Does this setup contravene any regs or is it ok?

[Jjc]

So how is this any different from say connecting a spur to a ring final from the MCB? Or installing say some hardwired smokes and taking a supply cable from a lighting MCB?

You're not wrong, the assessor is just being a super picky d1ck!

One, two, three, four cables leaving an MCB... it's not the cables that define what a particular circuit is, it's the MCB labelling. If it says Lobby and Attic Lighting, and it has one cable going up to the attic and one to the lobby, then whats the problem?

How would you record the Zs... you'd do what you do for any other circuit... test at each point and record the highest value.

How then do you know which cable is for which circuit?

 

[Toneyz]

How then do you know which cable is for which circuit?

Label it.

 

[Pete999]

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

1 OCPD =1 circuit

 

[Pete999]

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

How then do you know which cable is for which circuit?

1 OCPD =1 circuit

 

[Ian1981]

Don't you need to leave a certain percentage of spare ways for future use?

Is there such a regulation?

 

[SparkyChick]

Is there such a regulation?

I don't believe it's a regulation, but it is suggested that you leave a percentage of spares. Last one I did, it got 2 spares for 8 circuits. I can't remember the percentage though.

As for the question from @Jjc about identifying which cable is which... as @anthonybragg said... label it Simples And if that hasn't been done, used some basic fault finding techniques to identify it... link L-E on one, N-E on the other and a quick continuity check will establish which is which.... then you label it.

 

[Jjc]

I don't believe it's a regulation, but it is suggested that you leave a percentage of spares. Last one I did, it got 2 spares for 8 circuits. I can't remember the percentage though.

As for the question from @Jjc about identifying which cable is which... as @anthonybragg said... label it Simples And if that hasn't been done, used some basic fault finding techniques to identify it... link L-E on one, N-E on the other and a quick continuity check will establish which is which.... then you label it.

Spare ways just good practice if installing new board doubling up of cables in circuit breakers is in my opinion rough practice

 

[SparkyChick]

Spare ways just good practice if installing new board doubling up of cables in circuit breakers is in my opinion rough practice

Fundamentally I agree, but like many other things, there are times when it's a good plan.

If it's the choice between cable -> junction -> cables and multiple cables in an MCB... surely it's preferable to guarantee the split point is accessible and obvious for the life of the installation rather than chucking the split in a junction box somewhere (the location of which probably won't be recorded anywhere). Just my thinking

 

[Simonslimline]

He is correct and has backed it up with a Reg number.

How would you record Zs etc on the cert with two finals coming from one MCB?

They are the same circuit as they come from the same protective device.

 

[Deleted member 26818]

Not sure how Brianmoooore can disagree with my post?
Are you saying that I would not do as I have suggested?

 

[Lucien Nunes]

This has rumbled on for a while but no-one has described the situation yet the way I see it. Let's assume it's logical for the two points in question to be on one MCB - it does seem this way from the description of the lobby and loft. Conventionally, one cable would run from CU to point 1, to point 2. That's a conventional radial circuit fed from one end.

In this case there's still one run of cable but it goes from point 1 to CU, to point 2. The same things are connected together but in a different order. The circuit is fed in the middle, instead of one end.

The only bearing this has on anything is that having found the point with the highest loop impedance and proven it good, it is not true to say that the other points must also be good because they must be upstream of it. But this doesn't hold true of many lighting circuits anyway because of daisy-chained switch drops, 2-way strappers, multiple circuits visiting one multi-gang box, hidden branches at MF junctions etc. So having the feed point in the middle doesn't really affect testing to any practical extent either.

Thought experiment. Two points, one each end of a long corridor. CU in the middle. What would you do - run to one point and then back past the CU to the other end, or feed out in both directions from the CU?

 

[brianmoooore]

Just the first paragraph.
Reg. in question is (as someone else mentioned) to cover the likes of borrowed neutrals.
I have always designed domestic lighting installs so that if one light is out, then the next is not only on a different MCB, but on a different RCD as well. For instance, on a first floor, all the rooms would be on one or more MCBs, but on the same RCD, and the passage/stairs light would be on another RCD.
On the "more than one circuit into one MCB" argument, I consider it good design to bring lighting circuits near the consumer unit back separately and into the same MCB because of the help it gives to fault finding.
The very last fault finding job I did was to sort a s/c on a lighting circuit, and there were three "circuits" originating from the same MCB, affecting considerable part of the house. After a couple of minutes testing at the consumer unit, I was able to reinstate all but couple of utility room lights, which were left to the following week.

 

[Jjc]

I don't believe it's a regulation, but it is suggested that you leave a percentage of spares. Last one I did, it got 2 spares for 8 circuits. I can't remember the percentage though.

As for the question from @Jjc about identifying which cable is which... as @anthonybragg said... label it Simples And if that hasn't been done, used some basic fault finding techniques to identify it... link L-E on one, N-E on the other and a quick continuity check will establish which is which.... then you label it.

Yes I know all about circuitry and tracing circuits what about three phase boards if for some reason someone connected one of the two cables into a breaker
on a different phase? We are not talking simple domestics now.

 

[SparkyChick]

Yes I know all about circuitry and tracing circuits what about three phase boards if for some reason someone connected one of the two cables into a breaker
on a different phase? We are not talking simple domestics now.

Then it's two separate single phase circuits supplied by two separate OCPD in a three phase board.

 

[Octopus]

Is there such a regulation?

That's a very good point - wonder how many RCD's the OP has got in his double stacked board - more than 2?