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Gas Supply And Manifold Check
Gas supply pressure and manifold pressure with the burners operating must be as specified on the rating plate.
Gas Inlet Pressure Check
Gas inlet pressure must be checked and adjusted in accordance to the type of fuel being consumed.
With Power And Gas Off:
1. Connect a water manometer or adequate gauge to the inlet pressure tap of the gas valve.
Inlet gas pressure can also be measured by removing the cap from the drip leg and installing a predrilled cap with a hose
fitting.
With Power And Gas On:
2. Put unit into heating cycle and turn on all other gas consuming
appliances.
NOTE: Inlet Gas Pressure Must Not Exceed the Maximum Value Shown
in the Inlet Gas Pressure chart.
If operating pressures differ from above, make necessary pressure regulator adjustments, check
piping size, etc., and/or consult with local utility.
Manifold Pressure Check
1 Turn OFF gas to furnace at the manual gas shutoff valve external to the furnace.
2. Turn off all electrical power to the system.
3. Back outlet pressure test screw (inlet/outlet pressure boss) out one turn (counterclockwise,
not more than one turn).
4. Attach a hose and manometer to the outlet pressure boss of the valve.
5. Turn ON the gas supply.
6. Turn on power and energize main (M) solenoid. Do not energize the HI solenoid.
7. Measure gas manifold pressure with burners firing. Adjust manifold pressure using the Manifold
Gas Pressure table.
8. Remove regulator cover screw from the low (LO) outlet pressure regulator adjust tower and
turn screw clockwise to increase pressure, or counterclockwise to decrease pressure.
9. Energize main (M) solenoid as well as the HI terminal.
10. Remove regulator cover screw from the HI outlet pressure regulator adjust tower and turn
screw clockwise to increase pressure, or counterclockwise to decrease pressure.
11. Turn off all electrical power and gas supply to the system.
12. Remove manometer hose from outlet pressure boss.
13. Turn outlet pressure test screw in to seal pressure port (clockwise,
7 in-lb minimum).
14. Turn on electrical power and gas supply to the system.
15. Turn on system power and energize valve.
16. Using a leak detection solution or soap suds, check for leaks at
pressure boss screw. Bubbles forming indicate a leak. SHUT OFF
GAS AND FIX ALL LEAKS IMMEDIATELY.
NOTE: For gas to gas conversion, consult your dealer for appropriate
conversion.
Gas Input (Natural Gas Only) Check
To measure the gas input use a gas meter and proceed as follows:
1. Turn off gas supply to all other appliances except the unit.
2. With the unit operating, time the smallest dial on the meter for one complete revolution. If this is a 2 cubic foot dial, divide
the seconds by 2; if it is a 1 cubic foot dial, use the seconds as is. This gives the seconds per cubic foot of gas being delivered
to the unit.
3. INPUT=GAS HTG VALUE x 3600 / SEC. PER CUBIC FOOT
Example: Natural gas with a heating value of 1000 BTU per cubic foot and 34 seconds per cubic foot as determined by Step 2, then:
Input = 1000 x 3600 / 34 = 106,000 BTU per Hour. NOTE: BTU content of the gas should be obtained from the gas supplier. This
measured input must not be greater than shown on the unit rating plate.
4. Relight all other appliances turned off in step 1. Be sure all pilot burners are operating.
Main Burner Flame Check
Flames should be stable, soft and blue (dust may cause orange tips but they must not be yellow) and extending directly
outward from the burner without curling, floating or lifting off.
INLET GAS PRESSURE
Natural
Propane
Gas
Natural
Low Stage
High Stage
Propane
Low Stage
High Stage
17
Min. 5.0" W.C., Max. 10.0" W.C.
Min. 11.0" W.C. , Max. 13.0" W.C.
Inlet Gas Pressure
Gas Line
Gas
Shutoff
Valve
Gas Line
To Furnace
Drip Leg Cap
With Fitting
Manometer Hose
Measuring Inlet Gas Pressure
Alternate Method
Manifold Gas Pressure
Range
1.6 - 2.2" w.c.
3.2 - 3.8" w.c.
5.7 - 6.3" w.c.
9.7 - 10.3" w.c.
Manifold Gas Pressure
Open To
Atmosphere
Manometer
Nominal
2.0" w.c.
3.5" w.c.
6.0" w.c.
10.0" w.c.
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