Trane VUV Installation, Operation And Maintenance Manual page 108

Diagnostics and Troubleshooting
Electric Heat with ZN520 Controllers
Table 56. Electric heat not operating
Probable Cause
Normal operation
Requested mode: off
Communicated disable
Manual output test
Diagnostic present
Unit configuration
No power to the controller
Unit wiring
ECM motor/Motor control board
failure
Hot water is present on a
changeover unit
Fresh Air Damper with ZN520 Controllers
Table 57. Fresh air damper stays open
Probable Cause Explanation
The controller opens and closes the fresh air damper based on the controller's occupancy mode and fan status. Normally, the fresh
Normal operation
air damper is open during occupied mode when the fan is running and closed during unoccupied mode.
The controller includes a manual output test sequence that verifies analog and binary output operation and associated output wiring.
Manual output test
However, based on the current step in the test sequence, the fresh air damper may not be open. Refer to
The controller must be properly configured based on the actual installed end devices and application. When the unit configuration does
Unit configuration
not match the actual end device, the damper may not work correctly.
The wiring between the controller outputs and the fresh air damper must be present and correct for normal damper operation. Refer
Unit wiring
to the unit wiring diagrams on the unit.
Table 58. Fresh air damper stays closed
Probable Cause Explanation
The controller opens and closes the fresh air damper based on the controller's occupancy mode and fan status. Normally, the fresh
Normal operation
air damper is open during occupied mode when the fan is running and closed during unoccupied mode.
The controller includes both a warmup and cooldown sequence to keep the fresh air damper closed during the transition from
Warmup and cooldown
unoccupied to occupied. This is an attempt to bring the space under control as quickly as possible.
It is possible to communicate the operating mode (such as off, heat, cool) to the controller. When off is communicated to the controller,
Requested mode: off
the unit closes the fresh air damper.
The controller includes a manual output test sequence that verifies analog and binary output operation and associated output wiring.
Manual output test
However, based on the current step in the test sequence, the fresh air damper may not be open. Refer to
Diagnostic present A specific list of diagnostics effects fresh air damper operation. For more information, see
The controller must be properly configured based on the actual installed end devices and application. When the unit configuration does
Unit configuration
not match the actual end device, the damper may not work correctly.
If the controller does not have power, the fresh air damper does not operate. For the controller to operate normally, a 24 Vac input
No power to the controller
voltage must be applied. When the green LED is off continuously, the controller does not have sufficient power or has failed.
The wiring between the controller outputs and the fresh air damper must be present and correct for normal damper operation. Refer
Unit wiring
to the unit wiring diagrams on the unit.
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Explanation
The controller cycles electric heat on and off to meet the unit capacity requirements.
It is possible to communicate the operating mode (such as off, heat, cool) to the controller. When off is communicated to the
controller, the units shuts off the electric heat.
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.
The controller includes a manual output test sequence that verifies analog and binary output operation and associated output wiring.
However, based on the current step in the test sequence, the electric heat may not be on. Refer to
A specific list of diagnostics affects electric heat operation. For more information, see
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 electric heat may not work properly.
If the controller does not have power, electric heat does not operate. For the controller to operate normally, a 24 Vac input voltage
must be applied. When the green LED is off continuously, the controller does not have sufficient power or has failed.
The wiring between the controller outputs and the electric heat contacts must be present and correct for normal electric heat
operation. Refer to the unit wiring diagrams on the unit.
ECM controls include sophisticated fan proving / interlock circuitry that will disable electric heat if one or more motors are not
performing normally
On units with changeover coil and electric heat, simultaneous operation of hydronic heat and electric heat is not allowed.
"Manual Output Test," p.
"Diagnostics and Troubleshooting," p.
"Manual Output Test," p.
"Manual Output Test," p.
"Diagnostics and Troubleshooting," p.
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