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3. Gas supply pressure to the furnace must be greater than
4.5- -In. W.C. (0.16 psig ) but not exceed 14- -In. W.C. (0.5
psig).
4. Check all manual- -reset switches for continuity.
5. Install blower compartment door. Door must be in place to
operate furnace.
6. Replace outer door.
Start- -Up Procedures
WARNING
!
FIRE AND EXPLOSION HAZARD
Failure to follow this warning could cause personal injury,
death and/or property damage.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made specifically for
the detection of leaks to check all connections. A fire or
explosion may result causing property damage, personal
injury or loss of life.
1. Purge gas lines after all connections have been made.
2. Check gas lines for leaks.
3. Verify furnace shut down by lowering thermostat setting
below room temperature.
4. Verify furnace restarts by raising thermostat setting above
room temperature.
Adjustments
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in injury, death
and/or property damage.
DO NOT bottom out gas valve regulator adjusting screw.
This can result in unregulated gas valve outlet pressure and
result in excess overfire and heat exchanger failures.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in reduced furnace
life.
DO NOT redrill orifices. Improper drilling (burrs,
out- -of- -round holes, etc.) can cause excessive burner noise
and misdirection of inlet gas. (See Fig. 33)
Furnace gas input rate on rating plate is for installations at
altitudes up to 2,000 ft. (610 M). Furnace input rate must be
within +/- -2 percent of furnace rating plate input.
1. Determine the correct gas input rate. Refer to the unit
rating plate. The input rating for altitudes above 2,000 ft.
(610 M) must be reduced by 2 percent for each 1,000 ft.
(305 M) above sea level. For installations below 2,000 ft.
(610 M), refer to the unit rating plate. For installation
above 2,000 ft. (610 M), multiply the input on the rating
plate by the derate multiplier in Table 10 for the correct
input rate.
2. Determine the correct outlet gas pressure adjustment.
a. Obtain average yearly gas heat value (at installed altitude)
from local gas supplier.
Table 10 – Altitude Derate Multiplier for U.S.A.
ALTITUDE
(FT. / M)
0–2000 (0--- 610)
2001–3000 (610--- 914)
3001–4000 (914--- 1219)
4001–5000 (1219--- 1524)
5001–5400 (1525--- 1646)
* Derate multiplier factors are based on midpoint altitude for altitude
range.
b. Obtain average yearly gas specific gravity from local gas
supplier.
c. Find closest natural gas heat value and specific gravity
in Tables 12
through
d. Follow heat value and specific gravity lines to point of
intersection to find outlet pressure setting for proper
operation.
3. Check Inlet Gas Pressure
The inlet gas pressure must be checked with the furnace
operating. This is necessary to make sure the inlet gas pressure
does not fall below the minimum pressure of 4.5 in. w.c.
a. Make sure the gas supply is turned off to the furnace and
at the electric switch on the gas valve
b. Loosen set screw on inlet tower pressure tap no more than
one full turn with a 3/32
1/8
in. NPT plug from the inlet pressure tap on the gas
−
valve.
c. Connect a manometer to the inlet pressure tap on gas
valve.
d. Turn on furnace power supply.
e. Turn gas supply manual shutoff valve to ON position.
f. Turn furnace gas valve switch to ON position.
g. Jumper R and W thermostat connections at the furnace
control board.
h. When main burners ignite, confirm inlet gas pressure is
between 4.5 in. W.C. (1125 Pa) and 13.6 in. W.C. (3388
Pa).
i. Remove jumper across thermostat connections to
terminate call for heat. Wait until the blower off delay is
completed.
j. Turn furnace gas valve electric switch to OFF position.
k. Turn gas supply manual shutoff valve to OFF position.
l. Turn off furnace power supply.
m. Remove manometer from the inlet pressure tap of the gas
valve.
n. Tighten set screw on inlet tower pressure tap with
3/32
in. hex wrench, or if 1/8
−
removed, apply pipe dope sparingly to end of plug and
re
install in 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.
4. Adjust gas valve outlet pressure determined in Step 2. to
obtain correct input rate.
a. Turn gas valve ON/OFF switch to OFF.
24
PERCENT
DERATE
OF
MULTIPLIER
DERATE
FACTOR*
0
1.00
4--- 6
0.95
6--- 8
0.93
8--- 10
0.91
10--- 11
0.90
14.
−
in. hex wrench or remove the
in. NPT plug was
−
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