SERVICING
121
LINE VOLTAGE NOW PRESENT
WARNING
3. Turn ON the gas and electrical power supply and oper-
ate the furnace.
4. Measure gas manifold pressure with burners firing. Ad-
just manifold pressure using the table below.
3.5" w.c.
10.0" w.c.
Manifold Gas Pressure
Natural Gas
Propane Gas
The final manifold pressure must not vary more than ± 0.3 “
w.c. 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. To adjust the gas valve pressure regulator, remove the
regulator cap.
6. Turn the adjustment screw clockwise to increase the
pressure, or counterclockwise to decrease the pressure.
7. Securely replace the regulator cap.
WARNING
HIGH VOLTAGE
D
ISCONNECT ALL ELECTRICAL POWER AND SHUT OFF GAS
SUPPLY BEFORE SERVICING OR INSTALLING THIS UNIT.
MULTIPLE POWER SOURCES MAY BE PRESENT. FAILURE TO
DO SO MAY CAUSE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH.
8. Disconnect manometer after turning off gas at manual
shutoff valve. Reinstall gas valve outlet pressure tap plug
before turning on gas to furnace.
9. Turn on gas to furnace and check for leaks. If leaks are
found, repair and then reinstall burner compartment door.
10. Turn on electrical power and verify proper unit operation.
Gas Manifold Pressure Measurement and Adjust-
ment (80% & 90% Two-Stage Furnaces)
Natural Gas Adjustments
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
ELECTRICAL POWER AND SHUT OFF GAS SUPPLY
BEFORE SERVICING OR INSTALLING.
1. After turning off gas to furnace at the manual gas shutoff
valve external to the furnace, remove burner compart-
ment door to gain access to the gas valve.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at the gas valve outlet pressure
tap. Refer to previous Measuring Manifold Gas Pres-
sure figure for proper connection.
L
INE VOLTAGE NOW PRESENT
WARNING
3. Turn ON the gas and electrical power supply and oper-
ate the furnace.
4. Remove the cap screw from the high stage manifold
pressure regulator.
5. Using a 3/32" Allen wrench, adjust the high stage mani-
fold pressue regulator to the required pressure setting.
6. Reinstall high stage cap screw and recheck manifold
pressure setting with cap on.
7. Remove the cap screw from the low stage manifold pres-
sure regulator.
8. Using a 3/32" Allen wrench, adjust the low stage regu-
lator to the required pressure setting.
9. Reinstall low stage cap screw and recheck manifold
pressure setting with cap on.
WARNING
HIGH
VOLTAGE
D
ISCONNECT
ALL
ELECTRICAL POWER AND SHUT OFF GAS SUPPLY
BEFORE SERVICING OR INSTALLING.
10. Disconnect manometer after turning off gas at manual
shutoff valve. Reinstall gas valve outlet pressure tap
plug before turning on gas to furnace.
11. Turn on gas to furnace and check for leaks. If leaks are
found, repair and then reinstall burner compartment
door.
12. Turn on electrical power and verify proper unit opera-
tion. Make sure furnace operates at the proper mani-
fold pressure at both high and low stage outputs.
Gas Rate Range Nominal
High Stage 3.2 to 3.8" w.c. 3.5" w.c.
Low Stage 1.6 to 2.2" w.c. 1.9" w.c.
Manifold Gas Pressure
Natural Gas
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