Is Fridge-Freezer Causing MCB to Trip?

[hiddenflight]

Hi All,

I have a worrying problem that I need to diagnose:

On three occasions over the last 2 weeks, the MCB on my mains circuit has tripped. Each time it has tripped, no appliances have been in use - except my fridge-freezer. Although the fridge-freezer is relatively new, I have noticed that it makes an oscillating noise, which seems to be getting louder over due time.

Could the cause of the MCB tripping be a faulty fridge-freezer, or/and could it be a fault in the mains circuit?


Best regards and many thanks.

 

[fireman22]

when you say mcb on mains circuit what do you actually mean. your 32A breaker trips feeding socket outlets? or you rcd main switch trips?

 

[Steve]

"oscillating noise"? how do you mean? if its vibration that goes on and off, its the compressor vibrating the fridge casing. A medium clout should sort it.

If it sounds like nothing you've ever heard before, it probably the refrigerant circulating, which will continue after the compressor is switched off. The refrigerant in our old hotpoint one used to make itself known very well to everyone in the kitchen (it was louder than the compressor )

and we need to know if its the MCB or an RCD (RCD will have a test button and more writing on it than an MCB)

 

[hiddenflight]

Thanks for the reply guys.

With regards to the breaker, I was referring to the 32A breaker located within the consumer unit (which is a standard breaker - not an RCD).

Hope that helps. Thanks

 

[JohnD]

The MCB? that should only trip from a substantial overload. Is the fridge-freezer connected with a 13-amp plug? Has the fuse in the plug ever failed? Have a look in the plug (if there is one) or the FCU, and see that it has a proper cartridge fuse in it. If you happen to know the rating of the FF you might be able to put the correct rating fuse in (e.g. it might be OK on a 5-Amp cartridge).

Although it is possible for an MCB to trip under a big overload faster than a fuse will blow, it would be unusual if this kept happening without the fuse ever going.

You might have a water leak or a rodent or a nail causing a short on a cable. To trip a 32a MCB (assuming it is not faulty, which is quite rare) takes a pretty big current - enough to cause smoking and hot smells, if not a fire (e.g. it would take the power of three 3kw electric heaters, full on, to make it trip immediately).

I presume you know for sure that the circuit is not supplying any other big loads, like air conditioning, cookers, electric shower, swimming-pool heater, cannabis plantation in loft or cellar; or as we use round here, home welding, smelting furnace, X-ray equipment, theatre lighting?

If you can't trace the prob, it may be time to call in a well-qualified electrician with good test gear.

 

[Steve]

i'd think a fridge freezer should have a 13A fuse - our old one at least had major startup surges. it would have blown anything less than a 13A.

and dont laugh at JohnD's cannabis farm joke - someone came on here asking how to build a light / electric irrigation system for such a project.

 

[JohnD]

You can laugh if you want to!

And all the other examples, people claim to have got in their sheds



(some of us are terrible liars)

 

[fireman22]

hiddenflight, if you think it could be your fridge freezer unplug it and plug it in via an ext lead to another ring circuit or your cooker control unit , (if it incorperates a socket outlet) if it trips this circuit you may be right

 

[JohnD]

a very sensible suggestion

should have thought of that A quick and simple fault trace.

 

[hiddenflight]

Thanks for all the responses. The suggestion from fireman22 is a good one.

I certainly hope there isn´t a short in one of the cables i.e. a nail etc.

The fridge-freezer is definately the only appliance that is active when the circuit has tripped.

I´ll let you know what the problem is, once (or if) diagnosed.


Thanks.

 

[hiddenflight]

Thanks for all the replies. fireman22´s suggestion is a very good one.

I certainly hope that there isn´t a short in the circuit i.e. a nail etc.

The fridge-freezer is definately the only appliance active when the circuit has tripped.

The fuse in the fridge-freezer has not yet blown.


Many thanks.

 

[Job_n_knock]

Do let us know what is causing it, and dont just assume that because it doesnt happen again that it is now resolved, some faults seem to stop simply because the actual short of the cables have burned away enough of a gap so a spark cant jump, in which case you may have lost some ring integrity.

Another possible reason (but very unlikely) could be a rise in head pressure on your Fridge. This can be caused by excessive heat behind the fridge not allowing the Condenser to cool the refrigerant and it starts making very loud noises and the Compressor starts to struggle and up goes the current. Just a thought.

 

[hiddenflight]

Thanks Job_n_knock.

It´s funny that you have mentioned the point about the fridge, as coincidently, it has been making loud noises and does get very hot at the back of it - so this may well be the problem.

 

[fender]

It's doubtful that a dirty condenser and raised discharge pressure would cause the problem, the compressor would normally just cut out on it's klixon overload.

Sounds more like an intermittent short somewhere, which in my experience, is often caused by a rodent using your cables as lunch!

G.

 

[Job_n_knock]

This is a domestic fridge we're talking about here, not a Condenser that has fans drawing cool air through it ALA Superstore refrigeration packs. Even those have been struggling this summer! I agree its unlikely ( i did say that) but it is possible. If it was me Id make sure and clamp the feed to see what the compressor is drawing. The main problem with these is where they are positioned. Usually under a fitted worktop with no moving air behind them. Yes they do tend to last for years like that but I wouldnt put my mortgage on a zero chance of excessive compressor current.