DIY Doctor

fault finding

Postby jasont82 » Mon Aug 04, 2008 4:52 pm

hi there.

friend of mine has a shop that has 5 frigde circuits on a seperate rcd consumer unit. the rcd kept tripping and they narrowed it down to a particular chill cabinet. they had a spark out but he couldnt find the problem. i went and had a look and thought pehaps its just nuisance tripping when moisture builds up as it only trips now and again like every 4 hours. so i took the circuit off the rcd to get it running as all there food and drinks were getting warm. so i thought it would be ok but now the breakers tripping. so its drawing too much current. i originally thought maybe its moisture between live and earth or nuetral and earth for the rcd to trip. for the breaker to trip it must be a live to neutral isnt it? but its still only a few times a day. any experienced fault finders have any suggestions what it could be? im gonna go back and unplug it then megger the circuit to check its not the circuit thats the problem but if it was the circuit it would trip straight away would it not? could it still just be moisture between the live and nuetral conductors? does anyone know why a breaker would trip but only sometimes? it must be a component on the refridgeration side that only comes on twice a day or something. i dont want to megger the fridge itself cos im sure there will be sometihng in there that cant be meggered and then i'll have destroyed it all together. ive suggested he get it serviced.

anyways if anyone has experience something like this before your help would be much appreciated.

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Simply Build It

Postby sparx » Mon Aug 04, 2008 10:32 pm

Hi Jason I have had probs with chill cabinets and found there is a small defrost heater which comes in circuit every so often and they get damp and so everytime they cut in the rcd goes off, but never taken mcb out.
What size fuse in plug/spur? should only need a 3/5A one this may narrow search down to individual cabinet.
If you think you have found which one can you get a clamp on ammeter around one core of circuit and monitor current , i use a short extention lead with cores unsleeved for this purpose & I have a clamp meter that reads down to mA so I can measure leakage current direct from earth core.
The worst type cabinet In my experience is the type in pubs with double glass doors, used for bottled drinks, first port of call in fault finding!!
regards SPARX
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Postby ericmark » Tue Aug 05, 2008 12:07 pm

I agree with Sparx I think it may be defrost cycle went wrong once in Algeria on refer and cooked all the meat inside.
Maybe you can disconnect defrost function until you can get it repaired?
On home freezer it's all built into PIC controller but on industrial often simple time clock on one in Algeria I removed supply to clock in Hassi R'mel in sharia not too much moisture so got away with it.
All best Eric

Postby jasont82 » Tue Aug 05, 2008 6:26 pm

hey guys thanks for your quick reply
i havent taken it off an mcb. just off the rcd. still protected by a 10amp breaker. will try suss things out on the defrost side.
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