62
High Limit Switch
Two high limit switches are provided on all
furnace configurations.
One limit control is mounted in the air stream
and will shut-off the gas supply in the event
of overheating due to reduced airflow over
the heat exchanger. This limit is an automatic
reset type and will cycle the burners back on
when the temperature drops below the preset
differential. The furnace will continue to
cycle on limit until the cause of the reduced
air flow is corrected.
Figure 45 - High Limit Switch in Air Stream
The other limit control is mounted on the
induced draft fan housing and will shut-off
the gas supply in the event of excessive flue
gas temperatures. This switch is an automatic
reset type.
Figure 46 - High Limit Switch on Fan
Housing
Table 19 - Gas Heater LED Diagnostics
LED
Code
Description
Stead on
Indicates power is applied
1 flash
Control in 1 hour lockout
2 flash
Pressure switch open with inducer on
3 flash
Pressure switch closed with inducer off
4 flash
Limit switch is open
5 flash
False flame 1 hour lockout