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!