Lighting Circuit....

[whazza22]

Is it acceptable to do a normal lighting circuit but have 2 x 1.5mm twin and earths coming out of 1 6a MCB for a full rewire?

Reason being is that the house has an awkward step upstairs which makes it difficult to get cables to the other two rooms.

Thanks

 

[Amp David]

Why will running two circuits from the same MCB make avoiding the step any easier?

 

[Darkwood]

I see nothing wrong in doing this, its common to see lighting doubled up in mcb's

 

[whazza22]

Will be made easier because the consumer unit is below the top of the stairs, hence avoiding the step. The other end is being picked up from a switch on the other side of the step.

 

[malcolmsanford]

Like ole Amp espicially on a full rewire I would be loathed to double up in a mcb, and would try my hardest not to do it on a refurb, but there is nothing against it, just bad practice really.

I suppose it could be argued that under section 3 of the regs it could be frowned upon with design but there is nothing that states you can't do it

 

[Amp David]

Will be made easier because the consumer unit is below the top of the stairs, hence avoiding the step. The other end is being picked up from a switch on the other side of the step.

AH I see, sort of

 

[Darkwood]

Like ole Amp espicially on a full rewire I would be loathed to double up in a mcb, and would try my hardest not to do it on a refurb, but there is nothing against it, just bad practice really.

I suppose it could be argued that under section 3 of the regs it could be frowned upon with design but there is nothing that states you can't do it

I dont find it a bad practice issue, ideally you shouldnt have to do this in a domestic nature if rewire or new but it can make life easier if you are doing other installations with numerous e/m lighting etc, keeping these joints at the dist board makes it ideal for splitting for testing or fault finding without having to work out where the hell the joint is, some councils even ask for e/m lighting to be run from mcb and not terminated mid lighting circuit for this very reason, if it does concern you then marking the wires up for identification may make future testing easier but in 20yrs ive never come across any argument against it either from the regs or the NIC-man.
Im now interested on other peoples response to this now you have brought it up.

 

[Amp David]

Stiil dont really see why using just the one breaker will make the job easier TBH

 

[malcolmsanford]

I dont find it a bad practice issue, ideally you shouldnt have to do this in a domestic nature if rewire or new but it can make life easier if you are doing other installations with numerous e/m lighting etc, keeping these joints at the dist board makes it ideal for splitting for testing or fault finding without having to work out where the hell the joint is, some councils even ask for e/m lighting to be run from mcb and not terminated mid lighting circuit for this very reason, if it does concern you then marking the wires up for identification may make future testing easier but in 20yrs ive never come across any argument against it either from the regs or the NIC-man.
Im now interested on other peoples response to this now you have brought it up.

I suppose it might be a generation thing when I did my apprenticeship it was one circuit 1 mcb/fuse full stop.

I can though see as an example you have a ground floor lighting circuit and someone builds an extension and the easiest way to wire it is from the protection device,as you say using it as the JB. So you maintain all the ground floor on the one protection device.

If I had done it that way as an apprentice I would have had a rollicking by the sparks and told to change it, I suppose old habits do die hard. That is why I said it's bad practice, for me it is but I do take your point and appreciate it.

 

[Risteard]

It is one circuit though by the very definition of a circuit.

Can also be useful with heavy loaded circuits to reduce voltage drop/earth fault loop impedance on each leg.

Can't see how it could possibly be described as bad practise so long as it has been designed that way having given consideration to economic design.

 

[Des 56]

I had never heard of any problem or percieved bad practice associated with more than one wire in an mcb until I heard it in the last few years on these forums
There is not one single reasoned argument I have heard since then that makes me think for one moment that I would ever hesitate to double or tripple even up on an mcb
Where did this percieved bad pracyice originate from I would like to know and what is the reasoning behind that thinking
This is one issue where I am way out of thinking as far as the more modern sparks are prepared to accept
Can anyone give an electrical safety reason why I see no problem whatsoever in the practice of double feeding a circuit,after all the standard ring is a doubled up circuit

 

[malcolmsanford]

Des 56 your quite right there is nothing wrong, or against the regs not to double inside a protection device.

As I said it is something that when I did my apprenticeship it was not the done thing and I hoped that I pointed that out and even can see in some cases it is an advantage and appreciate that.

For me though it's like fly earthing a back box. Regs say if 1 solid lug no need, I still do and always will, when I see a box that don't have one I fit one .............old habit, but to me bad practice.

With all the plus arguments for sometimes doubling up cables in a protective device, I would still try my hardest to avoid it, and there is no logical reason. It is something I was taught not to do, perhaps by the sparks I was with becasue he didn't like it.

I hope though I would be honest and say that though I think it's bad practice I know there is nothing in the regs to prevent it, so it's an honest opinion

 

[UNG]

I had never heard of any problem or percieved bad practice associated with more than one wire in an mcb until I heard it in the last few years on these forums

I'm with Des on this one, I'm amazed at the number of times the term "bad practice" is used without good reason. We have all picked up preferences for the way we do things over the years but there are times when economics have to be considered during the design and installation process.

My questions would be:
Is it bad practice to carry out an installation or design without consideration to the cost
If an installation was designed to have two cables at an MCB would you alter the installation to suit your installation preference and not install to the design criteria or query it as bad practice with the designer

 

[Darkwood]

Well Malcomsanford i understand why you consider it bad practice as you were clearly led to believe that by your misguided peers, but hopefully using this forum and getting a wider scope on the issue may change your mind, id seriously question those who taught you and ask them to justify why it is bad practice especially as some councils request this method is used.
I realise that we are all taught different ways and can develope stubborn attitudes to other methods but hopefully on this particular point you can change your view its definately not considered bad practice on the wide scope but just in maybe a few smaller firms, i believe this misconception came about due to bad practices of connecting several circuits to the same rewirable fuse in the days when boards were smaller and the need for more circuits in houses was common, with no regulatory authority to monitor firms alot of people just double up different circuits as you may have come across if upgrading or rewiring a house this was the bad practice i think your firms views stem from.

 

[malcolmsanford]

All I will say concerning this ...............I have yet worked to a set of drawings produced by a designer that specifies a double cable into a protection device, apart from a ring final circuit, if you guys have then all well and good.

Be hard to contradict my peers unless I can dig the majority of them up. As for changing my practices, I'm afraid it won't. As I've now mentioned twice I would not in any way condenm you guys wanting to do it, it's safe, it's not against the regs and as ring final circuits have been doubled since they were instiagted it's acceptable.

Darkwood is absolutely correct in what he says, in older installations a CU would perhaps have 4 ways only. Over the years as installations got larger doubling up was done. There could be a time when someone would put a 1.5mm into a larger protection device because "other protection devices are doubled as well" and those doing this never understood why this is wrong. So I was trained 1 device 1 cable, it is old fashioned but I'm afraid in some respects so am I.

But can assure you darkwood that my peers were far from misguided, they trained someone that in 37 yrs in the electrical industry as never had somoene injured or a serious incident resulted from an installtion I have designed, installed or tested. They must have done something right.