Check Safety Controls; Checklist - Carrier 58CTA Installation And Service Instructions Manual

THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
10 TURNS
FROM UNIT 24-V
CONTROL TERMINALS
EXAMPLE: 5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
Fig. 54—Amp Draw Check With Ammeter
b. Turn Dip switch 2 and 3 ON or OFF for desired blower off
delay. (See Table 12 and Fig 32.)
10. Set thermostat heat anticipator.
a. Mechanical thermostat—Set thermostat heat anticapator to
match the amp draw of the electrical components in the
R-W/W1 circuit. Accurate amp draw readings can be
obtained at the wires normally connected to thermostat
subbase terminals, R and W. The thermostat anticipator
should NOT be in the circuit while measuring current.
(1.) Set LHT switch on furnace control board to ON.
(2.) Remove thermostat from sub-base or from wall.
(3.) Connect an amp meter as shown in Fig. 54 across the
R and W subbase terminals or R and W wires at wall.
(4.) Record amp draw across terminals when furnace is in
low heat and after blower starts.
(5.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
(6.) Turn LHT switch OFF.
(7.) Install blower access door.
b. Electronic thermostat: Set cycle rate for 3 cycles per hr.
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11. Set airflow CFM for cooling
Select the desired blower motor speed lead for cooling
airflow. See Table 5-Air Delivery-CFM (With Filter). See
Table 11 for lead color identification.
Step 4—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(es)
This control shuts off combustion system and energizes
air-circulating blower motor, if furnace overheats. By using
this method to check limit control, it can be established that
limit is functioning properly and will operate if there is a
restricted return-air supply or motor failure. If limit control
does not function during this test, cause must be determined
and corrected.
HOOK-AROUND
AMMETER
R Y W G
= 0.5 AMPS FOR THERMOSTAT
ANTICIPATOR SETTING
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 draft safeguard switch.
The purpose of this control is to cause the safe shutdown of the
furnace during certain blocked vent conditions.
a. Verify vent pipe is cool to the touch.
b. Disconnect power to furnace and remove vent connector
from furnace vent elbow.
c. Restore power to furnace and set room thermostat above
room temperature.
d. After normal start-up, allow furnace to operate for 2
minutes, then block vent elbow in furnace 80 percent of
vent area with a piece of flat sheet metal.
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e. Furnace should cycle off within 2 minutes. If gas does not
shut off within 2 minutes, determine reason draft safeguard
switch did not function properly and correct condition.
f. Remove blockage from furnace vent elbow.
A96316
g. Switch will auto-reset when it cools.
h. Re-install vent connector.
NOTE: Should switch remain open longer than 3 minutes,
furnace control board will lockout the furnace for 3 hours. To reset
furnace control board, turn thermostat below room temperature or
from HEAT to OFF and turn 115-v power OFF, then back ON.
3. 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
pressure switch is functioning properly, hot surface igniter
should NOT glow and control diagnostic light flashes a
status code 32. If hot surface igniter glows when inducer
motor is disconnected, shut down furnace immediately.
e. Determine reason pressure switch did not function properly
and correct condition.
f. Turn off 115-v power to furnace.
g. Reconnect inducer motor wires, replace outer door, and
turn on 115-v power.
h. Blower will run for 90 seconds before beginning the call
for heat again.
i. Furnace should ignite normally.
Step 5—Checklist
1. Put away tools and instruments. Clean up debris.
2. Verify that switches for LHT and OFF-DELAY are blower
OFF-DELAY are selected as desired.
3. Verify that blower and burner access doors are properly
installed.
4. Cycle test furnace with room thermostat.
5. Check operation of accessories per manufacturer's instruc-
tions.
6. Review User's Guide with owner.
7. Attach literature packet to furnace.
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