MCB advice

[woodypup59]

The above MCB occasionally cuts when my fridge (ordinary under-counter type) comes on.

Is there a "slower blow" type I can get ?

[Simpo Two]

I'd check the plugs and sockets for good connections first.

[xstian]

Simpo Two said:

I'd check the plugs and sockets for good connections first.

What sort of advice is that?

Surely it's just a matter of finding the right size nail you can jam in there.

[hairyben]

That specific type of MCB is no longer made.

TBF you need a pretty large surge to trip a 30A type 2 breaker, I'd be addressing the fault rather than the symptom.

[woodypup59]

OK fair point.

I should have mentioned this only happens occasionally - say every couple of months.

Lots of other big kitchen loads on this circuit - freezer, washing m/c, dishwasher, kettle etc which have never tripped it.

I've plugged these loads individually into other circuits for a few days / weeks at a time, but the trip is so rare its difficult to be certain.

Maybe in just that the fridge is old. I've just heard it start and it comes on with an audible pop.

I'll try meggering it.

[Simpo Two]

xstian said:

What sort of advice is that?

Surely it's just a matter of finding the right size nail you can jam in there.

1) Because it's worked for me

2) Because if the problem is a lose wire, fitting a new breaker won't fix it

3) It costs nothing

If it still trips then fair enough, but at least you tried the easy free option first

[AndrewO]

It's poss to replace with one that takes a higher start current but as others have said, do some checks first. Maybe plug the fridge in separately on an extension lead (from another mcb cct) and see if it trips.

New MCBs come in 3 types: type B, type C & type D.
Type B is used for the great majority of domestic MCBs, and has the quickest magnetic tripping of the 3
Type C is a little slower acting and a little less prone to some types of nuisance trip
Type D is used where more tolerance of short term overcurrent is wanted, and is thus the least prone to nuisance trips. Use of type D MCBs requires careful calculation to ensure that adequate protection is provided for the circuit cables in the event of a fault.
The current needed to trip a MCB in 0.1 seconds is:
Type B: between 3x and 5x rated current
Type C: between 5x and 10x rated current
Type D: between 10x and 20x rated current
The following trip response graphs give exact details (click for enlargement):

[LotusMartin]

It might just have 'gone' ? I had one in my last (rented) house that the landlord insisted it was my electrical equipment plugged in around the house. I invited him round with literally nothing plugged in and it still tripped. Replaced it and all was good.

Its unusual, but they do fail.