Compressor shut off will not start.

Questions & AnswersCompressor shut off will not start.
Bill Wood asked 6 months ago

We have  Kaeser SK15

It is a couple of years old and has run 24/7 no issues 

we do regular maintenance and so on.

at some point last 2 weeks ago during a night shift it went down with no alarms. the production staff were able to get it started again. 

This morning it went down again, no alarm no warning.

the under load display was on yet no running. temperature was with in normal range…

I could not get it to start before I hit the e-stop and then reset then on and has been running since.. 

I need some insight as to how and why this is happening. We do have a back up compressor but would rather fix the problem that mask it with a spare compressor.


Thanks Bill

1 Answers
Cas Staff answered 6 months ago

Hi Bill,

I don’t know the exact cause of this, but what I suspect is there’s an electrical problem.

I’ve seen this some times – unexpected stops without alarm. And almost always it was an electrical problem (inside the cabinet – bad relay, bad connection, etc).

You say “the under load display was on yet no running” … so it the controller ‘thinks’ the compressor is running, but it was stopped.

Most likely it’s a problem with the main contactors, or the control power to the main contactors.

If this happens again (display showing it’s running loaded, but it’s stopped) – please open the cabinet and check this:

– what is the state of the main contactors (there are 3 – 2 should be on/engaged, the ‘line’ and ‘delta’ contactors, and 1 should be off, the ‘star’ contactor).
– If they are indead open when they shouldn’t be – check the control power to the contactors. Is it there? (could be 12v, 24v or 110/220v depending on make/model).
– If the control power is not there, work your way up to the controller to see where it’s lost.

Often the contactors control power is routed trough auxiliary contacts on the other contactor – this to make sure the star and delta contactors never engage at the same time (it would create a full 3phase short circuit). I have often seen that these auxiliary contacts have gone bad.

Wish I could help more – hope this is useful. Let me know what you find out.

All the best,

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