Minor Works Certificate – Details of Departures from BS7671?

[Richard Burns]

Overall I feel that the easiest thing to do is replace the MCB with an RCBO, if possible (not in this case) or fit an external RCD into the circuit as it leaves the CU as Malcolm suggests.

I believe (now) that you could also fit an RCD at the point of the start of your addition, to RCD protect the cable (if required) and the socket and comply with the regulations. Similarly if you did not need to RCD protect the cable then you could fit an RCD S/O. The first would be a real nuisance to do, however and is not usually the easy option.

The NICEIC inspector did not give this as an option but did not exclude it either, he only suggested three options that are the easiest to do (and give maximum safety for the circuit; why not protect the whole circuit? especially if it is easiest to do).

 

[JamesBrownLive]

Overall I feel that the easiest thing to do is replace the MCB with an RCBO, if possible (not in this case) or fit an external RCD into the circuit as it leaves the CU as Malcolm suggests.

I believe (now) that you could also fit an RCD at the point of the start of your addition, to RCD protect the cable (if required) and the socket and comply with the regulations. Similarly if you did not need to RCD protect the cable then you could fit an RCD S/O. The first would be a real nuisance to do, however and is not usually the easy option.

The NICEIC inspector did not give this as an option but did not exclude it either, he only suggested three options that are the easiest to do (and give maximum safety for the circuit; why not protect the whole circuit? especially if it is easiest to do).

Richard,

There's no way what the inspector suggested is simpler than just fitting a RCD socket combo, so I don't believe that to be the case. I believe he suggested those options because, in his opinion, they were the only options open that complied with the regs. Alas however, he is not here to ask so we will never really know.

Maybe you can tell me something I have never been 100% sure about... Is the point of an RCD protected cct to provide sole protection for the devices plugged into it, or is it also supposed to provide some protection to the wiring that it supplies.... i.e provide protection against persons drilling into it, sawing through it etc.

Obviously if the former, then it could be argued that the RCD Socket combo addresses this, if it is the latter, then this would explain why the need to bring the whole circuit under RCD/RCBO protection.

Cheers

 

[Richard Burns]

JamesBrownLive

An RCD S/O would not cover the cable feeding the socket so would not be an option if the cable is in the wall at <50mm. The RCDFCU at the start of the modification would protect the whole of the addition but would mean cutting out a socket box; more work than fitting an RCD at the CU.
The best method is to enhance the safety of the whole circuit.

30mA RCDs (ignoring larger current RCDs) are for Additional Protection only it provides this additional protection by disconnecting quickly at low (hopefully non fatal) current (rather than low (touch) voltage). It is there to protect against electric shock.

The RCD requirement is used in cases where there is enhanced risk of shock due to external conditions or inexperienced users. In the case of a fault or careless use, whether in the attached device or in the supply cable, the RCD will provide this additional protection.

I think it is considered that where the cable is visible no one is going to nail through it so lower risk and RCD not required. For S/O <=20A (general use) or S/O <=32A likely to be used outside or power supplied in wet conditions there is an increased risk of electric shock so RCD protection required.

 

[Deleted member 26818]

James.
The introduction of the requirement to RCD protect socket-outlets was not brought in as a whim, it was originally to protect persons using portable equipment outdoors.
At the time, there had been a noticable increase to the number of injuries and fatalities due to the increased use of the new fangled electric mowers and hedge trimmers.
The original requirement was that all socket-outlets that may reasonably be used to supply portable equipment outdoors must have RCD protection.
Since that requirement was introduced, it has been found that many designers, inspectors and electrical installers have been over-zealous in applying this requirement, to such an extent that they include socket-outlets that would not reasonably be expected to be used to supply portable equipment outdoors. Such as those used to supply integrated appliances etc.

It was decided with the introduction of the 17th edition, to clarify the requiremnts to RCD protect socket-outlets, and to not only require that those used to supply portable equipment outdoors, but to include portable equipment used by unskilled persons indoors as well.
To this end two requirements were introduced, one requiring any socket-outlet intended for general use by ordinary persons to be RCD protected, and the other requiring specifically any socket-outlet that is used for mobile equipment outdoors should also be RCD protected.
As such, if you have a socket-outlet that could be used to supply mobile equipment outdoors, but you don't use it for that purpose, there is no requirement for it to be RCD protected.
However if that socket-outlet is used for a hoover, for charging laptops or any of the other myriad of new fangled items we now have, it must also have RCD protection.
Socket-outlets intended for specific use, such as to supply integrated appliances, boilers etc. do not require RCD protection, as it is unlikely that someone will be lugging such applances around and the likely hood of someone recieving a shock is slim.

