Dodgy wiring

[sparky1508]

Hi all,

Changed some standard pendant lights today and the wiring was a bit dodgy.

The first light I looked at had 3 red ( normal ) 1 switch line ( normal ) but 3 neutral and 2 cpc. One I the cpc was sheathed in black and connected in the neutral of the light a continuity check confirmed it was connected to earth.
Second thing the light is on 2 way switching and in the first switch was 3 reds connected together 1 of which was from 3 core and cpc which went to the common of the second switch. 2 strappers yellow and blue in the correct place. There is 2 blacks in the first switch connected together and I disconnected them and checked and one was continuous with earth so when connected they both are. I disconnected the whole lot in the switch and ceiling rose and ran an IR test. L - N >500 Mohm
L - E >500Mohm
N - E failed.
Can anyone shed some light on this or is this a danger. My thoughts are that the earth in the light fitting shout not be connected to the neutral at any time and also is this likely to liven up anything connected to earth. His circuit is not on the RCD either.

 

[Leesparkykent]

Hi all,

Changed some standard pendant lights today and the wiring was a bit dodgy.

The first light I looked at had 3 red ( normal ) 1 switch line ( normal ) but 3 neutral and 2 cpc. One I the cpc was sheathed in black and connected in the neutral of the light a continuity check confirmed it was connected to earth.
Second thing the light is on 2 way switching and in the first switch was 3 reds connected together 1 of which was from 3 core and cpc which went to the common of the second switch. 2 strappers yellow and blue in the correct place. There is 2 blacks in the first switch connected together and I disconnected them and checked and one was continuous with earth so when connected they both are. I disconnected the whole lot in the switch and ceiling rose and ran an IR test. L - N >500 Mohm
L - E >500Mohm
N - E failed.
Can anyone shed some light on this or is this a danger. My thoughts are that the earth in the light fitting shout not be connected to the neutral at any time and also is this likely to liven up anything connected to earth. His circuit is not on the RCD either.

Struggling to make sense of it at a quick read but what was the earthing arrangement?

 

[sparky1508]

TN-C-S. CPC at ceiling sleeved black and connected to neutral. 2 black conductors at switch have earth continuity without the CPC at light being disconnected. This tells me there is a CPC neutral crossover somewhere else in the circuit.

 

[sparky1508]

I will attempt to draw a diagram when I get home and post.

 

[Leesparkykent]

TN-C-S. CPC at ceiling sleeved black and connected to neutral. 2 black conductors at switch have earth continuity without the CPC at light being connected. This tells me there is a CPC neutral crossover somewhere else in the circuit.

was the main switch off?

 

[sparky1508]

was the main switch off?

Yes main switch off.

 

[westward10]

That sounds like fun, not clear why cpc is being used as neutral, seen it sleeved red and used as a line conductor. This is irrelevant but is it black sleeving or a bit of insulation from a black wire, you rarely see black sleeving.

 

[sparky1508]

That sounds like fun, not clear why cpc is being used as neutral, seen it sleeved red and used as a line conductor. This is irrelevant but is it black sleeving or a bit of insulation from a black wire, you rarely see black sleeving.

It is insulation from a black wire but it has earth continuity unless it is used as neutral and the CPC neutral fault I have is causing it to have continuity. Have done R1 R2 and get continuity.

 

[westward10]

The only thing that springs to mind is that there is a broken neutral conductor and someone has resolved it by using the cpc.

 

[sparky1508]

The only thing that springs to mind is that there is a broken neutral conductor and someone has resolved it by using the cpc.

Possibly I suppose but isn't that bad? Failed IR tests for a start and the possible risk of shock increases massively

 

[westward10]

It is bad but you see all sorts. What I would do is reconnect the cpcs sleeved black from neutral back to earth, leave them sleeved black so you know which ones they were. Then redo the IR test and see if it clears the fault. If it does I would then get a long wander lead and do continuity tests from the CU neutral to all points in the circuit to see if the neutral is okay.

 

[sparky1508]

It is bad but you see all sorts. What I would do is reconnect the cpcs sleeved black from neutral back to earth, leave them sleeved black so you know which ones they were. Then redo the IR test and see if it clears the fault. If it does I would then get a long wander lead and do continuity tests from the CU neutral to all points in the circuit to see if the neutral is okay.

I did the IR test with all conductors disconnected at the switch and ceiling and still failed.

