On the display
The control panel shows CHILLED LIQUID - FLOW SWITCH OPEN; the manuals print the message in this wording only. It is one of the YMC2's cycling shutdown messages, listed with the condenser and evaporator flow faults.
What it means
The message reports a loss of the chilled liquid flow signal while the chiller is running or starting: the Chilled Liquid Flow Switch has been seen open at a moment when the chiller is running or starting. The control treats it as a cycling fault rather than a lockout — the chiller stops on the condition but comes back on its own once the condition clears, as described under reset below. In the software version covered by the service bulletin, this fault has been changed from a Standard Soft Shutdown to a Fast Soft Shutdown.
Why it appears
- The Chilled Liquid Flow Switch has remained open for 5 continuous seconds while the chiller was running.
- The switch has remained open for 5 continuous seconds while the chiller was in soft shutdown.
- The switch was still open at least 45 seconds after MBC startup is initiated — the software bulletin words it as the Chiller State being MBC Startup with the time in the MBC Startup State greater than 45 seconds.
Setpoints and thresholds
- 5 seconds — the open-time threshold: the fault is set only after the Chilled Liquid Flow Switch has been open for 5 continuous seconds.
- 45 seconds — the startup threshold: during MBC Startup the fault applies once the chiller has been in that state for at least 45 seconds (greater than 45 seconds in the software bulletin's wording).
Reset and restart
There is no manual reset for this message. The chiller will automatically restart when the Chilled Liquid Flow Switch closes. The fault also clears without a restart if the run command is ceased: The fault will be released when the Chilled Liquid Flow Switch closes, or when the Run Permissive is False and the Chiller State is Stopped.
In short, restoring the flow signal brings the chiller back by itself, while stopping the chiller clears the message.
Questions engineers ask
What does CHILLED LIQUID - FLOW SWITCH OPEN mean on a YORK YMC2?
It means the Chilled Liquid Flow Switch has stayed open for 5 continuous seconds while the chiller was running, in soft shutdown, or at least 45 seconds after MBC startup was initiated — a loss of the chilled liquid flow signal while running or starting.
How do I reset the CHILLED LIQUID - FLOW SWITCH OPEN fault on a YMC2?
No manual reset is needed. The chiller automatically restarts when the flow switch closes, and the fault also clears if the run command is ceased — the Run Permissive goes False and the Chiller State becomes Stopped.
Why does my YMC2 show CHILLED LIQUID - FLOW SWITCH OPEN during startup?
During MBC Startup the message is only set once the chiller has spent more than 45 seconds in that state with the switch still open, so at startup the message appears only after that point.
Is CHILLED LIQUID - FLOW SWITCH OPEN a lockout on the YMC2?
No. The manuals list it among the cycling shutdown messages, and the service bulletin notes that in this software version it is a Fast Soft Shutdown rather than a Standard Soft Shutdown, with the chiller restarting automatically once the flow switch closes.
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