Can you double up cables is a consumer unit?

[LearnerDave]

Hi Guys,

This week I saw two consumer units installed side by side (one for power and the other for lights) The incoming feed was wired into the first boards main switch and was doubled up to supply the second board. i.e. both cables where in the same port. Is there anything wrong with doing this? With this particular setup, the first board is fed by MICC cable so I would imagine something like Henley blocks would be out of the question because of the CPC arrangement.

If the doubling up is not allowed how would you tackle a similar situation.

I am sure I been told before that there should be only one cable per MCB/port except for a ring final circuit, I am looking through my text books but havn't found anything yet. If there is anything in the regs that says you cant double up, if there is would you mind pointing me in the right direction

Cheers Dave

 

[ezzzekiel]

a spur can be taken from the origin so yes although not sure where it would say it in the book but it is acceptable.

 

[malcolmsanford]

There is noting in the regs not allowing you to terminate this way, all the regs advise that each connection between conductors and equipment shall provide durable electrical continuity and adequate mechanical strength and protection reg 526.1

A MICC main could be as small as 6mm and you may find that you can achieve quite a good connection on a BS 60947-3 or most likely on your CU the BS 5419 switch

 

[johnboy6083]

I don't see a problem with this. As to your question, the only other way to split the tails with pyro would be to use a JB. You could use a plastic JB, but you would have to use a banjo, or a steel JB, which would be the No 1 choice.

 

[SPARTYKUS]

Hi Guys,

This week I saw two consumer units installed side by side (one for power and the other for lights) The incoming feed was wired into the first boards main switch and was doubled up to supply the second board. i.e. both cables where in the same port. Is there anything wrong with doing this? With this particular setup, the first board is fed by MICC cable so I would imagine something like Henley blocks would be out of the question because of the CPC arrangement.

If the doubling up is not allowed how would you tackle a similar situation.

I am sure I been told before that there should be only one cable per MCB/port except for a ring final circuit, I am looking through my text books but havn't found anything yet. If there is anything in the regs that says you cant double up, if there is would you mind pointing me in the right direction

Cheers Dave

Hello Dave

yes thats what tends to be taught but its like a driving test and crossing one's hands on a steering wheel. Kind of messes it up when you spur a socket near the CU from the ring main MCB (perfectly allowable) - then there's three cables. And then the extra light outside from the down lights MCB - again, perfectly acceptable.


So don't worry about it

 

[LearnerDave]

Thanks you very much. Nice one.

 

[LearnerDave]

Hi Spartykus,

I am always a little cautious taken as gospal what I hear on site, I like to go home and look it up for myself.

I think it was at college that I was told 1 conductor 1 MCB (Except ring final CCTS) Though I do realise the college way is sometime far removed from what happens on site!

Thanks very much.
Dave

 

[malcolmsanford]

Dave with regard to the part about final circuits and division of the installation have a read of the 4 regulations under section 314 of the regs

 

[LearnerDave]

Thanks Malcolmsanford,

So where 314.4 says - "Where an installation comprises more than one final circuit, each final circuit shall be connected to a seperate way in the distribution board. The wiring of each final circuit shall be electrcially seperate from that of every other final circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated."

From this can I conclude that if I doubled up like for like. e.g. a new lighting circuit conductor in the exisiting mcb with an exisiting circuit, that this is fine as if you isolate the lights MCB then all associated lights would be isolated.
But heaven forbid if I put a lighting circuit conductor in with a ring final circuit, then there is a chance of confusion that if the lighting circuit is isolated for future works, then there is a risk to the installer that part of the lighting circuit would still be live.

Cheers Dave

 

[malcolmsanford]

As Ezze quoted in post #2 you can extend a circuit or spur a circuit from the protection device no problems.

As you say mate you would not put a light extension on a Ring Final protection device because not only would it fail 314.4 and also because the 1.00/1.5mm cable would not be adequate.

What it really refers to is say a house that as 2 lighting circuits up and down and a ground floor extension was built and you ran the feed back to the CU and decided as it was easier to connect it into the upstairs lights, that would be dangerous as far as division of the installation was concerned.

 

[LearnerDave]

Thanks malcolmsanford

And thanks to all, I somethimes have issues understanding the wording in the BGB, and the way you all explain it, always makes sense.
Cheers

 

[Marvo]

Hi Dave,

what you describe would strike me acceptable but if you could attach a couple of photos you'll attract specific comments which might be more helpful to you.