Borrowed neutral discovered when changing CU and discussion on DIY CU change

[rsmck]

Re: Borrowed Neutral discovered after changing CU

Dead Tests... Errrrm lets start with IR (L-E) what was your reading?

I will freely admit I didn't test every circuit in the existing installation - although I did in my own home *rewire*

It was a quick change done as a favour and for short term.

It's safer than the previous installation (with a damaged fuse cover and exposed live) - I'd be surprised if anyone was to disagree with that :/

 

[rsmck]

Re: Borrowed Neutral discovered after changing CU

- - - Updated - - -
Or is the OP tester the 99p variety that comes from china in the form of a driver ?

No, a Fluke 1652... Wouldn't touch those neon screwdrivers with a bargepole

 

[trev]

Re: Borrowed Neutral discovered after changing CU

To be fair Rsmck you can't expect to come on a forum for and populated by electricians and make the claims you have without experiencing a little animosity. You claim to understand what your test gear tells you (and indeed this may be the case) then claim that somehow a blatant insulation resistance fault would have went un noticed until the RCD tripped. You could not have performed the IR tests on these circuits or did not get what the meter was telling you.
I appreciate your willingness to have a go but feel that you're in a lot deeper than you realise which is a dangerous position to be in. I hope I'm wrong for your sake though.

Edit

You posted #31 while I was typing this.

 

[bigbaddave]

Re: Borrowed Neutral discovered after changing CU

Since you ask - I worked in IT/Telecoms for a long time including data centre management, whilst I didn't wire these myself (obviously) I have a good understanding of the *use* of such electrical installation and the concepts associated with them - e.g. UPS systems, transfer switches, generators etc and monitoring the power usage of such installations. I was also responsible for regular testing of equipment.

Outside of this I work as a theatre lighting technician (In theatre this is often actually referred to as "an electrician" - bit of an unfortunate misnomer) and so again need to understand testing, safe wiring practices (many venues make up their own cables including 3 phase cables) and various other electrical things mainly concentrating on lighting.

In terms of formal training - none, just experience and never being afraid to ask if I'm unsure, and getting someone else to do it if I still don't fully understand the answer.

As far as testing, my current home is the first that I've carried out full IR/Zs testing etc following a full rewire (replacing a 1950s VIR installation)

Note - I do not consider myself an electrician - but am happy to undertake basic electrical work for family (fitting lights, new sockets etc) and adhere to all relevant regulations where practicable (obviously old installations won't comply with everything!) and more extensive ones (like rewiring) for my own home.

As an aside this has been discussed (at length) in previous posts

With respect any idiot can make an electrical circuit work.. Thats the easy part. The hardest part is designing the install safety.

Buts its clear as day you arnt up to scratch with your testing otherwise the fault you had would have been apparrant before the system was energised.... What other faults did you find when testing the install? Be interested to here some of your result.

 

[Guest111]

Re: Borrowed Neutral discovered after changing CU

Anybody can within reason carry out the tests as laid down in the big book,understanding what the results tell you now thats another matter.

 

[rsmck]

Re: Borrowed Neutral discovered after changing CU

To be fair Rsmck you can't expect to come on a forum for and populated by electricians and make the claims you have without experiencing a little animosity. You claim to understand what your test gear tells you (and indeed this may be the case) then claim that somehow a blatant insulation resistance fault would have went un noticed until the RCD tripped. You could not have performed the IR tests on these circuits or did not get what the meter was telling you.

Thanks for the balanced response - I didn't conduct tests on those circuits before changing over the CU - should I have, yes most probably, but I wouldn't have been able to correct anything as I was pretty limited in what I was there to do in the eyes of the homeowners - change one fuse box for another... silly me thinking it would be a straightforward swap I guess.

I appreciate your willingness to have a go but feel that you're in a lot deeper than you realise which is a dangerous position to be in. I hope I'm wrong for your sake though.

