RCD tripping

[garrymum]

Last night, we lost all power to the plug sockets, the RCD had tripped. I isolated it down to the garage as if I turned off power to the garage (from the main CU in the house) the RCD could be re-set. As soon as I restored power to the garage the RCD tripped again.

I went out into the garage and turned off the small chest freezer in there and tried to restore power - it still tripped. This morning I turned off the small CU in the garage and tried to restore power and it tripped again. We have some outside lights and also a weather proof plug in the rear garden.

We had some gates fitted on Friday. The power to the garage runs along the fence and then goes underground to the garage where the post for the gate has been concreted in. On Friday they did trip the power as they had all there drills plugged into an extention taken from the garage. Once it tripped on Friday, it re-set fine and they then took power from the house. I am now thinking worse case scenario and they have somehow nicked the cable whilst digging and possibly damaged it, hence it constant tripping even though nothing is plugged in. I am presuming the cable is SWA although just had a look at the cable as it enters the garage and there is no writing on it what I can see. The cable is black, about 15-20mm diameter and is very rigid.

If there is no way of damaging SWA, would else could I try to isolate the problem and restore power back to the garage without it tripping the RCD?

TIA

 

[RF Lighting]

I think the best thing to do first of all would be to disconnect the SWA cable at both ends, and carry out an insulation test between each core, and each core to earth.

 

[garrymum]

I think the best thing to do first of all would be to disconnect the SWA cable at both ends, and carry out an insulation test between each core, and each core to earth.

You are talking Chinese there to me . Looks like I'm going to have to get a pro in to take a look.

 

[jujubean]

Aahh my friend...RCD tripping..its a real pain is that
What you have to do sadly is get a pro in He or she (got to be politically correct nowadays) will put an insulation test on the main consumer unit and as I do disconnect all the neutrals so you dont get any confusing results...Then test each circuit individually...phase to earth and neutral to earth
Dont forget that simply switching the chest freezer off does not isolate that appliance from the supply...You have to withdraw the plug top from the socket
I would be supprised if the armoured cable feeding the garage is damaged as they are pretty robust
Perhaps some external light fittings may have water in them?...its usually things like that or more commonly fridges freezers and washing machines that cause the tripping
Finally it wouldnt harm to test the actual RCD to see if it too sensitive .An RCD tester switched on to its 50% range will determine this.
But again thats a job for the pros
Good luck

 

[julioarca]

I would be supprised if the armoured cable feeding the garage is damaged as they are pretty robust


I work in Street Lighting where we use loads of SWA, it is not robust and can still be nicked / damaged and give an earth fault, fortunatly in Street Lighting, earth / neutral faults are not a problem, but for a householder they are.

 

[electronicsuk]

Sadly, the fact that the fault still occurs even when the isolator in the garage CU is off (assuming it's double pole) means that the fault isn't with any off the appliances in the garage. From what you've said there's quite a good chance the builders have damaged something, let us know what the electrician finds!

 

[garrymum]

Had a word with the gate fitters today. He said there was a cable there but it was not SWA and it it possible he may have nicked it. It looks like the house builders have used SWA between the house and the detached garage and whoever has one the rear garden lights / plug has taken his feed from the garage feed but not used SWA.

So, now need someone to replace a short run (approx 4 foot) with a new SWA cable.

 

[garrymum]

RF lighting - are you interested, sent you an email. I am in Leeds

 

[ebee]

Leeds,
I`m about an hours drive away ( in Lancashire).
LOL.

Right sorry back to the thread,

In reallity it might be cable nicked but then again it could be other things too, so a pro with the correct equipment should be used.

As for RCDs being oversensitive, I wouldn`t say it can`t happen but in my experience the reverse is true, ie it might not be working correctly or at all.

 

[garrymum]

I disconnected the white pvc cable from the weatherproof junction box on the side of the house, leaving the SWA going to the garage still connected. This allowed me to turn on the power for the garage (at the main house CU) without tripping the RCD. So, chances are that the gate people have damaged the white pvc cable. At least I now have power back on in the garage. I can handle not having rear garden patio wall lghts or an external plug for the time being.

I presume I can do replace this cable myself with SWA but would need to get it certified by a part p electrician?

Do electricians 'want' to come out and just do the certification (afterall it is taking work away from them).

 

[ban-all-sheds]

That's not how the notification requirements of Part P work.

If you want to be lawful, you must either:

1) Notify the council in advance of the work, and pay their fee, in which case they become responsible for inspecting and testing (no matter what else they might try and fob you off with - that's what the fee is for)

2) Have the work done by an electrician who is registered to self-certify compliance with the Building Regulations.

You might find an electrician prepared to test your work for safety, but he won't "certify" it, and no way will he tell your LABC that he installed it.

 

[nozspark]

Generally Part P registered electricians are not allowed to certify others work (it's part of the membership rules).
The only way you could legally do this is for you to pre-notify (& pay a fee to) you LABC, carry out the work and have them into inspect and test it.

 

[ban-all-sheds]

Generally Part P registered electricians are not allowed to certify others work (it's part of the membership rules).

It's also the law, if you're talking about Building Regs certification.

They can of course issue EICs (Inspect & Test part) against other people's work.