Does this setup contravene any regs or is it ok?

[driverman]

Bit random: When designing an installation, should the distribution board/consumer unit have 25% spare capacity when installation completed?

 

[SparkyChick]

Bit random: When designing an installation, should the distribution board/consumer unit have 25% spare capacity when installation completed?

I can't remember the percentage, but there is a recommendation somewhere that you leave some spare capacity.

 

[Wilko]

No regulation that I'm aware of.

 

[Ian1981]

What’s the point of it if there was one?
If you fitted an 10 way DB for 8 circuits and someone came along and used the 2 spare ways then does that mean the board needs changing to 12 way?
It would never end.

 

[davesparks]

I think the regulations recommend that consideration be given to foreseeable future expansion to the installation somewhere near the beginning of the book.
I may be recalling this from previous editions though.

 

[Michael J]

BYB Definitions

Circuit. An assembly of electrical equipment supplied from the same origin and protected against over current by the same protective device(s)

314.4 Where an installation comprises of more than 1 final circuit, each final circuit shall be connected to a separate way in the distribution board ....

Neither of these state that a final circuit only has 1 cable

so............ I would say that the OP's original circuit complied 100%

Or the OP could have whipped out a short length of T&E, plus some Wago's and joined the 2 cables just before the MCB and then what

 

[Michael J]

very good point

 

[DPG]

very good point

.

 

[Nigel]

Bit random: When designing an installation, should the distribution board/consumer unit have 25% spare capacity when installation completed?

No.

 

[markythesparky]

I’m afraid I agree with Stroma. The regs may not be written in the clearest way to avoid confusion or prevarication, but the intention of the regulation in my opinion is clear.

Just a thought, if the OP did that with two lighting circuits to free up some space, why not do it with some other circuits including Rings (loads accepted)?

 

[SparkyChick]

So, you believe this set up is a contravention of regulation 314.4 (I believe that's what the OP stated as being the reg that Mr. Assessor was citing as the reason this arrangement was non-compliant)... care to explain how it contravenes the regulation?

 

[markythesparky]

So, you believe this set up is a contravention of regulation 314.4 (I believe that's what the OP stated as being the reg that Mr. Assessor was citing as the reason this arrangement was non-compliant)... care to explain how it contravenes the regulation?

As I said, the wording is not perfect but it is obvious to me at least that the intention of the Reg is clear.

Would you do the same with other circuits in that board if the loads allowed? Rings?

 

[SparkyChick]

So, the regulation itself....

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

That's pretty straight forward.

On to the definitions...

Final circuit. A circuit connected directly to current-using equipment, or to a socket-outlet or socket-outlets or other
outlet points for the connection of such equipment.

That seems pretty straight forward to me. Lighting circuits IIRC so they fit the definition.

Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

Two legs of a radial circuit supplied by the same origin and protected by the same protective device.

To answer your question... have you never put two circuits of any kind together onto a single breaker as a temporary stop gap solution? I have, and would do it again in a heartbeat providing there is a suitable breaker available... by that, I'm not stupid enough to put a lighting circuit on a 16A breaker (although technically a lot of lighting circuits could handle that) or stick a ring final socket circuit on a 20A breaker onto a 32A breaker with another RFC because there is probably a very good reason the one is limited to 20A (installation methods maybe). So yes, I possibly would because then the two final circuits become one circuit (supplied by the same protective device from the same origin) and as such are still compliant with the regulations.

How is it non-compliant? What do you believe the intention of the regulation is? That's all I'm asking... expand on why you believe it is non-compliant. Your explanation might make me (and others) look at it in a different light, it might change our minds.

 

[markythesparky]

The wiring of each final circuit shall be electrically separate from that of every other final circuit, so as to prevent the indirect energizing of a final circuit intended to be isolated.

These are in fact two circuits and I will explain this later, and assuming this, these are not now electrically separate as they have been connected together.
This brings us to the definition of what a circuit is.

Final circuit. A circuit connected directly to current-using equipment, or to a socket-outlet or socket-outlets or other
outlet points for the connection of such equipment.

Circuit. An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s).

This is where your argument gains ground and I have sympathy with it although consider this; when the OP designed the installation it is clear that he intended these to be two circuits. This is impossible to argue against. Assuming that you agree with that statement, then the definition above needs clarification. Or does it? What is the meaning of 'origin' in this case?' Are you relating the word origin to what we know as the 'origin of the installation', in which case you have some foundation. but if the word 'origin' in this case means the same piece of cable, then your argument does not stack up. These two circuits do not have the same origin they have two!

To answer your question... have you never put two circuits of any kind together onto a single breaker as a temporary stop gap solution? I have, and would do it again in a heartbeat providing there is a suitable breaker available...

You seem to be conflicted.
Yes I have ‘lumped’ two circuits together as ‘temporary stop gap solution’.
I did it as a temporary stop gap solution knowing that, in my view and yours presumably as you have inferred, it’s ok as a temporary fix. But if its ok as a temporary fix, by definition it isn't meant as a permanent solution. Therefore the man from Stroma is correct. It doesn’t comply with the intention of the regulation. It is electrically safe taking into consideration the anticipated loads on those circuits but is does not comply. My temporary fix was not left like it.

I'm not stupid enough to put a lighting circuit on a 16A breaker (although technically a lot of lighting circuits could handle that) or stick a ring final socket circuit on a 20A breaker onto a 32A breaker with another RFC because there is probably a very good reason the one is limited to 20A

Theres nothing wrong with having a lighting circuit on a 16a breaker as long as the cable is sufficient. I'm not sure what you mean by the ring on a 20a breaker though.

My question is would you wire two ring circuits into one 32a breaker allowing of course for the loads anticipated on those circuits and leave it like it permanently and sign a completion certificate saying that it fully complies with BS7671.

 

[Deleted member 26818]

Personally, I would not have wired the lobby and the attic as one circuit. If I were to come across such an installation, I’d be wondering what the original installer was thinking of.

I would probably go with wiring the lobby in with the rest of the ground floor and lable the circuit as Ground Floor.
If there were a separate circuit for the stairs, I might consider wiring the lobby in with the stairs.

If I were to add attic lighting to an existing installation, I would most likely come off the upstairs lighting.

The origin of any final circuit is the DB/CU.