Consumer unit change

[stilllearning]

Recently changed a consumer unit and had a problem with the upstairs lighting as it kept tripping rcd removed all lamps and checked all fittings , circuit tested out fine when insulation resistance r1+r2 and Zs but still kept tripping rcd so put circuit on non rcd side of consumer unit would I have to note this as deviation on the test sheet ? And add it in to the 'comments on existing installation ' section any ideas please ?

 

[snowhead]

What about finding the fault?

 

[Leesparkykent]

Recently changed a consumer unit and had a problem with the upstairs lighting as it kept tripping rcd removed all lamps and checked all fittings , circuit tested out fine when insulation resistance r1+r2 and Zs but still kept tripping rcd so put circuit on non rcd side of consumer unit would I have to note this as deviation on the test sheet ? And add it in to the 'comments on existing installation ' section any ideas please ?

No you should find and rectify the fault. Upstairs lights and downstairs lights on separate RCDs by any chance?

 

[stilllearning]

It was tripping the rcd when the 2way switching was operated ? Downstairs and upstairs lighting on separate Rcds any ideas on fault posibbility ?

 

[Leesparkykent]

It was tripping the rcd when the 2way switching was operated ? Downstairs and upstairs lighting on separate Rcds any ideas on fault posibbility ?

shared neutral, one of the most common faults you will come across!

 

[stilllearning]

How would you rectify that fault then as I can't see how too ?

 

[telectrix]

try a forum search on borrowed neutral. this is a classic case. landing light fed with L from downstairs cct.and N from upstairs cct.

 

[stilllearning]

Iam unable to rectify the fault as the property has been decorated and customer is unwilling to have fault rectified the circuit will have to stay on a Mcb now what are my options do I note it as a departure from bs7671 ?

 

[telectrix]

what you have to do is put both lighting circuits onto the same RCD. preferably also on the same MCB.

 

[davesparks]

Iam unable to rectify the fault as the property has been decorated and customer is unwilling to have fault rectified the circuit will have to stay on a Mcb now what are my options do I note it as a departure from bs7671 ?

You carry out testing for this before you start the job, not after you have finished it, and agree the fault finding and repair with the customer before starting. If they refuse to have it done then you walk away from the job.

If you leave the lighting circuit without RCD protection then the work you have done does not comply with the regulations, and makes a mockery of the point of installing a new CU. You have identified a potentially dangerous fault which could place the life of anyone working on the installation at risk, you now need to do something about this to make it safe.

If you have not made the customer aware of the possibility of finding such faults and the need to rectify them before starting then you may well have to carry out the repairs at your own cost.

 

[kenai36]

I come across this one quite a lot. It's not ideal but if the customer really doesn't want the circuits segregated and you've already changed the board I'd put them both on one RCD and MCB as telectrix said. Not ideal but better than having one circuit not protected by an RCD.

 

[davesparks]

I come across this one quite a lot. It's not ideal but if the customer really doesn't want the circuits segregated and you've already changed the board I'd put them both on one RCD and MCB as telectrix said. Not ideal but better than having one circuit not protected by an RCD.

Then it is your fault for changing the board without testing the installation properly beforehand, and you should be fixing it at your own expense.

 

[kenai36]

I worded that badly. I always test mine was advising the first guy.

 

[newtothis]

I have this situation in my house.
Whoever installed experienced the same issues with tripping.
He did what Telectrix suggested.

I think I have a non destructive solution, can someone please critique ?
Put both circuits on the RCD side in separate MCBS

At the landing switch, wire it as a one way switch terminate cables.
Same with the hall swicth
Then fit a discreet flush mounted pir to operate the landing light. ?

 

[gnselectricals]

I would definitely put them on the same mcb as you would have risk of shock due to the borrowed neutral.

 

[Pete999]

Your profile lists you as an Electrical Apprentice, question is should you be doing this type of work unsupervised? not having a dig but any self respecting Electrician should have tested this installation prior to changing the CU, another question, why the need to change it in the first place, might be a good idea to get access to the trainee section get a bit more help in there, good luck.

 

[IzzyS]

I have this situation in my house.
Whoever installed experienced the same issues with tripping.
He did what Telectrix suggested.

I think I have a non destructive solution, can someone please critique ?
Put both circuits on the RCD side in separate MCBS

At the landing switch, wire it as a one way switch terminate cables.
Same with the hall swicth
Then fit a discreet flush mounted pir to operate the landing light. ?

Definitely don't do that. It's a breach of 314.4, and the EAWR too. And you may kill a fellow spark or hapless DIYer.

 

[Leesparkykent]

As Pete has quite rightly pointed out, it should be done under supervision of an electrician as the OP is an apprentice.

 

[SparkyAndGeorge]

Would you not find the fault before hand unless you did the R1 + RN continuity test on that particular circuit? How often do people do the R1 + RN test?

