73
Rev. 2
SERVICING
If the anticipator current draw is unknown, then an amp
draw should be taken to determine the anticipator set-
ting. Use an amprobe as shown in the following drawing.
10 TURNS OF
THERMOSTAT WIRE
(From "W" on thermostat)
STATIONARY JAW
OF AMPROBE
READS 4 AMPS
CURRENT DRAW
WOULD BE .4 AMPS
Checking Heating Anticipator Current (Amp) Draw
S-3C Cooling Anticipator
The cooling anticipator is a small heater (resistor) in the
thermostat. During the "OFF" cycle it heats the bimetal
element helping the thermostat call for the next cooling
cycle. This prevents the room temperature from rising too
high before the system is restarted. A properly sized an-
ticipator should maintain room temperature within 1 1/2
to 2 degrees range.
The anticipator is fixed in the subbase and is not to be
replaced. If the anticipator should fail for any reason, the
subbase must be changed.
S-4 CHECKING TRANSFORMER AND CON-
TROL CIRCUIT
A step-down transformer 120 volt primary to 24 volt sec-
ondary, 40 VA (Heating and Cooling Models) supplies
ample capacity of power for either operation.
WARNING
Disconnect Electrical Power Supply:
1. Remove blower compartment door to gain access to
the thermostat low voltage wires located at the fur-
nace integrated control module.
2. Remove the thermostat low voltage wires at the fur-
nace integrated control module terminals.
With Power On (and Door Interlock Switch closed):
WARNING
LINE VOLTAGE NOW PRESENT.
3. Use a voltmeter, check voltage across terminals R and
C. Must read 24 VAC.
4. No voltage indicates faulty transformer, open fuse, bad
wiring, bad splice, or open door interlock switch.
5. Check transformer primary voltage at incoming line volt-
age connections, fuse, splices, and blower door inter-
lock switch.
6. If line voltage is available to the primary side of trans-
former and not at secondary side, the transformer is in-
operative. Replace.
7. After completing check and/or replacement of transformer
and check and/or repair of control circuit, reinstall blower
compartment door.
8. Turn on electrical power and verify proper unit opera-
tion.
S-5 CHECKING PRIMARY LIMIT CONTROL
These furnaces use a nonadjustable, automatic reset, Klixon
type limit control (stat on a stick), part number 107283_ _.
Style 1 is an open face limit, styles 2 and 3 are closed face
limits. Limit styles are not interchangeable, use only the
limit listed for that furnace. The following drawing illustrates
the different styles of limit switches.
Style 1 & 3
Style 2
