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935SB: Installation, Start-up, Operating and Service Maintenance Instructions
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 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
2
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.
15. 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
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.
Fig. 65 – Gas Control Valve
16. 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.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
tower pressure tap no more than one
Fig.
65)
b. Jumper R and W thermostat connections at the furnace control
board.
c. Run furnace for 15 minutes in heating operation.
d. 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.
e. For cubic ft. of gas per hr
f. 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.
17. Restore furnace to normal operating condition.
a. When correct input rate and temperature rise is achieved, turn
gas valve ON/OFF switch to OFF.
b. Remove manometer or similar device from gas valve.
c.
Tighten set
screw on outlet tower
wrench.
d. Turn gas valve ON/OFF switch to ON.
e. Check for gas leaks and verify furnace operation.
Adjust Temperature Rise
18. 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 door must be installed when taking temperature rise
reading. Leaving blower door off will result in incorrect temperature
measurements, due to possible changes in duct static pressure and
airflow.
This furnace must operate within the temperature rise ranges specified
on the furnace rating plate. Determine the air temperature as follows:
a. Place duct thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not "see" heat
exchangers so that radiant heat does not affect thermometer
readings. This is particularly important with straight run ducts.
b. When thermometer readings stabilize, subtract return-air
temperature from supply-air temperature to determine
temperature rise.
If the temperature rise is outside this range, check the following:
(1.) Gas input for heating operation.
(2.) Derate for altitude if applicable.
(3.) Return and supply ducts for excessive restrictions causing
static pressures greater than 0.50-in. w.c.
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury or death.
Blower access door switch opens 115-V power to control. No
component operation can occur unless switch is closed. Caution must
be taken when manually closing this switch.
c. Adjust air temperature rise by adjusting blower speed. Increase
blower speed to reduce temperature rise. Decrease blower speed
to increase temperature rise
d. Turn thermostat down below room temperature and remove
blower access door.
A180231
e. Refer to the FURNACE CONTROL PROGRAMMING AND
NAVIGATION section of this manual for instructions on
adjusting the blower speed.
f. Repeat steps a through e until temperature rise is within range on
rating plate.
51
(Table
26).
pressure tap with 3/32 in. hex
WARNING
!
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