I hope you are too... but it's been two years since I did my own home and we've had no problems, so I'm optimistic I've done it properly. And yes, I did carry out all the relevant testing in that installation.

 

[bigbaddave]

Re: Borrowed Neutral discovered after changing CU

I will freely admit I didn't test every circuit in the existing installation - although I did in my own home *rewire*

It was a quick change done as a favour and for short term.

It's safer than the previous installation (with a damaged fuse cover and exposed live) - I'd be surprised if anyone was to disagree with that :/

Enough said... So no checking whether you have an external earth. No checking the resistance on you ring mains and not checking that the RCD you installed actually does the job you intend to do..

Ive had enough of this one... Im out..

:46:

 

[Dan the spark]

Re: Borrowed Neutral discovered after changing CU

I will freely admit I didn't test every circuit in the existing installation - although I did in my own home *rewire*

It was a quick change done as a favour and for short term.

It's safer than the previous installation (with a damaged fuse cover and exposed live) - I'd be surprised if anyone was to disagree with that :/

It seems that you are falling into the same old rookie/diyer delusion that by 'changing the fuseboard without testing and thinking that if there was a problem then the rcd will find it' thinking that you could well be causing a lot more danger than you are preventing.
i think that if they are getting it retired by a professional in the near future that you should have just left well alone and got someone in that knows what they are doing. Just out of interest what was the make of the old board?

 

[rsmck]

Re: Borrowed Neutral discovered after changing CU

Buts its clear as day you arnt up to scratch with your testing otherwise the fault you had would have been apparrant before the system was energised.... What other faults did you find when testing the install? Be interested to here some of your result.

Ok, I'll admit I was wrong in NOT carrying out extensive testing on the dead circuits before energising them (but as those were 'professionally installed' albeit many years ago it foolishly thought it reasonable to assume that there was no *major* faults - guess not)

As for the live cable nicked by a screw it makes no sense to me that it hadn't taken out the fuse before then and I guess that there may have been another fault that was corrected when I reterminated that cable, but there was nothing else apparent at the time. And yes, testing would have revealed it.

 

[trev]

Re: Borrowed Neutral discovered after changing CU

I hope you are too... but it's been two years since I did my own home and we've had no problems, so I'm optimistic I've done it properly. And yes, I did carry out all the relevant testing in that installation.

All I can say to that is a few weeks ago I was in a restaurant carrying out an EICR and found an RFC wired in 1mm T&E with a 40 amp MCB. The restaurantuer said the same thing, It had been that way for a couple of years and worked fine, he even showed me a certificate for the job

 

[bigbaddave]

Re: Borrowed Neutral discovered after changing CU

It seems that you are falling into the same old rookie/diyer delusion that by 'changing the fuseboard without testing and thinking that if there was a problem then the rcd will find it' thinking that you could well be causing a lot more danger than you are preventing.
i think that if they are getting it retired by a professional in the near future that you should have just left well alone and got someone in that knows what they are doing. Just out of interest what was the make of the old board?

Or Condemned..

 

[Dan the spark]

Re: Borrowed Neutral discovered after changing CU

Or Condemned..

Damn u auto correct.....rewired!

 

[Octopus]

Re: Borrowed Neutral discovered after changing CU

And people wonder where all the decent members have gone??

Threads like this is the reason.

 

[plugsandsparks]

Re: Borrowed Neutral discovered after changing CU

Went to all that trouble changing the CU and didn't establish whether it was safe, and then left one neutral energised by two MCBs, nice for the next poor sod to get his hands spiked.
2/10 for effort

 

[rsmck]

Re: Borrowed Neutral discovered after changing CU

Enough said... So no checking whether you have an external earth. No checking the resistance on you ring mains and not checking that the RCD you installed actually does the job you intend to do..

Ive had enough of this one... Im out..

Ze was 0.4

Didn't check the resistance on the existing ring mains, but equally I didn't make any change to them - ergo I should not have adversely affected the safety of them by changing a fuse for an MCB.

I did test the RCDs, they operate as expected.