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58SU0A: Installation, Start-up, Operating and Service and Maintenance Instructions
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
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
Table 12
through
Table
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−in. hex wrench or remove the 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.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
Table 10
for the correct input
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
15.
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−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.
4. Adjust gas valve outlet pressure determined in Step NO TAG to
obtain correct input rate.
a. Turn gas valve ON/OFF switch to OFF.
b. Loosen set screw on outlet tower pressure tap no more than one
full turn with a 3/32 in. hex wrench, see
c. Connect a water column manometer or similar device to pressure
tap on the gas valve.
d. Turn gas valve ON/OFF switch to ON.
e. Manually close blower door switch.
f. Set thermostat to call for heat.
g. Remove regulator seal cap and turn regulator adjusting screw
counterclockwise (out) to decrease input rate of clockwise (in) to
increase input rate.
h. Install regulator seal cap.
i. Leave manometer or similar device connected and proceed to
next step.
*
NOTE: If orifice hole appears damaged or it is suspected to have been
redrilled, check orifice hole with a numbered drill bit of correct size.
Never redrill an orifice. A burr-free and properly sized orifice hole is
essential for proper flame characteristics.
5. Verify natural gas input rate by clocking meter.
NOTE: Gas valve regulator adjustment cap must be in place for proper
input to be clocked.
a. Turn off all other gas appliances and pilots served by the meter.
b. Run furnace for 3 minutes in heating operation.
c. Measure time (in seconds) for gas meter to complete 1 revolution
and note reading. The 2 or 5 cubic feet dial provides a more
accurate measurement of gas flow.
d. Refer to
Table 11
e. Multiply gas rate (cu ft./hr) by heating value (Btuh/cu ft.) to
obtain input.
If clocked rate does not match required input from Step 1, increase gas
valve outlet pressure to increase input or decrease gas valve outlet
pressure to decrease input. Repeat steps b through e until correct input is
achieved. Reinstall regulator seal cap on gas valve.
6. Set temperature rise. The furnace must operate within the
temperature rise ranges specified on the furnace rating plate. Do not
exceed temperature rise range specified on unit rating plate.
Determine the temperature rise as follows:
NOTE: Blower access door must be installed when taking temperature
rise reading. Leaving blower access door off will result in incorrect
temperature measurements.
21
WARNING
!
Fig.
32.
for cubic ft. of gas per hr.
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