MCB keeps tripping RCCB

Kitchen circuit keeps tripping RCCB. Problem stays with circuit , as tested by wiring circuit into another MCB. 

No appliances connected. 4 double sockets, 2 fused spurs with fuses out. 

As soon as 30A MCB is flicked on, RCCB trips.

Advise welcome.

TIA

Patrick

low insulation resistance fault, most likely L-E. you will need test kit to find it

First make sure EVERYTHING is unplugged from that circuit, it may well be something faulty plugged in.

ProDave said:

First make sure EVERYTHING is unplugged from that circuit, it may well be something faulty plugged in.

Click to expand...

Everything has been unplugged before I tested the MCB. Still get fault. Found a loose earth wire in a socket, still tripping.

You will need to do insulation resistance tests between each of the conductors on the circuit. (this should have been done before any power was applied to the circuit). If the circuit all tests out correctly on the 'dead tests', then you will have wired it up wrong with the Neutral either not passing back via the RCCB or you have it bridged across onto another circuit, sometimes called a borrow neutral.  This is of course assuming that the RCCB is working correctly and is not over-sensitive. 

Doc H.

Doc Hudson said:

You will need to do insulation resistance tests between each of the conductors on the circuit. (this should have been done before any power was applied to the circuit). If the circuit all tests out correctly on the 'dead tests', then you will have wired it up wrong with the Neutral either not passing back via the RCCB or you have it bridged across onto another circuit, sometimes called a borrow neutral.  This is of course assuming that the RCCB is working correctly and is not over-sensitive. 

Doc H.

Click to expand...

Interesting response.  From that, you are assuming it is a new or altered circuit?

I just read the OP that this has just started to happen on an existing circuit that was previously working.

It would help further speculation A LOT if the OP could clarify is this an existing circuit that was working and has just started to trip, if not the FULL story would help.

ProDave said:

Interesting response.  From that, you are assuming it is a new or altered circuit?

I just read the OP that this has just started to happen on an existing circuit that was previously working.

It would help further speculation A LOT if the OP could clarify is this an existing circuit that was working and has just started to trip, if not the FULL story would help.

Click to expand...

Well the opening post says no appliances connected and it has been swapped to a different MCB. Even if it is existing I would be looking at testing the integrity of the wiring next as the OP suggest the symptoms occur with no loads connected.

Kitchen circuit keeps tripping RCCB. Problem stays with circuit , as tested by wiring circuit into another MCB. 

No appliances connected. 4 double sockets, 2 fused spurs with fuses out. 

As soon as 30A MCB is flicked on, RCCB trips.

Advise welcome.

TIA

Patrick

Click to expand...

Doc H.

he says 4 socket with no appliance connected and 2 spurs with fuses out, but if past fault finding jobs is anything to go by, he's missed a few sockets that have multiple appliances plugged in, unknown fused spurs still with fuses in feeding garage, nothing is plugged in when really there still plugged in but switched off...

A classic case where a small bit of extra information could make a big impact of the suggested best course of action. e.g. answers to three questions; (a) Has the circuit ever worked? (b) Have there been any recent alterations to the circuit? (c) Has the fuse box been changed recently?  would be a good start.

I made the assumption that as the question is in the DIY section that some DIY has been carried out. Rather than a general question to a fault problem that has randomly started with no recent changes made. 

Doc H.

Andy™ said:

he says 4 socket with no appliance connected and 2 spurs with fuses out, but if past fault finding jobs is anything to go by, he's missed a few sockets that have multiple appliances plugged in, unknown fused spurs still with fuses in feeding garage, nothing is plugged in when really there still plugged in but switched off...

Click to expand...

The circuit is an existing circuit (old red & black coloured cable). Circuit has been working for years.

Small flat kitchen circuit.

1 fused spur for washing machine.

1 fused spur for fridge.

4 other double sockets for microwave / toaster etc.

Wired circuit into another MCB. RCCB tripped.

Wired another circuit into tripping MCB. RCCB didn't trip.

Therefore problem with kitchen circuit.

Washing machine originally tripped RCCB. Unplugging it didn't solve problem.

Patrick

Thanks for the clarification. I assume you have unplugged the fridge as well?

Check there are not any other sockets or spurs from this circuit, i.e while this circuit is off, is there anything else in the flat that is not working? Immersion heater for example?

It sounds like it's time to get an electrician as I am pretty sure you won't have the equipment to do the tests required, and to buy it for a one off fault would cost more than just getting an electrician in.

Flats are notoriously known for taking a spur through the back of a socket to the other side of the wall, be sure that this is not the case here, best way to find individual circuits is with a small table lamp, turn of each Mcb and then from here switch on one and go round all sockets with lamp. Write down some notes for future reference. 

mgmti said:

The circuit is an existing circuit (old red & black coloured cable). Circuit has been working for years.

Small flat kitchen circuit.

1 fused spur for washing machine.

1 fused spur for fridge.

4 other double sockets for microwave / toaster etc.

Wired circuit into another MCB. RCCB tripped.

Wired another circuit into tripping MCB. RCCB didn't trip.

Therefore problem with kitchen circuit.

Washing machine originally tripped RCCB. Unplugging it didn't solve problem.

Patrick

Click to expand...

I'd start by looking at the Fused Spur for the washing machine...

Checking for any signs of melting, overheating, discoloration etc..

around the terminals and the fuse holder...

I have known the internals of a spur burn out before now..

also, is it a double pole switch or single pole on the spur?

It could be an internal 'N' to 'E' washing machine fault that is not disconnected with only the fuse out.

opcorn  

SPECIAL LOCATION said:

I'd start by looking at the Fused Spur for the washing machine...

Checking for any signs of melting, overheating, discoloration etc..

around the terminals and the fuse holder...

I have known the internals of a spur burn out before now..

also, is it a double pole switch or single pole on the spur?

It could be an internal 'N' to 'E' washing machine fault that is not disconnected with only the fuse out.

opcorn  

Click to expand...

Live to Live loop test pass.

N to N loop test pass.

Fridge all wires disconnected.

Washing machine all wires disconnected.

Still tripping.

That just proves continuity.

What about L-E & N-E IR tests?

mgmti said:

Live to Live loop test pass.

N to N loop test pass.

Fridge all wires disconnected.

Washing machine all wires disconnected.

Still tripping.

Click to expand...

What do you mean by loop test pass?

Murdoch said:

What do you mean by loop test pass?

Click to expand...

Murdoch,

Having had my telling off, it was me who scoobed you for that.

Peace now eh?

Sidewinder said:

Murdoch,

Having had my telling off, it was me who scoobed you for that.

Peace now eh?

Click to expand...

Peace? Was there a war? was there a muppet?

mgmti said:

Live to Live loop test pass.

N to N loop test pass.

Fridge all wires disconnected.

Washing machine all wires disconnected.

Still tripping.

Click to expand...

Proving the continuity of the loops is nothing to do with identifying the cause of RCCB tripping, you need to test the insulation resistance between L-E, N-E. And you probably need to verify the trip times and sensitivity of the RCCB. Testing loop continuity for this fault is like checking the washer bottle of your car to see if the tyre treads are worn.  It is a valid test, but the wrong test for your symptoms. i.e. breaking open a ring circuit would not cause an RCD to tip.   

Doc H.

Have to outlets been IR tested. the sockets themselves etc.. bit of dampness low IR on the socket,will cause it to trip. Had it many a time dropped the fronts off ir tested all clear stick socket back on nearly a dead short.