Check Safety Controls; Checklist - Carrier 58UXT Operating Instructions Manual

Recheck the temperature rise. It must be within the limits
specified on the unit rating plate. Recommended operation is
at midpoint of rise range or slightly above.
6. Set thermostat heat anticipator.
a. When using a nonelectronic thermostat, the thermostat heat
anticipation must be set 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/W1.
Fig. 23 illustrates an easy method of obtaining actual amp
draw. The amp reading should be taken after blower motor
has started and furnace is operating in low fire. To operate
furnace in low fire, first move SW-2 to ON position, THEN
connect ammeter wires as shown in Fig. 23. The thermostat
anticipator should NOT be in this circuit while measuring
current. If thermostat has no subbase, the thermostat must
be disconnected from R and W/W1 wires during current
measurement. Return SW-2 to final desired location after
completing the reading. See thermostat manufacturer's
instructions for adjusting heat anticipator and for varying
the heat cycle length.
b. When using an electronic thermostat, set cycle rate for 3
cycles per hr.
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
R Y W G
10 TURNS
FROM UNIT 24-V
CONTROL TERMINALS
5.0 AMPS ON AMMETER
EXAMPLE:
10 TURNS AROUND JAWS
Fig. 23—Amp Draw Check with Ammeter
Step 5—Check Safety Controls
The flame sensor, gas valve, and pressure switches were all
checked in the Start-Up section as part of normal operation.
HOOK-AROUND
AMMETER
0.5 AMPS FOR THERMOSTAT
=
ANTICIPATOR SETTING
A96316
1. Check primary limit control.
This control shuts off the combustion control system and
energizes the circulating-air blower motor if the furnace
overheats.
The preferred method of checking the limit control is to
gradually block off the return air after the furnace has been
operating for a period of at least 5 minutes. As soon as the
limit has shut off the burners, the return-air opening should be
unblocked. By using this method to check the limit control, it
can be established that the limit is functioning properly and
operates if there is a motor failure.
2. Check draft safeguard switch.
The purpose of this control is to permit the safe shutdown of
the furnace during certain blocked vent conditions.
a. Disconnect power to furnace and remove vent connector
from furnace flue collar. Be sure to allow time for vent pipe
to cool down before removing.
b. Restore power to furnace and set room thermostat above
room temperature.
c. After normal start-up, allow furnace to operate for 2
minutes, then block flue outlet 100 percent. Furnace should
cycle off within 2 minutes.
d. Remove blockage and reconnect vent connector to furnace
flue collar.
e. Wait 5 minutes and then reset draft safeguard switch.
3. Check flow-sensing pressure switches.
This control proves operation of draft inducer blower.
a. Turn off 115-v power to furnace.
b. Remove control door and disconnect inducer motor lead
wires from wire harness.
c. Turn on 115-v power to furnace.
d. Close thermostat switch as if making normal furnace start.
If hot surface igniter does not glow within several minutes
and control flashes code 32, then the flow-sensing switches
are functioning properly.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace control door, and
turn on 115-v power.
g. Blower will run for 90 sec before restarting furnace.
Step 6—Checklist
1. Put away tools and instruments and clean up debris.
2. Check SW-1 through SW-4 after completing installation to
ensure desired settings for thermostat type (SW-1 and SW-2)
and blower off delay (SW-3 and SW-4). Refer to Tables 7 and
8.
3. Verify manual reset switches have continuity.
4. Ensure blower and control access doors are properly installed.
5. Cycle test furnace with room thermostat.
6. Check operation of accessories per manufacturer's instruc-
tions.
7. Review User's Manual with owner.
8. Leave literature packet near furnace.
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