75
Rev. 2
SERVICING
WARNING
Disconnect Electrical Power Supply:
1. Remove burner compartment door to gain access to the
primary limit.
2. Remove low voltage wires at limit control terminals.
3. With an ohmmeter, test between these two terminals
as shown in the following drawing. Should read continu-
ous unless heat exchanger temperature is above limit
control setting. If not as above, replace the control.
Volt / Ohm
Meter
Testing Primary Limit Control
4. After completing check and/or replacement of primary
limit control, reinstall burner compartment door.
5. Turn on electrical power and verify proper unit operation.
To aid in identifying these controls, refer to the T.O.D. Pri-
mary Limit chart on the previous page for style number, tem-
perature setting and sleeve color(s) code.
S-6 CHECKING AUXILIARY LIMIT CONTROL
A manual reset limit is located on the lower side of the blower
deck, near the center, as shown in the following drawing.
Auxilary Limit
Control
(Blower Deck)
If this limit control opens, the air circulation blower and vent
blower will run continuously. On models with the 50A50,
50A51, HSI 1-1A and HSI-2 ignition controls the diagnostic
light will flash four times. These symptoms are identical to a
trip of the primary limit control.
The auxiliary limit control is designed to prevent furnace op-
eration in case of main blower failure on horizontal installa-
tions. It may also open if the power supply is interrupted
while the furnace is firing.
The auxiliary limit control is suitable for both horizontal right
and horizontal left installations. Regardless of airflow direc-
tion, it does not need to be relocated.
WARNING
Disconnect Electrical Power Supply
1. Remove blower compartment door to gain access to the
auxiliary limit control located in the furnace blower com-
partment area.
2. Remove the wires from the auxiliary limit control termi-
nals.
3. Use an ohmmeter, test for continuity across the two ter-
minals (refer to the following auxiliary limit control fig-
ure). No reading indicates the control is open. Push red
reset button, test again - if still open, replace the con-
trol.
Color
Identifing
Tab
Red
Reset
Button
VOLT / OHM
METER
GN
D
Testing Auxiliary Limit Control
WARNING
To avoid possible fire, only reset the auxiliary limit
control once. If it should open a second time, a quali-
fied servicer must determine why the auxiliary limit
opened before resetting again.
Note: If it becomes necessary to slide the blower assembly
out of the furnace, the auxiliary limit control should be re-
moved first. After the blower assembly is reinstalled, the
auxiliary limit must be reinstalled.
Содержание GCIA045A30
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