Two cables connected to mcb

[Jay89]

Evening All

Im sure this will have been discussed at some point (if so please point me to a relevant thread)

I have been to look at some remedial work where a previous inspector has flagged up on multiple circuits 'DBx Cx has two cables in mcb, need separating - C2'

These circuits are either lighting or radial power circuits supplying a small amount of sockets. All suitably rated and with decent R1+R2 readings.

I have never seen this to be worthy of a mention let alone a C2 code, i have spoken to my CPS technical and they said they cant see an issue. Just looking for anyone else's opinion

Thanks in advance!

 

[Deleted member 9648]

fight ! handbags at dawn.

Ooher!
No handbags but I think Westwards needs to bear in mind that the type of code he is suggesting may result in a needless DB change just to gain ways.....

 

[westward10]

You must be on a wind up quoting reg numbers from the 16th

Wrist slapped, I was quoting from the top of my head which is generally empty.

 

[westward10]

Westward your argument has as much logic as the neutrals in switches argument. Some people just seem to stick their head in the sand and ignore facts.
You seem to admit that it complies with 7671 and yet insist on coding it!
You need to remember that coding can cost the occupier money, a lot of money. Unless you can justify a safety issue or a departure you CANT code.
Coding because of your personal views is simply unacceptable.

Don't recall suggesting it complied with BS7671 nor is it a personal view. I read Reg 314.4 that each final circuit should be given individual circuit protection that is it which I C3.

 

[Deleted member 9648]

Ok. No point in going round in circles.

 

[charlie76]

I am of the same opinion as @davesparks on this. It is one circuit no matter where the circuit is supplied from. If you have 2 radials in one MCB it is still one circuit with the supply to that circuit in the middle rather than at the end. If you consider the practicality of it, it actually is also safer. Consider you loose earth continuity on on leg of the circuit for whatever reason, the other leg of the circuit maintains its earth continuity. Also reduced loading if having 2 radials to the circuit means the overall length is reduced.

My interpretation of 314 and specifically in this case 314.4 is that for example you had 2 circuits, say upstairs lighting and downstairs lighting, these should not be connected to one MCB.

I would say it is down to the design and interpretation as to whether they should be separate circuits. If in the OP's case both radials in the MCB served a defined area (lets say downstairs) and the breaker is labelled so then I would personally say that is the downstairs lighting circuit. If one radial served the downstairs and the other radial served a light in the loft I would perhaps code it as C3 as there is a risk here of indirectly energising a final circuit intended to be isolated.

On a tangent: Why does a BRITISH standard have an American spelling of energising?

 

[GMES]

...........

 

[ChrisElectrical88]

I note it on the certificate as for example in conductor sizes 3x1.5 3x1.0 and note that in some cases more than one conductor is terminated into one protective device and this is how it can be noticed.

I know a lot of people who C3 this

 

[ChrisElectrical88]

Never a C2, someone was after a dist board change.

However if I am changing a CU for other reasons I will ensure there is enough ways to seperate these out.

Also as Westward says, this is normally cause someone has lashed a extra circuit in and can't be arsed

 

[andyb]

Don't recall suggesting it complied with BS7671 nor is it a personal view. I read Reg 314.4 that each final circuit should be given individual circuit protection that is it which I C3.

So 2 rooms with say 3 sockets in each room,

Each room fed from it's own mcb ok (1 conductor in mcb)
Both rooms wired on the same ring ok (2 conductors in mcb)
Room 1 wired as a radial with room 2 spurred from any socket in room 1 ok (1 conductor in mcb)
Both rooms on same circuit but wired independently back to the same mcb not ok (2 conductors in mcb)

 

[davesparks]

Final circuit, and yes I will still C3 it lawyers or no lawyers.

You can't just state 'final circuit' without giving a definition for it.
How do you define what constitutes a final circuit and, crucially to this debate,what does not constitute a single final circuit.

At the moment it appears that your definition includes a requirement that a final circuit must only have one conductor at the ocpd.

If there is a 1' piece of cable connected from the ocpd to a JB and then two cables leave that JB to each serve two sockets, is that one circuit or two?

 

[davesparks]

Don't recall suggesting it complied with BS7671 nor is it a personal view. I read Reg 314.4 that each final circuit should be given individual circuit protection that is it which I C3.

I read the reg exactly the same, it is not that reg which is at debate, it is the definition of a circuit.

If the two cables were not both serving sockets, lets say one feeds sockets and the other a pillar drill, then I would be inclined to agree with you. But when both cables are serving sockets, and if there is no overload as a result of the number of sockets, then I see nothing to comment on.

 

[westward10]

You can't just state 'final circuit' without giving a definition for it.
How do you define what constitutes a final circuit and, crucially to this debate,what does not constitute a single final circuit.

At the moment it appears that your definition includes a requirement that a final circuit must only have one conductor at the ocpd.

If there is a 1' piece of cable connected from the ocpd to a JB and then two cables leave that JB to each serve two sockets, is that one circuit or two?

See "definitions".

 

[westward10]

I read the reg exactly the same, it is not that reg which is at debate, it is the definition of a circuit.

If the two cables were not both serving sockets, lets say one feeds sockets and the other a pillar drill, then I would be inclined to agree with you. But when both cables are serving sockets, and if there is no overload as a result of the number of sockets, then I see nothing to comment on.

Your latter statement is somewhat contradictory and why you keep harping on about definition of circuit whilst it is the Reg to which I debate I have no idea.

 

[Bobster]

See "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."

