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I’ve had 2 YCWS’s at one site do that occasionally. It happens maybe once a year, if that. They’re about 10 years old.

I would see it happen occasionally on YKs and I never got to the bottom of it , I would reboot and everything was fine for a few more months, updated software too but never knew if that really fixed it. I think the logic gets stuck in a loop and goes around in circles under certain circumstances and you just have to break the cycle to wake it up and get it working normally again.
We ran on simulators too in York but could not replicate the problem


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Auto Lead lag Raptyr.
Auto restart after power failure ect

There is actually noting wrong with the chiller, just I'd like to know whey it happened.
I also seen it happening on a YCAJ many moons ago, and never got to the bottom of it.

Auto lead lag or manual ?


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In local model. She likely would have started. Just that I was on site at the time.
it had gone to 11 DegC and still said no cool load.
i had system # 2 switch off as i was doing a service on it. But sys # 1 just sat there with no cool load and the temp was up at 11.

Dropped it down to 5 and she kicked in the first compressor, put the setpoint back to 7 as that what the site wants and she was fine.
It has a +/- 1.1 diff.
BMS just monitors for alarms, everything else is chiller controlled.

Was it on local control or remote ?


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quote from the book

1) The display will show the anti-coincidence timer status for the lag compressor, followed by ‘NO COOL LOAD’ until it is called to operate by the control system.

2) LLSV off

Internal timers. For what, I’ll try to find out

Is there some kind of chilled water reset that is affecting the setpoint? So that the "active" setpoint is higher?

But the chiller is off and waiting to start. The CHW temp is climbing and she still doesn't kick in?
Just sits there with no cool load.

Software internal load timers. If load is dropping at current demand timers will stop and start on temp fall speed

Nope. Had one today. Set point at 7 DegC. Range at 1 DegC. LWT was at 11 DegC. Not controlled by remote set point either. Had to drop set point to 5 before it would kick in a compressor. YLAA chiller.
Seen it happening on a YCAJ also.

Differential to start ?

No cool load

Does anyone know why some York chillers display a 'No cool load' when clearly there is a cool load and sometimes you got to drop the setpoint to start a compressor?