Power tripping

[gazza1]

Hi guys, just joined, hope you can help me.
I have power running from the house to the garage where it goes into a consumer unit. I have added a 2nd switch in the garage to operate a couple of lights. I now have 2 1 gang switches (1 by each door).
My problem is when I turn the garage C/U off, so no lights or sockets are on and try and work on the wiring, when a couple of wires touched they tripped the house CU. Is this because the wiring in the garage is not earthed so it trips the house CU and this is normal. This happened on the lighting and socket circuit. By the way, the lights and sockets work fine, until I do any further wiring.

 

[ricicle]

//www.diynot.com/wiki/electric...ergised_circuits_with_neutral_to_earth_faults

 

[sparkwright]

It sounds like the garage is protected by an RCD in the house.

Touching neutral to earth would cause this to trip.

That said, isolating the main switch at the garage consumer unit SHOULD isolate both live and neutral, so working on the garage circuits shouldn't trip the RCD.

Did you isolate the garage by isolating the main switch on the garage consumer unit?

 

[flameport]

If the garage CU is off, and yet tampering with wires in the garage still causes the house CU to trip, the garage is wired wrongly - quite possibly in a dangerous way.

 

[sparkwright]

Turning off individual circuit breakers/fuses on the garage consumer unit would only isolate the lives, and not the neutrals.

The main switch in the garage should isolate live and neutral. If you have been turning off this main switch, assuming you even have one, your wiring may be incorrect.

Pictures would be extremely useful.

 

[gazza1]

I do isolate the garage on the c/u. The house is still on, but then trips. When everything is wired in and I am not fiddling it works 100%, lights and sockets. The other thing I just remembered was that it trips in the house on both lighting and the socket circuit. Must be a common denominator. Thanks for your prompt replies.

 

[gazza1]

What I meant was, it trips in the house when I am working on the lighting or socket circuit in the garage.

 

[ban-all-sheds]

I do isolate the garage on the c/u.

Did you isolate the garage by isolating the main switch on the garage consumer unit?

 

[ericmark]

No it is not normal. In the main a consumer unit (CU) has all pole switching so once switched off it should not effect the house.

I have seen in the past where an isolator has become faulty that some one has linked out the neutral on the isolator and I would suspect this is the case with you?

However switching on high loads can produce spikes which in turn can trip a RCD. In theory in my house leaving all MCB's active and re-setting the RCD should be no different to switching off all MCB's then resetting RCD and after turning on all MCB's. But in the real world I know that switching off all MCB's first is less likely to trip the RCD on a reset.

 

[gazza1]

Thanks for the advice guys, I will investigate further and then get an electrician around.