 

[Deleted member 9648]

As far as I'm concerned if you take two separate lighting circuits on two separate mcb's, and connect them together into one mcb then they become a single circuit. As long as the schedule and board are correctly labelled and identified there is no issue. It may be claimed that this could result in confusion, anyone confused by a correctly identified circuit consisting of two radials linked at the OCPD shouldn't be touching it in the first place.

 

[DPG]

How would you code an RFC which also has a spur fed from the same MCB, ie. at the consumer unit? Refer to on-site guide and and Appendix 15 regs before answering.
The answer is: nothing wrong with it - it's one circuit.

 

[Tuttle]

The On Site Guide (page 71) says you can connect a non-fused spur from a ring final circuit "at the origin of the circuit in the distribution board", which I think would mean three conductors in the MCB and would look like a ring and a radial connected to the same protective device.

If spurring off a ring final inside a consumer unit is allowed then surely having a radial go off in two or more different directions from a consumer unit is ok as well.

What if you add a light or a socket in an under stairs cupboard near the consumer unit, surely you can connect that to an existing lighting or socket circuit in the consumer unit.

 

[Tuttle]

How would you code an RFC which also has a spur fed from the same MCB, ie. at the consumer unit? Refer to on-site guide and and Appendix 15 regs before answering.
The answer is: nothing wrong with it - it's one circuit.

You beat me to it

 

[davesparks]

Your latter statement is somewhat contradictory and why you keep harping on about definition of circuit whilst it is the Reg to which I debate I have no idea.

What are you debating about the reg? The reg requires that each circuit be fed from a separate way. It does not make any mention of the number of cables which can be connected to an ocpd, merely the number of circuits.
In order to comply with this reg you must have a definition of what a circuit is, otherwise the reg is meaningless.

In definitions a circuit is defined as:
"An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)"
A final circuit is defined as:
"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."

Neither of these makes any mention of the number of cables which make up a circuit.

 

[westward10]

Sounds like there is a lot of lashing on going on.

 

[Bobster]

So you're just trolling then?

 

[charlie76]

Sounds like there is a lot of lashing on going on.

@westward10, not arguing with your opinion on this but out of interest, someone used the principle above, say you were adding a light to an under stairs cupboard, where the consumer unit was and all cables coming out of the CU were buried and there are no spare ways. How would you do this?

 

[westward10]

Unless I could enable the supply by alternative means I would suggest the consumer unit has inadequate capacity for the provision of an additional circuit.

 

[davesparks]

Unless I could enable the supply by alternative means I would suggest the consumer unit has inadequate capacity for the provision of an additional circuit.

But there will almost certainly be capacity to supply the new light from an existing circuit.

 

[Jay89]

Unless I could enable the supply by alternative means I would suggest the consumer unit has inadequate capacity for the provision of an additional circuit.

If they wanted an additional socket in the cupboard, how would you feel about taking a spur off a RFC at the consumer unit?

 

[westward10]

If they wanted an additional socket in the cupboard, how would you feel about taking a spur off a RFC at the consumer unit?

Perfectly acceptable or incorporate into the ring final. A lot going on in this cupboard.

 

[davesparks]

Perfectly acceptable.

How does that differ from doing it with a radial circuit?

 

[charlie76]

All you are doing is the following. Still one circuit as far as i'm concerned. How is this an issue?

 

[streamer]

Unless I could enable the supply by alternative means I would suggest the consumer unit has inadequate capacity for the provision of an additional circuit.

And the customer would think you were at it!

 

[westward10]

And the customer would think you were at it!

At what.

 

[streamer]

At what.

They would think you are trying to invent work by suggesting the only way to put a light in the cupboard would be to change the consumer unit or get to a feed at the nearest switch or light fitting.

 

[westward10]

I wouldn't suggest changing the CU at all.

 

[streamer]

So if there wasn't a spare way in the consumer unit would you insist on finding a feed elsewhere?

 

[Cadgey123]

314-01-04 off the top of my head but I suspect you know this.

Quick enough to jump down someone else's throat when regulations need quoted???

A joint is a joint regardless of at a switch, socket or MCB in consumer unit.

 

[charlie76]

Well, well, well. Just look at the diagram below from an IEE Wiring Matters article. The diagram is taken from the IET Electricians Guide to the Building Regulations.
I think they have 2 radials in one MCB there or I could be seeing things.
Someone better notify the IET that their diagram does not comply with their regulations...

Right, thats put that one to bed. Now i'm off to bed...

 

[Octopus]

^^ not sure I agree with your perhaps C3....

The most common time I see 2 cables is into lighting circuits.... Where a second cable goes to the bell transformer..... But it's still only 1 circuit!

 

[Deleted member 9648]

 

[ChrisElectrical88]

I think the way @Westward was putting this he sees it a lot, like me where we may do more EICRs in factory's and large commercial installs where some of this stuff is absolutely lashed in and clotheslined all over the place, then they have piggy backed off an MCB and lashed the N &CPC in any old terminal. There is thousands of installations with rough work. Not all of this refers to neatly adding mrs jones a new light fitting under the stairs

Edit: There is no disputing the regs and evidence people have put forward but I will always continue to note it the same way I described in an earlier post

 

[Deleted member 9648]

^^^ Noting it is fine, coding something which is not a departure and may result in unnecessary expenditure is not.

 

[davesparks]

Well, well, well. Just look at the diagram below from an IEE Wiring Matters article. The diagram is taken from the IET Electricians Guide to the Building Regulations.
I think they have 2 radials in one MCB there or I could be seeing things.
Someone better notify the IET that their diagram does not comply with their regulations...

Right, thats put that one to bed. Now i'm off to bed...


View attachment 37331

Without the whole article the picture is a bit useless, for all we know the article could be using the picture to illustrate incorrect design.