60
440 01 4801 00
Specifications subject to change without notice.
8. When main burners ignite, confirm inlet gas pressure is
Between 4.5 in. w.c. and 13.6 in. w.c.
9. Remove jumper across thermostat connections to terminate
call for heat. Wait until the blower off delay is completed.
10. Turn furnace gas valve electric switch to OFF position.
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.
14. Tighten set screw on inlet 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 re--install in the gas
valve.
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.
!
WARNING
Adjust Manifold Pressure
1. Adjust manifold pressure to obtain low fire input rate. See
Fig. 64.
INLET PRESSURE TAP
SET SCREW: 3/32” HEX HEAD
ACCEPTS 5/16” HOSE
CONNECTION
ON/OFF SWITCH
MANIFOLD PRESSURE TAP SET SCREW:
3/32” HEX HEAD ACCEPTS
5/16” HOSE CONNECTION
REGULATOR SEAL CAP
(REGULAR ADJ. UNDER CAP)
OUTP
1/2” NPT
INLET
1/2” NPT
OUTLET
Representative drawing only, some models may vary in appearance.
A170117
Fig. 64 -- Gas Valve with Tower Pressure Ports
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 the 1/8 inch NPT plug from the manifold
pressure tap on the 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. Move setup SW1--2 on furnace control to ON position to
lock furnace in low--heat operation. See Fig. 60 and 38.
f. Manually close blower door switch.
g. Jumper R and W/W1 thermostat connections on control to
start furnace. See Fig. 38.
h. Remove regulator adjustment cap from low heat gas valve
pressure regulator and turn low--heat adjusting screw (3/16
or smaller flat--tipped screwdriver) counterclockwise (out)
to decrease input rate or clockwise (in) to increase input
rate. See Fig
.
64.
DO NOT set low--heat manifold pressure less than 1.3--in. w.c.
(324 Pa) or more than 1.7 in. w.c. (423 Pa) for natural gas. If
required manifold pressure is outside this range, change main
burner orifices to obtain manifold pressure in this range.
NOTICE
i. Install low--heat regulator adjustment cap.
j. Move setup switch SW1--2 to OFF position after complet-
ing low--heat adjustment.
k. Leave manometer or similar device connected and proceed
to Step 2.
2. Adjust manifold pressure to obtain high fire input rate See
Fig. 64.
a. Jumper R to W/W1 and W2 thermostat connections on fur-
nace control. This keeps furnace locked in high--heat oper-
ation.
b. Remove regulator adjustment cap from high--heat gas
valve pressure regulator and turn high heat adjusting screw
(3/16--in. or smaller flat--tipped screwdriver) counterclock-
wise (out) to decrease input rate or clockwise (in) to in-
crease input rate. See Fig. 64.
DO NOT set high--heat manifold pressure less than 3.2--in.
w.c. (797 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 to obtain manifold pressure in this
range.
NOTICE
c. When correct input is obtained, replace caps that conceal
gas valve regulator adjustment screws. Main burner flame
should be clear blue, almost transparent See Fig. 65.
Burner Flame
Burner
Manifold
A89020
Fig. 65 -- Burner Flame
d. Remove jumpers R to W/W1 and R to W2.
Clocking the Meter
1. 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 the
meter.
b. Move setup switch SW1--2 to ON position. This keeps fur-
nace locked in low--heat operation when only W/W1 is en-
ergized..
c. Jumper R to W/W1.
d. Run furnace for 3 minutes in low--heat operation.
e. Measure time (in sec) for gas meter to complete one revolu-
tion and note reading. The 2 or 5 cubic feet dial provides
a more accurate measurement of gas flow.
f. Refer to Table 21 for cubic ft. of gas per hr.
g. Multiply gas rate cu ft./hr by heating value (Btuh/cu ft.) to
obtain input rate.
h. 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 of Step 1 until correct low--heat input is achieved. Re--in-
stall low heat regulator seal cap on gas valve.
i. Jumper R to W/W1, and W2. This keeps furnace locked
in high--heat operation when both W/W1 and W2 are ener-
gized.
j. Repeat items d through g for high--heat operation, repeat-
ing Step 2 and adjusting the high--heat regulator screw as
required.