It has also been determined that ordinary persons are quite thick, and will now indulge in DIY (especially when there is a bank holiday).
These people will insist on drilling and nailing where any reasonable person would not.
So the requirement to additionally protect cables concealed in walls has been extended to include RCD protection.

For some reason (which is a mystery to me) it has been decided to allow these people to have socket-outlets in their bathrooms.
I have seen an installation, where a 42" flat screen TV was installed into a stud wall of a bathroom. The TV was sealed off from the bathroom by some acrylic plastic, and the socket-outlet was outside the bathroom. Apparently it is possible now to obtain a TV that can be tiled into a bathroom or shower, and that when it is not on, doubles up as a mirror.
So you can now watch TV whilst showering, then quickly squeeze your pimples during the commercial breaks.
As such these socket-outlets also require RCD protection, along with them being 3.6m from the bath or shower. Perhaps it has been decided that these people will not have long extension leads.

It was decided that sensible or skilled persons would not be too thick to just start putting pictures, shelving and flat screen TVs up willy nilly without first determining whether there were concealed cables in the way, and that they would not use mobile equipment indoors with damaged cables. So exceptions were made for these persons to the requirements for RCD protection. Not that sensible that any exceptions for RCD protection in bathrooms or for mobile equipment used outdoors to be allowed.

Obviously, the easiest way to protect the socket-outlets that do need RCD protection, and at the same time cables concealed in walls, is to protect the whole circuit.
However to accomodate such installations where cables are not concealed in walls, where other aditional protection is used and where some socket-outlets are required whithout RCD protection, RCD protection for circuits other than in special locations is not required.

 

[Guest123]

Mark Coles wrote an article on the introduction of RCD protection to additions & alterations to final circuits.

 

[Deleted member 26818]

Mark Coles wrote an article on the introduction of RCD protection to additions & alterations to final circuits.

Yes and Mark is now no longer the Chief Engineer since that article was published.

 

[JamesBrownLive]

Mark Coles wrote an article on the introduction of RCD protection to additions & alterations to final circuits.

Thanks Lenny,

That article has confirmed that the RCD S/O and the FCU RCD options that have been suggested are not compliant.

Just what I needed to know.

Thanks also to Richard and Spin, for taking the time with their longish (Long in Spin's case) responses. I was already aware of the main reasons behind RCDs but somehow, the requirement because of concealed cables <50mm had evaporated from my mind, even though I now remember learning it. I guess I'm just getting old :sad:

Cheers

 

[Richard Burns]

I think I will rely on the testing complying with BS7671 rather than fully upgrading an entire ring circuit to BS7671 for a socket addition, that could be a bit expensive. Though I would normally protect the entire circuit with an RCD (if required).

 

[Jeffmo65]

Long gone thread maybe , but where do we stand then on replacement of say a broken external back box or broken socket , with regards to RCD protection and or even testing . ????? . Or shall i just put the Gas Safe sticky tape back on , thank her for the cuppa and bugger off .

 

[Jeffmo65]

Gas safe sticky tape by the way that was on it when i arrived , whilst she was happily working on her lap top from said socket which happened to suddenly be void of neutral on minor wobble of said skt . ooooh scary , poor Danish student .

 

[Knobhead]

Long gone thread maybe ,

Yes it is so why resurrect it?

Try using the search facility and read first before asking questions that have been answered ad nauseam.

 

[Jeffmo65]

Nineed tobe so touchy Tony . It may be I'm not fully ofey with the way the site works . Sorry sparky not IT expert

 

[malcolmsanford]

Jeff are you asking if your repairing an accessory and the circuit/ accessory does not have RCD, protection should we fit it.

No mate your carrying out maintenance as such, see the definition in part 2

 

[gibbyisking]

could of fitted an rcd socket mate

 

[Mark42]

… It has also been determined that ordinary persons are quite thick, and will now indulge in DIY (especially when there is a bank holiday).
These people will insist on drilling and nailing where any reasonable person would not.

An amusing, informative, and well-written post. Thanks.

I wonder if the inspector would have accepted an RCD spur? I suspect not: even if it might (just) be within the letter of the regulations, surely it isn’t within the spirit. It smacks of a ‘jobsworth’ interpretation: there you go, MY single additional socket complies, but stuff the other twenty sockets on the same RFC.

It does (sort of) make sense that if you have to RCD-protect new or additional work, then you should protect the whole circuit which feeds that work. It could be argued that ALL the final circuit cabling supplying your new socket is now adopted by you and hence falls under current regulations.

But what about existing cabling which is not installed in the ‘safe zones’. It would clearly be absurd to have to tell a client that in order to add a single new socket somewhere you have to change all the cabling in the walls of maybe many rooms, because it doesn’t run in just exactly the right places. Apologies if this is specifically excluded and I’ve missed it.