Chapter 12 Troubleshooting
90 CNT-SVX12C-EN
Table 31. Heat does not energize
Probable cause Explanation
Unit wiring The wiring between the controller outputs and the electric heat contacts must be present
and correct for normal electric heat operation. Refer to applicable wiring diagram.
Failed end device Check electric heat element, including any auxiliary safety interlocks, to ensure proper
operation.
Normal operation The controller controls electric heat on and off to meet the unit capacity requirements.
Requested mode off You can communicate a desired operating mode (such as off, heat, and cool) to the con-
troller. If off is communicated to the controller, the unit shuts off all electric heat.
Unit configuration Check to make sure unit is not in the 4-cool configuration.
Communicated dis-
able
Numerous communicated requests may disable electric heat, including an auxiliary heat
enable input and the heat/cool mode input. Depending on the state of the communicated
request, the unit may disable electric heat.
Manual output test The controller includes a manual output test sequence you can use to verify output oper-
ation and associated output wiring. However, based on the current step in the test
sequence, the electric heat may not be on. Refer to the “Manual output test” on page 74.
Diagnostic present For information about diagnostics, see Table 28 on page 79.
No power to the con-
troller
If the controller does not have power, electric heat does not operate. For the ZN517 con-
troller to operate normally, you must apply an input voltage of 24 Vac. If the green LED is
off continuously, the controller does not have sufficient power or has failed.
Table 32. Outdoor air damper remains closed
Probable cause Explanation
Unit wiring The wiring between the controller outputs and the outdoor air damper must be present
and correct for normal outdoor air damper operation. Refer to applicable wiring diagram.
Failed end device Check damper actuator to ensure proper operation.
Normal
operation
The controller opens and closes the outdoor air damper based on the controller’s occu-
pancy mode and fan status. Normally, the outdoor air damper is open during occupied
mode when the fan is running and closed during unoccupied mode.
Warm up and cool
down
The controller includes both a morning warm up and cool down sequence to keep the
outdoor air damper closed during the transition from unoccupied to occupied. This is an
attempt to bring the space under control as quickly as possible.
Requested mode off You can communicate a desired operating mode (such as off, heat, or cool) to the control-
ler. If off is communicated to the controller, the unit closes the outdoor air damper.
Manual output test The controller includes a manual output test sequence you can use to verify output oper-
ation and associated output wiring. However, based on the current step in the test
sequence, the outdoor air damper may not be open. Refer to the “Manual output test” on
page 74.
Diagnostic present For information about diagnostics, see Table 28 on page 79.
To Next Page
Loading...
