Separate CPC

uksparks · Jul 23, 2015

Hi,

im doing a partial reword for someone at the moment, some of it was going to stay but have convinced them otherwise.

some of it that was going to stay is wired as below, I've ripped all of it now, but it was wired with grey twin cable no CPC then a separate un sheathed earth as per picture, I'll be honest it's not one I've seen before.

the line and neutral are in a ring but the CPC is a radial.

telectrix · Jul 23, 2015

that's not lead sheathed twin, is it?

Dave OCD · Jul 23, 2015

I wondered that too, but more likely to be mucky grey PVC ?

uksparks · Jul 23, 2015

It's just grey twin, it's rather tuff to strip.

ive been trying to convince him to change the CU for a new one but he's being tight and wont spend the money.

ive put a few new breakers in it, going to swap the others out tomorrow. I need more space in it to be honest.

Whats lead sheathed twin? Is it literally what it sounds? What would you do with the old wiring? I'm right to think it's time for an upgrade aren't I? I'm sure it will test out ok, but he wanted so many changes, not only that I don't feel happy extending from that.

Dave OCD · Jul 23, 2015

I think you're absolutely right to strongly recommend a rewire, after all it's your name going against the work. But if that's the case you'll need a new CU anyway as that's an old 16th edition one with no RCD for some circuits ? Has a ring been extended from the CU - the 2.5s in connectors ?
Twin lead sheathed is exactly that, the inner core insulation was a sort of cotton type braided material and the sheath was used as the earth with tin junction boxes to maintain continuity incorporating clamps for the sheath - I'm not THAT old, just seen it a few times.:redface:

Lazlo · Jul 23, 2015

Tot up the work and quote customer, if he can't afford a proper job based on your advice....walk away?

Richard Burns · Jul 23, 2015

The board is OK, you just need some RCBOs on the non RCD side.
Just ensure that you do not put in a large number of separate circuits, they will never be overloaded anyway.

The normal thing for old wiring seems to be to leave it under floors in great heaps, however I am not sure this is quite best practice!
Wherever possible remove the old cable (and recycle it).

The separate earth should be around 1950s or so, I think; adding this extra safety feature. A bit like standalone RCDs today!

Lead sheathed cable is exactly what it sounds like, replace the outer PVC sheath of twin (and earth) with lead and there you go, a nice strong, yet flexible cable, what could possibly go wrong!

I had some circuits that were still wired in lead and found a bit of lead sheathed connected into a metal junction box with the rubber insulation crumbling away, ha ha found the fault I thought... no the lead was fine, it was the new(er) PVC that was at fault.

davesparks · Jul 23, 2015

I hate those boards, what possessed Wylex to put the neutral bar directly behind and just above the top of the mcb?

uksparks · Jul 23, 2015

He isn't touching the light circuits and only wants sockets done, so have redone all up and down and new kitchen ring and cooker circuit, so have 4 ways on the rcd side that I can use now as have cut the old stuff off. There's no immersion either now so I have just got enough space.

i was going to put a couple of rcbo's in but they won't fit due to the neutral bar as Dave says, those new Mcb's only just fit.

uksparks · Jul 23, 2015

Im not sure of the age of the property but would guess at 1950.

Midwest · Jul 24, 2015

uksparks said:
He isn't touching the light circuits and only wants sockets done, so have redone all up and down and new kitchen ring and cooker circuit, so have 4 ways on the rcd side that I can use now as have cut the old stuff off. There's no immersion either now so I have just got enough space.

i was going to put a couple of rcbo's in but they won't fit due to the neutral bar as Dave says, those new Mcb's only just fit.

Why don't you fit a couple of Henley blocks and put in a small CU for your new circuits?

davesparks · Jul 24, 2015

uksparks said:
i was going to put a couple of rcbo's in but they won't fit due to the neutral bar as Dave says, those new Mcb's only just fit.

They would have fitted better if you'd used the right MCBs for the board. You've got NHX MCBs when you needed NSB MCBs, both types are readily available.