Back boxes for Dob & Dab?

[DonutHole]

As has been explaind, having all circuits protected by a single RCD would not be a very good idea (and most would say is non-compliant with current regs.).

However, I'm getting a little confused by the discussion here, and wonder whether it is not perhaps ranging a little more widely than may be strictly necessary for you.

Although it is obviously desirable that your (or anyone's) entire electrical installation should be brought into compliance with current regulations, there is no requirement for that, and BC's only interest in the electrics should relate to the electrics in, and/or associated with, your new extension. From what you say, that probably amounts to just the new sockets ring circuit and an extension to an existing lighting circuit.

Your CU appears to have two unlabelled RCD-protected ways - are they 'spare'? If so, one of those could be used to provide an RCD-protected supply for the new ring (which, being a sockets circuit, now must have RCD protection, regardless of how the cable is routed and protected). As for the extension's lighting, any requirements for RCD protection (which would depend upon cable routing etc.) could, as has been said, be satisfied by changing the MCB protecting that (currently not RCD-protected) circuit to an RCBO.

Am I missing something?

Kind Regards, John

Ahhh so I don't have to update to RCBO's in order to get LABC approval.
Yes John there are 3 spare MCB's, 2 RCD protected & 1 not, although I hope to keep 1 for Aico smoke alarms, & if I follow Owains advice one for an electric cooker, although I will be installing a gas cooker, it will future proof me. I already have a down and upstairs lighting circuit, and a front and rear ring main for sockets, and would have thought I can simply add the new kitchen to the rear sockets ring, and downstairs lighting circuits.

 

[JohnW2]

John is right to point out you don't need to do anything for now, just concentrate on the alterations you're making, which is why I recommended mechanical protection of lighting drops if you're on a budget and/or don't want to mess around inside the CU. Do that and board either side (5mm cable +2mm clip +3mm steel = 10mm, take 19 for dabs and board = 9, easily bonded then skimmed).

Someone presumably needs to 'mess around in the CU' to install the new sockets circuit, so swapping just one MCB for an RCBO (assuming one would fit) at the same time would not be much additional effort - and, if it were me, I would regard that as definitely preferable to messing around with 'mechanical protection' (an, of course,one would then have 'other benefits' of the circuit being RCBO-protected). However, 'opinions may vary'!

Kind Regards, John

 

[JohnW2]

Ahhh so I don't have to update to RCBO's in order to get LABC approval.

Exactly - at least, that's how it should be. LABCs can attempt to be 'laws unto themselves', but if they tried to say otherwise, I think you should argue vigorously!

Yes John there are 3 spare MCB's, 2 RCD protected & 1 not, although I hope to keep 1 for Aico smoke alarms, & if I follow Owains advice one for an electric cooker, although I will be installing a gas cooker, it will future proof me. I already have a down and upstairs lighting circuit, and a front and rear ring main for sockets, and would have thought I can simply add the new kitchen to the rear sockets ring, and downstairs lighting circuits.

Fine for the lighting, but it would probably (IMO) be desirable to have a separate new circuit for the new kitchen sockets ring (for which your CU has capacity).

Kind Regards, John

 

[DonutHole]

you might as well put the cable in for an electric cooker point now; you or someone in the future might want an electric cooker. The extra cost is marginal - if you're tight on MCB ways just leave the cable spare near the CU for now.

Thank you for your advice Owain, I didn't intend to, but now you have mentioned it I might well take your advice. So for a cable run of about 13-14 metres, and a standard domestic 600mm wide electric double oven with 4 hobs, any idea's on cable, and RCBO size?

 

[Taylortwocities]

DoNut. You really need an electrician. The questions you ask are very very basic, I don't want to turn you away from DIY electrics, but LABC will expect you be able to at least specify and design a circuit. Then to test and certify it.
And if you get it wrong, the possibility is a visit from the fire brigade.

The very first thing is to determine the load. So saying

standard domestic 600mm wide electric double oven with 4 hobs

is not very specific. There are about 5,000 appliances that meet that description.

The "oven" may need 16amps, or 20, or 32amps. An induction hob could require 40amps just on its own.

Or maybe you do not mean "oven". Perhaps its a cooker with oven(s) and hob all in one unit? Perhaps its a gas hob?

 

[DonutHole]

DoNut. You really need an electrician. The questions you ask are very very basic, I don't want to turn you away from DIY electrics, but LABC will expect you be able to at least specify and design a circuit. Then to test and certify it.
And if you get it wrong, the possibility is a visit from the fire brigade.

The very first thing is to determine the load. So saying

standard domestic 600mm wide electric double oven with 4 hobs

is not very specific. There are about 5,000 appliances that meet that description.

The "oven" may need 16amps, or 20, or 32amps. An induction hob could require 40amps just on its own.

Or maybe you do not mean "oven". Perhaps its a cooker with oven(s) and hob all in one unit? Perhaps its a gas hob?

