Connecting new induction hob.

[Michael Chare]

I am installing a new 4 ring Bosch induction hob to replace a Neff ceramic hob where one of the rings had failed. I was very pleased to find that it fits in the same size hole in the work top. (I had checked to ensure that there would be no large gap.)

I did not look at the electrical specification very closely before I made the purchase, but the manual says that the rings are 2500, 2500,

1800 and 3700 watts when boost function is used, so I was surprised when I found at label saying that the maximum current is 20 amps. Presumably the electronics makes sure that the rings are used in turn to conform to this limit.

The previous hob was connect by a grey flat twin and earth that goes to the cooker switch. The new hob has its own round cable. Ideally, I would like to connect the cables together using a junction box which I could mount on the wall and which has a support for the cooker cable. Can anyone suggest a suitable product?

(Disconnecting the grey cable from the cooker switch might require taking more of the kitchen apart than I would like as the cable runs behind some tiles.)

Needless to say two of the pans that we have that I hoped might work, actually don't work!

[Tim Streater]

Make sure the hob is actually configured to use 20A. Ours (Neff) came with the default max power level of 13A, and there was a badly documented sequence we went through to up it to 20A.

[Tim Watts]

Yes - that is indeed what happens.

2 things:

Cookers have a diversity factor applied - that means the short term

*average* total load is not assumed to be the sum of all the elements. It might peak above 20A with a dumb hob, but cables and fuses/breakers are quite happy with short term overloads. Damage occurs when cables and devices overheat, and that will not happen for 10 minutes of significant overload. Indeed, a Type B breaker (the most common) has a tripping characteristic designed to accommodate this.

Even if you jack all rings to full power, within a few minutes things are boiling and the full power of the ring is no longer required.

The other factor, and the one that probably applies here: this is a smart hob and the electronics can and probably will regulate the overall load. Some are even programmable so that they will run off lower powered circuits, right down to a 13A plug in some cases of twin hobs I've seen.

You can in general wire these hobs up to either a 20A or 32A (more usual) hob/cooker circuit. And for a 20A hob, no reason it cannot share a common 32A/40A single cooker circuit with an oven. Again, ovens heat up then start duty cycling on the thermostat fairly quickly.

Cooker flex outlet is the usual method:

Can be surface mounted if required (and there is space)

[Michael Chare]

I think this one was the same. When I saw the 20 amps on a label, I started to read the manual. Took a couple of goes to set the 20 amps limit.

[Michael Chare]

Thanks.

[Graham.]

If I can tag on my own question here gents,

Is this correct? The manual for the budget double oven I have installed says I need a

*fused* isolator switch. They couldn't be talking about a BS1362 fuse for a double oven, nearly 5.5kW, is the stipulation just bollocks?

[John Rumm]

Which coincidentally if you do the sum for diversity on a cooker - Peak load of 45A, so take the first 10A then add 30% of the remainder, and it neatly gives you about 20A ;-)

[Tim Watts]

They mean a fused circuit.

You won't find a fused isolator above 13A unless you go to some old style industrial switchgear.

[Brian Gaff]

But don;t accidentally leave a screwdriver on the hob when you are testing it.... Brian