Goodman Mfg VC8 - Manual (Page 25)

25
S
TART
-
UP
P
ROCEDURE AND
A
DJUSTMENT
Gas Line
Gas
Shutoff
Valve
Gas Line
To Furnace
Drip Leg Cap
With Fitting
Manometer Hose
Manometer
Open To
Atmosphere
Measuring Inlet Gas Pressure (Alt. Method)
G
AS
M
ANIFOLD
P
RESSURE
M
EASUREMENT AND
A
DJUSTMENT
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
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.
Range Nom inal
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.
Manifold Gas Pressure
Gas
G
AS
I
NPUT
R
ATE
M
EASUREMENT
(N
ATURAL
G
AS
O
NLY
)
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.