59CU5A: Installation, Start-up, Operating and Service and Maintenance Instructions
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
50
A180238
Fig. 67 – Orifice Hole
Furnace gas input rate on rating plate is for installation at altitudes up to
2,000 ft. (610 M). Furnace input rate must be within +/-2 percent of
furnace rating plate input.
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 for the correct input rate, see
Table 20 – Altitude Derate Multiplier for USA
1. Determine the correct gas input rate. Refer to the unit rating plate.
2. Determine the correct outlet gas pressure adjustment.
a. Obtain average yearly gas heat value (at installed altitude) from
local gas supplier.
b. Obtain average yearly gas specific gravity from local gas
supplier.
c. Find closest natural gas heat value and specific gravity, see
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
−
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.
g. Jumper R and W/W1 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
4. Adjust gas valve outlet pressure determined in Step 2. to obtain
correct input rate.
a. Turn gas valve ON/OFF switch to OFF.
b. Loosen set screw
on outlet to
wer 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 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.
A180231
Fig. 68 – Gas Control Valve
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.
a.
Jumper R an
d W/W1 t
hermostat connections at the furnace
control board.
b. Run furnace for 15 minutes in heating operation.
ALTITUDE
(FT. / M)
PERCENT
OF
DERATE
DERATE
MULTIPLIER
FACTOR
*
*. Derate multiplier factors are based on midpoint altitude for altitude range
0–2000 (0-610)
0
1.00
2001–3000 (610-914)
4–6
0.95
3001–4000 (914-1219)
6–8
0.93
4001–5000 (1219-1524)
8–10
0.91
5001–5400 (1525-1646)
10–11
0.90
BURNER
ORIFICE
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.
GAS OUTPUT
GAS INPUT
ON & OFF TOGGLE
INLET PRESSURE TAP SET
SCREW: 3/32” HEX HEAD.
ACCEPTS 5/16” HOSE
CONNECTION
GAS VALVE OUTLET
PRESSURE TAP
SET SCREW:
3/32” HEX HEAD.
ACCEPTS 5/16” HOSE
CONNECTION
1/2” NPT
OUTLET
1/2” NPT
INLET
REGULATOR
ADJUSTMENT
CAP (REGULATOR
ADJ. UNDER CAP)
