
36
441 01 2101 05
Specifications are subject to change without notice.
Table 14 – Speed Selection
COLOR
SPEED
AS SHIPPED
White
Common
BLW
Black
High
COOL
Yellow
Med-High
SPARE
Orange†
Med
SPARE
Blue
Med-Low
HI-HEAT
Red
Low*
LO HEAT
* Continuous
−
blower speed
−
as shipped default
Not all models equipped with 5 speed motors
Figure 50
−
Amp. Draw Check with Ammeter
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
A96316
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.
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% of vent
area with a piece of flat sheet metal.
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.
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 will flash
a status code 3. 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 TT and heat 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
instructions.
6. Review User’s Guide with owner.
7. Attach literature packet to furnace.