 

[telectrix]

just by switching off the MCB ( or pulling the fuse) for upstairs lights and seeing if the landing light stayed on would give you a good indication.

 

[SparkyAndGeorge]

just by switching off the MCB ( or pulling the fuse) for upstairs lights and seeing if the landing light stayed on would give you a good indication.

Yes that's probably the simpler option haha

 

[Pete999]

Didn't think that I "spoke down" to the OP, my advice was clearly the right thing to do, I agree with you that Apprentices learn better by doing, rather than being told how to do things, but I stand by what I said, the OP ought to be supervised when doing this sort of work. And as a Mentor I take objection to being accused of not being nice, if you bothered to check any more of my posts to trainees, you will find out how fair I am, if the OP has taken objection to my post, then I will apologize to him/her, there was no malice intended.

 

[davesparks]

Experience gained under the supervision of an experienced electrician, not doing it off their own back as and when they feel like it then relying on a forum to help them with the most basic problems.
He hasn't been spoken down to yet, but it could easily be arranged.

 

[camerabloke]

Give Pete a break! The guys an apprentice and needs supervision. Get a grip

 

[newtothis]

Definitely don't do that. It's a breach of 314.4, and the EAWR too. And you may kill a fellow spark or hapless DIYer.

Thanks for the feedback, I've just read that reg and I think you might of read my post wrong.
I'm saying each in it's own mcb both rcd protected - not ideal when it trips I suppose.
Or maybe I've got it wrong I'm still new to all this

 

[IzzyS]

I think you'll still have a shared neutral? I don't think your solution didn't mention separating the two circuits - the quickest safe way is to put them both on the same MCB, making them into 1 single circuit.

This guy explains it much better than I can on here.

https://www.youtube.com/watch?v=7C7Tkge5gvQ&noredirect=1

 

[Deleted member 9648]

I've said it before and I'll say it again.
It always comes up on this sort of post that tests should be carried out before changing a CU. Fine. But given that most CU change requests involve a quote beforehand,I'll be b*****d if I'm going to carry out pretty much a full EICR for nothing on a job that I might not even get. OK,there's no harm in carrying out an IR test and a few Zs readings on the quote visit,but that still leaves a host of potential issues that only extensive testing will identify.The alternative,and my approach,is to carry out some basic tests at the quote stage,and include in the quote that full testing will be carried out while the CU is being replaced and that any faults which require rectifying may incur additional cost. It works for us and we quote and get loads of CU changes.
Quite frankly if anyone tells me they carry out full tests likely to find faults such as breaks in cpc continuity,breaks in rfc continuity,borrowed neutrals etc before every CU change I dont believe them.

 

[newtothis]

I think you'll still have a shared neutral? I don't think your solution didn't mention separating the two circuits - the quickest safe way is to put them both on the same MCB, making them into 1 single circuit.

This guy explains it much better than I can on here.

https://www.youtube.com/watch?v=7C7Tkge5gvQ&noredirect=1

Thanks very much mate, I understand now. I see you're right. Cheers for posting the video I found it very useful.

 

[davesparks]

I've said it before and I'll say it again.
It always comes up on this sort of post that tests should be carried out before changing a CU. Fine. But given that most CU change requests involve a quote beforehand,I'll be b*****d if I'm going to carry out pretty much a full EICR for nothing on a job that I might not even get. OK,there's no harm in carrying out an IR test and a few Zs readings on the quote visit,but that still leaves a host of potential issues that only extensive testing will identify.The alternative,and my approach,is to carry out some basic tests at the quote stage,and include in the quote that full testing will be carried out while the CU is being replaced and that any faults which require rectifying may incur additional cost. It works for us and we quote and get loads of CU changes.
Quite frankly if anyone tells me they carry out full tests likely to find faults such as breaks in cpc continuity,breaks in rfc continuity,borrowed neutrals etc before every CU change I dont believe them.

You don't leave all of the testing until after fitting the new board do you?
I do the dead testing prior to removing the old board, then fit the board, then live testing.
I don't do any testing when quoting for the job but do allow a few hours of fault finding time plus have provision in the terms and conditions that says I will test the installation and not proceed if a major fault exists.

 

[Deleted member 9648]

You don't leave all of the testing until after fitting the new board do you?
I do the dead testing prior to removing the old board, then fit the board, then live testing.
I don't do any testing when quoting for the job but do allow a few hours of fault finding time plus have provision in the terms and conditions that says I will test the installation and not proceed if a major fault exists.

No,like you at least an IR test before removal. Usually RFC tests/R1+R2 during replacement,as the usual rats nest makes these tests much easier once the old boards out the way and you just have the cables. I've only come badly unstuck once,when a seemingly simple CU change uncovered an absolute nightmare. It took two days to complete the change and sort all of the issues...obviously an EICR before hand would have found it out and had I known I would have recommended a full rewire!
I reckon most issues when I do a CU change rarely add more than an hour or two to the job,often a lot less.