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I-EEDU (02-21) 150492-A
Figure 30. Typical Fan Control Wiring Diagram
Gas Control Valve
⚠ WARNING ⚠
The operating valve is the prime safety shutoff. All gas supply lines must be free of dirt or scale
before connecting the unit to ensure positive closure.
All furnaces are equipped with a 24V combination valve that includes an automatic electric ON-OFF valve controlled
by the room thermostat, a pressure regulator, and a manual shutoff valve . The standard gas valve allows for single-
stage control from a single-stage, 24V thermostat .
Optional Two-Stage Operation (Heating Only)
NOTE: This option is not available on unit size 075 propane models.
The standard combination control valve is replaced with a two-stage combination gas control valve that provides
for low fire or high fire operation controlled by a two-stage thermostat . First stage (low fire) is factory-set (not field-
adjustable) . Both high and low stages are controlled by a Servo regulator, that maintains a constant gas input
under wide variations in gas supply pressure . Refer to the instructions provided with the unit for specific gas valve
specifications, wiring, and operating instructions .
Optional Two-Stage Operation (Makeup Air)
NOTE: The makeup air option requires a field-installed fan control (refer to
This option is not available on unit size 075 propane models.
•
Two-stage makeup air units are equipped with a two-stage gas valve, but instead of control from a two-stage room
thermostat, the outlet air temperature is monitored and controlled by a two-stage ductstat . When the discharge
air temperature drops to the setpoint, low fire is energized . If low fire cannot satisfy the ductstat setting, high fire
is energized .
•
Makeup air applications are usually adjusted to discharge an outlet air temperature between 65°F and 75°F . In
all applications, the allowable temperature rise of the furnace in the installation dictates the limits of the ductstat
temperature setting .
•
Depending on the option selection, the factory-installed sensor is either field-connected by capillary tubing to the
unit-mounted ductstat (option AG3) or electrically-connected to a remote electronic remote temperature selector
(option AG15) .
