Sharing MCBs


Postby Fellwalker » Tue Aug 19, 2008 7:34 pm

Given the limited number of MCBs available on a two RCCB consumer unit, is it acceptable to connect more than one similar circuit to the same MCB. Say two minor lighting circuits, obviously not the main upstairs and downstairs lights. I am interested in evenly distributing such circuits but ensuring they are well within the load value of the MCB. Any MCB which had more than one circuit would be clearly shown on the particular way label. Again it is not my intention to combine major power or lighting ccts.
Regards, Paul
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Postby BLAKEY1963 » Wed Aug 20, 2008 11:13 am

[quote="Fellwalker"]Given the limited number of MCBs available on a two RCCB consumer unit, is it acceptable to connect more than one similar circuit to the same MCB. Say two minor lighting circuits, obviously not the main upstairs and downstairs lights. I am interested in evenly distributing such circuits but ensuring they are well within the load value of the MCB. Any MCB which had more than one circuit would be clearly shown on the particular way label. Again it is not my intention to combine major power or lighting ccts.
Regards, Paul[/quote]

FELLWALKER

I would contact a local electrician to advise u on this.

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Postby ericmark » Wed Aug 20, 2008 3:43 pm

I note Appendix 15 of BS 7671:2008 says an unfused spur may be connected to the consumer unit. So I can't see why any other circuit should not be doubled up. Years ago I was told one hole = one wire but is seems no one follows that now. As to consumer unit size I see double deck ones are now available and how in any normal house anyone needs more that 30 ways I do not know. But I must advise adding any circuits to a consumer unit in a domestic premises in England and Wales comes under Part P.
As to lights the main thing is to keep under 6 amp. Many people seem to think they can use 16 amp MCB's but the BS 7671:2008 says we must follow manufacturers recommendations who have for years rated ceiling roses at 6 amp so limiting lighting circuits in the main to 6 amp.
Rather than space in consumer unit cost of RCBO's is more of an issue.
Eric
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