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SERVICING
If operating pressures differ from above, make necessary
pressure regulator adjustments, check piping size, etc.,
and/or consult with local utility.
Checking Pressure Transducer
NOTE: *PU3M models utilize a pressure transducer (in
place of a pressure switch).
The pressure transducer is a pressure sensing device that
allows the control to modulate the inducer motor through
the heating cycle. The transducer contains electronic
circuitry and must not be subjected to any voltage source
other than factory wiring. Refer to the Troubleshooting chart
beginning on page 36 for diagnosing suspected issues.
Sensing Range Specification: 0.0-4.0 inches W.C.
Voltage Specifications:
• Steady State: 5.0 vDC from red to green wire
(transducer wiring harness input)
• With Inducer off: 0.5 vDC from black to green wire
(transducer wiring harness output).
• During operation: Output range equals 0.5 - 4.5 vDC
Potential Errors:
1. Control board does not receive 0.25 vDC for inducer
motor with motor off
A. Will result in 2-flash error code on the control
board
2. Control board does not receive the required voltage
change (0.5 - 4.5 vDC) during inducer motor
operation.
A. Will result in 3-flash error code on the control
board
Pressure Sensor: The pressure sensor is mounted near
induced draft blower. Its function is to regulate the induced
draft blower's speed in order to maintain proper air-fuel
ratio for clean and reliable combustion. The pressure
sensor also guards against insufficient airflow (combustion
air and flue products) through the heat exchanger.
The pressure sensor should read approximately -2.5 in.
w.c. for the 40,000 BTU/hr models, -2.2 in. w.c. for the
60,000 BTU/hr models and -1.9 in. w.c. for the 80,000 BTU/
hr models.
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be
present. Failure to do so may cause property
damage, personal injury or death.
Field Test Mode
Function: When the SW1 button is pressed and held until
the LED is blinking in AMBER (more than 10 seconds, less
than 15 seconds), the control will execute a field test mode
sequence to cycle through component operation.
Operation: The control must be powered and the
thermostat satisfied (no call for heat or cool). Depress and
hold the SW1 button for more than 10 seconds, but less
than 15 seconds until the LED is blinking in AMBER, then
release. The control will execute the following functions:
1. Inducer - "Run" setting throughout the test
2. Igniter (DSI) - ON for 15 seconds
3. Blower - "Fan" Speed for 15 seconds
4. Blower - "Heat" Speed for 15 seconds
5. Blower - "Cool" Speed for 15 seconds
6. Return to OFF mode
Once the Field Test Mode is initiated, all thermostat inputs
will be ignored until the field test sequence is completed.
If the SW1 button is held for more than 15 seconds, the
button press will be ignored, and the LED display will return
to its prior state.
WARNING
33
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