37
If supply pressure differs from table, make the necessary adjustments to pres-
sure 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 MANIFOLD PRESSURE MEASUREMENT AND ADJUSTMENT
Only small variations in gas pressure should be made by adjusting 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. White-Rodgers 36J54 valve: Back outlet pressure test screw (inlet/outlet
pressure tap) out one turn (counterclockwise, not more than one turn).
4. Attach a hose and manometer to the outlet pressure barb fitting
(Honeywell valve) or outlet pressure tap (White-Rodgers valve).
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. White-Rodgers 36J54 valve: 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. 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 tap plug (Honeywell valve) or screw (White-Rodgers valve). Bubbles
forming indicate a leak. SHUT OFF GAS AND REPAIR ALL LEAKS IMMEDI-
ATELY!
NOTE: For gas to gas conversion, consult your dealer for appropriate
conversion.
GAS INPUT RATE MEASUREMENT (NATURAL GAS ONLY)
The actual 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 gas-burning appliances except the furnace.
Gas Line
Gas
Shutoff
Valve
Gas Line
To Furnace
Drip Leg Cap
With Fitting
Manometer Hose
Measuring Inlet Gas Pressure (Alt. Method)
Figure 47
T
O
PREVENT
UNRELIABLE
OPERATION
OR
EQUIPMENT
DAMAGE
,
THE
GAS
MANIFOLD
PRESSURE
MUST
BE
AS
SPECIFIED
ON
THE
UNIT
RATING
PLATE
. O
NLY
MINOR
ADJUSTMENTS
SHOULD
BE
MADE
BY
ADJUSTING
THE
GAS
VALVE
PRESSURE
REGULATOR
.
CAUTION
Range Nominal
Natural Low Sta
e 1.6 - 2.2" w .c. 1.9" w .c.
Hi
h Sta
e 3.2 - 3.8" w .c. 3.5" w .c.
Propane Low Sta
e 5.7 - 6.3" w .c. 6.0" w .c.
Hi
h Sta
e 9.7 - 10.3" w .c
10.0" w .c.
Manifold Gas Pressure
Gas
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