Domestics again

[SUNRAY]

A simple "Are you busy? Upstairs lights have stopped working".
Customer insists nothing has been done, judging by the amount of dust in the lampshade and dead bugs in the rose I feel it is genuine:

For clarity that's one red in 'N', 4 blacks in 'LOOP' and 3 reds in 'L'. My instant guess being this is a total L & N reversal. I unhooked the flex and started loosening the rest before I took the pic.

All testing done with a LED screwdriver found 'N' is the only 'live' terminal.
2 (CFL and LED) of the other 4 lights are wired as very standard 'Loop at rose', the other 2 are a bathroom LED fitting and a brass chandelier style (yellow single wire, tested continuity to brass fitting) with 3 small looking CFL which I didn't open as they are without roses.

And the HO skirt

contained a blown 75W bulb.

I rewired it as standard Loop, repowered and when I switched the light on the RCBO tripped due to a damaged switch drop in the loft and I suspect this was the reason neutral switching had been attempted.

 

[ETAF]

is the diagram how you rewired the rose

the switch is going from all the Live connections and then comes back to the neutral block - effectively a short

Electrics:Lighting Circuit layouts

www.diynot.com

 

[ericmark]

I did need to read a few times, it seems the switch drop in the loft has enough line to earth current to trip the RCBO but not enough neutral to earth current to trip it?

I can see how switching neutral gets around the problem, and I was myself surprised to see three-phase motors using just double pole switches, so the motor even when not running had a 230 volt supply, I was told at the time permitted, but

132.14.2 No switch or circuit-breaker, except where linked, or fuse shall be inserted in an earthed neutral conductor. Any linked switch or linked circuit-breaker inserted in an earthed neutral conductor shall be arranged to break all the related line conductors.

431.3 Disconnection and reconnection of the neutral conductor Where disconnection of the neutral conductor is required, disconnection and reconnection shall be such that the neutral conductor shall not be disconnected before the line conductors and shall be reconnected at the same time as or before the line conductors.

So it would seem not permitted, and of course one has to consider the leakage due to damage getting worse. Lucky, today there are wireless systems which can get rid of the switch wire drop, so easy enough to just disconnect that cable.

But with domestic we do want the premises habitable, and we have that dilemma, do we do a temporary fix? I suppose it is a form of risk assessment, without lights the occupant is clearly at risk, is that risk greater than switching the neutral, and I can't hand on heart work out how that is a risk, even if not compliant.

However much, we intend to return, it does not always happen, I remember doing some, what I considered dodgy work, with every intension of returning, but the firm went to the wall, and my next job was abroad, and the boss was aware of what had been done, so he may have well corrected it anyway, to return to house and knock on the door, and ask did my old boss return and do the work, was not really an option as house sold before my return, and one would assume fault found when EICR was done. This must be some 25 years ago, and I still worry was it ever corrected.

So the debate is, should we break the rules with temporary repairs, or simply say no? I never completed a certificate for that job, so there is nothing to show I did it, and it was before the installation certificate had been raised, so likely one of my co-workers did correct it when testing for the installation certificate, and my work was done before any supply to the house, so I can say it should have been tested first, but still it worries me.

With most of my work, it was temporary, and when not, by now the Schiehallion, which I worked on being built, has been scrapped, it was not my fault honest. And batching plants etc, have all be moved to new locations etc. Even the Jayes factory in Mold is no more, the only work which is likely to still be in use is the domestic work, commercial work the EICR is done, so anything done wrong will be corrected after 10 years, except for domestic. And it is domestic where we are most likely to try and keep things running.

 

[SUNRAY]

is the diagram how you rewired the rose

No how I found it

the switch is going from all the Live connections and then comes back to the neutral block - effectively a short

Not quite correct the live supply was the single red to the 'N' terminal, but apparently it worked!

Electrics:Lighting Circuit layouts

www.diynot.com

EDIT: This was the final circuit with 2 loopouts

 

[SUNRAY]

I'm surprised no one has queried

For clarity that's one red in 'N',

... found 'N' is the only 'live' terminal.
View attachment 376785

EDIT: Except I didn't read ETAFs #2 properly

 

[ETAF]

is the diagram how you rewired the rose

????

 

[SUNRAY]

I did need to read a few times, it seems the switch drop in the loft has enough line to earth current to trip the RCBO but not enough neutral to earth current to trip it?...

My high impedance multimeter saw something high like 1MΩ, the damaged cable was touching a 60 year old and very brown copper pipe.

 

[SUNRAY]

????

Sorry for the confusion. My post #1 sketch was as found, my edited #4 is the final circuit.

 

[ETAF]

no problem, sorry i'm not being helpful.

 

[SUNRAY]

no problem, sorry i'm not being helpful.

Don't apologise, perhaps this makes it easier to see how it was working:

And now

 

[ETAF]

ok,
but
image below - should never have worked

UNLESS the switch was NEVER Switched ON

 

[SUNRAY]

ok,
but
image below - should never have worked

UNLESS the switch was NEVER Switched ON

The whole point is it did, the switch would turn the 75W buld on/off and when off the other low power lights would work.

The light in question is the spare bedroom and I suspect rarely used.

The fact that none of the lights lit meant I was not looking at blown bulbs initially.

 

[SUNRAY]

I hadn't mentioned the CU was replaced in 2022 with full documentation.

 

[ETAF]

ok, ignore me, i missread the diagram as a light is there - hopefully other members may help as to why NOW

I rewired it as standard Loop, repowered and when I switched the light on the RCBO tripped due to a damaged switch drop in the loft and I suspect this was the reason neutral switching had been attempted.