YORK YK — LCSSS - Logic board processor

The panel reads LCSSS - Logic board processor. The control documentation prints the same message as LCSSS - LOGIC BOARD PROCESSOR, so either form on the display points to the same shutdown. It belongs to the liquid cooled solid state starter messages of this chiller and behaves as a cycling shutdown: the starter logic detected the loss during operation and stopped the compressor rather than latching a permanent trip. The full text on the display is the message itself, with no phase letter or system number appended.

This message reports a watchdog loss between the two processors of the solid state starter. The main system microprocessor and the digital signal processor (DSP) on the LCSSS logic/trigger board normally talk to each other every 3 mSec. If the DSP stops answering, the watchdog counts the missed responses; after 80 attempts without a reply a cycling shutdown occurs and the DSP is rebooted. In short, communication between the microprocessor and the DSP on the LCSSS logic/trigger board has been interrupted. Note that the watchdog timer itself only resets if communications have actually been established again — it does not return to normal by merely counting down while the DSP stays silent.

• The link between the main system microprocessor and the DSP on the LCSSS logic/trigger board has been interrupted, so the DSP stopped answering the watchdog that polls it every 3 mSec.
• The manual names no external cause — no wiring point, sensor or supply condition — for this message. The only repair it names, should the problem continue, is to replace the Logic/Trigger Board.

1. Let the shutdown complete its cycle: the control reboots the DSP, and the watchdog timer resets only when communications have been established again.
2. Watch the display. Because this is a cycling shutdown, the message should drop out once the DSP answers the watchdog again, and the chiller restarts by itself when communications are restored.
3. If the problem continues — the message keeps coming back — replace the Logic/Trigger Board. The manual lists no intermediate test, sensor or adjustment for this message; board replacement is the step it gives.

• Watchdog polling interval: the main system microprocessor and the DSP normally communicate every 3 mSec.
• Shutdown threshold: if the DSP does not respond after 80 attempts, a cycling shutdown occurs and the DSP is rebooted.

No manual reset action is described for this message — the recovery is automatic. The control documentation states: The chiller automatically restarts when communications are restored. The starter manual adds that restart is automatic after coastdown, provided the shutdown is no longer active and the compressor switch is still in the run position, so leave the compressor switch where it is and let the unit come back. Remember that the watchdog timer only resets once communications have been re-established, so a repeatedly silent DSP will keep the message active instead of restarting.