Disconnect electrical power before changing speed tap (or
removing cap on 5-speed motors). A failure to follow this
warning can cause personal injury or death.
NOTE: For furnaces with 5-speed motors, ensure that unused
speed tap is either capped or placed on SPARE terminal on control
center before power is restored.
d. To change motor speed selection for high heat, remove
blower motor lead from control HIGH-GAS-HEAT termi-
nal. (See Fig. 10 and Fig. 14.) Select desired blower motor
speed lead from 1 of the other terminals and relocate it to
HIGH-GAS-HEAT terminal. See Table 11 for lead color
identification. Reconnect original lead to PARK terminal
(or cover with insulating cap, if used in furnaces using
5-speed blower motors). Follow this same procedure for
proper selection of cool and low-gas-heat speed selection.
6. Set thermostat heat anticipator.
a. When using a non-electronic thermostat, the thermostat
heat anticipation must be set to match amp draw of
electrical components in R-W/W1 circuit. Accurate amp
draw readings can be obtained at wires normally connected
to thermostat subbase terminals R and W/W1. Fig. 17
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 heat. To operate
furnace in low heat, first move SW-2 to ON position,
THEN connect ammeter wires as shown in Fig. 17. The
thermostat anticipator should NOT be in this circuit while
measuring current. If thermostat has no subbase, thermostat
MUST be disconnected from R and W/W1 wires during
current measurement. Return SW-2 to final desired location
after completing reading. See thermostat manufacturer’s
instructions for adjusting heat anticipator and for varying
heating cycle length.
b. When using an electronic thermostat, set cycle rate for 3
cycles per hr.
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 combustion control system and ener-
gizes circulating-air blower motor if furnace overheats.
The preferred method of checking limit control is to gradually
block off return air after furnace has been operating for a
period of at least 5 minutes. As soon as limit has shut off
burners, return-air opening should be unblocked. By using this
method to check 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 permit safe shutdown of he
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, pressure switches are func-
tioning properly.
e. Turn off 115-v power to furnace.
f. Reconnect inducer motor wires, replace gas control door,
and turn on 115-v power to furnace.
4. Check auxiliary limits.
Table 11—Speed Selection
COLOR SPEED AS SHIPPED‡
White Common C
OM
Black High Cool
Orange† Med SPARE or Capped
Yellow Med-High SPARE
Blue Med-Low High-Gas-Heat
Red Low* Low-Gas-Heat
* Continuous fan speed.
† Available on 5-speed blowers only.
‡ Terminal on control center.
Recheck temperature rise. It must be within limits specified
on unit rating plate. Recommended operation is at midpoint of
rise range or above.
Fig. 17—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
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