25
Troubleshooting
Questionable Unit
Operation
Table 14
: Compressor(s) not running
Probable Cause
Explanation
Normal operation.
The controller compressor(s) turn on and off to meet the unit capacity
requirements.
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 shuts off all
unit compressor(s).
Communicated disable.
Numerous communicated requests may disable the compressor, including a
compressor enable input. Depending on the state of the communicated request,
the unit may disable the compressor.
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 compressor(s) may not be on. Refer to the manual
output overrides on page 9.
Diagnostic present.
A specific list o f diagnostics affects compressor operation, depending whether
the unit is configured as heat pump. For more information, see the Diagnostics
section on page 27.
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 device, the compressor may not work correctly.
No power to the controller.
If the controller does not have power, the compressor does not operate. For the
ZN510 controller to operate normally, a voltage input of 24 VAC must be applied.
When the green LED is off continuously, the controller does not have sufficient
power or has failed.
Unit wiring.
The wiring between the controller outputs and the compressor contacts must be
present and correct for normal compressor operation.
Table 15
: Outdoor air damper stays open
Probable Cause
Explanation
Normal operation.
The controller opens and closes the outdoor air damper based on the controller’s
occupancy mode and fan status. Normally, the outdoor air damper is open
during occupied mode when the fan is running and closed during unoccupied
mode. Refer to the outdoor air damper section on page 8.
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 outdoor air damper may not open. Refer to the
manual output overrides on page 9.
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 device, the outdoor air damper may not work correctly.
Unit wiring.
The wiring between the controller outputs and the compressor contacts must be
present and correct for normal damper operation.
