Correct isolators

[pedr0]

Hello,

Please could you tell me what isolator switches I need for my oven and hob. I've got two radial supplies coming in - one currently goes to a 'cooker' isolator which also has a socket, the other goes to a single switch with a neon. I would like to replace both isolators with two single switches (no neon, no extra socket). Would that be OK? What rating do the switches have to be?

Sorry I don't have the power specs, but the oven is a single built-in low-end whirlpool fan oven. I haven't bought the hob yet but it will be a 4-hob ceramic thing.

Thanks!

P.S. I'm not doing the work - a qualified sparky is. But in order to keep costs down I said I would get all the stuff he needs.

 

[luminaire]

Hello,


P.S. I'm not doing the work - a qualified sparky is. But in order to keep costs down I said I would get all the stuff he needs.

To keep the costs down I would suggest let the electrician purchase what he needs.
He has more experience of what is best and what is more suitable.
He will be able to purchase it cheaper than you anyway.

 

[Taylortwocities]

Sorry I don't have the power specs, but the oven is a single built-in low-end whirlpool fan oven. I haven't bought the hob yet but it will be a 4-hob ceramic thing.

I would be unable to advise you given this level of information. Its like asking "How long is a piece of string"

I could ask my special friend for you

 

[JohnD]

the power rating of the switches must be no less than the rating of the fuse or MCB of the circuit that supplies them.

so must the cable

and the fuse or MCB should be meet the max load of the appliances you intend to supply.

you say you don't know the power rating of the appliances you intend to purchase. I certainly don't.

. I'm not doing the work - a qualified sparky is.

don't believe you.

 

[pedr0]

Thanks for the speedy responses.

To each of you in turn:
luminaire - thanks for having the best interests of my wallet in mind - believe me, so do I. I've negotiated a great rate from my electrician on the premis that I get all the supplies myself. Of course, this is going to cost me a quid or two over what he could get each item for, but it's small compared to the 75 quid I managed to knock off the price for doing all the leg work.

Taylortwocities - unfortunately that doesn't really help me at all, but thanks for checking out my post and replying. P.s. You can do what ever you like with your special friend

JohnD - I guess I might not have used the correct lingo in my original post. I don't think it's the fuses within the isolators that I'm worried about - I'm sure he'll have a selection of fuses and if not I can always nip to DIY shop when he's doing the work - It's the unit itself that I'm unsure about. A flick through screwfix seems to suggest that I ought to buy two 45A double pole cooker switches. Am I on the right lines?

Thanks!

 

[pedr0]

Just noticed your closing gambit JohnD.

It's a shame that you've lost trust in people. But you're wrong - simple as that. Don't know what else to say really other than it's a shame.

 

[electronicsuk]

pedr0, there are no fuses contained within 45A DP isolators, in fact you're very unlikely to find electrical accessories in a domestic environment with anything larger than a 13A fuse. Where appliances with high power demand are concerned, standard practice is to run them from a radial circuit with appropriate fuse/MCB protection at the CU.

In your case, it will probably be possible to control the oven from a switched FCU, assuming the oven is rated at less than 3kW. However, electric hobs tend to require a lot more power, you'll need to use a 45A DP isolator as you already suggest. Since you already have a spark involved it's safe to assume that the cabling that has been installed is all suitably rated for the appliances you plan to install.

For aesthetic purposes it would make sense for you to install two identical 45A DP switches, one for the oven and the other for the hob. Because the oven is likely to require no more than 13 Amps your electrician will likely want to install/replace the MCB protecting that circuit with something of a suitable rating. For example, even if the cable and accessories are good for 45A, installing a breaker of that capacity affords no protection to the appliance if it only requires 13A. In that scenario a fault could occur inside the oven allowing it to draw more than 3 times its rated current for an indefinite period without any interruption to the circuit.

 

[Taylortwocities]

it's safe to assume that the cabling that has been installed is all suitably rated for the appliances you plan to install.

LMFAO

He doesnt even know what the hob is, yet.

 

[pedr0]

Hey thanks electronicsuk. That's really helpful. Starting to understand that I've got a bit more work to do before sparky comes next Wednesday. So changing the current 'Cooker and socket' isolator switch to a single 45A DP isolator is OK as long as an appropriate MCB is fitted at the CU - I'll ask sparky about what MCB I need to get for that. However, as brash as Taylortwocities is, he at least has drawn my attention to the fact that I need to choose my hob first. I had assumed that one ceramic hob was very similar to another ceramic hob and so the existing cables etc (only 10 years old) would be sufficient, especially as it is on its own radial supply.

 

[electronicsuk]

it's safe to assume that the cabling that has been installed is all suitably rated for the appliances you plan to install.

LMFAO

He doesnt even know what the hob is, yet.

Either way, a professional spark will make sure the cabling is suitable for the job at hand, and I'm happy to take the OP's word that he will be having a professional in to take care of this part of the work.

I think I misinterpreted a little in that I was under the impression that the spark had already been in for first fix, but now it seems the old cables are to be used. If they are undersized then they'll have to be replaced or an oven/hob selected specifically not to overload the existing cabling. Again, the electrician will be able to advise here.

 

[securespark]

In that scenario a fault could occur inside the oven allowing it to draw more than 3 times its rated current for an indefinite period without any interruption to the circuit.

Not if the OP's electrician fits an FCU or similar arrangement as you suggested...

 

[electronicsuk]

Not if the OP's electrician fits an FCU or similar arrangement as you suggested...

Indeed, although I also suggested an alternative involving two 45A DP isolators for aesthetic reasons, so it seemed prudent to mention the rating of the protective device.

 

[securespark]

IF you are fitting 45A switches, there should be fusing down elsewhere.

 

[pedr0]

Thanks for the continued advice. Seems as though my lack of knowledge in these areas may have meant my first post was misleading. I'm not bothered about the cable, because the electrician is supplying that. I'm only concerned about the aesthetic stuff - i.e. the isolators, and possibly the MCB - don't know if he would supply that or not (will have to ask him). I didn't realise what a can of worms this is. I'm only having some sockets moved, changing the white plastic fascias for steel ones and changing an old hob for a newer one with less scratches. In that process I was hoping to change the array of different isolators (1 for extractor, 1 for oven, 1 for hob and 1 for washing machine) for similar looking single switches (with no neons and no additional sockets). I had hoped that the answer was as simple as: "buy two 45A DP switches for the oven and hob and buy two 13A fused switches for the appliances". I'm wrong aren't I?

Wow this has been quite a journey with more hostility and scepticism along the way than I had anticipated.