Shared / Borrowed Neutrals

[Vessy]

Hi, does anybody know (through experience) where borrowed neutrals are normally picked up?

1960's house, CU in garage, both lighting circuits only have reds at the CU, wiring routes from garage through wall to top of stairs (under floor).

Havent had a chance to lift the floor as yet, just wondered if they would be commonly in this area where all the cables combine or if it could be anywhere?

I'm also presuming it would probably use a neutral from the ring circuit?

Have never had to deal with shared neutrals as yet so any info from experiences would be great.

Thanks, Mark

 

[telectrix]

1960's --- look under floor for spliff dog ends.

 

[telectrix]

no, seriously, could be anywhere under floor. look for junction boxes, or follow lighting circuits back from lights. beware of lighting wired in twin, no cpc

 

[oldtimer]

Good chance the lights are run in conduit 5/8 or 16mm in new money so they would have run 2 reds and 1 black and if it is run this way look at the upstairs landing
and if you are very lucky you will see 2/3 short floor boards lift them and if there is a 3x3 joint box look for the pipe with the 2 reds &1 black one of the reds should go to the common joint and the other should pass through the box.
Forgot to add it depends about the layout of the house most JBs are on the landing or a central area

 

[Vessy]

Hopefully will be where makes sense!

Lighting circuit is quite quirky, two single reds from CU (one up one down) this is looped through the light switches, no cpc at switches. light fittings have a neutral loop (single black) but the fittings do have a cpc, this is a single bare cable loop to each fitting.

Love the fun jobs!!

 

[SirKit Breaker]

usually you will find the lights wired loop in live at the switches from 3 or 4 fuses at the CU, this will give isolation on one lighting circuit from each fuse, but they only run one neutral back to the CU, this make splitting circuits up a bit of a pig on dual RCD boards. I have also found added wall lights supplied from lighting circuits with the neutral taken from an adjacent socket.

Cheers..........Howard

 

[oldtimer]

SirKit you say it is a pig of a job to duel RCD so my question is where do we stand when changing a CU and the lighting circuit is either run in conduit with no seperate cpc or in the case of this post has a shared neutral

 

[johnboy6083]

if lighting is in tube, then can we not just pull new CPC? as for shared neutral, if the circuits together are not pulling more than the CCC of the cable, then can you not common the feeds into one MCB/fuse? so all of the lighting is then one big unconventional circuit?

 

[oldtimer]

Yep you could pull a a cpc in the conduit but one small problem if you are in a flat then the guy upstair would not be too happy if you wanted to lift his laminated floor to find the joint box the reason I asked the question is I am getting enquires from customers who are in this situation and me being a timed served 14th (yes 14th) edition spark who was taught that if the conduit is "mechanically and electrically sound" then you could drill and tap an earth stud into the conduit or switch box in other word the light circit is encased in one big earth and I was just looking for an interpetition or definition

 

[Paul.M]

Yep I am getting enquires from customers who are in this situation and me being a timed served 14th (yes 14th) edition spark who was taught that if the conduit is "mechanically and electrically sound" then you could drill and tap an earth stud into the conduit or switch box in other word the light circit is encased in one big earth and I was just looking for an interpetition or definition

14th edition. I had to look that up.1969 so you know all the 60's houses then, good member to know. Found out on Home - Voltimum UK - Electrical Installation Products and Contracting...... Very interesting history on there. But I won't call you old, oldtimer

 

[oldtimer]

Yea Yea I started my time in 1975 and funny enough I worked in the industrial commercial environment I did not go near housing unless I was doing a job for the family

 

[SirKit Breaker]

SirKit you say it is a pig of a job to duel RCD so my question is where do we stand when changing a CU and the lighting circuit is either run in conduit with no seperate cpc or in the case of this post has a shared neutral

Unless it is convenient to get new neutrals into the lighting then unfortunately they will all have to go onto the same side of the board, not ideal but it is compliant. If you cant pull a new earth in then you will have to bond the conduit and use that, again not ideal but it is better than no cpc at all.

Cheers..........Howard

 

[malcolmsanford]

Yea Yea I started my time in 1975 and funny enough I worked in the industrial commercial environment I did not go near housing unless I was doing a job for the family

You young boys in the trade for 5 minutes ........................1972 bet you had to file down the 1" conduit to get the 25mm^ dyes to bite as well mate. My old boss was that tight I reckon he bought all the old imperial conduit up, Hammer and rawlplug tool as no cordless drills and the Yellow book

 

[oldtimer]

Listen Malcolm do not open up old wounds when I started we were using metric gear on imperial jobs and as for the dreaded rawplug tool all I remember is rubbing cream on the soars at the end of the day so could I give battery powered Dewalt a run for its money ? Not bloody likely Mind you I sometimes go into the garage and look out my rawplug tool (yep still got it just in case it makes a comeback) to bring back fond memorys (not)

 

[malcolmsanford]

Lol ................ as an apprentice we rewired an old telephone excahnge in London. Myself and another lad marked out the runs, pinged the lines and the sparks came along to mark the saddles position for the galv conduit.

This was a battery in the basement so concrete. Off I go for the drill and was given hammer. rawlplug tool and 3 No10 bit's with the advice "off you go son and mind that's all the bits your going to get so break them, you buy new ones" ............happy days