Induction hob cable

[hard-work]

Hob is 7.4kW, 32A
A John Lewis induction hob which is made by Electrolux/AEG. It doesn't not come with the short flex heat resistant cable from the cable outlet box to the hob - 90C. I see TLC do a 4mm heat resistant cable available by the metre as well. It is rated at 35A. This is pushing it a little, although the cable will only be around 0.5m in length.
https://www.tlc-direct.co.uk/Products/CA4TQ3slash50.html

Does anyone know who supplies 6mm flex heat resistant cable? It seems to be rare stuff.

Or, do most of you fellas fit the 4mm heat resistant cable for the last 0.5m? It is within range.

 

[motorbiking]

Why does it need to be heat resistant? I used standard T&E in 6mm. 40A rating. I have an AEG hob and there would be a lot of plastic that would melt before the cable got hot

The conductor is rated for up to 70 degrees. So I assume the outer could cope with say 50.

 

[hard-work]

The makers specify `heat resistant` cable. Guarantee purposes. The 4mm is within range by 3A but it would be nice to have 6mm all the way.

 

[motorbiking]

http://www.ebay.co.uk/itm/Tough-Rub...-240v-3-Core-Cooker-Hobs-40a-HR-/111876869459

Or
http://www.ebay.co.uk/itm/6MM-BLACK...647555&hash=item339adb1446:g:LE4AAOxyDEVSbsET

 

[hard-work]

Thanks. A good alternative.

 

[motorbiking]

I have no electrical qualifications, but my sparkies signed mine off with 6mm T&E. That's after they installed it without bridging the duel lives, which I had to correct to make the b****y hob work.

 

[JohnW2]

The 4mm is within range by 3A but it would be nice to have 6mm all the way.

For a start, there are undoubtedly generous safety margins built into the current-carrying-capacities of cables we work with, so having a load which is 'only' 3A below the max rating of a cable is no problem at all, even if you are of a 'cautious' frame of mind.

More to the point, when working out the 'effective load' created by a cooking appliance, one is allowed to apply the concept of 'diversity', which recognises that all parts will not simultaneously be 'fully on' for substantial periods of time. If the 7.4kW is quoted at 240V (hence ~32A), one can regard that as an 'after-diversity' current of only 16.6A (at 240V) - so any cable capable of carrying that current would theoretically be acceptable,

Kind Regards, John

 

[hard-work]

Thanks JohnW2. If all hobs are on saying doing the Christmas dinner, it will draw 32A. It is that one or two times per year that is the prime point requiring focus.

Another side point. A full on induction hob at 32A, an oven on at 14A, the kettle is turned on at 10A and then the dishwasher at 10A, then it is 66A. Is the 60A electrical supply too small? Or does diversity cover this and its is all OK? But in that scenario the 60A main fuse will blow.

This is a flat, not on the ground floor so no easy exit through windows, so I am conscious of electrical fires. All circuits will have RCBOs.

 

[hard-work]

For a start, there are undoubtedly generous safety margins built into the current-carrying-capacities of cables we work with, so having a load which is 'only' 3A below the max rating of a cable is no problem at all, even if you are of a 'cautious' frame of mind.

JohnW2, so you would use the heat resistant 4mm flexible cable from TLC to connect up the 32A induction hob?

 

[JohnD]

The hob and the oven elements each draw their full power only for a short time as they come up to temperature from cold. For a hob it might be a minute or two (practically nothing if induction) but an oven might be ten minutes or more. After that, each element will cycle on and off to maintain temperature.

The dishwasher - mine heats for 11 minutes after about 10 mins of cold rinsing at the start, then again for the final hot rinse.

It is possible, but quite difficult, to synchronise them so they are all drawing maximum power for a few minutes, but not longer.

 

[EFLImpudence]

The makers specify `heat resistant` cable. Guarantee purposes. The 4mm is within range by 3A but it would be nice to have 6mm all the way.

Why? Apart from what JohnW2 has just written, there is no requirement to exceed the specifications by a certain percentage.

Thanks JohnW2. If all hobs are on saying doing the Christmas dinner, it will draw 32A. It is that one or two times per year that is the prime point requiring focus.

No it won't. The oft quoted Christmas situation is a fallacy.

Another side point. A full on induction hob at 32A, an oven on at 14A, the kettle is turned on at 10A and then the dishwasher at 10A, then it is 66A. Is the 60A electrical supply too small? Or does diversity cover this and its is all OK? But in that scenario the 60A main fuse will blow.

Yes it's ok. You are worrying unnecessarily.

Have you ever blown a 60A main fuse?

 

[JohnD]

P.s.

A 60A main fuse will carry 60A permanently.

It will not blow at 61A.

It will blow at higher current, the bigger the overload, the quicker it will blow.


edit
misleading mistake removed, see below for corrections

 

[JohnW2]

Thanks JohnW2. If all hobs are on saying doing the Christmas dinner, it will draw 32A. It is that one or two times per year that is the prime point requiring focus.

This Christmas Dinner argument is essently a myth. Even if you have four hob elements all 'on full', by virtue of their thermostatic control the average current over any appreciable period of time will not me much more tha half of the theoretical 32A 'maximum'.

Another side point. A full on induction hob at 32A, an oven on at 14A, the kettle is turned on at 10A and then the dishwasher at 10A, then it is 66A. Is the 60A electrical supply too small? Or does diversity cover this and its is all OK? But in that scenario the 60A main fuse will blow

As you say, diversity again applies. Over any significant period of time, the hob can be regarded as ~16.6A and the oven as ~11.2A. In any event, you can be reassured that it takes a lot more than 60A to blow a 60A fuse!

Kind Regards, John

 

[JohnW2]

It will blow at higher current, the bigger the overload, the quicker it will blow. At about 45% overload it will blow pretty well instantly.

I suppose it depends upon what you mean by "pretty well instantly", but (graphs not to hand - so guesswork!) I think it would take more than a "100% overload" (i.e. 120A for a 60A fuse to blow it in, say, 10 minutes

Kind Regards, John

 

[JohnW2]

JohnW2, so you would use the heat resistant 4mm flexible cable from TLC to connect up the 32A induction hob?

Yes, I would be happy to use that.

For what it's worth, I personally don't like using twin & earth to connect cooking appliances.

Kind Regards, John