7.6kW Induction Hob - need to select cable and fuse size

[kels bels]

Hi everyone

I'm installing a Samsung induction hob - all 4 hobs total 7.6kW

Am I to apply diversity to this to work out the fuse size? I can imagine the 4 hobs being used at full throttle quite regular and don't want to put it on a 32A fuse and it keep tripping if I put it on a 32A fuse - what do you think?.

I was going to go with 10mm cable on a 40A fuse - can 6mm be used on a 40A fuse?

 

[Engineer54]

So what's the fitted flexible cable size from the induction hob, 6mm, ...10mm perhaps ?? haha!!

 

[kels bels]

I'm not sure, it doesn't say in the manual and I can't tell just by looking at it. I'll call the manufacturers.

 

[MDJ]

7.6kw? well allowing for diversity a 10mm2 cable will probably be way overkill unless your calculations you never posted up here say differently.

 

[kels bels]

Well that's the whole point in my question. Why would you apply diversity when it's highly probable that all 4 hobs might be used at the same time on full throttle?

 

[MDJ]

why would they be used on full throttle at the same time for a decent period of time, very unusual IMO

 

[Engineer54]

Well that's the whole point in my question. Why would you apply diversity when it's highly probable that all 4 hobs might be used at the same time on full throttle?

I have an induction hob, of around the same KW rating, and it's supplied by 6mm cable which also supplies my built in oven via a Dual connection unit. The RCBO protection at the CU is 32A...

 

[Geoffsd]

All domestic cookers will be ok on a 32A mcb.

In any case 7.6kW @ 240V (which is what the manufacturer will state) is less than 32A.

Equal to 7.0kW @230V = 30.4A.

 

[kels bels]

Thanks for your advice! Kelly

 

[markc123]

Just to be awkward, and taking on aboard all the above comment's, i would actually probably upgrade.

Yes, 99 times out of 100 every cooker will be more than adequate on a 32A breaker, but if there is the slight possibilty of it ever going over...id upgrade, it'll be just you're luck that the customer does have 4 on full throttle for ages and it trips then she trys to claim for the loss of more food than the house can take let alone the cooker.

As above, 7.6kW is just over 33amps....therefore the smallest possible chance of it overloading albeit VERY unlikley i still personally wouldn't risk it and would rather go overkill.

As above, yes at 230volts it would be below 32amps, and yes the manufactures do state it at 240, but as everyone well knows the supply is never at 230, always between 225 and as high as 250 at times.....

I can see the above points, that it would be overkill to upgrade and can understand why most electricians wouldn't as a 32amp breaker is pretty much more than adequate, but if you're wanting my opinion i would upgrade.

 

[kels bels]

They were exactly my thoughts, and some of the comments left me feeling a little silly to be questioning it - nice to hear I'm not the only one who would rather be safe than sorry!

 

[benji]

just fitted a fagor ind. hob about 8kw when talking to fagor about load was told it has 2 zones lh & rh each zone has a back ring and front ring , the temp adjustment is 0-9 however if if you set the back ring to 9 then turn the front to 9 the back ring will ramp down to 6 and visa versa so you cannot have all 4 rings on full, you can have a lh ring on full and a rh ring on full but the others will be on lower level

 

[gonefishing]

Anyone thought of using an amp meter to check what an induction hob 7.8 kw pulls at 230 v- 245v? and nobody has mentioned how the cable is installed ?

 

[benji]

might be difficult to measure amps as the rings (or elements) seem to pulse when on so getting a true reading when all 4 are on would be a bit hit or miss


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[Geoffsd]

Just to be awkward, and taking on aboard all the above comment's, i would actually probably upgrade.

Then you will be ripping-off your customer.

Yes, 99 times out of 100 every cooker will be more than adequate on a 32A breaker, but if there is the slight possibilty

There isn't.

of it ever going over...id upgrade, it'll be just you're luck that the customer does have 4 on full throttle for ages and it trips then she trys to claim for the loss of more food than the house can take let alone the cooker.

Then you don't undestand how they work.

As above, 7.6kW is just over 33amps...

No it isn't. See my previous post. It is correct.
The 230V values are what you should use for calculations.

therefore the smallest possible chance of it overloading albeit VERY unlikley i still personally wouldn't risk it and would rather go overkill.

There isn't a possibility.
If it complies with the regulations then overkill is just that and needless.

As above, yes at 230volts it would be below 32amps, and yes the manufactures do state it at 240, but as everyone well knows the supply is never at 230, always between 225 and as high as 250 at times.....

Then you don't understand.

I can see the above points, that it would be overkill to upgrade and can understand why most electricians wouldn't as a 32amp breaker is pretty much more than adequate, but if you're wanting my opinion i would upgrade.

An opinion is something to which you are entitled.
However, these are facts and you are wrong.

[/anger]

 

[markc123]

If we're going into basics....7.6 x 4.4 = 33.4

What you should use calculations for and what is reality isn't the same. Thats why the regs are non-stat.

end.

 

[Geoffsd]

If we're going into basics....7.6 x 4.4 = 33.4

What's that got to do with anything? 7600 / 240 = 31.7 & 7000 / 230 = 30.4
If you had even done that correctly you would have 7.6 x 4 = 30.4

What you should use calculations for and what is reality isn't the same. Thats why the regs are non-stat.

In what other circumstances do you dismiss the regulations?

Are the regulations only for circumstances when you don't have a silly idea?

end.

If you want but you're still wrong.

 

[yellowvanman]

Don't forget in certain conditions the 6mm can be protected by a 40A MCB anyway. So put in a 32A and if that trips (very very unlikely) then change it top a 40A if the cable current carrying capacity allows.

 

[Geoffsd]

What's wrong with everyone tonight?

The hob doesn't even come to 32A even if you work it out wrongly.

Nearly every cooker, including much larger, is on 6mm and 32A.

 

[shocking_eg]

What's wrong with everyone tonight?

The hob doesn't even come to 32A even if you work it out wrongly.

Nearly every cooker, including much larger, is on 6mm and 32A.

+1 true