507651-01
Page 28 of 32
Issue 1907
Other Unit Adjustments
Primary Limit
The primary limit is located on the heating compartment
vestibule panel. The secondary limits (if equipped) are
located in the blower compartment, attached to the back
side of the blower. These auto reset limits are factory-set
and require no adjustment.
Thermal Switch
These manually reset switches are located on the front of
the box.
Pressure Switch
The pressure switch is located in the heating compartment
adjacent to the combustion air inducer. The switch checks
for proper combustion air inducer operation before allowing
ignition trial. The switch is factory-set and requires no
adjustment.
Temperature Rise
After the furnace has been started, and supply and return
air temperatures have been allowed to stabilize, check the
temperature rise. If necessary, adjust the blower speed to
maintain the temperature rise within the range shown on
the unit nameplate. Increase the blower speed to decrease
the temperature. Decrease the blower speed to increase
the temperature rise. Failure to adjust the temperature rise
may cause erratic limit operation.
Fan Control
The heat fan-on time of 30 seconds is not adjustable. The
heat fan-off delay (amount of time that the blower operates
after the heat demand has been satisfied) may be adjusted
by changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan-
off delay setting of 90 seconds. The fan-off delay affects
comfort and is adjustable to satisfy individual applications.
Adjust the fan-off delay to achieve a supply air temperature
between 90° and 110°F at the moment that the blower
is de-energized. Longer off delay settings provide lower
return air temperatures; shorter settings provide higher
return air temperatures. See Figure 26.
Constant Torque Motor
These units are equipped with a constant torque ECM
motor. It has a DC motor coupled to an electronic control
module both contained in the same motor housing. The
motor is programmed to provide constant torque at each of
the five selectable speeds. The motor has five speed taps.
Each tap requires 24 volts to energize.
HEAT FAN
‐
OFF TIME IN SECONDS
To adjust fan-off timing, reposition jumper across pins to
achieve desired setting.
NO JUMPER
60 90
12
0
18
0
60 90
12
0
180
60 90
12
0
180
60 90
120 18
0
60 Second
off Time
90 Second
off Time
120 Second
off Time
180 Second
off Time
Figure 26. Heat Fan Off Time in Seconds
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. A
voltage of 12 to 33VAC is required to energize the motor.
Expected current draw will be less than 20mA.
Blower Speeds
Follow the steps below to change the blower speeds.
1. Turn off electrical power to furnace.
2. Remove blower access panel.
3. Disconnect existing speed tap at integrated control
speed terminal.
NOTE:
Termination of any unused motor leads must
be insulated.
4. Place unused blower speed tap on integrated control
“PARK” terminal or insulate.
5. Refer to blower speed selection chart on unit wiring
diagram for desired heating or cooling speed. See
Product Specifications for blower performance data.
6. Connect selected speed tap at integrated control
speed terminal.
7. Resecure blower access panel.
8. Turn on electrical power to furnace.
9. Recheck temperature rise.
Electronic Ignition
The integrated control has an added feature of an internal
Watchguard control. The feature serves as an automatic
reset device for integrated control lockout caused by
ignition failure. This type of lockout is usually due to low
gas line pressure. After one hour of continuous thermostat
demand for heat, the Watchguard will reset and remake
thermostat demand to the furnace and automatically reset
the integrated control to begin the ignition sequence.
