SERVICING
30
3. Turn ON the gas and electrical power supply and operate
the furnace.
4. Measure gas manifold pressure with burners firing. Adjust
manifold pressure using the table below.
Manifold Gas Pressure
Natural Gas
2.8 -3.2" w.c.
The final manifold pressure must not vary from the above
specified pressures. Any necessary major changes in gas flow
rate should be made by changing the size of the burner orifice.
5. White-Rodgers 36J22 Valves:
a. Back outlet pressure test screw (inlet/outlet pressure
boss) out one turn (counterclockwise, not more than
one turn).
b. Attach a hose and manometer to the outlet pressure
outlet pressure boss.
c. Turn ON the gas supply.
d. Turn on power and close thermostat “R” and “W”
contacts to provide a call for low stage heat.
e. Measure the gas manifold pressure with burners firing.
Adjust manifold pressure using the
Manifold Gas
Pressure
table shown below.
f. Remove regulator cover screw from the outlet pressure
regulator adjust tower and turn screw clockwise to
increase pressure or counterclockwise to decrease
pressure. Replace regulator cover screw.
i. Turn off all electrical power and gas supply to the
system.
j. Remove the manometer hose from the hose barb fitting
or outlet pressure boss.
k. Turn outlet pressure test screw in to seal pressure port
(clockwise, 7 in-lb minimum).
WARNING
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AY B
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6. Turn on gas to furnace and check for leaks. If leaks are
found, repair and then reinstall burner compartment door.
7. Turn on electrical power and verify proper unit operation.
Pressure Regulator
Adjustment
(Under Cap Screw)
Gas Valve
On/Off
Selector
Switch
INLET
OUTLET
Inlet Pressure
Tap
Outlet Pressure
Tap
WARNING
H
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OLTAG
E
D
IS
CONN
E
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ALL
E
L
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AND
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NG.
WARNING
CHECKING HOT SURFACE IGNITER
120V Silicon Nitride Igniter
- ULN furnaces use a 120V
silicone nitride igniter, part #0130F00717. The normal
operating temperature is approximately 2156°F - 2678°F. At
room temperature the igniter ohm reading should be from
20-100 ohms.
L
I
N
E
V
OLTAG
E
NO
W
P
RESE
NT
WARNING
CHECKING PRESSURE TRANSDUCER (96% ULN)
The 96% ULN products utilize a pressure transducer. The
pressure transducer signals the control board to modulate the
heating cycle during a call for heat by regulating the induced
draft motor speed. By regulating the speed of the induced
draft motor, proper air-fuel ratios are maintained.
Sensing range specification: 0.0-2.0 inches W.C.
Voltage specifications:
• Steady State: 5.0 vDC from red to green wire (transducer
wiring harness input)
• With Inducer off: 0.25 vDC from black to green wire
(transducer wiring harness output).
• During operation: Output range equals 0.25 - 4.0 vDC
Potential errors:
1. Control board does not receive 0.25 vDC for inducer motor
with motor off
a. Will result in 2-flash error code on the control board
2. Control board does not receive the required voltage
change (0.25 - 4.0 vDC) during inducer motor operation.
a. Will result in 3-flash error code on the control board