 

[sparky1508]

It is bad but you see all sorts. What I would do is reconnect the cpcs sleeved black from neutral back to earth, leave them sleeved black so you know which ones they were. Then redo the IR test and see if it clears the fault. If it does I would then get a long wander lead and do continuity tests from the CU neutral to all points in the circuit to see if the neutral is okay.

Is there an increased risk of shock from exposed conductive parts?

 

[westward10]

I would say yes and no. You have a TN earthing system so neutral and earth are deemed as being at the same potential. The danger is where the cpcs are being used for an alternate purpose, are there parts of the circuit which are now without an earth. Also if there is a break in the neutral and the cpcs have been used to resolve this then the cpcs at some point, if disconnected may have mains voltage present.

 

[sparky1508]

I would say yes and no. You have a TN earthing system so neutral and earth are deemed as being at the same potential. The danger is where the cpcs are being used for an alternate purpose, are there parts of the circuit which are now without an earth. Also if there is a break in the neutral and the cpcs have been used to resolve this then the cpcs at some point, if disconnected may have mains voltage present.

That is my thinking and back to the MET and mains voltage on all circuit CPCs. Is that possible.

 

[westward10]

Without more info as to why this has been done all sorts of scenarios are possible, I would concentrate on resolving the issue.

 

[Lagentium]

How old is the installation?

 

[sparky1508]

How old is the installation?

About 16 years or so I think

 

[sparksburnout]

is this an idiots guide "how to be an electrician"??

 

[sparky1508]

is this an idiots guide "how to be an electrician"??

Not sure what you mean??????

 

[sparksburnout]

Not sure what you mean??????

Sorry I might have misunderstood, are you an "electrician" doing this for a paying customer or just mucking about with your own electrics?

 

[sparky1508]

Sorry I might have misunderstood, are you an "electrician" doing this for a paying customer or just mucking about with your own electrics?

Here you go. What's the answer.

 

[sparky1508]

Not worried about switch 2. Ceiling rose and switch 1. Black sleeved cpc is continuous with earth and so are the 2 neutrals at the switch. Please teach me as to why it is wired this way.

 

[sparksburnout]

Not worried about switch 2. Ceiling rose and switch 1. Black sleeved cpc is continuous with earth and so are the 2 neutrals at the switch. Please teach me as to why it is wired this way.

You might need to ask one of the moderators but there is a trainee section you can post this sort of thing in, sorry I thought you were an actual electrician from your profile.

 

[sparky1508]

You might need to ask one of the moderators but there is a trainee section you can post this sort of thing in, sorry I thought you were an actual electrician from your profile.

I am a newly qualified domestic installer. I am assuming you dont know the answer either then as you haven't given one. Without taking the whole circuit apart and checking every length of cable to see what goes where it's impossible to know what is going on. Clearly I'm the idiot and you must be the guide from your comment so please guide me.

 

[sparksburnout]

Well, you may find it a bit disappointing to realise that very often in the great world outside the training room there will be all sorts of non-standard, strange, bodged, lashed up and generally quite confusing wiring arrangements. Lighting circuits are often in this category, and, I would say, amongst the worst. I have heard that more guys are killed working on lighting circuits (in domestic environments) that anything else, not sure myself but can well believe it. At the end of the day I would not try and attempt to work it out from a description or smoke-packet type drawing, what you need to do is employ your inspection and testing skills to determine whats is going where and what needs to be done to sort it. You may well have to take the whole circuit apart if that is what needs to be done, welcome to the wonderful world of domestic electrics!!

 

[sparky1508]

Ok thanks for the insight. In the meantime I will investigate further.

 

[sparksburnout]

Ok thanks for the insight. In the meantime I will investigate further.

That's what it boils down to mate. You will spend hours poking around some grotty loft trying to work out what some DIY'er has cobbled together, and yes, sometimes you will be better off starting from scratch, time-wise. I'm not trying to be funny, it's just how it is. The only relief is when you give them the bill.........

 

[Midwest]

Agree with sparksburnout, my fare is kitchen & bathroom refurbishments, but spend most of my installs putting right the DIY of yesteryear, should be a law against it, DIY that is


PS still no like button?

 

[sparksburnout]

Oh and as a footnote pinching the CPC for various uses is quite a favourite of the DIYer and even some "electricians"!!

