MCB TRIPPING

[shaunsparks]

Hi ,we recently moved into a bungalow with a outside shed approximatly 15 mtrs down the garden the garden.In the shed we have a consumer unit feeding a 500watt halogen light and sockets feeding a fridge this is all fed by armoured cablec buried under the garden spured from the house ring main.The problem we have is that the mcb in the house consumer unit trips every now and again and it seems to be more when we have wet and damp weather.Could there be damp entering the cable somewhere . any suggestions.
cheers.

 

[JohnD]

The thing that trips, is it an MCB? Is it marked "B32" or what?

Does it have a "test" button on it, in which case it is an RCD?


An armoured cable is very unlikely to let water in; unless either it has been damaged by garden implements; or it has been joined and the join is not watertight. Rain in a fitting, especially an outside light, is more likely.

 

[shaunsparks]

It is a b32

 

[RMS]

You may have to carry out an insulation resistance test on the cable. Is there an rcd on the main switch of the consumer unit?

 

[JohnD]

That sound quite bad, it means you have a current of 50Amps or so on the circuit.

Firstly, you say the supply is spurred off the ring. Is it a fused spur (it should be) with a switch and a cartridge fuse? If so, then the fuse ought to blow, and isolate the external supply.

Is there an RCD protecting the outside circuits (either in the house or the shed? (there should be).

Armoured cable is fairly expensive, and burying it is hard work, so it may be that you can rectify the house end. However you may need a proper electrician to find and rectify the fault, as well as bringing it to a better standard.

 

[shaunsparks]

there is no fused spur ,there is a plastic box where the ring main comes in and out either side and the armoured cable is joined in the middle.

 

[shaunsparks]

also i should have said but there is no RCD at in the consumer unit

 

[Steve]

I would disconnect it ASAP, as JohnD says, there's a lot of current running when the MCB trips, and theres a possibility that this curent is running continuously, and sometimes tips the scales and trips the MCB. And there should be an FCU instead of that box.