in Fig. 16. 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.
b. When using an electronic thermostat, set cycle rate for 3
cycles per hr.
E.
Check Safety Controls
The flame sensor, gas valve, and pressure switches were all
checked in the Start-up 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 furnace over-
heats.
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 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 will operate if there is a motor failure.
2. Check draft safeguard switch.
The purpose of this control is to cause 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
connector 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 gas 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 ignitor does not glow within several
minutes and control flashes code 32, then flow-sensing
switches are functioning properly.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace gas control door,
and turn on 115-v power.
g. Blower will run for 90 sec before restarting furnace.
F.
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).
3. Verify manual reset switches have continuity.
4. Ensure blower and gas 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.
Fig. 16—Amp Draw Check With Ammeter
A96316
R
Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
HOOK-AROUND
AMMETER
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
=
0.5 AMPS FOR THERMOSTAT
ANTICIPATOR SETTING
FROM UNIT 24-V
CONTROL TERMINALS
—21—
