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Hello, I have tried to search the forum but have not found anything although this must have been asked a thousand times.

When completing a board change for example and there is no end to end on the neutral does downgrading the mcb to a 20amp and effectively running two radials from the same MCB comply with BS7671 ?

End to end on r1 and r2 are good (I just can not for the life of me find the break in rn, other than to identify its likely under the floor under some nice new tiles)

Im happy to do some reading if someone could point me to the correct chapter in the book.

And if this is ok (2 radials from one MCB) having taken into account demand, how would the results be recorded on the schedule ?
 

Pete999

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Arms
Hello, I have tried to search the forum but have not found anything although this must have been asked a thousand times.

When completing a board change for example and there is no end to end on the neutral does downgrading the mcb to a 20amp and effectively running two radials from the same MCB comply with BS7671 ?

End to end on r1 and r2 are good (I just can not for the life of me find the break in rn, other than to identify its likely under the floor under some nice new tiles)

Im happy to do some reading if someone could point me to the correct chapter in the book.

And if this is ok (2 radials from one MCB) having taken into account demand, how would the results be recorded on the schedule ?
Read the definition of a Circuit in BS7671 "Definitions" page 24
"Circuit" An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)
 
New board change I would make separate radials from them over separate protective devices.
Post automatically merged:

I would personally be looking to eliminate the section of cable with the broken neutral completely. Sometimes however this can leave an unfortunate split of the outlets whereby if you have ten points one radial may include nine of them.
 
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  • Thread Starter Thread Starter
  • #4
Read the definition of a Circuit in BS7671 "Definitions" page 24
"Circuit" An assembly of electrical equipment supplied from the same origin and protected against overcurrent by the same protective device(s)

so my interpretation, an assembly of electrical equipment (accessories on 2 radials) supplied from the same origin (DB at origin) and protected against overload protection by the same protective device (s) (MCB at DB)

So yes 2 radials from one MCB is by the letter of the law one circuit ?.

And having 2 radials from one MCB is not in contravention of BS7671 ?
 
That is debatable. If you are putting a new board in eliminate the faulty section of cable and split onto two 20A devices. Why leave a broken connection in situ.
 
  • Thread Starter Thread Starter
  • #6
That is debatable. If you are putting a new board in eliminate the faulty section of cable and split onto two 20A devices. Why leave a broken connection in situ.
I agree very debatable, and lots will have different opinions. I suppose what I want to try and find out is does BS7671 forbid the use of 2 radials in one MCB. If so whats the reg number ?
 
Are you going to eliminate the faulty section creating two separate radials?
I side with Regulation 314.4 whereby each final circuit which each radial is shall be connected to a separate way in a distribution board, this is Division of Installation. Others argue the days away with the definition of a circuit as opposed to final circuit which this Regulation refers to, each to their own.
 
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Pete999

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Arms
so my interpretation, an assembly of electrical equipment (accessories on 2 radials) supplied from the same origin (DB at origin) and protected against overload protection by the same protective device (s) (MCB at DB)

So yes 2 radials from one MCB is by the letter of the law one circuit ?.

And having 2 radials from one MCB is not in contravention of BS7671 ?
Not really the right way to install two radials, but as far as 7671 is concerned no it isn't but doing it from scratch, two separate ciricuits will be the best way, have a look at Appendix 15 in BS7671 for details on RFCs and radial circuits.
 
  • Thread Starter Thread Starter
  • #9
Are you going to eliminate the faulty section creating two separate radials?
I side with Regulation 314.4 whereby each final circuit which each radial is shall be connected to a separate way in a distribution board, this is Division of Installation. Others argue the days away with the definition of a circuit as opposed to final circuit which this Regulation refers to, each to their own.
Absolutely
Are you going to eliminate the faulty section creating two separate radials?
I side with Regulation 314.4 whereby each final circuit which each radial is shall be connected to a separate way in a distribution board, this is Division of Installation. Others argue the days away with the definition of a circuit as opposed to final circuit which this Regulation refers to, each to their own.
yes, will eliminate faulty section
 
  • Thread Starter Thread Starter
  • #11
n
I see no point in connecting them to the same protective device.
No I agree but running out of space on the board, already added a new circuit which has taken last MCB. Just wanting to check that when Im signing the eic (and the two radials are in the same MCB) the work completed by my complies with BS7671.

I know I should have planned for leaving a couple of spare ways !
 

Andy78

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Mentor
Arms
Esteemed
There is nothing wrong in using multiple cables in one termination provided that terminal is designed for that purpose and you are not using the terminal past its capabilities.

The circuit was on one protective device before so I see no reason why it can't go back onto one as two legs of a radial.

It would be best to divide them up if possible but not essential.

As mentioned, the most important thing is that you disconnect the faulty leg of cable and make safe the ends. This usually means connecting them to the installation earth.
 

H

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Arms
Can you not fault find the cable run with the break / open circuit and pull a new leg in to reform the ring?
 

Pete999

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Arms
Can you not fault find the cable run with the break / open circuit and pull a new leg in to reform the ring?
Could be just a bad connection at one of the accessories.
 

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