Fault - test meter broke need help

[axel132132]

Hi all,

my auntie has moved into this house that has had a part rewire - the full house has been done apart from the shower and the kitchen. She has a new split rcd board

the issue is this she says when she first moved in the rcd kept tripping when drills, vacs etc were plugged in then this eventually stopped and she could use her vac.

she then said she had a new shower installed its a 9.5kw shower and the existing cable is 6mm on a 40a breaker - now when you turn this on it works fine, low setting fine, medium setting fine.. Put it to its hottest and it trips the RCD

at first i thought prob the small cable but then im now thinking could it be the RCD or a faulty shower because surely if the cable was too small it would trip on a low setting also and wouldnt it trip the breaker not the rcd

i would test the rcd but my test meter has just broken

please advise as i was suggesting trying to swap the rcd and then possibly the shower but if this sounds like the cable i can then inform them that the cables too small and she needs to rewire it

 

[trev]

Without a tester you're guessing mate.

 

[axel132132]

It also confuses me how if it is small shower cable causing it to trip on a high setting how come it was doing it with drills and vac.. Just dont want to travel all way to my aunties to swop the rcd if its not the rcd (she lives about an hour an half away)

thats what i was thinking trev is it a possability that a small cable 6mm on a 40a breaker funning a 9.5kw shower could cause the rcd to trip? Or would the rcd still not trip if it was small cable (im crap with rcds dont fully know the ins and outs of them)

 

[Plonker 3]

As Trev said, unless you have one of these?

 

[Darkwood]

Your an Arms member so then assuming you have your own business or the like, your testers are your primary tool box item so to come on here and say your tester is bust is not an excuse, buy a new one, repair the old one, borrow one or hire one.... without it you shouldn't be working on electrics unless your first fixing or the like.

Get a tester, test your circuit and come back to us with any questions, of the cuff your shower may be a 3 element tank and the 3rd element may have a leakage on it while the other 2 are fine, but who knows without test equipment.

If its just a matter of been in repair tell your aunt to have a bath till you get your meter back or don't put it on high heat.

 

[Lucien Nunes]

Put it to its hottest and it trips the RCD... at first i thought prob the small cable

I cannot imagine why you would think that.

when she first moved in the rcd kept tripping when drills, vacs etc were plugged in

So there's plenty of evidence of a fault

i would test the rcd

I'd test the circuits first.

 

[Guest111]

I had something similar on a RFC at a mates place recently,cutting a long story short in the end it turned out to be a damaged cable and damp had got into it,it took me the best part of a day to find and that was with all the test gear,without it I fear you are just peeing into the wind.

 

[Pete999]

I'll go along with darkwood on this

 

[axel132132]

No longer run business so no need buy myself one for my aunt - now work for board

 

[trev]

Surely there must be someone you can borrow a tester from. Mine messed up on me 3 or 4 weeks ago, I borrowed one immediately to keep me going till I bought a new one.

 

[tony mc]

If you can not get access to the correct test equipment your Aunt will have to employ a spark to sort out this issue .

IMO the person that part rewired the house should of been called when she first moved in as a fault was clearly there.

I would also make sure the person she employs is competent with fault finding and how RCD's actually work.

Let us know the outcome!

 

[HandySparks]

...im crap with rcds dont fully know the ins and outs of them

In which case, you are misrepresenting yourself by using the title 'electrician' in your profile.

 

[trev]

For Info Axel
https://www.google.co.uk/url?sa=t&r...=rRqKB4lRaQDFKA5BlpiO4g&bvm=bv.80642063,d.ZGU
https://www.google.co.uk/url?sa=t&r...=fVkAhm3zF0_RbZxv1hlf2Q&bvm=bv.80642063,d.ZGU
https://www.google.co.uk/url?sa=t&r...=32lyjdVDpijBDtc6bAKh6g&bvm=bv.80642063,d.ZGU
https://www.google.co.uk/url?sa=t&r...=7u_iiItG00njTHXTIQTAiw&bvm=bv.80642063,d.ZGU

 

[axel132132]

As usual the ever so helpful forum.. Not!

and no it is not mis reprisentation i am a qualified electrician did a 4 years c&g apprenticeship working for two different companies to get myself through it. I know the general rule behind rcd's but the one thing i didn't know is if cable size can trip an rcd due to leakage which was basically all i was asking but as usual this useless forum didnt provide lol

someone needs to give it a shake up as the forum is here to help people - not to argue, winge and moan at people who don't have as much experience or knowledge as others.. It is also here to help people gain that knowledge that they may not have

i can happily admit i do not know all the ins and outs behind electric and how it all works - yes i got taught it but i dont rember it and this is what this forum is here for to help not criticise so its whole purpose is pointless if people are not willing to help but are only here to moan and winge at people

im 24 did a 4 year apprenticeship then 1 year in the job.. Thats 1 year qualified experience obviously im not going to know as much as a 25 year vet! Hence coming here. Im here for advice and guidance to make sure i do everything to the book not to be criticised its people like u lot that make unexperienced people like me think **** it why ask for help ill just do it 'and potentially do it incorrect' so the lot of u stop being childish and start helping people


anyway i found out the fault, but again i have no explanation for it hence now i shall post it and hopefully someone can give me a sensible explanation without trying to ricidule me because my knowledge is not that high but am trying to learn!

