PCC-3 Controller continually reboots
FILED UNDER: PCC-3, PCC-IISymptom
Upon a power restore the PCC-3 controller reboots in a sequence providing valuable information. The ROM Chip Version is first displayed followed by a self check of the main board and any subsequent daughter boards installed. If any one of the boards fails the self check, the controller will continue to reboot. You will also notice the green CPU led flashing.
If the controller continues to repeat cycling through this process it does NOT necessarily mean there is a fault with the controller itself requiring an immediate board replacement.
Steps to Troubleshoot
While observing the controller take note of the A/D status OK vs NG. Each Boards Analog to Digital Converter (A/D) will be displayed in series. IE…Main OK, A/D OK, A/D 1 (Daughter Board 1) OK, A/D 2 (Daughter Board 2) OK
If any one of the displayed A/D statuses shows NG as opposed to OK the issue you are experiencing is within the associated board. For instance there is a display cycling that shows A/D 1 NG… This shows that the daughter card in slot 1 of the main board is not functioning properly and showing a fault.
To confirm this as the problem, disconnect power from the controller or panel and remove the terminal strip of the slot 1 daughter card. Power the controller. As the PCC-3 reboots pay close attention to the A/D status of each board and if the controller powers up correctly. If the controller is now stable, CPU light is steady green, and the PCC-3 remains powered correctly, the issue is most likely in the wiring of that daughter card terminal strip.
Disconnect the power to the PCC-3 controller or panel and using a digital ohm meter, ohm (continuity check) out each wire on the slot 1 daughter card to a known ground and between wire to wire. In most cases you will find that there is a field grounded or a pair of shielded 24vdc wires shorted together.
In extreme instances, years after an initial start-up, wiring that was installed too closely to a boiler stack or radiant heat source could be the location of the short. In previous troubleshooting of job sites, we have found aged wiring that was installed closely to a radiant heat source would be melted and frail and may cause the reboot experience to be only intermittent. Check all wiring leading to the daughter card associated terminal strip for a short circuit and correct as necessary. In most cases this diagnoses will correct this problem. Once the wiring has been verified. Plug in the terminal connector of the daughter board and power the panel. While watching the display the daughter card A/D 1 NG message should be replaced by A/D 1 OK. The PCC-3 controller is a durable multi-loop controller and in most instances an A/D fault after corrected will not require replacement of the card or the main board.
Resolution
Use the same troubleshooting tips if the main board or another slot daughter card shows this fault.
If you see the error A/D NG (main board A/D converter) Power the controller down and remove the smaller wiring terminal strips for terminals 1-28 and follow the same troubleshooting steps outlined
