108 UNT-SVX07B-EN
Diagnostics
• Generic temperature failure
• Discharge air low limit
Resetting Diagnostics
There are a number of ways in which diagnostics are reset:
1. Automatic reset by the controller
2. By initiating a manual output test at the controller
3. By cycling power to the controller
4. Through Rover™, Trane’s service tool
5. Tracer ZN520: by using any other communicati
ng device ab le to access the controller’s
diagnostic reset input.
6. Tracer ZN520: by cycling the fan switc
h from Off to any speed setting.
Automatic Reset by the Controller
The controller includes an automatic diagnostic reset function that attempts to automatically
restore the unit when a low temperature diagnostic occurs.
Note: The controller implements the automatic diagnostic reset function only once every
24 hours. For the controller to increment the 24 hour timer, you must maintain power to the
controller. Cycling power resets all timers and counters.
After the controller detects the first special diagnostic, the unit waits 30 minutes before invoking
the automatic diagnostic reset function. The automatic diagnostic reset function clears the special
diagnostic and attempts to restore the controller to normal operation. The controller resumes
normal operation until another diagnostic occurs.
Note: The automatic diagnostic reset function does not operate during the manual output test
sequence.
If a special diagnostic occurs within 24 hours after an automatic diagnostic reset, the controller
must be manually reset. Other possible methods of resetting diagnostics are described in the
sections that follow.
Manual Output Test
To verify proper end device operation, press the controller’s Test button. This exercise will verify
all outputs in a predefined sequence, the first of which will attempt to reset the controller
diagnostics if any are present.
Cycling Power to the Controller
After removing and reapplying the 24 Vac power from the board, the unit cycles through a power-
up sequence. By default, the controller attempts to reset all diagnostics present at power-up.
Diagnostics present at power-up and those that occur after power-up are handled according to
Table 31, p. 109.
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