Goodman Mfg VC8 User Manual

25

Gas Line

Gas
Shutoff

Valve

Gas Line 
To Furnace

Drip Leg Cap 
With Fitting

Manometer Hose

Manometer

Open To
Atmosphere

O

nly small variations in gas pressure should be made by ad-

justing 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

boss plug.  Install an 1/8" NPT hose barb fitting into
the outlet pressure tap.

b. White-Rodgers 36G54 valve: 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

barb fitting (Honeywell valve) or outlet pressure boss
(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 boss.

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 boss plug and seal with a high quality
thread sealer.

b. White-Rodgers 36G54 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 boss plug (Honeywell valve) or screw (White-
Rodgers valve).  Bubbles forming indicate a leak.  SHUT OFF
GAS AND REPAIR ALL LEAKS IMMEDIATELY!
NOTE: For gas to gas conversion, consult your dealer for
appropriate conversion.

Natural

Low  Stage  1.6 - 2.2"  w .c.

1.9" w .c.

High Stage

3.2 - 3.8"  w .c.

3.5" w .c.

Propane

Low  Stage  5.7 - 6.3"  w .c.

6.0" w .c.

High Stage

9.7 - 10.3" w .c.

10.0" w .c.

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 gas-burning

appliances except the furnace.

2. While the furnace is operating, time and record one

complete revolution of the smallest gas meter dial.

3. Calculate the number of seconds per cubic foot (sec/ft

3

)

of gas being delivered to the furnace.  If the dial is a one
cubic foot dial, divide the number of seconds recorded in
step 2 by one.  If the dial is a two cubic foot dial, divide
the number of seconds recorded in step 2 by two.