ok ill do a serious one

[slingblade]

Service call to a york chiller approx 170 kw twin circuit.
trips on circ. 1 comp. thermistor pack (int 69) run pot and thermister res. starts at 300 ohms then rises to infinity. fault traced to popped fuses on start contactor supply(pws start) 63 amp. windings metered and meggerd, NO FAULT. fuses replaced after a full contactor strip down and no fault found. fuses replaced. job done, works fine. what was problem, anyone?

[andywill]

Tricky one......If I were to hazard a guess it would be either the part wind timer not engaging the second winding (intermittent fault), or be looking at the contactor, either a burnt contact, loose supply wire etc. or lastly a bad connection somewhere on the control circuit causing the contactor to chatter, you can't watch these things forever, it just annoys you when you can't find a physical fault..

[slingblade]

Yes it was an odd one, i did the usual wiggling contactor feed wires and tapping with screwdrivers but nothing seemed to be loose or burnt. 63 amp fuses do take some popping!:confused:

[taz24]

Yes it was an odd one, i did the usual wiggling contactor feed wires and tapping with screwdrivers but nothing seemed to be loose or burnt. 63 amp fuses do take some popping!:confused:


Oil switch!!!!

Does it have an oil pressure switch fitted?
If it does have one check it or better still for the cost of a new one replace it.

I have seen them chatter the contactor due to a bad contact in the oil switch. The chattering contactor either fails the comp or blows the supply fuses (if your lucky)..

Cheers taz.

[Chunk]

I`ve had those thermister modules causing problems and making the contactors chatter,Exact same thing,blowing 63 amp fuses.Put a new one on and 2 days later circuit 2 went down with the same fault.

[slingblade]

Not sure if it's oil switches or those electronic sensor things as it has a millenium hybrid controller thingy i will check next time i visit the site (120 miles away). nothing was chattering whilst i was there and i did inspect the contactor poles which seemed fine.
I think ill Kodak this one i.e. see what develops. if it blows up then so be it, it's not mine.

[chillin out]

Check the LP switch. Quite often I have found them faulty.

Test it and make sure it switches with a nice clear 'click'.

Chillin:):)

[slingblade]

Yes, thanks. I may have a look at all the system safety switches despite no apparent LP or HP problem, or indeed oil pressure, but how far should i go? This was a bizzare apparent one off fuse failure caused by ????.
When i left site the system was fully operational (good by york standards IMO). There were no apparent faults, how long at £50 an hour is a plastics factory going to let me stand and watch a chiller whilst playing with working components.
I am starting to wonder if the incoming mains supply was at fault at the time the compressor tried to start and fried the fuses.
Trust me, the windings are fine and the switchgear looks almost brand new.
It's an odd one.
cheers for the input gents.:)

[The MG Pony]

With how cheapthey are get your self some dataloggers!

A simple logic data logger will tell you if a switches is bouncing in its throw and by how much, A current/Voltage logger will tell you if any un-expected spikes or droops are happening. come in a week, assemble the data, and you'll be able to tell them they're in the clear or boned.