Oven and Hob Cable over current protection

[rryles]

Hi,

Been asked to look at installing an electric hob and electric oven to existing circuit in a rental property this evening. Details are a bit sketchy at the moment, but I do know:

The CU was recently replaced with a dual RCD unit. EIC and Part P certs are available.
The existing circuit is protected by a 32A MCB, and run in 6mm T+E. Length is < 10m.
There is an isolator switch above the worktops, this then goes to a flex outlet unit.
At the moment there is nothing coming from the flex outlet unit.
As far as I know, there is no FCU, although apparently the EIC states that the circuit serves 2 points.

I don't know what the ratings of the appliances are yet, but for now I'm assuming that the hob will be ~6200W, and the oven ~2400W. So, with diversity, they should both be OK on a 32A supply. Obviously I'll check the ratings when I see the appliances. I should also be able to see the manufacturer's instructions this evening.

My concerns are:
1) Will the flex outlet unit be suitable for two cables leaving it?
2) Will the cable from the outlet unit to the oven require fusing down to 13A?

If I do need to fuse down, I guess I can either use an FCU, or a socket and plug?

 

[telectrix]

i would be inclind to wire the hob direct and FCU the oven

 

[pushrod]

Hi,

My concerns are:
1) Will the flex outlet unit be suitable for two cables leaving it?

The only cooker outlets i have handled have been designed for a single flex/cable, and would be too cramped to get two in. I have searched for a double one (as might want one myself) but couldn't find one. However, i do have a recollection of seeing a double version, possibly posted on this forum (?)
Anyone come across a double outlet or have a link to one?
Or even an isolator that has space to supply two outlets?

 

[rryles]

I was afraid you'd say that. I was hoping I could just wire in, without modifying the fixed installation, as that makes it notifiable.

 

[i=p/u]

can you apply diverrsity if appliance allows all cylinders d fly at once.. cooking for 10 ppl

 

[pushrod]

can you apply diverrsity if appliance allows all cylinders d fly at once.. cooking for 10 ppl

but yes. Once ovens/hobs have been on a little while they are not using max power even if they are set on max temp.

 

[i=p/u]

hmmmm , pushrod you amaze me how little i know, can you define a sum for this. how would you work it out??? sorry if your busy

 

[terminator]

The first 10A of the rated current plus 30% of the remainder of the rated current plus 5A if a socket outlet is incorporated in the control unit. (from memory) - check OSG which is not beside me at the moment!

 

[pushrod]

temperature set switch ie thermostat constantly switching it on and off. Once it reaches the set temp it will spend a lot of the time being "off" , particularly a well insulated oven. The elements only come back on to raise the temp a little when it has cooled (to the set temp) and then switch off again.

 

[i=p/u]

if you remember the pg number i will be impressed, aand i will get my book and hve look

 

[i=p/u]

so if i have 30 amp cooker i can clip direct 1.5mm as can take more than 16 amp, which is you first 10amp + 30%

 

[pushrod]

OSG appendix 1, second table(?)

 

[terminator]

Ha ha - I'm at home having my lunch, copied that from old brown osg (red one at work -so may have changed) My memory is not that good

 

[rryles]

so if i have 30 amp cooker i can clip direct 1.5mm as can take more than 16 amp, which is you first 10amp + 30%

Yes, but only if you put it on a 16A breaker.

My original question wasn't really about diversity. It's about having a 10A (without diversity) oven connected to a 32A 6mm supply. Does it need to be fused down, or is overload of the cable unlikely enough that this isn't required?

 

[terminator]

Why don't you connect with 10mm as well - then no worries!

 

[terminator]

Hang on - I'm getting confused here. Just noticed your original post mentions 6mm T&E now you're talking about 10mm?

 

[pushrod]

Yes, but only if you put it on a 16A breaker.

And it would have to be a very short run as you would very quickly run into volt drop problems. In reality no one would do it.

My original question wasn't really about diversity. It's about having a 10A (without diversity) oven connected to a 32A 10mm supply. Does it need to be fused down, or is overload of the cable unlikely enough that this isn't required?

Thought you said 6mm? in OP . The breaker is there to protect cable. If you go down at the outlet to something that can't handle 32A then you would need to put a fuse in.

 

[i=p/u]

any cooker ive connected 1 cable, squeeze them in 1 isolater lol ive lot to learn

 

[pushrod]

any cooker ive connected 1 cable, squeeze them in 1 isolater lol ive lot to learn

Haven't we all

 

[i=p/u]

rryles , sure your not a window cleaner

 

[rryles]

Yes, 6mm. Don't know where 10 came from.

 

[rryles]

rryles , sure your not a window cleaner

Eh? Are you referring to my avatar?

 

[i=p/u]

no, it was personal joke, dont mind me,

 

[rryles]

The breaker is there to protect cable. If you go down at the outlet to something that can't handle 32A then you would need to put a fuse in.

I thought as much, but hoped otherwise. Maybe I'll be lucky and the oven will come with 4mm flex.

Just to check - I can fuse down using an FCU, or a BS1363 plug and socket?

I presume connecting a 2.4KW oven into the kitchen ring would be frowned upon? I seem to recall anything over 2KW should be dedicated circuit. Just want to be clear on all the options.

 

[i=p/u]

but why if it is designed already to take nearly 3kw

 

[pushrod]

I thought as much, but hoped otherwise. Maybe I'll be lucky and the oven will come with 4mm flex.

Just to check - I can fuse down using an FCU, or a BS1363 plug and socket?

I presume connecting a 2.4KW oven into the kitchen ring would be frowned upon? I seem to recall anything over 2KW should be dedicated circuit. Just want to be clear on all the options.

Agree

 

[nick611]

I thought as much, but hoped otherwise. Maybe I'll be lucky and the oven will come with 4mm flex.

Just to check - I can fuse down using an FCU, or a BS1363 plug and socket?

I presume connecting a 2.4KW oven into the kitchen ring would be frowned upon? I seem to recall anything over 2KW should be dedicated circuit. Just want to be clear on all the options.

yes this is what they say. but if you bought a tumble dryer you wouldnt do this, you would just plug it in. however a fixed applience should have an accesable means of isolation