24
Troubleshooting
Questionable Unit
Operation
Table 13
: Fan output does not energize
Probable Cause
Explanation
Random start observed.
After power up, the controller always observes a random start from 0 to 25
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:
z
The controller exits power up control wait once it receives commu-
nicated information.
z
The controller exits power up control wait once the power up control
wait time expires.
Cycling fan operation.
When configured to cycle with capacity, normally the unit fan cycles off with
heating or cooling. The heating/cooling sources cycle on or off periodically with
the unit fan to provide varying amounts of capacity to the space.
Unoccupied operation.
Even when the controller is configured for continuous fan operation, the fan
normally cycles with capacity during unoccupied mode. While unoccupied, the
fan cycles on or off with heating/cooling to provide varying amounts of heating
or cooling to the space.
Fan mode off.
When a local fan mode switch determines the fan operation, the off position
controls the unit fan off.
Requested mode off.
The desired operating mode (such as off, heat and cool) can be communicated to
the controller. When off is communicated to the controller, the unit controls the
fan off. There is no heating or cooling.
Diagnostic present.
A specific list of diagnostics affects fan operation. See Diagnostics section on
page 27.
No power to the controller.
If the controller does not have power, the unit fan does not operate. For the
ZN510 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.
Manual output test.
The controller includes a manual output test sequence that may be used to verify
output operation and associated output wiring. However, based on the current
step in the test sequence, the unit fan may not be on. Refer to the manual output
overrides on page 9.
Unit wiring.
The wiring between the controller outputs and the fan relays and contacts must
be present and correct for normal fan operation.
