Set Thermostat Heat Anticipator; Check Safety Controls; Checklist - Bryant 393AAV Installation, Start-Up, And Operating Instructions Manual

CAUTION: Recheck temperature rise. It must be within
the air temperature rise range specified on furnace rating
plate. Recommended operation is at midpoint of rise or
above.

3. Set thermostat heat anticipator.

The thermostat heat anticipator must be set to match the
amp draw of the electrical components in the R-W circuit.
Accurate amp draw readings can be obtained at thermostat
subbase terminals R and W. Fig. 15 illustrates an easy
method of obtaining the actual amp draw. The amp reading
should be taken after the blower motor has started. See the
thermostat manufacturer's instructions for adjusting the
heat anticipator and for varying the heating cycle length.
NOTE: When using an electronic thermostat, set the 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. 15—Amp Draw Check With Ammeter
E. Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked
in the Start-up Procedures section as part of normal operation.
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
HOOK-AROUND
AMMETER
0.5 AMPS FOR THERMOSTAT
=
ANTICIPATOR SETTING
A96316
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 functions and
operates properly if there is a motor failure.
2. Check blocked vent safeguard switch.
The purpose of this control is to cause 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 collar 100 percent. Furnace
should cycle off within 2 minutes.
d. Remove blockage and reconnect vent pipe to furnace
flue collar.
e. Wait 5 minutes and then reset blocked vent safeguard
switch.
3. Check pressure switch.
This control proves operation of draft inducer blower.
a. Turn off 115-v power to furnace.
b. Remove control door and disconnect inducer motor 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 status code light
flashes code 31. If hot surface igniter glows when
inducer motor is disconnected, shut down furnace im-
mediately. Determine reason pressure switch did not
function properly and correct condition.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace control door, and
turn on 115-v power.
F. Checklist
1. Put away tools, instruments, and clean up debris.
2. Verify manual reset switches have continuity.
3. Ensure blower and control access doors are properly in-
stalled.
4. Cycle test furnace with room thermostat.
5. Check operation of accessories per manufacturer's instruc-
tions.
6. Review User's Manual with owner.
7. Leave literature packet near furnace.,
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