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Yes. Its just that the table is in a "TT section" but it is refered to from a TN section. perhaps not the best idea, but that's the joy of BS7671 !! :lol:

I know that an RCD is not an OPD. Spark123, yes, a fault causing fault current can be phase to earth. I accept that. I thought it pretty clear that the RCD is providing protection against a phase to earth fault. Please bear with me and read 411.4.9, then chapter 43 (for the requirements...

411.5 is indeed headed TT systems. However, 411.4.9 (at the top of page 50) is part of 411.4 - TN Sytems. :wink: It refers to table 41.5, which incidentally is within "TT system". None the less it is table 41.5 which states the max Zs for a circuit protected by a 61008/61009 RCD <=32A...

Spark123 says the regs don't make sense. I say they do: That is a contradiction. No, the phase to earth fault is dealt with by the RCD. This will disconnect less than 0.4 seconds, even at 5xIn. Thats why EFLI is raised to 1667, as per table 41.5, and 411.5.3 (i) and (ii) being met.

Chri5, you asked for posts of 17th boards, then when one is posted, no comments ?

Makes perfect sense to me, the RCD is providing FAULT protection. The OPD is providing protection against OVERCURRENT and FAULT current. Fault protection and fault current are two entirely different things (see definitions, page 24)

Have a read of the current edition of BS7671 wiring regulations: Page 50. 411.4.9

I'm sorry, didn't read that properly! Still stand by my points on Zs max being 1667 thoough (well, 1666.6666666666666666666666666666....) for 30ma rcd circuit

always suggesting what ?? when have I suggested anyone shouldn't be in the industry, ever ????? I gave helpful advice on all of his points, didn't you read my post ? I also gave my opinion /concerns ! No, Life is precious an should be protected !

Its not ridiculous, quite the opposite. Its correct. Heres why: 1. The regs state if the circuit is protected by an RCD the maximum Zs is determined by InR < 50V. There is no regulation that states "the breaker type must suit EFLI conditions" - nonsense. The breaker is selected in accordance...

Yep crap board. , only one MEB terminal, MCB's dont sit well on rail, crap neutral terminals, (small screws) numbered wrong because they've adapted the case off a normal split load board so the sequence is alll over the shop , cheap stickers with only with one rcd sticker, all in all poor for...

Nice one. It goes to say even the assessors get gt wrong sometimes, like mine did with the shower (see above)

So none of your certs are compliant with bs7671 then?

But surely GaryMo you are not entering the MAXIMUM figure permitted by BS7671 ! And even for a non RCD circuit, why do you enter 80% figure? Thats an NICEIC recommended figure, not BS7671 This reminds me of another inspection where the NICEIC guy said I'd incorrectly entered 5s MAXIMUM...

No, working shortly, just waiting for merchants to open, so filling time on the forum !

Fair point pompey, but these are basics. If I didn't know these things I wouldn't be confident to replacing CU's in 80 year old folks homes ! (or any homes) which I suppose is why the OP is asking. And if the guy is with a scheme then should be asking their help line or reading their guides, the...

As pointed out at my last inspection, this should be 1667ohm not 1.5ohm for say a 32A mcb circuit protected by a 30mA RCD. (IR < 50V) Was I alone in entering anything other than 1667 for rcd circuits previously ? [edit: in a domestic installation]

How many ways are required ? Preferably not so run a cpc to them. If not willing to pay then use class 2 fittings and post a warning note next to CU to the effect that only class 2 fittings must be used. If there are any class 1 fittings then either replace or issue danger notice...

MI didn't say anything about not using oem MCB's. Can't see a problem with it anyway, if they fit OK. A bus bar and din rail are not exactly in the realms of rocket science !

Well spotted RF, to be honest I don't know. They (CEF) didn't have any M2 RCBO's in stock. Why would the use of a non M2 device be against regulations though ?