NOTE: If measuring gas pressure at the drip leg or Honeywell VR9205 gas valve, a
3.Turn ON the gas supply and operate the furnace and all other gas consuming appliances on the same gas supply line.
4.Measure furnace gas supply pressure with burners firing. Supply pressure must be within the range specified in the Inlet Gas Supply Pressure table.
Inlet Gas Supply Pressure
Natural Gas | Minimum: | 4.5" w.c. | Maximum: | 10.0" w.c. |
Propane Gas | Minimum: | 11.0" w.c. | Maximum: | 13.0" w.c. |
If supply pressure differs from table, make the necessary adjust- ments to pressure regulator, gas piping size, etc., and/or consult with local gas utility.
5.Turn OFF gas to furnace at the manual shutoff valve and disconnect manometer. Reinstall plug before turning on gas to furnace.
6.Turn OFF any unnecessary gas appliances stated in step 3.
Gas Line
Gas
Shutoff
Valve
Gas Line
To Furnace
Open To
Atmosphere
Drip Leg Cap
With Fitting
Manometer Hose
Manometer
Measuring Inlet Gas Pressure (Alt. Method)
GAS MANIFOLD PRESSURE MEASUREMENT AND ADJUSTMENT
CAUTION
TO PREVENT UNRELIABLE OPERATION OR EQUIPMENT DAMAGE, THE GAS MANIFOLD PRESSURE MUST BE AS SPECIFIED ON THE UNIT RATING PLATE. ONLY MINOR ADJUSTMENTS SHOULD BE MADE BY ADJUSTING THE GAS VALVE PRESSURE REGULATOR.
Only small variations in gas pressure should be made by adjust- ing the gas valve pressure regulator. The manifold pressure must be measured with the burners operating. To measure and adjust the manifold pressure, use the following procedure.
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.Outlet pressure tap connections:
a.Honeywell VR9205 valve: Remove the outlet pressure tap plug. Install an 1/8" NPT hose barb fitting into the outlet pressure tap.
b.
4.Attach a hose and manometer to the outlet pressure barb fitting (Honeywell valve) or outlet pressure tap
5.Turn ON the gas supply.
6.Turn on power and close thermostat “R” and “W1” contacts to provide a call for low stage heat.
7.Measure the gas manifold pressure with burners firing. Adjust manifold pressure using the Manifold Gas Pressure table shown below.
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. Replace regulator cover screw.
9.Close thermostat “R” and “W2” contacts to provide a call for high stage heat.
10.Remove regulator cover screw from the high (HI) outlet pressure regulator adjust tower and turn screw clockwise to increase pressure or counterclockwise to decrease pressure. Replace regulator cover screw.
11.Turn off all electrical power and gas supply to the system.
12.Remove the manometer hose from the hose barb fitting or outlet pressure tap.
13.Replace outlet pressure tap:
a.Honeywell VR9205 valve: Remove the 1/8" NPT hose barb fitting from the outlet pressure tap. Replace the outlet pressure tap plug and seal with a high quality thread sealer.
b.
14.Turn on electrical power and gas supply to the system.
15.Close thermostat contacts “R” and “W1/W2” to energize the valve.
Using a leak detection solution or soap suds, check for leaks at outlet pressure boss plug (Honeywell valve) or screw
NOTE: For gas to gas conversion, consult your dealer for appropriate conversion.
Manifold Gas Pressure
Gas | Rate | Range | Nominal | |
|
|
|
| |
Natural | Low Stage | 1.7 to 2.3" w.c. | 2.0" w.c. | |
High Stage | 3.2 to 3.8" w.c. | 3.5" w.c. | ||
| ||||
Propane | Low Stage | 5.7 to 6.3" w.c. | 6.0" w.c. | |
High Stage | 9.7 to 10.3" w.c. | 10.0" w.c. | ||
|
GAS INPUT RATE MEASUREMENT (NATURAL GAS ONLY)
The gas input rate to the furnace must never be greater than that specified on the unit rating plate. To measure natural gas input using the gas meter, use the following procedure.
1.Turn OFF the gas supply to all other
2.While the furnace is operating, time and record one complete revolution of the smallest gas meter dial.
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