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rcd as main switch?


monkey5

Question

hi, just a quick question can an rcd be used as a main switch? for some reason i think ive heard you cant but not sure now i said it, any help/advice i will be most greatful.

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24 answers to this question

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Not a good idea because if it trips household will be in darkness at night. Plenty of properties are but under 17th you cannot unless you are NICEIC approved.

Batty

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i just went to look a house for extra sockets and the main switch was an rcd thats what got me thinking. wat would you advise the customer, is it actually wrong or just bad practice coz if one circuit has a fault it will cause power loss to all circuits

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I have an RCD as my main switch

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i have seen them and i asked the same thing on here, was told to note it as a deviation

Think it was quite common on split load boards, especially TT ones done to the 16th?

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think tt have a timed delay rcd, split bords still have an main isolator

Mine doesn't 2 X 100mA

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NozSpark

If you are adding to an existing circuit and the CU has an RCD main switch then that is OK, but you note it in the "comments on the installation" section..

It is not a deviation.

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There are thousands even hundreds of thousand properties with voltage operated and current operated circuit breakers as main switches. As you know its not good practice but that was how it was done if electrical supplier did not give earth connection. You can only advise customer how it should be but at the end of the day its night sorry I mean they will only change things if they want to and pay you for doing it. Just remember what you are doing now in another ten yeards or less will not be to current regulations.

Batty

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glad thats cleared up, will put them down in comments not deviation.

every days a school day.

sorry apache not experienced with tt, 2 100ma

should there be a 30ma some were

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NozSpark

The thing is though, If you installed a CU with a RCD main switch then that would be a deviation..

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glad thats cleared up, will put them down in comments not deviation.

every days a school day.

sorry apache not experienced with tt, 2 100ma

should there be a 30ma some were

Ideally yes! But would mess the board up. Sockets on main switch RCD.

Suppose compromise would be to leave the two 100mA and get me sockets swapped to RCBO's.

BUT I have 3 radials in a small house!`

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NozSpark

TT used to be (16th ed)

100mA TD for protection of livestock and against fire

and

30mA for supplementary protection

Now (17th ed) you need 30mA for every socket outlet and buried cables (exceptions apply) so you tend to use twin 30mA RCD CU for everything domestic

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NozSpark

That would be unlikely.

16th ed CU's (split load) had a main switch that isolated some circuits and also fed an RCD which protected some more circuits.

16th TT CU's had a 100a / 100mA time delay RCD instead of a main switch

17th ed CU's (twin RCD) have a main switch which feed 2 seperate RCD's which protect some circuits each

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That would be unlikely.

16th ed CU's (split load) had a main switch that isolated some circuits and also fed an RCD which protected some more circuits.

16th TT CU's had a 100a / 100mA time delay RCD instead of a main switch

17th ed CU's (twin RCD) have a main switch which feed 2 seperate RCD's which protect some circuits each

Also high integrity which has space for a few Rcbo's ie cooker/immersion heater as well as two RCD's

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All circuits in a TT installation must be protected with at least a 100mA RCD.

All socket outlets below 20A must be protected by at least 30mA RCD.

All circuits with cables buried less than 50mm in walls must be protected by at least 30mA RCD.

All circuits in bathroom must be protected by at least 30mA RCD.

You could have an installation where the cabling is all in surface trunking, the sockets and bathroom circuits would have to be on 30mA RCDs, with all the other circuits on the 100mA main switch.

You are required by the Regs. to consider the effects of having more than one circuit on an RCD. There is no requirement to actually place all circuits on separate RCDs.

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hi, just a quick question can an rcd be used as a main switch? for some reason i think Ive heard you cant but not sure now i said it, any help/advice i will be most greatful.

the simple answer to this is yes

example garage cu with only two circuits

caravan cu

off peak cu

ect ect

not recommended on a domestic cu , but if you read the regs to the letter two rcds do not really comply, but they realised the cost and made this an exemption.

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