New hob - existing wiring

[daveaspy]

ok, I know this has been done a million times but just checking!

My existing electric hob is in real need of replacement so got a new one coming this week. The current hob is 6kW and there is a separate built under oven of 5.1kW. I have a 32A MCB, 6mm old colour cable via a cooker isolator (plus built in 13A socket). There is no cooker outlet but a standard junction box underneath the oven - where it splits into a 6mm cable to the oven and 2.5mm to the current hob (the plate on the bottom of the hob shows it requires 2.5mm cable)

I am replacing the current hob with a 7.35kW induction hob - as far as I can tell this cable setup is still big enough, given the diversity considerations, but would I still be better replacing the 2.5mm? The hob manual does state it should be wired with H05BB-F 70C heat resistant cable (which I believe is flex) - can this be used with the junction box above?

And the junction box itself - is that ok? I understand there is no specific need for a cooker connection unit other than making things neater/easier. If I get around to refitting the whole kitchen then that would probably get done with the rest of the electrics, but at the moment its just the hob so want to do as little as practicable.

 

[AndyPRK]

A dual cooker connection plate on the wall would be the sensible solution.

This would allow the hob flex cable to be safetly terminated with the existing conductors


Some hobs come with flex

 

[AndyPRK]

surface
https://www.ebay.co.uk/itm/Dual-Coo...=111804571122c7feec339c9446408c216fa5e40880d4


metal box sunk in wall

https://www.ebay.co.uk/itm/Click-PR...511288&hash=item288868882c:g:Q7EAAOSwy21dwcyV

 

[daveaspy]

thanks for the links - will have a measure up, but I don't think there is much clearance behind the oven - certainly don't think a surface box would fit, the sunken box in the wall might just.

 

[AndyPRK]

it's usually best to put them in the cuboard next to the oven, directly below the isolator switch.

i.e where the cable comes out the wall

 

[ericmark]

As to power, an induction hob heats the pan direct, so less heat is wasted, so it must use less power to do same job as a halogen hob, each heat area may be able to draw more power on switch on, but it will reach heat faster and start switching on/off with a larger space to mark ratio to the halogen, so in real terms it will use less power on average.

 

[spark13]

2.5mm to a 7.35kw hob am I missing something?
32 a breaker too big for 2.5 twin ???
Have I got this right sorry if misunderstood......

 

[EFLImpudence]

2.5mm to a 7.35kw hob am I missing something

Apparently - how to calculate the design current for cooking appliances.
7350 / 240 = 30.625A
So 20.625 x 0.3 = 6.19 + 10 = 16.19A

32 a breaker too big for 2.5 twin ???

It depends on the load - ring final spurs?

I see you have been a member since 2007.

 

[spark13]

Yeh cheers plus the load for the oven does this not take it over the current carrying capacity of 2.5mm cable if both oven and hob are on at same time ?

 

[EFLImpudence]

I don't think the oven and hob are on the same 2.5mm² cable.

 

[daveaspy]

Yeh cheers plus the load for the oven does this not take it over the current carrying capacity of 2.5mm cable if both oven and hob are on at same time ?

The 6mm cable went into a junction box that split it into a 6mm for the oven and 2.5mm for the hob. I have got some 6mm heat resistant flexible cable (as the hob manual "required") to replace that 2.5mm anyway.