Induction hob-cable size

[jstrong]

Morning

I'm thinking of buying an induction hob rated at 10.8Kw/50 amps.

I have a 6mm cable in place already on a 40amp breaker although I'm thinking the 40 amp should be swapped for a 32amp?

I've also got the oven on 6mm cable with a 40amp breaker should this too be 32amp? Both cable runs are short (max 7M).

Any thoughts appreciated.

 

[Taylortwocities]

OK. Are there already two circuits installed both 6mm² with 40amp breakers?

But next
Let's do a little ohms law here.

Ohms law says Power (watts) = Volts x Current

So

Current = Power/volts

OK so far?

so 10800watts/230volts makes the maximum current = 47amps

Would you like to explain
why on earth you would put in a 32amp breaker?
Or what would happen if you kept the existing 40amp breaker?
Or what would happen if you put in a 50amp breaker on the 6mm² cable?

Do NOT attempt any of the above.

 

[jstrong]

Both circuits are installed with 40amp breakers.

Just need to isolate the CU and change the CB's to the correct size if need be.

For your info one cable only supply's the oven and the other only supply's the hob.

 

[Taylortwocities]

Just need to isolate the CU and change the CB's to the correct size if need be.

The breaker in the consumer unit is there to protect the (6mm²) cable.
You can make it smaller if you must (but why?).

Your problem is that the hob has a max power requirement of 47amps.
Most induction hobs have a boost feature so you must size the circuit for a 47amp load.

So, the circuit cable size is too small. A larger cable needs to be installed with the appropriate breaker.

 

[jstrong]

Thanks for your reply.

In short if I were to buy this induction hob it must have a 10mm cable with 50amp breaker?

 

[ericmark]

It depends what the manufacturer asks for. My stand alone induction hob and oven needs a 32A supply even though the ratings of the hob alone is well above that.

Most British manufactures know that most British houses have a 32A supply for the cookers so make units to run on that supply.

What does it say you need in the book?

It's not a simple add up the watts and divide by 230 as manufactures do things to stop you overloading the circuit.

If you use a non British item it may not have same protection but I think most will. There are some German hobs that can be configured for different size supplies looked at one not induction but could even run on a 13A supply. Even though it had 4 rings. It could also be configured for 16A and 32A.

So there is no way to work out what it needs other than reading the manufacturers instructions.

 

[mfarrow]

I wouldn't be so worried - I've had a 7.2kW induction hob and single oven running off a 10mm cable protected by a 15A Type 2 MCB for 6 months now to no ill effect in terms of tripping.

The point load, i.e. the boost function, isn't of significant enough duration to cause nuisance trips.

I'd therefore plump for 32A breakers. They'll provide better fault protection.

 

[sparkybird]

Assuming that 50A is the total rating of the hob - I would have thought that you can apply diversity rule to this - which is first 10A plus 30% of the balance - this assumes you won't be using all four hobs at full power at the same time - as generally you won't.

So 50A actually becomes
10 A + 13.3 A = @ 24 A rounded up

So you cable will be fine but best to put it on a 32A breaker, to be on the safe side

SB

 

[phatboy]

The breaker in the consumer unit is there to protect the (6mm²) cable.
You can make it smaller if you must (but why?).

Your problem is that the hob has a max power requirement of 47amps.
Most induction hobs have a boost feature so you must size the circuit for a 47amp load.

So, the circuit cable size is too small. A larger cable needs to be installed with the appropriate breaker.

What are you on about - you seem to have no idea and are giving out terrible advice.

A 32amp or 40amp breaker would be FINE. Have you heard of diversity?!

If I turned on EVERY electrical item in my house I would blow the main fuse - should I ask my supplier to upgrade this so I can turn on every single electrical item in the house?!

 

[EFLImpudence]

10800 / 240 = 45A - coincidence ?

6mm² max.C.C.C. = 47A - coincidence ?

but of course, diversity works.

 

[jstrong]

Many thanks for all the replies.

I've decided to go for a Neff T44T80N1 which I understand will draw 7.2Kw maximum.

I would therefore imagine that my 6mm cable (7 metres long) connected to a 40 amp circuit breaker would suffice?

Can anyone recommend the correct way of connecting the 6mm cable to the cable from the hob.

Many thanks again

 

[ericmark]

Not sure how the Point & Twist control works. I hope it will allow instant reduction in heat? I had a problem with touch controls as it needed multi-touches and a amount of time for the touch to register. So when a pan was about to boil over it took too long to turn down the heat only option was to lift pan off the heat. My Belling has a knob for each heat area which is great one can turn knob as quickly as one can lift pan so no need to lift pan to switch off heat.

The Point & Twist control seems to be a combination device hopefully it redresses the problems associated with torch controls.

 

[jstrong]

eric

I've done a fair amount of research on Neff Induction hobs and others and read lots of reviews and the point & twist seems very popular.

Perhaps Neff came up with the point & twist design for the very reason that the touch controls were too fiddly and time consuming when you need to act quickly to stop a pan boiling over! I hope I've made the right choice, time will tell!

Thanks for your reply and input.

 

[Taylortwocities]

Can anyone recommend the correct way of connecting the 6mm cable to the cable from the hob.

The 6mm² cable from the consumer unit must terminate in a double pole isolation switch situated no more than 2 metres from the hob. You'll need a switch of at least 45amps.

If this is an existing circuit then there should already be a switch in the circuit.

From the load side of the switch there should be a length of 6mm² cable to a cooker connection point. Like THIS

The cable from the hob connects to this plate.

 

[jstrong]

TTC

Thanks very much for your reply, very helpful.

If the DP isolation switch is within reach of the cable from the new hob is it ok to wire it straight in to the DP unit and skip the cooker outlet plate?