BCXC-SVX01A-EN 53
Maintenance
Common Diagnostics
Table M-D-3. Fan Outputs Do Not Energize
Probable Cause Explanation
Random start After power-up, the controller always observes a random start that varies
observed between 0 and 30 seconds. The controller remains off until the random start
time expires.
Power-up control wait 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.
Cycling fan operation 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.
Unoccupied operation 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 diagnostics
according to pulse-width-modulation (PWM) logic.
Fan mode off When using the local fan mode switch to determine the fan operation, the off
position controls the unit fan to off.
Requested mode: 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.
Diagnostic present A specific list of diagnostics effects fan operation. For more information, see
the “Diagnostics” section.
No power to the If the controller does not have power, the unit fan does not operate. For
controller the Tracer
ZN 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 has failed.
Unit configuration The controller must be properly configured based on the actual installed end
devices and application. When the unit configuration does not match the
actual end devices, the valves may not work correctly.
Manual output test 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 .
Unit wiring The wiring between the controller outputs and the fan relays and contacts
must be present and correct for normal fan operation. Refer to the specific
unit wiring diagrams on the unit.
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