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11. Turn gas supply manual shutoff valve to OFF
position.
12. Turn off furnace power supply.
13. Remove manometer from the inlet pressure tap of the
gas valve.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Inlet pressure tap set screw must be tightened and
1/8−in. NPT pipe plug must be installed to prevent gas
leaks.
14. Tighten set screw on inlet tower pressure tap with
3/32−in. hex wrench, or if 1/8−in. NPT plug was re-
moved, apply pipe dope sparingly to end of plug and
re−install in the gas valve.
Adjust Manifold Pressure
1. Adjust manifold pressure to obtain proper gas input
rate. (See Fig. 3)
a. Turn gas valve ON/OFF switch to OFF.
b. Loosen set screw on manifold tower pressure tap no
more than one full turn with a 3/32−in. hex wrench,
or remove manifold pressure tap plug from gas valve.
c. Connect a water column manometer or similar
device to manifold pressure tap.
d. Turn gas valve ON/OFF switch to ON.
e. Manually close blower door switch.
f. Jumper R and W thermostat connections on control
to start furnace. (See Fig. 2)
g. Remove regulator adjustment cap from gas valve
pressure regulator (See Fig. 3) and turn adjusting
screw (3/16 or smaller flat−tipped screwdriver)
counterclockwise (out) to decrease input rate or
clockwise (in) to increase input rate.
NOTICE
DO NOT set low−heat manifold pressure less than 2.8−in.
w.c. (697 Pa) or more than 3.8−in. w.c. (947 Pa) for natural
gas. If required manifold pressure is outside this range,
change main burner orifices.
h. When correct input is obtained, replace cap that
conceals gas valve regulator adjustment screws.
440 04 7101 09
i. Remove jumper R to W.
2. Verify natural gas input rate by clocking meter.
NOTE: Contact your HVAC distributor or gas supplier for
metric gas meter Tables, if required.
a. Turn off all other gas appliances and pilots served by
b. Jumper R to W.
c. Run furnace for 3 minutes.
d. Measure time (in sec) for gas meter to complete 1
e. Refer to Table 3 for cubic ft. of gas per hr.
f. Multiply gas rate cu ft./hr by heating value (Btuh/cu
g. If clocked rate does not match required input from
3.
Restore furnace to normal operating condition.
a. Turn gas valve ON/OFF switch to OFF.
b. Remove water column manometer or similar de-
c. Tighten set screw on manifold tower pressure tap
d. Turn gas valve ON/OFF switch to ON.
e. Check for gas leaks and verify furnace operation.
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Manifold pressure tap set screw must be tightened
and 1/8−in. NPT pipe plug must be installed to
prevent gas leaks.
Specifications subject to change without notice.
Main burner flame should be clear blue, almost
transparent (See Fig. 12).
the meter.
revolution and note reading. The 2 or 5 cubic feet dial
provides a more accurate measurement of gas flow.
ft.) to obtain input. If clocked rate does not match
required input from Step 1, increase manifold
pressure to increase input or decrease manifold
pressure to decrease input. Repeat steps b through
e until correct input is achieved. Re−install regulator
seal cap on gas valve.
Step 1, increase manifold pressure to increase
input or decrease manifold pressure to decrease
input. Repeat steps b through e of Step 1 until
correct heat input is achieved. Re--install regulator
seal cap on gas valve.
vice from manifold pressure tap.
with 3/32−in. hex wrench, or if 1/8−in. NPT plug
was removed, apply pipe dope sparingly to end of
plug and reinstall in the gas valve.
WARNING
!
5
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