Help! Scary electrical problem

[benwatkins]

Hi,

This evening I wired in four LED downlights to replace the single 60w light bulb in my bathroom. Before starting I switched off the light and for good measure I switched off the circuit breaker in my consumer unit.

I had wired up nearly all of the lights using 1.5mm2 twin & earth and junction boxes in the traditional fashion and was just stripping the wire on the last light fitting when the RCD tripped and turned all the electric in the house off. I checked all my wiring and it all seemed correct so I turned the RCD back on again. I then put my meter across the bare wires I was working on and the meter read 0.1v (I was expecting zero!). Eventually I plucked up enough courage to finish wiring up the remaining downlight and turned the circuit breaker then light switch on. The lights worked fine and there was no smoke or fire!

So now I'm not suite sure what to do. Firstly, if I did do something wrong with my wiring, could I trip out the RCD even though I had switched off the circuit breaker for the circuit I was working on? Secondly, why have I got 0.1v in my lighting circuit when everything is supposed to be off?!

 

[riveralt]

When you isolate a circuit via the MCB you only isolate a single pole in this case the line (live) part of the circuit - the neutral is wired separately and you probably caused an imbalance in the RCD when you were wiring up your new torch lights.

Whether you have done something wrong with your wiring I cannot tell because you haven't given specific details about how you wired up the lights.
Whether you have done something wrong in terms of the law then more than likely you have breached the Building Regulations Part P and probably Parts B and L and others. Given you have used junction boxes you may well have breached the guidelines given in BS7671:2008.

You can read about it here:
//www.diynot.com/wiki/electrics:part_p:diy_electrical_work_and_the_law

 

[benwatkins]

Thanks for the help riveralt. I am aware that I am probably breaking building regs by wiring in new lights. In my opinion building regs like these ones go way to far. They are dreamt up by beurocrats with blunt instruments trying to legislate out idots who have no idea what they are doing. I don't see why DIY'ers with half a brain who are able to wire things up safely and properly should be penalised as a result. That's why I pretty much do my own thing and (normally) keep it quiet. No harm done.

I've just had a 'lightbulb on' moment. My bathroom has an extractor fan which is on the lighting circuit and I guess the 0.1v is residual charge from the capacitor.

 

[echoes]

Could be an induced voltage, residual charge due to capacitance of the cable, or most likely the accuracy limits of your meter.

 

[flameport]

Before starting I switched off the light and for good measure I switched off the circuit breaker in my consumer unit.

Does this mean you were considering doing this work after just turning the light switch off, and leaving the circuit breaker on?

 

[ELZ4742]

Before starting I switched off the light and for good measure I switched off the circuit breaker in my consumer unit.

Does this mean you were considering doing this work after just turning the light switch off, and leaving the circuit breaker on?

its all good, he was stood in the bath at the time

 

[Taylortwocities]

Thanks for the help riveralt. I am aware that I am probably breaking building regs by wiring in new lights. In my opinion building regs like these ones go way to far. They are dreamt up by beurocrats with blunt instruments trying to legislate out idots who have no idea what they are doing.

So you are also OK with driving at 160mph, driving after consuming 6 pints and exposing yourself to schoolgirls?
Or do you only select to obey the laws that suit you

 

[electronicsuk]

Thanks for the help riveralt. I am aware that I am probably breaking building regs by wiring in new lights. In my opinion building regs like these ones go way to far. They are dreamt up by beurocrats with blunt instruments trying to legislate out idots who have no idea what they are doing.

So you are also OK with driving at 160mph, driving after consuming 6 pints and exposing yourself to schoolgirls?
Or do you only select to obey the laws that suit you

A bit of an extreme analogy, still a fair point - the regs are there because, as this forum often demonstrates, there are plenty of DIY'ers who think they have some idea of what they are doing, when in reality they are less than clueless. I'm not saying that applies here, but merely as a general rule.

FWIW, I also think our national speed limit is too low, although perhaps 160MPH would be pushing it. I don't think my car would quite manage that.

 

[ban-all-sheds]

Thanks for the help riveralt. I am aware that I am probably breaking building regs by wiring in new lights. In my opinion building regs like these ones go way to far.

Be that as it may, have you thought about what you'll say if asked about notifiable work when you come to sell your house?

And is it just Building Regulation 12 you've decided to ignore, or have you also paid no attention to C2 and L1 in Schedule 1?

They are dreamt up by beurocrats with blunt instruments trying to legislate out idots who have no idea what they are doing.

I'd like to thank you for that wonderfully ironic observation - it really made me laugh.

I don't see why DIY'ers with half a brain who are able to wire things up safely and properly should be penalised as a result.

Possibly not.

Do you know one who could come and install these lights for you?

 

[bernardgreen]

They are dreamt up by beurocrats with blunt instruments trying to legislate out idots who have no idea what they are doing.

The writers also have some input from people with very sharp instruments. Mostly from doctors amd surgeons but also some input comes from pathologists.

 

[Chri5]

People have a choice, and many will be happy to do the odd bit of electrical work.

Up to minor works, shifting something, changing fittings, lights etc tend to be within 'scope' of ability for quite a few. I refuse to lambaste anyone for taking up the right to do work within their own property.

All I'd say is that being safe is the priority. Take the op's question.

A rcd can trip when the circuit is dead (as in breaker off at the board). It's doing it's job- there's is always likely to be some imbalance between the neutral and earth and you should now anticipate such happenings if you ever do electrical work again.
Such trips could be avoided by removing the neutral at the board in addition to isolating the live (easier to kill the whole system for the short time most connecting to circuits jobs take)

Hopefully the OP has worked within the requirements of 17th edition, is aware of heat issues / distance from joists, access requirements for jb's post works, cable size, circuit load, insulation, etc.

None are rocket science, but do a job you must accept that working to industry standards is a requirement.
Lashed up jb's, tape joints, dangerous routing of cables, earths not in sleeve deserves a beating with lumps of armoured cable as does anyone doing new circuits and not fully testing them.

 

[londonboy]

See no one gives a monkeys about electrics, then when it comes to gas they run a mile. Wish I had trained as a plumber

I'm fed up of hearing ' how much will it cost? £100. I aint paying that, I'll get the bits from B&Q for £5 and do it myself'

 

[GeoffPotts]

See no one gives a monkeys about electrics, then when it comes to gas they run a mile. Wish I had trained as a plumber

I'm fed up of hearing ' how much will it cost? £100. I aint paying that, I'll get the bits from B&Q for £5 and do it myself'

"I'm competent and know what I'm doing - oh and I have no idea where 0.1V came form or why my RCD tripped!" Wonder why he asked a forum a basic question when he is fully competent himself. If you dont' know why the RCd tripped put the scredrivers down and get it done safely

 

[sparkybird]

ooerr - he's not replied, so maybe he spoke to soon

"The lights worked fine and there was no smoke or fire....."

 

[GeoffPotts]

Ha ha,

very true! - and worrying? :S