ZN010, ZN510, and ZN520 Controllers
UNT-SVX07E-EN
141
Fans
Valves
Troubleshooting ZN010, ZN510, and ZN520 Controllers
Table 80. Fan does not energize
Probable Cause
Explanation
Random start observed
After power-up, the controller always observes a random start that varies 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 position, 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 affects fan operation. For more information, see
Table 78
and
Table 79, page 140
.
No power to the controller
If the controller does not have power, the unit fan does not operate. For the Tracer 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
“Manual
Output Test,” page 137
.
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.
Table 81.
Valves remain closed
Probable Cause
Explanation
Normal operation
The controller opens and closes the valves to meet the unit capacity requirements.
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.
Valve override
The controller can communicate a valve override request.This request affects the valve operation.
Manual output test
The controller includes a manual output test sequence to verify analog and binary output operation and the
associated wiring. However, based on the current step in the test sequence, the valves may not be open. Refer
to the
“Manual Output Test,” page 137
.
Diagnostic present
A specific list of diagnostics affects valve operation. For more information, see
Table 78
and
Table 79,
page 140
.
Sampling logic
The controller includes entering water temperature sampling logic that automatically invokes during 2-pipe
or 4-pipe changeover. It determines when the entering water temperature is either too cool or too hot for the
desired heating or cooling mode. Refer to
“Water Temperature Sampling Function,” page 103
.
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 valves may not work correctly.
No power to the controller
If the controller does not have power, the unit fan does not operate. For the Tracer ZN010, 510 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 wiring
The wiring between the controller outputs and the valve(s) must be present and correct for normal valve
operation. Refer to the unit wiring diagrams on the unit.
