Consumer unit change

[shanky887614]

Would you not find the fault before hand unless you did the R1 + RN continuity test on that particular circuit? How often do people do the R1 + RN test?

most electricians will on older properties.

you use to have a N+E cable between each light and seperart L etc to switch and back.

now if they put the live from downstairs lights to switch then upto light on stairs it can cause this issue.

how you test varies depending on visual inspection

 

[baldsparkies]

People living in Ivory towers !!
Luckily there are electricians out there who thankfully live in the real world.
A borrowed neutral on 2 way lighting is an unfortunate by product from by gone practices.
Left untouched in its original form it posed little problems, and guess what, you wont find many fatally electrocuted customers living in properties wired this way.
It was compliant with the regs of the time.
Whats important is that you do not feed the borrowed neutral circuits from different mcb's.
That would leave the installation with a potentially dangerous condition.
In an ideal world you would rewire the offending lighting circuit for compliance with current regs.
And make the customer aware of the requirement.
If for some reason this is not an option, ie customer refuses point blank because of costs and or disruption to decorations.
Well you could walk away !!
Which would leave those suggesting you do so, to move in and wire the lighting circuits onto 1 mcb effectively making them one circuit and in doing so removing a shared neutral scenario.
Of course you should list this as a departure, and make your comments on the existing installation as to the if's what's and whys.
Its your choice and a judgement call as a qualified sparks.
What it isn't, and never has been, is a shock horror, lets be drama queens run forest run scenario.
Presumably you are with a scheme provider considering a board change is notifiable and if your going to building control on your own back,it will cost you lots of ££££s
So if in doubt just phone there technical helpline and ask there advice.
They will give you exactly the same options as I have mentioned above, and at least that way you are getting sensible, and practical advice.
Forums are only as good as the people using them so be careful, and always get advice from qualified trusted sources as a cross check.
Hope that helps.

 

[baldsparkies]

what you have to do is put both lighting circuits onto the same RCD. preferably also on the same MCB.

As an example to the OP, THIS is advise from someone who knows what he's talking about.

With time and experience you get to know the difference.

 

[davesparks]

A borrowed neutral on 2 way lighting is an unfortunate by product from by gone practices.
Left untouched in its original form it posed little problems, and guess what, you wont find many fatally electrocuted customers living in properties wired this way.
It was compliant with the regs of the time.
.

How do you know it was compliant with the regs of the time? I can't find anything in the 13th or 14th which allows it.

 

[shanky887614]

People living in Ivory towers !!
Luckily there are electricians out there who thankfully live in the real world.
A borrowed neutral on 2 way lighting is an unfortunate by product from by gone practices.
Left untouched in its original form it posed little problems, and guess what, you wont find many fatally electrocuted customers living in properties wired this way.
It was compliant with the regs of the time.
Whats important is that you do not feed the borrowed neutral circuits from different mcb's.
That would leave the installation with a potentially dangerous condition.
In an ideal world you would rewire the offending lighting circuit for compliance with current regs.
And make the customer aware of the requirement.
If for some reason this is not an option, ie customer refuses point blank because of costs and or disruption to decorations.
Well you could walk away !!
Which would leave those suggesting you do so, to move in and wire the lighting circuits onto 1 mcb effectively making them one circuit and in doing so removing a shared neutral scenario.
Of course you should list this as a departure, and make your comments on the existing installation as to the if's what's and whys.
Its your choice and a judgement call as a qualified sparks.
What it isn't, and never has been, is a shock horror, lets be drama queens run forest run scenario.
Presumably you are with a scheme provider considering a board change is notifiable and if your going to building control on your own back,it will cost you lots of ££££s
So if in doubt just phone there technical helpline and ask there advice.
They will give you exactly the same options as I have mentioned above, and at least that way you are getting sensible, and practical advice.
Forums are only as good as the people using them so be careful, and always get advice from qualified trusted sources as a cross check.
Hope that helps.

how is having them fed from different mcb's a problem? if there on the same double pole rcd then the N wont be disconnected without the L anyway.

remember the N are usually commoned together

 

[shanky887614]

How do you know it was compliant with the regs of the time? I can't find anything in the 13th or 14th which allows it.

under the 13/14th you would only have 1 neutrel bar so they are all linked so would make no difference if it was fed from another mcb, not good practise but not against the regs of the time as far as im aware

 

[Leesparkykent]

how is having them fed from different mcb's a problem? if there on the same double pole rcd then the N wont be disconnected without the L anyway.

remember the N are usually commoned together

errm Shanky was you on the beer last night or something when you wrote this? Lol :dizzy2:

 

[shanky887614]

errm Shanky was you on the beer last night or something when you wrote this? Lol :dizzy2:

no i was on the whisky at relatives

 

[davesparks]

under the 13/14th you would only have 1 neutrel bar so they are all linked so would make no difference if it was fed from another mcb, not good practise but not against the regs of the time as far as im aware

You still only have one neutral bar but borrowed neutrals are just as bloody dangerous.
The last time I came across borrowed neutrals was between 2 adjacent TPN boards, live taken from one board and neutral from the other.

 

[IzzyS]

under the 13/14th you would only have 1 neutrel bar so they are all linked so would make no difference if it was fed from another mcb, not good practise but not against the regs of the time as far as im aware

It's been against the regs for at least 35 years, probably longer. And whether it complied or not, it's as dangerous now as it was then.

The problem arises when some poor sod comes along to change, for example, a ceiling rose.

With the MCB off/fuse removed on the circuit being working on, and the circuit proved dead work proceeds.

If there is a load on the other circuit (the one that is sharing the neutral) full line voltage will appear on the neutral as it is pulled from is terminal. It's f***ing dangerous (to electricians, handymen, diyers and anyone else likely to work on it) because safe isolation requires two (or more) MCBs to be turned off.

Under normal circumstances it does not pose any problem to the installation user.

 

[Leesparkykent]

no i was on the whisky at relatives

Happy days

 

[derbylad]

It's been against the regs for at least 35 years, probably longer. And whether it complied or not, it's as dangerous now as it was then.

The problem arises when some poor sod comes along to change, for example, a ceiling rose.

With the MCB off/fuse removed on the circuit being working on, and the circuit proved dead work proceeds.

If there is a load on the other circuit (the one that is sharing the neutral) full line voltage will appear on the neutral as it is pulled from is terminal. It's f***ing dangerous (to electricians, handymen, diyers and anyone else likely to work on it) because safe isolation requires two (or more) MCBs to be turned off.

Under normal circumstances it does not pose any problem to the installation user.

that's why you should knock the main switch off.

 

[Pete999]

that's why you should knock the main switch off.

Knock off the main switch? don't you mean carry out the safe isolation procedure? lol sent with humor in mind.

 

[IzzyS]

that's why you should knock the main switch off.

Doesn't help when there are multiple distribution boards and you can't shut down production.

Borrowed neutrals are not limited to domestics.

 

[davesparks]

that's why you should knock the main switch off.

If I'd done that on the last borrowed neutral if found then if have shut down a six screen cinema complex and part of a shopping centre, I don't think it would have been acceptable!