Oven and hob wiring

[MadAlicesDad]

I'm planning a new kitchen, in which there will be separate gas hob and electric double oven. I know the rules regarding installation by competent persons, special locations etc - at this point I'm just planning layouts.

I'm assuming the oven will need a dedicated circuit and an isolator (ie can't run off a 13A socket). I seem to remember that the isolator needs to be within 2m of appliance and accessible. Is this the case and is it ok to fit the isolator above the wall units behind a pelmet, ie accessible if you stand on a chair?
If we go for a single oven that can run from a 13A supply, would this need an accessible isolator?
Does the hob supply need to be isolated in the same way or can this run from a socket behind the cupboards?
TIA
Mike

 

[EFLImpudence]

[I'm assuming the oven will need a dedicated circuit and an isolator (ie can't run off a 13A socket).

Correct.

I seem to remember that the isolator needs to be within 2m of appliance and accessible. Is this the case

Correct.

and is it ok to fit the isolator above the wall units behind a pelmet, ie accessible if you stand on a chair?

Of course not.

If we go for a single oven that can run from a 13A supply, would this need an accessible isolator?

Maybe not, as such, but it would be advisable.

Does the hob supply need to be isolated in the same way or can this run from a socket behind the cupboards?

Maybe not, as such, but it would be advisable.

While you're at it it would be advisable to fit a proper cooker circuit in case a different appliance were required in the future.

With this in place you can run the oven(s), hob and hood (if one) off the one circuit which could all be quickly isolated in case of an emergency without any climbing being involved.

 

[MadAlicesDad]

I knew you'd say that, but thanks anyway!

I was going to run the oven/hob/hood off a dedicated cooker circuit anyway; there is an existing circuit that I could use but as I've got to run other cables to the CU anyway I'd probably fit a new one. At the moment the isolator is slap bang next to the cooker - I want to move it to somewhere less conspicuous.
Is the 2m distance measured horizontal or diagonal, and where is it measured from (centre of appliance, edge of appliance)
Is 'accessible' defined anywhere - an isolator mounted 2.2m off the ground is accessible to me but is well out of reach for my wife!

Cheers
Mike

 

[bernardgreen]

Is 'accessible' defined anywhere - an isolator mounted 2.2m off the ground is accessible to me but is well out of reach for my wife

When will you need to use the isolator ? Maybe when one or more of the controls have failed and or more elements are dangerously overheating.

Rapid and safe access to the isolator would then be necessary. A bit like putting the fire extinguisher in a cupboard and then in a hot and smokey panic situation forgetting where it is.

 

[ban-all-sheds]

is it ok to fit the isolator above the wall units behind a pelmet, ie accessible if you stand on a chair?

 

[MadAlicesDad]

I appreciate that, but my point (albeit not clearly made) was that accessible is an ambiguous term - is there a correct interpretation?
For example, do I have to put it somewhere that a disabled person in a wheel chair can access it, a bit like light switches in new houses a few years back which were accessible for the disabled but also dangerously so for inquisitive toddlers.

Junction boxes have to be accessible, yet they can be out of reach in a ceiling void behind a hatch. Admittedly they serve a different purpose, but it's the same word in the same regulations.

Cheers,
Mike

 

[EFLImpudence]

I appreciate that, but my point (albeit not clearly made) was that accessible is an ambiguous term - is there a correct interpretation?

It's not really ambiguous.

For a junction box which must remain accessible for testing your position would be acceptable.

For an isolation switch which must be accessible in an emergency it is rather obvious.
Normally on the wall at the back of the hob to one side. I suppose within two metres technically means from either side of the hob.

 

[bernardgreen]

must be accessible in an emergency it is rather obvious.

For many people it is not obvious that an emergency may happen in their ( well run ) house so they do not put "an emergency" into the planning of things to do.

 

[MadAlicesDad]

On the contrary, I'm looking at safety improvements from what I've got.
At the moment, it's 50mm from the potential fire source (electric hob) - meets the rules, but not really safe. In the event of a fire, I'd avoid the switch entirely and aim for the CU to cut the power - it's readily accessible and on the way out of the house as well.
I was looking to site the isolator in an accessible* position, away from the fire source, but high up so it's less obtrusive and makes cable runs easier.
Also bear in mind it will be a gas hob so the isolator won't kill the heat source from the hob, and if the (electric) oven overheats any fire will be contained giving more time to take action, especially if compared with the time it takes to run outside, open the gas box and turn the gas supply off.

Cheers,
Mike

*I wish I'd never mentioned 'behind a plinth' - It was meant facetiously to test the boundaries of what would meet the rules! Can we drop it now?

 

[MadAlicesDad]

On the contrary, I'm looking at safety improvements from what I've got.
At the moment, it's 50mm from the potential fire source (electric hob) - meets the rules, but not really safe. In the event of a fire, I'd avoid the switch entirely and aim for the CU to cut the power - it's readily accessible and on the way out of the house as well.
I was looking to site the isolator in an accessible* position, away from the fire source, but high up so it's less obtrusive and makes cable runs easier.
Also bear in mind it will be a gas hob so the isolator won't kill the heat source from the hob, and if the (electric) oven overheats any fire will be contained giving more time to take action, especially if compared with the time it takes to run outside, open the gas box and turn the gas supply off.

Cheers,
Mike

*I wish I'd never mentioned 'behind a plinth' - It was meant facetiously to test the boundaries of what would meet the rules! Can we drop it now?

 

[bernardgreen]

On the contrary, I'm looking at safety improvements from what I've got.

Which is when you need to have a very open mind as to what can go wrong.

In the event of a fire, I'd avoid the switch entirely and aim for the CU to cut the power

Using the isolator could prevent the fire.

If the fire has already taken hold then isolating at the CU will not have any useful ( to you ) result. The fire brigade could cope with the electrics possibly being live when they arrived.

Also bear in mind it will be a gas hob so the isolator won't kill the heat source from the hob,

Some gas hobs will cut the gas if the electrical power is removed. Worth considering that type for increased safety.

and if the (electric) oven overheats any fire will be contained giving more time to take action,

The oven door unless sealed and locked will prevent a fire, lack of oxygen inside the oven means the fire in the oven will be small but depending on what food is inside the oven there may be extremely hot and potentially in-flammable vapours coming out of the oven and these may spontanously ignite on meeting oxygen in the air. ( think chip pan fire on electric hob where there was no gas flame to ignite the super heated oil and vapour )

especially if compared with the time it takes to run outside, open the gas box and turn the gas supply off.

That is a good idea PROVIDED it is safe to do so. ( where is the key for the gas box kept ?)

Plinth ? Kick operated emergency stop switches can be effective safety items.