RCDs

Do all circuits of a house have to go through an RCD? What I am thing about is when it pops and you lose the lights during darkness. Can the lights bypass it, or do they have to have their own RCD?

Dave

Reply to
Dave
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Reply to
John Rumm

Depends on the type of your supply, some supply types require a 100mA time delayed RCD. Generally speaking the majority of installations do not require this and the lights can be before the RCD in a split load CU.

Reply to
Dave Liquorice

oops pardon the blank reply

The simplest answer these days is to assume that all circuits need RCD protection, however the protection should be divided up between several RCDs such that a single fault will not result in loss of lights.

Use of one RCD for everything is no longer acceptable.

Reply to
John Rumm

Thanks John, your answer will be posted to a non diy group if you don't mind. The poster was advised to have all circuits through one RCD which didn't make sense to me. THis was brought home to me when I was in my hobby room while the wife was away for 3 months. I had a power cut and couldn't find my way to the top of the stairs. It frightened the hits (anagram) out of me. I now have a torch within reach.

Dave

If I don't here from you within 24 hours, I'll assume that your permission has been granted. Thanks

Reply to
Dave

Yup that is fine... post a copy of this as well.

When RCDs first entered common use, one was used to protect a whole CU. However it soon became apparent that while it lowered the danger of electric shock, it increased the danger of trips and falls resulting from the house being plunged into darkness. So this type of configuration has been long deprecated (although it is common to see setups like it). If you have a setup like it, adding a few battery maintained emergency lights can help greatly.

For the 16th edition of the regs the usual solution was the split load CU with the lights and any other low shock risk circuits powered from the non RCD side.

The 17th edition includes extra requirements for the protection of concealed cables that in most cases will mandate use of a 30mA trip RCD on all circuits (unless other precautions are taken to protect the cables). So here the solution is multiple RCDs (or RCBOs).

The simplest (i.e. cheapest) solution is to use two - one protecting say the upstairs power circuits and downstairs lights, and the other vice versa. Better setups may use more RCDs and or RCBOs to better distribute the circuits and minimise follow on risks from trips.

For more information see:

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Reply to
John Rumm

This was true under the 16th edition, however the requirements of the

17th edition to protect concealed cables with 30mA trip devices changes this long standing practice somewhat.

You can still have unprotected circuits (or TT circuits with only the

100mA trip protection), but there are other hoops to jump through, which will tend to make them the exception rather than the norm.
Reply to
John Rumm

On this point, the backlight on mobile phones nowadays is very useful for findling your way round in this sort of situation - not exactly enough to light up the house, but good enough to pick your way through a darkened room if you're careful. Mine has helped me out of several tricky situations. Only applies to those of us insecure enough to need out mobile phones within reach at all times.

Cheers!

Martin

Reply to
Martin Pentreath

I was wondering if 17th ed was changing things.

Presumably this is down to plonkers killing themselves when drilling holes vertically or horizontally from a visible accesory or with 150mm of a corner or wazzocks hiding cables on a diagonal?

So have these "safe" zones gone in 17th edition and you can run cables willy nilly provided they are RCD protected?

Reply to
Dave Liquorice

And of course us smokers can use our lighters.

Adam

Reply to
ARWadworth

At the time of the blackout, I carried my phone in a clip on case on my belt. Not much use when it is downstairs being charged up though :-( I'll try the above when I can get enough darkness in the house.

Thanks

Dave

Reply to
Dave

I guess that would be part of the reasoning.

No, I think the zones concept stays (and makes sense - just because its safer to screw into a live wire, does not make it any more desirable!)

Reply to
John Rumm

Yes, it does somewhat. That's probably why it's numbered 17 rather than 16, amendment 5........ :-)

It has been brought in for a number of reasons, but yes, plonkers trying to shoot themselves up with mains power, using a nicely aimed sds loaded hypodermic drill were considered......

More specifically, the 17th does NOT simply insist that all circuits are RCD protected, as the above might suggest - it is only the case where you cannot confirm (and document) that concealed cables are buried (and if necessary, mechanically protected) to a depth of at least 50mm on all sides. The more astute among you may recall that this was considered for the 16th too.

And yes, it does apply to lighting circuits too.

And yes, it applies retrospectively now to ANY circuit having work completed on it, which requires certification.

And no, it does not mean that Part P no longer applies.

Nope. Did you mean "special" zones? No, anyway.

Reply to
Geddit

Yeah

This is why they manufacture devices called RCBO's.......

Reply to
Geddit

I did this when we were in India last year. At one hotel the power went off in the early hours and it was so dark you literally could not tell if your eyes were open or closed. Finding one's way to the loo in a strange hotel in the pitch dark was ... interesting. My mobile was on my bedside table, so I just used the backlight on that to find my way round.

Reply to
Huge

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