 

[7029 dave]

Here you go. What's the answer.
View attachment 32885View attachment 32886

Looking at the first pic, to me it looks like that is the S/L cable and somebody has used the cpc as a neutral down to the switch position.

 

[sparky1508]

Looking at the first pic, to me it looks like that is the S/L cable and somebody has used the cpc as a neutral down to the switch position.

That was my first thought but on doing R1/R2 it turns out that the cpc sleeved black is actually connected back to earth and so are the 2 actual neutrals in switch 1. They were still connected to earth with the entire 9 conductors separated at the ceiling so it tells me neutral and cpc are interconnected elsewhere.

 

[7029 dave]

That was my first thought but on doing R1/R2 it turns out that the cpc sleeved black is actually connected back to earth and so are the 2 actual neutrals in switch 1. They were still connected to earth with the entire 9 conductors separated at the ceiling so it tells me neutral and cpc are interconnected elsewhere.

So we know the switch line cable cpc is connected to N on the ceiling position where is it connected at the switch.?

 

[westward10]

Try not to rip this circuit apart you will get more confused. Break it down methodically and if necessary draw a plan to see if you can narrow the problem down.

 

[sparky1508]

So we know the switch line cable cpc is connected to N on the ceiling position where is it connected at the switch.?

Sleeved black again and connected to neutral which is also connected to earth. No idea where that neutral goes after that without starting to take the circuit apart. Customer can't afford to pay for full investigation as the job was only supposed to be changing the pendants as they are moving house and wanted to take other fittings with them.

 

[7029 dave]

I would say at a guess, that cpc is connected at the switch position to earth hence your NE interconnection, just take the switch plate off and look.

 

[westward10]

I know this is a bit late but for future reference always test the circuit before undertaking any works on it so this issue doesn't arise again.

 

[andyb]

That was my first thought but on doing R1/R2 it turns out that the cpc sleeved black is actually connected back to earth and so are the 2 actual neutrals in switch 1. They were still connected to earth with the entire 9 conductors separated at the ceiling so it tells me neutral and cpc are interconnected elsewhere.

Did you disconnect the neutral of this circuit at the board before testing?

 

[sparky1508]

I would say at a guess, that cpc is connected at the switch position to earth hence your NE interconnection, just take the switch plate off and look.

Done that, one of the 2 blacks at the switch is cpc sleeved with insulation from black conductor the other one is an actual neutral but it has continuity with earth even with all conductors at the ceiling separated. This is what make me think the interconnection is elsewhere in the circuit. I would need to dismantle the circuit bit by bit and do continuity on each section to find what's going on but like I said, I have spoken to the customer about the problem but they haven't got the budget to pay for and investigation that would probably take a whole day. I have told them of the risks and changed all light fitting to the standard plastic ones now so minimal risk but still a risk in my eyes.

 

[7029 dave]

Well going by your drawing it's 3plate and if it's been wired like that at every ceiling position, the interconnection will be at every point? you have trouble, you need to drop every rose and look. It can't be left.

 

[andyb]

Shouldn't take too long. It looks like someone has taken a live and neutral from the switch, as there was no neutral there they used the cpc of the switch wire. Disconnect the live and neutral coming away from the switch, not the 3 core or the switch wire, and see what doesn't work. Should tell you what's happened.

 

[sparky1508]

Did you disconnect the neutral of this circuit at the board before testing?

Disconnected all 3 conductors for testing once I saw how it was wired at the first lampholder. That's how I figured it had neutral earth connection as IR test failed on neutral to cpc.

 

[sparky1508]

Well going by your drawing it's 3plate and if it's been wired like that at every ceiling position, the interconnection will be at every point? you have trouble, you need to drop every rose and look. It can't be left.

It's not like that at every point. The first one in the toilet is fine, the second in the hall just has stranded 3 core flex coming out of a hole then there's this one in the living room, then a dining room and kitchen which are both wired standard 3 plate so this is the only one I have issues with.

 

[telectrix]

came across something like this some years ago. what had happened was that an outside light had been wired from the hall light switch and the guy who did it realised there was no N at the switch so he used the cpc of the switch drop, connected it to N in the rose to get a N at the switch.

 

[gazdkw82]

Id start by drawing a proper wiring diagram going from light to light and then work out what's going where. If you can narrow down which is the feed from the previous rose and which is the feed to the rose it means you only have to figure out what's going on between the rose in question and the switch.

Thay being said, if all cieling roses are like this one you have your work cut out