Thanks for your feedback 'TTC', but I think you missed 'Owain's' point. I didn't specify the type or Kw of the electric cooker, because I am installing a freestanding gas cooker. Owain suggested I should put in an electric cooker point while I was at it, so I would have to flexibility to install an electric cooker in the future without having to re-plaster and re-tile. So I was asking what size cable and RCBO would cover most 600mm wide freestanding electric stoves because that is the gap that will be left between worktops. Obviously if I'm only future proofing then I'm asking for a specification that would cover the majority (say 95%) of stoves of this size. I appreciate this thread is now quite long so it is easy to get lost. I hope this doesn't sound angry it's not, all the advice really is much appreciated.

 

[JohnW2]

The very first thing is to determine the load. So saying

standard domestic 600mm wide electric double oven with 4 hobs

is not very specific. There are about 5,000 appliances that meet that description. ... The "oven" may need 16amps, or 20, or 32amps. An induction hob could require 40amps just on its own. ... Or maybe you do not mean "oven". Perhaps its a cooker with oven(s) and hob all in one unit? Perhaps its a gas hob?

With respect, I think this is a little unfair. The OP is not designing a circuit for a known load. He is merely responding to OwainDIYer's suggestion that he should take the opportunity to install cabling for a possible future cooker circuit, not even to be connected to the CU at present, in case he or a subsequent occupier of the house requires it. As such, he obviously cannot know the specification of whatever appliance might be installed years into the future - so presumably was hoping for advice as to what cable would be reasonable to install which would probably be suitable/adequate for a 'standard large cooker' at some point in the future.

Kind Regards, John

 

[EFLImpudence]

OP - I haven't read the rest.

The new Kitchen will have a free standing gas stove but with electric clock and oven light

 

[DonutHole]

The very first thing is to determine the load. So saying

standard domestic 600mm wide electric double oven with 4 hobs

is not very specific. There are about 5,000 appliances that meet that description. ... The "oven" may need 16amps, or 20, or 32amps. An induction hob could require 40amps just on its own. ... Or maybe you do not mean "oven". Perhaps its a cooker with oven(s) and hob all in one unit? Perhaps its a gas hob?

With respect, I think this is a little unfair. The OP is not designing a circuit for a known load. He is merely responding to OwainDIYer's suggestion that he should take the opportunity to install cabling for a possible future cooker circuit, not even to be connected to the CU at present, in case he or a subsequent occupier of the house requires it. As such, he obviously cannot know the specification of whatever appliance might be installed years into the future - so presumably was hoping for advice as to what cable would be reasonable to install which would probably be suitable/adequate for a 'standard large cooker' at some point in the future.

Kind Regards, John

Thanks John, you nailed it!

 

[JohnW2]

OP - I haven't read the rest.

The new Kitchen will have a free standing gas stove but with electric clock and oven light

Am I missing your point? Where I come from a clock plus an oven light don't really require a new 'cooker circuit' to be installed for them

Kind Regards, John

 

[DonutHole]

OP - I haven't read the rest.

The new Kitchen will have a free standing gas stove but with electric clock and oven light

Am I missing your point? Where I come from a clock plus an oven light don't really require a new 'cooker circuit' to be installed for them

Kind Regards, John

It's a big clock John

 

[JohnW2]

Where I come from a clock plus an oven light don't really require a new 'cooker circuit' to be installed for them

It's a big clock John

Ah. I overlooked that possibility - does the clock perhaps heat the whole house?

Kind Regards, John

 

[OwainDIYer]

you might as well put the cable in for an electric cooker point now; you or someone in the future might want an electric cooker. The extra cost is marginal - if you're tight on MCB ways just leave the cable spare near the CU for now.

Thank you for your advice Owain, I didn't intend to, but now you have mentioned it I might well take your advice. So for a cable run of about 13-14 metres, and a standard domestic 600mm wide electric double oven with 4 hobs, any idea's on cable, and RCBO size?

6 mm might do it, 10 mm to be on the safe side, depending on mounting method ie whether cable enclosed in thermal insulation. 32 Amp circuit protection. Run to a 45mm deep double back box for the switch, and then to an outlet box behind the cooker.

If you have an MCB for it now, you can put a 13A socket on the outlet box for now and plug your gas cooker into that.

A quick check of cable price suggests £50 from Wickes (ha!) but it will save destroying the tiling etc at a later date.

 

[mfarrow]

Someone presumably needs to 'mess around in the CU' to install the new sockets circuit

Good point.

I would regard that as definitely preferable to messing around with 'mechanical protection'

It's not messing around, it's one of the several specified ways of meeting the regulation, and the only one which prevents damage to the cable when drilling.

 

[EFLImpudence]

But the usual metal capping is not 3mm. thick and does not afford protection and would have to be earthed.

Were you referring to something different?