Cooker Wiring

[EFLImpudence]

Yeah, I see your logic there but isn't that one of the little oddities accompanying the whole RFC lashup? If that sketch was in a test I'd define it as a radial not a ring final

It is a radial.

The 2.5mm² will be protected by the plug fuses as long as only one double socket is on each branch.

RFC also stands for Radial Final Circuit.

 

[Gordon1959]

This is getting more complicated than I anticipated. I assumed RCD protection was only necessary on a bathroom, shower room or outside circuit. The pond pumps will have the plug in unit which I use now. One double socket only on each 2.5mm² branch is what I intend so as not to burden the wiring too much. I will look at a more substantial junction box to use, a 60A is available which would be a better idea judging by the help given here. Also, the use of conduit is because I'll be hiding the cable behind a cover for the combi boiler and I would think that protection for the cable would be best.
I'm also off to bed now but thanks for the info, lots to ponder.

PS. Just read this so it looks like an additional RCD protection will be required.
"Also, if any part of the circuit cable is concealed in a wall or partition, it must be provided with additional protection by an RCD (In ≤ 30 mA) as required by Regulations 522.6.202 and 522.6.203."

 

[JohnW2]

The 2.5mm² will be protected by the plug fuses as long as only one double socket is on each branch.

Indeed - but, as I've just written, that is, strictly speaking, only true if the CCC of the 2.5mm² cable is at least 26A (which, in practice, means only if it is Method C, or 'in free air').

Kind Regards, John

 

[JohnW2]

This is getting more complicated than I anticipated. I assumed RCD protection was only necessary on a bathroom, shower room or outside circuit.

No. RCD protection is now required for most things - in particular any new socket any any new (or extended) lighting circuit and, effectively, for all new buried cables (unless they are in steel conduit - which I think yours may be).

Kind Regards, John

 

[EFLImpudence]

Indeed - but, as I've just written, that is, strictly speaking, only true if the CCC of the 2.5mm² cable is at least 26A (which, in practice, means only if it is Method C, or 'in free air').

I suppose I should have mentioned that - although the OP did say "I need to chase for any additional fittings".

 

[Gordon1959]

No. RCD protection is now required for most things - in particular any new socket any any new (or extended) lighting circuit and, effectively, for all new buried cables (unless they are in steel conduit - which I think yours may be).

Kind Regards, John

Yes, it will be in steel. I may have to forego the nice black nickel coloured sockets for plain RCD protected ones unless I can get a suitable junction box.
Anyway, now I'm really going to bed. Thanks for the help.

 

[JohnW2]

I suppose I should have mentioned that - although the OP did say "I need to chase for any additional fittings".

His did, but I think you'll find that the chasing was for the burying of steel conduit!

Edit: I meant to add that, as you presumably realised, the comments I made in the final paragraph of my response to oldbutnotdead (post #29) related to the fact that some people seem to interpret 433.1.204 as meaning that the cable of an unfused spur from a ring final (as well as of the ring itself) need only have a CCC of 20A (even if it is supplying a double socket).

I personally doubt that that is the intended interpretation - it seems to me that the requirements for that cable should be the same as required for any cable (other than that in the ring of a ring final) per the remainder of the regs. If that is the case, then, as I said, strictly speaking 2.5 mm² cable (protected upstream by a 32A OPD) would only be acceptable for an unfused spur to a double socket if it were installed per Method C (which, as I understand it, is not what the OP in this thread is intending).

Kind Regards, John

 

[ericmark]

I did look at the current rating for double sockets, it seems down to make and model. Found some rated at 13A a pair and others 13A each and both were MK.

When 17th came out I looked at alitube cable with the idea of fitting RCD at end of cable rather than at the start of cable run, however the problem is cost, and RCD sockets are expensive and so is alitube so very quickly one realises no real option but to swap consumer unit.

In my other house I don't have a consumer unit as yet, just two fuse boxes, both fed from a RCD it was done before distribution boxes with built in RCD's were around, but today to get metal boxes for add on RCD's would not be much cheaper than a problem consumer unit, and today distribution boxes for use by general public should be type tested.

I suppose there is nothing stopping anyone fitting a CU and doing all sorts of other work which does not comply with the law, however it only causes problems latter so may as well get it all done with correct paperwork to start with, there is a good reason why you should not DIY a consumer unit change, it is dangerous.

 

[JohnW2]

I did look at the current rating for double sockets, it seems down to make and model. Found some rated at 13A a pair and others 13A each and both were MK.

In the absence of quotes, I'm not sure whether that comment relates to earlier posts (about the undesirability of heaving loading both outlets of a double socket) or to my most recent comments about 'downstream overload protection'.

If the later, then the rating of the sockets is irrelevant - what matters is that the downstream overload protection will be provided, at worst, by 2 x 13A fuses (in plugs).

If the former, you've done a lot better than I/we have in the past if you really have found definitive information. If you recall, even with MK sockets, although they are 'rated' (per their Technical Datasheet) at "13A per socket outlet", no-one in their Technical Support department I spoke to was sure whether a double socket had one or two "socket outlets" (adding that 'Technical Datasheets' were usually written by the marketing department!).

As you know, BVS1363 requires that a double socket passes a 'temperature rise test' with 20A total (slightly bizarrely, 14A + 6A) being derawn. However, that tells us little/nothing about 'ratings', since there's nothing stopping anyone manufacturing a product which exceeds the minimum requirements of BS1363.

Kind Regards, John

 

[ericmark]

The same MK sheet for sockets with filters said total, and that word was missing for standard sockets.

 

[JohnW2]

The same MK sheet for sockets with filters said total, and that word was missing for standard sockets.

Indeed - as does the MK datasheet for 3-gang sockets ("13A total") - but, of course, they have a (maximum 13A) fuse in them (maybe the ones with filters also do??).

Kind Regards, John