Lighting CPC Options

[rythmicben]

Hi all, new to the forum so firstly hello!

We’ve recently moved into a new to us house, long ago enough to spot a few gremlins! I’m planning to have the consumer unit replaced as the current one is an old type with plug in mcb’s but no RCD protections.

I’m keen to rectify a few smaller issues around the place in readiness for a full check of the property prior to CU change. Small things like trunking some cables that aren’t secured sufficiently etc.

One issue I’ve spotted is that the upstairs lighting doesn’t have earth feeds to the ceiling roses. There are 2 metal pendant fittings which is obviously not good. I have good access from above and I’ve traced the feeds to a junction box in the loft but the earth on the incoming feed doesn’t have continuity with the earth bonds (checked via multimeter to the nearby boiler bonds and via test wire back to the earthing point at the cu).

I figure I have a couple of options. Run a cpc feed from cu to the loft space separately to the power feed (feels like half a job) or my preferred plan is to replace the wiring feeds to the ceiling roses with new 1.5mm2 twin and earth. I’d like to avoid having to run a whole new feed to the loft if I can so I figure there are a few options:
- Within a foot of the lighting junction box is the shower/fan isolator pull switch which has a good earth. I’d guess it would be bad practice to take an earth feed from this to the junction box for the lights?
-There’s also a larger cpc feed to the boiler which I could take an earth feed from (again I’m guessing this wouldn’t be approved of?)
-Finally there’s a terminated 2.5mm2 t&e feed in the loft which must be from an old water heater installation. It appears to run directly to the cu but is currently fed from the sockets mcb. My thinking was this could become the upstairs lighting feed and be reterminated to it’s own block on the new cu when I get that installed. Does that sounds like a feasible option?

Naturally I’d be having any work signed of by an qualified electrician and/or getting them to do the work in it’s entirety just wanted to sound out if that seems like a reasonable solution.

 

[ericmark]

Pre 1966 there was no need for an earth to lights, so it is missing in many old properties, I remember working on a farm, actually on the Falklands but that does not matter, and trying to connect the earths, twin and earth had been used, but earth not connected, and it seems I was chasing my tail, in the end realised some where in the loft space there must have been a junction box, and no loft hatch.

As long as you have full RCD protection then the current in any earth wire is low, but until that happens the earth loop impedance is important, and in 1966 I don't think I had seen a loop impedance meter except in collage.

Also 1954 when dad's house was built it had rubber insulated cable, so needed a full rewire by 2000, it was 2014 before that happened, but I felt I was walking on egg shells while I waited to get it done.

Really should be a full EICR but I would say ask an electrician to have a look and quote for a new consumer unit, and get some comments as to general state of wiring before starting work, if after spends weeks trying to improve it, your told it all needs replacing you would not be amused.

 

[EFLImpudence]

As long as you have full RCD protection then the current in any earth wire is low, but until that happens the earth loop impedance is important,

I think that will confuse all DIYer and most electricians.

 

[rythmicben]

Really should be a full EICR but I would say ask an electrician to have a look and quote for a new consumer unit, and get some comments as to general state of wiring before starting work, if after spends weeks trying to improve it, your told it all needs replacing you would not be amused.

Yeah good shout! I’m hopeful the EICR won’t be too bad, it seems like as each room has been improved they’ve done the electrics along the way. The up lighting seems to be the exception so fingers crossed it’ll be some simple remedials. Just wondered if my suggested solutions would be at all viable but as you’ve said probably need to stop pondering and just get them in for the test!

 

[winston1]

I have good access from above and I’ve traced the feeds to a junction box in the loft but the earth on the incoming feed doesn’t have continuity with the earth bonds (checked via multimeter to the nearby boiler bonds and via test wire back to the earthing point at the cu).

Presumably the earth on the incoming feed is not connected at the other end (consumer unit). Could you not trace it and connect it?

I figure I have a couple of options. Run a cpc feed from cu to the loft space separately to the power feed (feels like half a job) or my preferred plan is to replace the wiring feeds to the ceiling roses with new 1.5mm2 twin and earth.

You don't need 1.5mm2, 1.0mm2 is more than adequate.

-Finally there’s a terminated 2.5mm2 t&e feed in the loft which must be from an old water heater installation. It appears to run directly to the cu but is currently fed from the sockets mcb. My thinking was this could become the upstairs lighting feed and be reterminated to it’s own block on the new cu when I get that installed. Does that sounds like a feasible option?

Yes.

 

[RF Lighting]

Please ignore any advice given by winston1. It may not be factually accurate.

 

[winston1]

RF Lighting. I warned you. Now reported to mods.

 

[sparkwright]

Why don't you just re-wire the lighting back to the mains?

 

[ericmark]

I looked at my dad's house, remember I am a commercial electrician, and considered re-wiring bit at a time, there where a number of problems, one being my mother was being cared for in the house and it seemed the carers loved to wag their tongues, and it seemed likely they would report what I was doing, so it would all need to be above board and notified to the LABC.
We had previously tried to have a new consumer unit with RCD protection fitted, and we could not get the RCD to hold, the electrician doing the work fitted an isolator instead and was to return next day, never to be seen again. So we knew there were problems.
It came to a head when mother saw a red neon on an extension lead and thought it was on fire so put it in a bucket of water, lucky no harm done, but realised RCD protection was a must, and a couple of weeks latter she went into hospital, so while she was out of the way, got a firm in to re-wire, only basic, and I did the re-plaster, but it was around £2.5k and they were in and out in the week, and it was going to cost me around £600 a week for mother in a care home, so money well spent.
I then added extras latter, but the big bit was all done while she was out of the house.
This is something you have to consider, I estimate had I tried to do it all my self it would have likely takes 6 weeks, I would say the firm spend around 150 man hours on the job, they blitzed it on last day and a half to finish it with around 6 men. And pulling in cables on your own is not easy. My test equipment was out of calibration so if DIY it would have likely cost £500 for LABC fees and test equipment calibration or hire. I was lucky got a good firm who honoured their price even when it needs the extra labour at the end.

So yes you can DIY, but you will likely be living in a building site for a couple on months, my son was re-wiring his house for a year, it was one of those JUST jobs, OK he put in a lot of unnecessary extras like a rack server in the loft, and smoke alarms etc. Where with mothers house it was bare basics. But we have all done it, JUST swap that socket to a double with USB while we are at it, it will only take half an hour, but it's two hours latter when you finally put the vacuum cleaner away.

It is easy on a forum to say JUST run a new wire, then you find there no room for extra wire in back box, so you need a deeper box, and so it goes on, so you need to really consider is it worth it?