remodelled one-bedroom flat

[ajrobb]

I have just bought a one-bedroom flat that needs remodelling, which includes changing partitions and moving the kitchen. It currently has:

• semi-enclosed fuse box
  single ring final circuit
  cooker point
  immersion heater
  lights

There will be:

• lounge with galley kitchen
  bedroom
  dressing room with washer and combi-boiler
  bathroom

What should I expect if I get it completely rewired? Would this be reasonable?

• twin RCD CU
  2.5mm² radial to oven
  2.5mm² radial to hob
  32A radial to kitchen sockets
  20A radial to rest of lounge sockets
  20A radial to bedroom and dressing room sockets
  20A radial to washer & boiler
  6A lights

Initially, I plan to install a 13A oven and a 13A hob, each protected with a 16A CB and each with a 20A isolator switch above the counter.

 

[slup]

A lot of european ovens need 16A supplies so you might be better off fitting a cooker outlet plate instead of a 13A socket.

 

[1john]

I presume there is access to rewire, like an attic above and floorboards below. Around here there are lots or flats with one but not the other and the majority of them have no access to conceal cables, they are all concrete with buried conduit in them.

13A hob? So not a 4 ring then? or is it gas? The minimum for an electric hob would be a 32A with 6.0mm depending on factors.

I know it's a small flat but I still like to have more than one lighting circuit.

I prefere to have the boiler on it's own supply.

Make sure you use deep boxes on the kitchen radial.

Yadda yadda, part P, building control,

 

[slup]

Your 32A kitchen radial would probably require 6mm cable which will be difficult to fit in most (all) accessories.

 

[ajrobb]

I presume there is access to rewire, like an attic above and floorboards below.

It is a converted flat in a Regency building. There are floorboards but the ceiling/coving must not be altered. Currently the bedroom, lounge and kitchen are knocked into one room, so it is a weird bedsit. I plan on making them back into 2 rooms with a drywall acoustic partition where the original wall was knocked through. Cables could be run up this partition to the new galley kitchen.

I am doing this to sell and don't intend to do the wiring itself as a professional re-wire should be a positive selling point. However, I need to plan for it.

 

[1john]

well there is no point in planning too much to be honest, different sparks will have different ideas and you dont wanna put their noses out of joint by telling them how to do their job. You may not get any quotes back from them. Ask for a full spec quotation and see what you get back. I rarely spec circuits ect, I think you will be unlikely to get a quote with any circuit details on.

How are you plannign on having the lighting re-wired??

Will the cables be in a prescribed zone if they are in your new partition wall?

How much insulation will be around them while they are in this wall?

With out a floor plan it is hard to understand exactly what you are explaining, also a professional re-wire would make no difference to the resale value IMO, people just care what carpet there is and if they like the kitchen and bathroom. A chippy will be looking at your butt and scribe joins on the skirting and the size of the architraved, a sparky will be looking at the bonding and consumer unit, a plumber will be looking at your pipework, rads and boiler brand.

 

[ajrobb]

13A hob? So not a 4 ring then? or is it gas? The minimum for an electric hob would be a 32A with 6.0mm depending on factors.

Thanks, yes typically 7200W i.e. 30A. Possibly 4mm² 32A?

I know it's a small flat but I still like to have more than one lighting circuit.

You have a point, our 6B MCBs always tripped when a tungsten filament bulb blew. Not such a problem now with CFL. If there were stairs, yes, I would want two circuits on different RCDs. I'm only considering a short corridor with borrowed lights or glazed doors.

I prefere to have the boiler on it's own supply.

For a house maybe. However, I do plan to have it on a fixed appliance circuit.

Make sure you use deep boxes on the kitchen radial.

35mm for masonry walls. How about drywall?

Yadda yadda, part P, building control,

If a sparks does it, he'll have to sort that. Otherwise, I'm already doing that in a house for couple of sockets in the kitchen and converting an immersion heater circuit to a fixed appliance radial, which led on to a new CU, 25mm² meter tails and 10mm² bonding...

 

[1john]

standard 6.0mm for a cooker circuit, some like to use 10mm but 6 is fine. Usually with diversity you can connect the oven to this too.

A seperate MCB on the other RCD side and a few meters of cable to make two circuits are going to cost £5 in materials and take very little ectra time to install.

Disagree with you on the boiler.

You can get deep drywall boxes too, you may was well install thte largest that will fit in the wall, as for masonary walls, bury the 35mm flush and then tile to gain a bit more room, 2 x 4mm cables are hard work

 

[ajrobb]

standard 6.0mm for a cooker circuit, some like to use 10mm but 6 is fine. Usually with diversity you can connect the oven to this too.

I'm worried that the oven might require protection at 16A, say, and that a 32A or 40A CB wouldn't comply. Could I install 10mm² 45A CB through a cooker point as an isolator above the counter and down to another CU (fuse box) in a kitchen cupboard?

 

[holmslaw]

..

 

[1john]

No, in general property developers do the bare minumum in every aspect. Doesn't make it a good thing mind.

 

[flameport]

Main switch CU with RCBOs for each radial circuit:
32A for cooker point
20A for kitchen sockets
20A for sockets in other rooms
6A for lighting

Boiler connected to the kitchen 20A radial.

 

[ajrobb]

Main switch CU with RCBOs for each radial circuit:
32A for cooker point
20A for kitchen sockets
20A for sockets in other rooms
6A for lighting

Boiler connected to the kitchen 20A radial.

Thanks. I'm concerned that a lot of hobs require at least 30A and most ovens need 16A protection (although many single ovens can be protected by a 13A socket), I don't see how a single cooker point can supply both without an additional CU.

I'm thinking of maybe a 13A oven on one of the 32A-circuit (not 20A) kitchen sockets. The other kitchen sockets should still be adequate for a kettle, toaster and microwave. With careful design, the kitchen sockets could safely go on a 2.5mm² ring final, but maybe a larger (4mm²) radial.

My worry with 32A through 4mm² is that it might overheat if run together with other cables. Otherwise I worry that 6mm² might be too large to wire multiple sockets.

The boiler is in the other direction to the kitchen from the CU. It will be above the washer in a dressing room cupboard. A 20A radial could serve the cupboard. However, I agree that 20A should be enough for all the other sockets in the flat and keep the existing lighting circuit.

 

[flameport]

Thanks. I'm concerned that a lot of hobs require at least 30A and most ovens need 16A protection (although many single ovens can be protected by a 13A socket), I don't see how a single cooker point can supply both without an additional CU.

A 32A circuit will be suitable for the majority of cooking setups, whether that is an all in one cooker or a separate oven and hob. The only instance where it might not be is where two single ovens, or a large double oven is fitted together with an electric hob.
Large double meaning two actual ovens, not the usual things sold as doubles, which are a main oven and a much smaller oven or grill.

Most of those ovens which allegedly require a 16A circuit only say that because they are intended to be sold in Europe, where 16A circuits are common and 13A socket outlets / FCUs don't exist. In most cases, they draw less than 13A when in operation.
To prove this look here: http://www.espares.co.uk/parts/cookers-and-hobs/elements/p/1595
Those are replacement elements for thousands of different ovens. 99% of them are less than 3kW, and those for ovens requiring a top and bottom element are almost always 1.5kW or less.

A 4mm radial is completely OTT. So is a 32A ring.

 

[1john]

Last oven I installed for a customer was rated at 2400W @ 240V