Form O-Y P/N 273647R5, Page 39
*
Heat sections with dual furnaces. When only one size is listed, both furnaces are the same size and two identical high pressure
switches are used. Dual furnace heat sections with electronic modulation Option AG74 have one low pressure switch.
Combustion Air Switches for Above 6000 ft. (1830 m) - (cont’d)
Heat
Section
Option
Heat
Size(s)
(Btuh)
High Pressure Switch
Heat
Section
Option
Heat
Size(s)
(Btuh)
High Pressure Switch
Setpoint
Off
Label
Color
Switch
P/N
Setpoint
Off
Label
Color
Switch
P/N
Negative Pressure (iwc)
Negative Pressure (iwc)
H175*
75,000
1.35
Green
273554
G372* 150,000
1.35
Green
273554
100,000
1.35
Green
273554
225,000
1.35
Green
273554
H200
200,000
1.35
Green
273554
G452* 225,000
1.35
Green
273554
H202*
100,000
1.35
Green
273554
G452* 225,000
1.35
Green
273554
H300
300,000
1.45
Orange
273555
G525
225,000
1.35
Green
273554
H400
400,000
1.45
Green
273555
300,000
1.25
Blue
273553
H402*
200,000
1.35
Green
273554
G602
300,000
1.25
Blue
273553
H502*
200,000
1.35
Green
273554
300,000
1.45
Orange
273555
All gas furnaces are equipped with a temperature activated auto reset limit control.
Depending on size, the control is factory set at either 200°F or 250°F and is non-
adjustable. If the setpoint is reached, the limit control will interrupt the electric supply
to the gas valve. This safety device provides protection in the case of a lack of airflow
due to dirty filters or a restriction at the inlet or outlet.
The limit control switch is mounted on the side of the heat exchanger
Temperature Limit
Control
CAUTION: The auto reset limit control will continue to shut
down the heat section until the cause is corrected. Never by-
pass the limit control; hazardous conditions could result.
Service:
If the limit switch needs to be replaced, use a factory-authorized replace-
ment designed for the application.
Combustion Air Inlet
Openings
The combustion air inlet openings are located in the doors on the control end of the
unit.
Keep all openings clean and free of obstructions.
High Temperature
Limit Control,
Auto Reset
Flame Sensor
FIGURE 27 -
Ignitor showing
required Spark
Gap Measurement
Ignitor
- Locate the ignitor. Disconnect the wire;
remove the screw and the ignitor. Clean the ignitor
assembly with an emery cloth.
Spark gap must be maintained to 1/8". See
FIGURE
27
shown below.
Flame Sensor
- Locate the flame sensor on the
burner. Disconnect the wires; remove the screws and
the flame sensor. Clean with an emery cloth.
Ignitor
Ignitor and Flame
Sensor
