On the display
The OptiView panel shows MBC - DSP WATCHDOG. This is one of the unit's Safety Shutdown messages, and the manuals print it in this single form only — there are no other display variants of this message.
What it means
The MBC has determined, through its Watchdog device, that there has been a lapse in its internal microprocessor activity — one manual locates this activity on the Control Board. The MBC Watchdog Fault contacts open (the other manual prints this as the MBC Fault contacts open). While the shutdown is active, the MBC will not react to a levitation mode change command via serial comms and remains in the levitation mode it was in when the fault occurred, until power is removed.
Why it appears
- The MBC's Watchdog device determines a lapse in internal microprocessor activity on the MBC (described in one manual as activity on the Control Board). The manuals print no other cause for this Safety Shutdown.
Reset and restart
Recovery starts with removing power from the MBC, and the manuals describe this in two ways. In one, power is removed automatically: when the VSD is stopped and the precharge command ceases, the DS bus, which powers the MBC, depletes. In the other, power must be removed from the UPS to the MBC. Once the condition is released, the restart is: The chiller can be started when the condition is released and the OptiView panel CLEAR FAULTS button is pressed.
Questions engineers ask
What does MBC - DSP WATCHDOG mean on a YORK YMC2?
It is a Safety Shutdown: the MBC's Watchdog device has detected a lapse in the MBC's internal microprocessor activity, and the MBC Watchdog Fault contacts open. The MBC also stops reacting to levitation mode change commands sent over serial comms.
How do I clear MBC - DSP WATCHDOG on a YMC2?
Power must first be removed from the MBC — automatically, when the VSD is stopped and the precharge command ceases so the DS bus depletes, or by removing power from the UPS to the MBC. When the condition is released, press the CLEAR FAULTS button on the OptiView panel and the chiller can be started.
Why does my YMC2 trip on MBC - DSP WATCHDOG?
The only cause the manuals give is a lapse in internal microprocessor activity on the Control Board, which the MBC determines through its Watchdog device. No other causes are listed for this shutdown.
Will the MBC change levitation mode while MBC - DSP WATCHDOG is active?
No. The MBC will not react to a levitation mode change command via serial comms and stays in the levitation mode it was in when the fault occurred until power is removed.
Messages next to this one
Source
Written from the manufacturer's manuals for the YORK YMC2; every number and designation on this page is checked against them before publication. The row of the manual this message comes from:
All YORK YMC2 messages: fault codes · YORK YMC2 documentation · YORK manuals