SYSTEM OPERATION
44
2. Remove the burner compartment door and move the
furnace gas valve manual control to the OFF position.
3. Close the manual gas shutoff valve external to the furnace.
4. Replace the burner compartment door.
GAS SUPPLY PRESSURE MEASUREMENT
Figure 46A
Figure 46B
Natural Gas Minimum: 4.5" w.c. Maximum: 10.0" w.c.
Propane Gas Minimum: 11.0" w.c. Maximum: 13.0" w.c.
INLET GAS SUPPLY PRESSURE
CAUTION
T
O
PREVENT
UNRELIABLE
OPERATION
OR
EQUIPMENT
DAMAGE
,
THE
INLET
GAS
SUPPLY
PRESSURE
MUST
BE
AS
SPECIFIED
ON
THE
UNIT
RATING
PLATE
WITH
ALL
OTHER
HOUSEHOLD
GAS
FIRED
APPLIANCES
OPERATING
.
The line pressure supplied to the gas valve must be within
the range specified below. The supply pressure can be mea
-
sured at the gas valve inlet pressure tap or at a hose fitting
installed in the gas piping drip leg. The supply pressure must
be measured with the burners operating. To measure the gas
supply pressure, use the following procedure.
1. Turn OFF gas to furnace at the manual gas shutoff valve
external to the furnace.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at either the gas valve inlet pressure
tap or the gas piping drip leg. See White-Rodgers 36J54
gas valve figure for location of inlet pressure tap
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.
If supply pressure differs from table, make the necessary
adjustments 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 MANIFOLD PRESSURE MEASUREMENT AND
ADJUSTMENT
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
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:
White-Rodgers 36J27
valve: Remove 1/8” N.P.T. plug
using 5/16” Allen wrench & connect proper adapter for
manometer connection.
4. Attach a hose and manometer to 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 heat.
7. Measure the gas manifold pressure with burners firing.
Adjust manifold pressure.
8. Use the modulation adjustment screw on the gas valve
and turn clockwise one click using a pocket screwdriver
to increase gas flow. Allow the gas flow to adjust ap
-
proximately 15 seconds before moving the adjustment
screw again. Turn the modulation adjustment screw
counterclockwise with a pocket screwdriver to decrease
gas flow if this adjustment is needed. Allow the gas flow
to adjust approximately 15 seconds before moving the
adjustment screw again. These changes should only be
done to fine tune the gas flow.
