Jack, (our retiree) is not happy. It started when his twin rcd socket in his workshop was condemned by an EICR to the effect of = C2 potentially dangerous. Jack had bought and installed his socket around 3/4 years ago and as far as he was concerned it was from a reputable shop,and met the regulations at the time. It wasn't his place to wade through endless British Standards and guide books, and fitting was not rocket science. He got an electrician friend to confirm the trip time. All was well. Now every time the trip goes he has to take a brisk walk to the meter cupboard in the house. However, on the internet one evening he decided to do some digging. He found a piece in a publication "Wiring Matters" from 2015 that covered his type of trip sockets in detail. To his disbelief he found the paragraph, "there is no advantage to have two RCDs in series in his situation". Funny he thought, this was the header of Lisa Miles new topic from the new Wiring Matters, "new amendment to BS 7671" which says these devices now must have an upstream device as well. "These people don't know what they are talking" about he thought.
Jack has now reinstalled his SCRD in the workshop (and removed the RCD from the house)
It would also be a bit daft to say that a double pole FCURCD with its removable fuse cannot be used as a isolator, but a single pole RCBO upfront of the circuit can or for that matter a cooker control unit switch without a removable fuse or the facility to lock it off can.
BS7671 defines isolation as:
”Function intended to make dead for reasons of safety all or a discrete section of the electrical installation by separating the electrical installation, or a section thereof, from every source of electrical energy.
Section 537 Isolation and switching starts with:
537.1 General
This section provides requirements for:
(I) non-automatic local and remote isolation and switching measures for the prevention or removal of dangers associated with electrical installations or electrically-powered equipment and machines, and
(ii) functional switching and control.
Non-automatic local isolation surely means that you can turn the isolator off by hand and/ or pull the fuse out of it.
Table 537.4 then gives guidance on the selection of isolation devices which includes fuses, which obviously have to be removed by hand and are single pole.
This thread seems to be drifting towards the old argument as to whether BS 7671 is retrospective or not.
The statutory obligation is to be found in Part P of Schedule 1 to the Building Regulations 2010:
"P1. Reasonable provision shall be made in the design and installation of electrical installations in order to protect persons operating, maintaining or altering the installations from fire or injury."
The Approved Document gives guidance:
"1.1 Electrical installations should be designed and installed in accordance with BS 7671:2008 incorporating Amendment No 1:2011." It might have been better to have said "... in accordance with the current edition of BS 7671."
My interpretation of "reasonable provision" is that new circuits should comply with the current edition of BS 7671; but an electrician is entitled to use professional judgement when altering or adding to an existing circuit. The use of a BS 7288 device may be, in my opinion, reasonable.
Further to what Alcomax said above, I pointed out in another discussion that ended up drifting onto this subject that FCURCD devices are manufactured to two British Standards, BS8277:1990 and BS1363-4:1995, so are perfectly capable of providing isolation, the IET says so.
Also I am still making alterations and additions to electrical circuits protected by BS4293 RCDs, but they are no longer listed in the current Wiring Regulations, so is that wrong, is there an issue about using these to provide RCD protection? If there is an issue millions of consumer units with working and safe RCDs that need replacing to undertake minor alterations and additions to existing electrical installations.
I'd say that there's no more of an issue than re-using red & black cables (which won't conform to the current version of BS 6004), BS 3871 MCBs or BS 1361 fuses. If anything a properly functioning BS 4293 RCD might even give better protection than a modern BS EN one - being that they'll disconnect within 200ms instead of 300ms (at 1x).
In my time working as an electrician I have had to buy seven editions of the Wiring Regulations, this is the first one I bought and have on my shelf.
So when I started working as an electrician there clearly was not any issues about using BS7288 RCD devices, bearing in mind that then and now they are made to the British Standard BS7288:1990, which is still current for a few more weeks. Exactly how and why was it decided that there could be an issue with these RCD devices? I suggest that there is no issues with the BS8277:1990 versions, only the new BS8277:2016 versions that are just now being released for sale.
Also I am still making alterations and additions to electrical circuits protected by BS4293 RCDs, but they are no longer listed in the current Wiring Regulations, so is that wrong, is there an issue about using these to provide RCD protection? If there is an issue millions of consumer units with working and safe RCDs that need replacing to undertake minor alterations and additions to existing electrical installations.
I'd suggest not. They're two different concepts. ADS (as described by 411) requires c.p.c., earthing and protective devices co-ordinated with Zs - additional protection doesn't demand any of that and can be applied to situations where there's no ADS at all - e.g. circuits protected completely by double or reinforced insulation (non-domestic of course) - e.g. called up the cables concealed in a wall regulations.
BUT then again it could be argued that a fuse "blowing" does not, strictly, provide isolation ...
Absolutely. I've seen some BS 3036 fuse carriers where the ceramic "shield" around the fusewire as been so "spattered" with condensed(?) copper after the fusewire blew I'd wondered if it wasn't conductive itself - likewise some ruptures are so gentle that you only get a tiny gap in the fusewire. Eitherway the achievement of a 3mm+ gap and associated creepage clearances don't seem to be reliably achievable. I'm not sure of the effect of sand (or similar) in cartridge fuses, but would suspect again that we don't necessarily end up with a clear 3mm gap equivalent. There's been no suggestion of outlawing fuses for ADS, so I have a fairly strong suspicion that only manual isolation is being asked for.
The first mention of Additional Protection [AP] in BS7671 is 410.1 [ scope of Chpt 41].....I think..
The first mention of AP with reference to RCD is 411.1... I think...
415.1.1 is very specific of what is expected of an RCD for AP.
That is all straightforward.
Then 531.1.1 : Devices for protection against electric shock by ADS shall be suitable for isolation in accordance with chpt 46 and 537.
There is the table for 537 as a "guide" for suitability for switching/ isolating etc. In the RCD bit it lists BS60947-2/61008/61009 as okay for isolation. Ah you think! But a removable BS1361 fuse , a switched fused connection unit, a plug and socket are also all suitable for isolation as listed in same table.
Again you have to ask "when is an RCD not an RCD?" Or even , "when is a plug and socket not a plug and socket?"
Perhaps they can be both RCD and plug and socket or RCD and fused connection unit.
Something is only isolated [properly] when there is some means to prevent it being energised again inadvertently, such as locking off , removing the fuse or unplugging [ though strictly the last two may need further steps if the mischievous are about ].
If it is not an RCD do not call it an RCD, as it is generally expected an RCD is a protective device and BS7671 says they are for additional protection, if the correct rating.
The BS says these devices only provide "supplementary" protection they require upstream "Additional Protection"
I'd assumed that the references to "supplementary protection" and "additional protection" meant the same thing - after all BS 7671 itself used to use the term "supplementary protection" to mean what we now call "additional protection" (e.g. 16th Ed BS 7671:2001+AMD2:2004 reg 412-06 "Supplementary protection by residual current device") - i.e. I suspect there's no more significance in the use of the two different terms than that the writers of BS 7288 haven't been entirely consistent in adopting the new vocabulary.
RCDs do not provide protection for upstream only downstream of the device.
Yes of course - agreed.
Do you agree they are not suitable when Additional Protection is required?
Well I can't really see the point in having Socket RCDs (or FCU RCDs) (or a BS for the same) if we necessarily have to provide 30mA RCD protection upstream. I can see the logic in them making (labouring even) the point that they don't provide upstream protection, hence if additional protection is required for the upstream wiring they you're going to have to make some other arrangements - but in the cases where BS 7671 doesn't demand any additional protection (by RCD or supplementary bonding) for the upstream wiring, I can't see the logic in BS 7288 demanding it.
