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avinalarf

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I'm a newly qualified electrician and am yet to undertake the advanced fault finding course. Never was I in such need as that sort of knowledge as I am now... :_|

Not sure where to start, but whilst away last week, the builders were working (plastering in particular) and said the the downstairs ring tripped. I turned it on this morning and it was fine, went out, only for them to call me to say it had happened again.

I have unplugged all appliances on the ring and it's still tripping. I broke into the ring several weeks ago and added 3 additional sockets and it's been ok up until now. Sockets are still hanging out and I've checked them for dampness or the like from the plastering, but they all seem ok.

Whilst doing extensive work over the past few months, I've noticed many junction boxes on the ring main and have tried tracing where they go to, but with walls, furniture, etc. it's proving extremely difficult. I'm quite sure I haven't created a ring within a ring, but how can I check if I have?

Is there anyone out there who can even begin to explain how I can find out what is causing the circuit to trip?

Eternally grateful for any feedback.

Cheers

Nat

 

DonkeyDong

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Hi there,

Have you got anymore info ?

Define tripping ? RCD or MCB ?

What tests have you done ? IR, R1, R2?

Chances are its a wet socket or a cut cable- damn plasterers!!! :(

Do an IR, depending on that, start splitting the ring in half, test each half, then split into quarters.

Keep going until you find the leg/socket that is causing the problem.

simple :D

D.

 

cheggers

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I'm a newly qualified electrician and am yet to undertake the advanced fault finding course. Never was I in such need as that sort of knowledge as I am now... :_| Not sure where to start, but whilst away last week, the builders were working (plastering in particular) and said the the downstairs ring tripped. I turned it on this morning and it was fine, went out, only for them to call me to say it had happened again.

I have unplugged all appliances on the ring and it's still tripping. I broke into the ring several weeks ago and added 3 additional sockets and it's been ok up until now. Sockets are still hanging out and I've checked them for dampness or the like from the plastering, but they all seem ok.

Whilst doing extensive work over the past few months, I've noticed many junction boxes on the ring main and have tried tracing where they go to, but with walls, furniture, etc. it's proving extremely difficult. I'm quite sure I haven't created a ring within a ring, but how can I check if I have?

Is there anyone out there who can even begin to explain how I can find out what is causing the circuit to trip?

Eternally grateful for any feedback.

Cheers

Nat
the only way you are going to find this fault is to do ir tests and split the ring in halves

 

The Godfather

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the only way you are going to find this fault is to do ir tests and split the ring in halves
Well yes, let's check continuity then the IR, and take it from there.

Don

 

avinalarf

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Thanks for all the replies.

I've disconnected the part of the ring which I had extended (assuming it must be an error on my part, although all has been well for over 2 months!) but the RCD is still tripping as soon as I put the MCB on.

It's getting a bit late now, so I'll do the IR and continuity tests tomorrow, then try to start breaking down the ring...

Will keep you posted

Cheers

N

 

avinalarf

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No slips, I'm not Part P registered yet - the job was submitted to LABC before I started as part of renovation work and luckily it's my own home!

My reason for the question was because the ring had been tested when I first made my additions and all was well - just puzzled as to why it would suddenly start tripping!

 

mikel

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Better the chasing out and rewiring rather than the uncertainty of the unknown. :)

 

hamlettphil

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is the power staying on, with nothing plugged in?? if you put load on the circuit and it trips, could be unbalanced load? could be u have ur neutral cables mixed up. only a suggestion. i had this experience before and it took me around 3 hours to see ehat i had done!!!

 
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I`m with slipslap & mikel here. Rip it out, and start again. If there`re THAT many JB`s on the cct, chances are that the ring isn`t sound, or has spurred spurs, etc. If I lived in a house with this issue, I`d consider it the only option.

Failing that, Follow DD, and seperate the ring into sections, as best you can.

 

avinalarf

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Don't s'pose any of you guys live near the Cambridge area do you? The thought of taking this on on my own, being a newby an' all, isn't filling me with good cheer! :_|

 
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Don't s'pose any of you guys live near the Cambridge area do you? The thought of taking this on on my own, being a newby an' all, isn't filling me with good cheer! :_|
What sort of test gear have you got?

i.e. a decent calibrated or proven mutitester or similar?

go back to basics a bit.. re prove the bits you are assuming..

1/ Verify the values for continuity of the ring is appropriate for the estimated cable length.

e.g table 9A page 157 On-site-Guide.

2.5mm copper is 7.41 mili-ohms per meter.

1.5mm copper is 12.10mili-ohms per meter.

so a 20m ring would have 0.15ohm reading on live & neutral

and a 0.24ohm if a 1.5mm earth wire is used.

or a 50m ring would have 0.37ohm reading on live & neutral

and a 0.61ohm if a 1.5mm earth wire is used.

2/ you can then cross live & neutral at the CU..

and the reading at each socket (if a ring)

will be approx (live r1 + neutral r2)/4.

with the circuit completely disconnected from the fuse box check for any continuity back to the main electrical earth from each of the open circuit conductors.

3/ short one end of the ring out..

then read between L&N at each socket to see if you can establish the cable order.. i.e gets bigger further down circuit you go..

will probably think of more later..

:) ;)

 
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