the issue was a neutral fault on the external light, the light worked fine and didnt trip the rcd until the shower was pulling a large load - why is this? It is my belief that if a neutral fault was on the light whej the sensor was detected then surely that should have tripped the rcd.. Not everything working fine until you put a shower on full or plug a heavy duty drill in..

if anyone has a sensible explanation so i can grow my knowledge id appreciate that

 

[telectrix]

i would suspect that the fault on the external light was causing insufficient leakage to trip the RCD, but added to some L-E leakage on the shower was enough to take the leakage to the RCD threshold.

 

[tony mc]

axel I am sorry you feel this way re the response.

RCD tripping issues can be very frustrating to say the least and not that straight forward to locate.

As a spark you should at least know the workings of one and what they do when installed IMO!

For someone to tell you that the fault is A or B would just be guessing as without carrying out any tests would be that a guess!

A IR test of the lighting circuit at your Aunts house would of had alarm bells ringing as under test IMO the readings would be low and prompt you to look further into that circuit!

I take it you managed to borrow some equipment to find the fault as per your explanation!

Thanks for letting us know.

 

[Guest111]

It's no use coming on here then throwing a strop when you don't get the answer you wanted! Any FOOL can rewire a house,it's testing and fault finding that seperates the men from the boys,simple fact is we are on a forum,we have no physical access to the fault,we have only the info you supply us with to make an educated guess at where the problem may lie,and it is just that a guess.At the end of the day if you cannot give us readings because you have no test gear then don't moan at the responses you receive.If you don't like it you shouldn't have joined.perhaps the screwfix forum would be more to your liking,after all that's full of people who haven't got test gear and expect a diagnosis over the internet.

 

[PEG]

As usual the ever so helpful forum.. Not!

and no it is not mis reprisentation i am a qualified electrician did a 4 years c&g apprenticeship working for two different companies to get myself through it. I know the general rule behind rcd's but the one thing i didn't know is if cable size can trip an rcd due to leakage which was basically all i was asking but as usual this useless forum didnt provide lol

someone needs to give it a shake up as the forum is here to help people - not to argue, winge and moan at people who don't have as much experience or knowledge as others.. It is also here to help people gain that knowledge that they may not have

i can happily admit i do not know all the ins and outs behind electric and how it all works - yes i got taught it but i dont rember it and this is what this forum is here for to help not criticise so its whole purpose is pointless if people are not willing to help but are only here to moan and winge at people

im 24 did a 4 year apprenticeship then 1 year in the job.. Thats 1 year qualified experience obviously im not going to know as much as a 25 year vet! Hence coming here. Im here for advice and guidance to make sure i do everything to the book not to be criticised its people like u lot that make unexperienced people like me think **** it why ask for help ill just do it 'and potentially do it incorrect' so the lot of u stop being childish and start helping people


anyway i found out the fault, but again i have no explanation for it hence now i shall post it and hopefully someone can give me a sensible explanation without trying to ricidule me because my knowledge is not that high but am trying to learn!

the issue was a neutral fault on the external light, the light worked fine and didnt trip the rcd until the shower was pulling a large load - why is this? It is my belief that if a neutral fault was on the light whej the sensor was detected then surely that should have tripped the rcd.. Not everything working fine until you put a shower on full or plug a heavy duty drill in..

if anyone has a sensible explanation so i can grow my knowledge id appreciate that

Hi dude,imagine hearing THAT statement from your vet,as he opens up the family dog...:conehead:

 

[Lucien Nunes]

I know the general rule behind rcd's but the one thing i didn't know is if cable size can trip an rcd due to leakage

I fear this is the crux of why you got some silly responses - it's a silly question! Why would an undersize cable have anything to do with it? The total lack of sense stood out like a sore thumb, raising all sorts of doubts.

As for the actual fault, I expect you'll find some good explanations by searching the forum - I've certainly answered the same question a few times before. In a nutshell, the VD resulting from current in the supply N (from any of your own circuits or even other consumers) causes a fraction of the current arriving at N busbar to flow through the RCD into the faulted circuit's N, returning via its CPC and thus causing imbalance in the RCD.

 

[Knobhead]

if anyone has a sensible explanation so i can grow my knowledge id appreciate that

I could explain it to you but if you don’t know the principals behind the operation of a RCD there’s not much point is there?