I've just had a bit of a 'mare

[Ladaman]

I went in the garage tonight to do a bit more on my "new" suspension.

But I've borrowed a plasma cutter off a mate at work, so I dicked about getting the airline to fit to my compressor, and cracked it up on a bit of 5mm scrap metal.

Very impressed.

When I'd finished, I turned it off at the plug socket, and it blew all the electricity in the whole house. After lots more dicking about, the only way I could get any power on in the garage was to remove the neutral wire from inside the garage fuse board for the LIGHTING circuit

So a whole evening wasted, with no idea how to get my lights working again until my son gets home on Sunday

[windsor]

Sounds like youre gunna have a dark weekend

[kiwizook]

okay mate, lets see if we can do some diagnostics. what happens if you turn the power on with the light neutral connected, does the fuse blow, or the circuit breaker break? does it have rcd's(residual current device, earth leakage switch, or whatever you want to call it)?

this all happened at the very exact time you turned off the power to the plasma cutter? is the power point fine with the light neutral removed in the board?

sound to me like you have a fault on the light circuit, but it should blow the fuse/mcb to the light circuit, not all power.

I'm a sparky, so let's nut this out!

[Ladaman]

Thanks for the offer Kiwizook. OK then.

The house has a consumer unit (CU) with one RCD and a number of MCB's. One MCB is connected to a cable running to a detached garage. In the garage I have another consumer unit. This is an old fuse wire type. I have a lighting circuit and ring main running from it.

The moment I turned the plasma cutter off atthe switched socket (looking back the plasma was still switched on), the RCD tripped killing ALL electricity, house and garage.

The only way I could reset the RCD was to leave the garage CU turned off at the main switch. I then removed the socket front thinking it had damaged it, and put connecting blocks on to get it back to normal. Still tripped the RCD.
I removed all the fuses in the garage CU, still tripped the RCD.
Removed the neutral to the garage ring, still tripped it.
Removed the neutral to the light circuit. Power back on to the ring main in the garage and the house.

At no point did a fuse or MCB trip, just the RCD. So it would suggest a light issue.

1. Why would that happen, it has never been at fault before?
2. What do I do to fault find the light circuit?

I have five double fluorescent lights in the garage, that are a bit past their best, and could do with changing if I'm honest, but than can wait, possibly.I just need lights back on to be able to carry on with my Suzuki.

[kiwizook]

ok, that really helps a lot.

seeing it doesn't want to power up without fuses, it is possibly a neutral earth fault, which will trip the rcd, but not the mcb's. fluro's have balast's in them, which are like transformers, and are notorious for breaking down on the inside. you might smell it, but in this case I don't think so. try disconnecting each light completely in turn, and try to power up the light's. I think you will find that with the faulty light disconnected (and the cable made safe obviously!), the rest of the light's will power up without problem. you might have more than one faulty light, but this is unlikely.

if this fails, to just get you by, you can try to disconnect the main earth connection in the board, just to get you up and running. please note this can be extremely dangerous, and should only be done temporarily, and you should have a professional fix the problem as soon as possible!

[Ladaman]

Thanks for that I will give that a go on Saturday when there is some daylight. Failing that, I might just let my son look at it hopefully on Sunday as he is a sparky, but working in London until then.

A strange coincidence for it to blow then?

[Darrell]

Blooming strange one
Would the plasma transformer create a surge when switched off.
Am I right in thinking a socket outlet has a single pole switch.
The cutter would probably have a double pole switch.
Would switching it off at the socket send a surge on the neutral.
Would this damage the light ballast, especially if it has the electronic type.
Sorry just thinking out loud

As said I would assume one of the light fittings has a neutral to earth fault/leak.
As the whole system tripped do you have a 100ma rcd protecting the lot and a earth stake outside.

[kiwizook]

a surge on the neutral shouldn't do anything, as it'll be diverted to the earth system if the neutral gets overloaded. let's see what happens if he tries these things.

and I was thinking it might pay to first try to disconnect the lighting circuit earth, as this will keep all else earthed, and will be safer

[turbo-tom]

We had a similar problem I think with our compressor we have. Turns out it was just a faulty circuit breaker for the garage main power.(fuseboard in the house) not the fuseboard in the garage.

[kiwizook]

it might not have been faulty tom, it's probably the wrong type. there's different type's, and some can cope with the huge startup current of motors and compressors, and others can't. this could have been all your problem was!