3 core feeding 2 lighting circuits sharing a neutral

[Lukerthomas]

Hi can any one help please doin some work on a house and one of the problems on the test report is there's a 3 core feeding 2 breakers ( red feeding downstairs lights and yellow feeding upstairs lights) and only the one nuetral. Now if I could rewire it I would cables concreted into the floor and can't find the other end to sort it (old house probably plastered behind a wall) now can I put both lives into one breaker feeding both circuits with one neutral solving the problem as it's now one circuit ( 2 feeds lol) I no probably not but any help would be appreciated

 

[davesparks]

Are they the only two circuits in the place? Is the load on each circuit low enough for this to work?

 

[Lukerthomas]

Are they the only two circuits in the place? Is the load on each circuit low enough for this to work?

Hi there's a couple other breakers on the board all lighting old rewirable board , is that what you ment? The load should be ok but I haven't measured yet it's on a 5 amp at the mo I think. could I put a 10 amp in on a 1.5 can't remember what max current is for 1.5 will check THANKS FOR REPLY

 

[davesparks]

Hi there's a couple other breakers on the board all lighting old rewirable board , is that what you ment? The load should be ok but I haven't measured yet it's on a 5 amp at the mo I think. could I put a 10 amp in on a 1.5 can't remember what max current is for 1.5 will check THANKS FOR REPLY

'Should be ok' ?????

 

[7029 dave]

IMO, class that as 1circuit anyway, so yes.

 

[Lukerthomas]

Thanks only thing is I'm not the tester and if he pulls me or the client up on it (tester probably won't know) be nice to know if the general Senecas is its ok lol I'll screen shot it so if there's any other opions would be good thanks again

 

[davesparks]

Thanks only thing is I'm not the tester and if he pulls me or the client up on it (tester probably won't know) be nice to know if the general Senecas is its ok lol I'll screen shot it so if there's any other opions would be good thanks again

You will be testing it and signing your name to it after you have completed the remedials though so it is up to you to make sure it is safe and compliant.

 

[Dave OCD]

I would imagine the three core would go to a junction box under the boards somewhere then two T&Es will be connected to that for the two respective lighting circuits with the common neutral.
So although it's not right I don't think this would give rise to danger due to an 'open neutral' on either circuit- however the best compromise is to put the yellow and red in the same OCPD, how many lights are there in total on the existing set up and are there any multi lamp GU10 spots or anything like that ?

 

[7029 dave]

I would imagine the three core would go to a junction box under the boards somewhere then two T&Es will be connected to that for the two respective lighting circuits with the common neutral.
So although it's not right I don't think this would give rise to danger due to an 'open neutral' on either circuit- however the best compromise is to put the yellow and red in the same OCPD, how many lights are there in total on the existing set up and are there any multi lamp GU10 spots or anything like that ?

That goes without saying Dave.

 

[Andy78]

Hi there's a couple other breakers on the board all lighting old rewirable board , is that what you ment? The load should be ok but I haven't measured yet it's on a 5 amp at the mo I think. could I put a 10 amp in on a 1.5 can't remember what max current is for 1.5 will check THANKS FOR REPLY

Don't forget to use the maximum wattage possible for every lighting point, and derate to known installation methods including Cf if connecting to a BS3036.

 

[davesparks]

I would imagine the three core would go to a junction box under the boards somewhere then two T&Es will be connected to that for the two respective lighting circuits with the common neutral.
So although it's not right I don't think this would give rise to danger due to an 'open neutral' on either circuit- however the best compromise is to put the yellow and red in the same OCPD, how many lights are there in total on the existing set up and are there any multi lamp GU10 spots or anything like that ?

You don't think this is dangerous!
What planet are you on?

 

[Lukerthomas]

That's the thing I don't no if it's compliant? Also I won't be testing or signing the tester will be coming back to check the work is done then he will be retesting and issuing cert

 

[7029 dave]

That's the thing I don't no if it's compliant? Also I won't be testing or signing the tester will be coming back to check the work is done then he will be retesting and issuing cert

Go round and have an count up, if under 1100 watts stick it on 1 breaker.

 

[Lukerthomas]

It's not many it's the rear lights of downstairs and 1st floor no gu10s or nothing ye tried finding where it joined off to can't find it anywhere so this is pretty much the option I'm left with! The tester has condemned the way it is in 2 breakers sharing neutral but if I put into one breaker current promitting will it count as one circuit and get away with it?

 

[Dave OCD]

You don't think this is dangerous!
What planet are you on?

Ok you tell me how you'd get an open neutral at any fitting on either circuit with the appropriate fuse out, if it's wired as I suggest ?

 

[7029 dave]

Yes it will be 1 circuit, you should know that.

 

[Andy78]

That's the thing I don't no if it's compliant? Also I won't be testing or signing the tester will be coming back to check the work is done then he will be retesting and issuing cert

Maybe you need to check in the regs to see whether it will be compliant or not then ? I would start with the area of the regs that deals with the size of neutral conductors.

 

[Dave OCD]

It's not many it's the rear lights of downstairs and 1st floor no gu10s or nothing ye tried finding where it joined off to can't find it anywhere so this is pretty much the option I'm left with! The tester has condemned the way it is in 2 breakers sharing neutral but if I put into one breaker current promitting will it count as one circuit and get away with it?

Unless the client is prepared to pay for rewiring I'm afraid that's the best you can do. Use a 6 amp B type MCB though,nothing bigger, that will be fine as the lights will never all be on together for any significant time and even if they were you'd be under 6 amps.

 

[Lukerthomas]

Go round and have an count up, if under 1100 watts stick it on 1 breaker.

Ok thanks for the help

 

[Dave OCD]

Ok you tell me how you'd get an open neutral at any fitting on either circuit with the appropriate fuse out, if it's wired as I suggest ?

No reply davesparks ??