Troubleshooting - Trane UniTrane Installation Operation & Maintenance

Table 15. Fan Outputs do not Energize
Probable Cause
Random start
observed
Power-up control wait
Cycling fan operation
Unoccupied operation
Fan mode off
Requested mode: off
Diagnostic present
No power to the
controller
Manual output test
Unit wiring
UNT-IOM-6

Troubleshooting

Explanation
After power-up, the controller always observes a random start that varies
between 0 and 25 seconds. The controller remains off until the random start
time expires.
When power-up control wait is enabled (non-zero time), the controller remains
off until one of two conditions occurs:
1. The controller exits power-up control wait once it receives communicated
information.
2. The controller exits power-up control wait once the power-up control wait
time expires.
When the fan mode switch is in the auto postion, the unit fan cycles off when
there is no call for heating or cooling. The heating/cooling sources cycle on or
off periodically with the unit fan to match the capacity according to pulse-width-
modulation (PWM) logic.
The fan cycles with capacity when the unit is in unoccupied mode. This occurs
even if the unit is in continuous fan operation. While unoccupied, the fan cycles
on or off with heating/cooling to provide varying amounts of heating or cooling to
the space. to match the capacity according to pulse-width-modulation
(PWM) logic.
When using the local fan mode switch to determine the fan operation, the off
position controls the unit fan to off.
It is possible to communicate the operating mode (such as off, heat, and
cool) to the controller. When "off" is communicated to the controller, the unit
controls the fan to off. The unit is not capable of heating or cooling when the
controller is in this mode.
A specific list of diagnostics effects fan operation. For more information, see the
"Diagnostics" section on page 50.
If the controller does not have power, the unit fan will not operate. For the
controller to operate normally, it must have an input voltage of 24 VAC. When
the green LED is off continuously, the controller does not have sufficient power
or the controller has failed.
The controller includes a manual output test sequence to verify binary output
operation and the associated wiring. However, based on the current step in the
test sequence, the unit fan may not be powered on. Refer to the "Manual
Output Test" section on page 51.
The wiring between the controller outputs and the fan relays and contacts must
be present and correct for normal fan operation. Refer to the typical unit wiring
diagrams in the Appendix of this manual.
®
Tracer ZN.010
and ZN.510
53