Carrier PG92MSA Installation, Start-Up, Operating And Service And Maintenance Instructions page 58

PG92MSA: Installation, Start-up, Operating and Service and Maintenance Instructions
3. Restore furnace to normal operating condition.
a. Turn gas valve ON/OFF switch to OFF.
b. Remove water column manometer or similar device from
manifold pressure tap.
c. Tighten set screw on manifold tower pressure tap with 3/32-in.
hex wrench, or if ⅛-in. NPT plug was removed, apply pipe dope
sparingly to end of plug and re-install in the gas valve.
d. Turn gas valve ON/OFF switch to ON.
e. Check for gas leaks and verify furnace operation.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal injury, death,
and/or property damage.
Manifold pressure tap set screw must be tightened and 1/8-in. NPT pipe
plug must be installed to prevent gas leaks.
Adjust Temperature Rise
4. 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.
WARNING
!
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.
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.
g. When correct input rate and temperature rise is achieved, turn
gas valve ON/OFF switch to OFF.
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
!
FIRE HAZARD
Failure to follow this warning could result in personal injury, death,
and/or property damage.
Reinstall manifold pressure tap plug in gas valve to prevent gas leak.
h. Remove manometer or similar device from gas valve.
i. Reinstall manifold pressure tap plug in gas valve.
!
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in reduced furnace life.
Recheck temperature rise. It must be within limits specified on the
rating plate. Recommended operation is at the mid-point of rise range
or slightly above.
5. Adjust heating blower-OFF delay. The blower-OFF delay has four
adjustable settings from 90 sec to 180 sec. Refer to the FURNACE
CONTROL PROGRAMMING AND NAVIGATION section of
this manual for instructions.
Factory off delay setting is 120 sec.
6. Set airflow CFM for cooling. See
filter).
7. Adjust cooling blower-OFF delay. Refer to the FURNACE
CONTROL PROGRAMMING AND NAVIGATION section of
this manual for instructions.
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked in the
Start-up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes
air-circulating blower motor, if furnace overheats. By using this
method to check the temperature limit control, it can be established
that the limit is functioning properly and that the limit will operate
if there is a restricted return-air supply or motor failure. If the limit
control does not function during this test, the cause must be
determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of cardboard or sheet
metal until the limit trips.
c. Unblock return air to permit normal circulation.
d. Burners will re-light when furnace cools down.
2. Check Pressure Switch(es)
This control proves operation of the draft inducer blower.
a. Turn off 115-V power to furnace.
b. Disconnect inducer motor lead wires from wire harness.
c. Turn on 115-V power to furnace.
d. Set thermostat to "call for heat" and wait 1 minute. When low
pressure switch is functioning properly, hot surface igniter
should NOT glow and control diagnostic light flashes a status
code (31.1). If hot surface igniter glows when inducer motor is
disconnected, shut down furnace immediately.
e. Determine reason low pressure switch did not function properly
and correct condition.
f. Turn off 115-V power to furnace.
g. Reconnect inducer motor wires, replace door, and turn on 115-V
power.
h. Blower will run for 90 sec before beginning the call for heat
again.
i. Furnace should ignite normally.
58
WARNING
WARNING
Table 18-Air Delivery CFM (with