cycle the valve several times to verify regulator setting.
7.
Remove manometer and replace the outlet pressure tap
plug.
Low Outlet Pressure Adjustment
1.
Turn off all electrical power to the system at main fuse or
circuit breaker.
2.
Attach a manometer to the outlet pressure tap of the
valve.
3.
Turn on power and energize main and redundant (P.M.)
solenoids. Do not energize HI terminal.
4.
Remove low adjustment seal screw, See Figure 36.
5.
To
increase
outlet pressure, turn the 3/32” set screw
below the low adjustment seal screw clockwise. To
decrease
outlet pressure, turn the set screw counter-
clockwise. Adjust regulator until pressure shown on
manometer matches the pressure specified on the appli-
ance rating plate.
6.
Replace high adjustment seal screw and tighten
securely. Cycle the valve two or three times to verify reg-
ulator setting.
7.
Remove manometer and replace the outlet pressure tap
plug.
.
Natural Gas
Low Fire
1.6 IWG
High Fire
3.5 IWG
WITH BURNER BOX COVER IN PLACE
WITH BURNER BOX COVER REMOVED
FIGURE 37 :
Reading Gas Pressure - Upflow Models
GAS VALVE
OUTLET
PRESSURE TAP
BURNER BOX PRESSURE
REFERENCE HOSE
BURNER BOX
WITH COVER
U-TUBE
MANOMETER
3.5 IN
WATER COLUMN
GAS PRESSURE
SHOWN
TEE
FITTING
6
5
4
3
2
1
0
1
2
3
4
5
6
GAS VALVE
OUTLET
PRESSURE TAP
BURNER BOX
PRESSURE
REFERENCE HOSE
(NOT USED)
U-TUBE
MANOMETER
3.5 IN
WATER COLUMN
GAS PRESSURE
SHOWN
BURNER BOX
WITH COVER
REMOVED
6
5
4
3
2
1
0
1
2
3
4
5
6
