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RCD - lighting circuits....


matt.leung

Question

matt.leung

I know that under the 17th edition new circuits should be RCD'ed protected, but what happens with lighting circuits.

If the cu has no RCD and you install an outside light as a new circuit, does this circuit need to be RCD'ed protected?

B-)

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14 answers to this question

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green-hornet
Not according to the IET Senior Engineer (Mark Coles). It is his contention that the whole circuit must be upgraded to comply; and that when working on a circuit in a bathroom, all circuits in the bathroom must also be upgraded.

Doctor? I think this is your que!ROTFWL

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Jono Pashley

Mark Coles a a idiot who shouldnt speak ever again..

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Apache

If any of the wire is buried in the wall less than 2" then yes (switch drops usually) you need RCD protection.

Yes if TT.

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Andy™

Depends on how you read the regs...

either

A: wiring you add should be RCD'd

or

B: entire circuit should now be RCD'd

id go with A, but there are cases where is easier to go B, although some argue you should RCD the circuit at all times

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I know that under the 17th edition new circuits should be RCD'ed protected, but what happens with lighting circuits.

If the cu has no RCD and you install an outside light as a new circuit, does this circuit need to be RCD'ed protected?

B-)

Matt. If it is a complete new circuit back to the C.U...then Yes you may be

required to protect it with a 30ma rcd [Additional Protection]

.

If you are extending an existing circuit then you have the choice of

two options as Andy has stated.

If you are extending an existing circuit then a simple solution could

be to install an rcd Spur unit at the point where you extend from the

existing wiring run......or more simpler take the supply from a

convenient socket outlet and mount the RCD Spur unit next to it .

This work could be notifiable particularly if you take the supply from

a kitchen circuit.

a1spark

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Revved Up Sparky

Yes, if you want your work to comply with 17th edition then your modified circuit should have RCD protection.

Page 55 of the On Site Guide lists the requirement for RCD's;

"RCD's are required;

i) ...where the earth fault loop impedence is too high to provide the required disconnection time, eg, where the distributor does not provide an earth - TT systems,

ii) ...for socket outlet circuits in domestic and similar installations,

iii) ...for circuits of locations containing a bath or shower,

iv) ...for circuits supplying mobile equipment not exceeding 32A for use outdoors,

v) ... for cables without earthed metallic covering installed in walls or partitions at a depth of less than 50mm and not protected by earthed steel conduit or similar,

vi) ... for cables without earthed metallic covering installed in walls or partitions with metal parts (excluding screws or nails) and not protected by earthed steel conduit or the like.

30 ma RCD's are required for ii to vi above"

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green-hornet

No, thats me just trying to be different.

1.5 swa to outside light there is no requirement to rcd.

Other than that you could use other cables that under the requirements do not need additional protection, and so do not need to be rcd protected.

Its a minefield these new regulations ae they not? :^O

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Evans Electric

And more amendments to come shortly , I can't wait !!

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professional
Yes, if you want your work to comply with 17th edition then your modified circuit should have RCD protection.

Page 55 of the On Site Guide lists the requirement for RCD's;

"RCD's are required;

i) ...where the earth fault loop impedence is too high to provide the required disconnection time, eg, where the distributor does not provide an earth - TT systems,

ii) ...for socket outlet circuits in domestic and similar installations,

iii) ...for circuits of locations containing a bath or shower,

iv) ...for circuits supplying mobile equipment not exceeding 32A for use outdoors,

v) ... for cables without earthed metallic covering installed in walls or partitions at a depth of less than 50mm and not protected by earthed steel conduit or similar,

vi) ... for cables without earthed metallic covering installed in walls or partitions with metal parts (excluding screws or nails) and not protected by earthed steel conduit or the like.

30 ma RCD's are required for ii to vi above"

BS7671 does not require a modified circuit to be rcd protected, only the modified portion of said circuit.

For the addition of an outside light, an rcd fused spur will serve two puposes :

1. Provide rcd protection

2. Provide the protection required by the manufacturer of the light fitting, usually DP isolation with 3A (max) fuse.

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Apache
No, thats me just trying to be different.

1.5 swa to outside light there is no requirement to rcd.

Other than that you could use other cables that under the requirements do not need additional protection, and so do not need to be rcd protected.

Its a minefield these new regulations ae they not? :^O

Assuming you would add a switch for the outside light - terminating the SWA might be tricky?!

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ericmark

I thought so long as you use something like Ali-tube to BS 8436 Guardian, Earthshield, Flexishield, or Afumex cable the only place where you need RCD protection on lights is the bathroom?

Why anyone would use twin and earth I don't know hard to seal as flat cable and if any of the cable is visible then ali-tube looks far better and cheaper than using an RCD.

Although I will admit DIY sheds don't seem to stock Ali-tube cable.

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matt.leung

thanks for all ur advice..

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Andy™

very few people use 8436 cable. easier just to stick it on an RCD

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spinlondon
BS7671 does not require a modified circuit to be rcd protected, only the modified portion of said circuit.

Not according to the IET Senior Engineer (Mark Coles). It is his contention that the whole circuit must be upgraded to comply; and that when working on a circuit in a bathroom, all circuits in the bathroom must also be upgraded.

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