On the display
The panel prints MBC - STARTUP FAILURE. The manuals use this single text for two shutdown levels: a Cycling Shutdown set by one failed start, and a Safety Shutdown set after repeated failures. The message text alone does not tell you which level is active — the fault history does.
What it means
At the cycling level, the shutdown is set when the chiller fails to exit the MBC startup state within 60 seconds, during a chiller start. At the safety level, it is set when the chiller initiates three MBC-STARTUP FAILURE Cycling Shutdowns in a 90 minute period — that is, a third MBC startup failure within 90 minutes.
Why it appears
- A chiller start in which the unit does not exit the MBC startup state within 60 seconds sets the Cycling Shutdown.
- Three MBC-STARTUP FAILURE Cycling Shutdowns initiated within a 90 minute period set the Safety Shutdown.
What to check
- Refer to the service manual for the conditions necessary to complete MBC startup successfully — the YORK YMC2 Service Manual (Form 160.78-M2), or the Basic Operation section of the YMC2 Model B Service Manual (Form 160.84-M2).
- Check the fault history details to determine which specific conditions were not met during the failed start.
- Use the fault history to confirm whether this start failed once (cycling level) or is the third failure within 90 minutes (Safety Shutdown level).
Setpoints and thresholds
- 60 seconds — the time a chiller start allows for exiting the MBC startup state; exceeding it sets the MBC - STARTUP FAILURE Cycling Shutdown.
- 90 minutes — the period in which three MBC-STARTUP FAILURE Cycling Shutdowns escalate the message to the Safety Shutdown.
Reset and restart
At the cycling level the unit comes back on its own: the chiller will automatically restart when the cycling condition clears
. At the safety level — three failures within 90 minutes — the shutdown tables describe no automatic restart; the action they prescribe is to check the fault history details for the conditions that were not met and to refer to the service manual for the conditions necessary to complete MBC startup successfully.
Questions engineers ask
What does MBC - STARTUP FAILURE mean on a YORK YMC2?
The chiller failed to exit the MBC startup state within 60 seconds during a chiller start. After three such failures within 90 minutes, the same message is set as a Safety Shutdown.
Why did my YMC2 fail to complete MBC startup?
The shutdown tables do not list the individual startup conditions; they direct you to check the fault history details to determine which specific conditions were not met, and to the service manual for the conditions necessary to complete MBC startup successfully.
Does the YORK YMC2 restart by itself after MBC - STARTUP FAILURE?
At the cycling level, yes: the chiller automatically restarts when the cycling condition clears. At the safety level (three failures in 90 minutes), the shutdown tables give no automatic restart; the prescribed action is to check the fault history details.
How many MBC startup failures trigger the YMC2 safety shutdown?
Three MBC-STARTUP FAILURE Cycling Shutdowns initiated within a 90 minute period set the Safety Shutdown.
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