Because in Europe they have 16A circuits so need two.
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5 core induction hob cable (1.5mm?) to 10mm supplied cooker outlet
- Thread starter BobT007
- Start date
OK ta
You could do that. I imagine that it comes like that so they can supply the same cable with their 1, 2 and 3-phase versions.
7.4KW comes out to something over 30A which would be 2.5mm² at a pinch, preferably 4mm² for just one 3 core flex.
As the appliance comes with a flex, simply use that wired just like this
The purists may state the grey requires blue sleeve/tape and the black requires brown sleeve/tape to identify them.
WHAT?????
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Does it?
It would (although only slightly over 30A (at 230V) if, as is common, the 7.4 kW relates to 240V) BUT only if one ignores diversity.
Yes I've been there too many times to replace heat damaged undersized cables for the overcurrent protection device.
If it was mine I'd use the double 1.5mm² cable as supplied. If that was not supplied I'd use 4mm² even though the assumed current is under 20A
I think you are probably the only person I've ever seen suggesting that application of diversity when determining cable sizes for cooking appliances can cause serious problems (or problems at all)! ... and this applies to 'diversity over time' for a single element of a cooker as well as diversity 'acro elements'.
I've posted the graph below in the past. As I've previously explained, I don't have an electric oven, but I do have a (thermostatically-controlled) 1,700 W fat fryer. As you can see, after initially being 'on' for about 8 minutes, until it gets 'up to temperature', the element is just occasionally 'on' again for 1-2 minutes, to to 'top up' the heat to the required temp as it cools down. I would expect an electric oven (or a hob ring etc.) to behave, conceptually, in much the same way.
Although the peak power drawn was 1,700 W (about 7.4 A at 230V), the average over the first 60 minutes was only about 482 W (about 2.1 A) - i.e. about 28% of the maximum. In other words, during the first hour (from cold) the fryer consumed only about 0.48 kWh ('units') of electricity, as compared with the 1.7 kWh it would have been had the element been 'on' continuously.
I don't dissagree, except I have been in the situation of heat damaged cables which are not adequately protected by the OCPD and as we are constantly being reminded on here the OCPD is only there to protect the cable.
Maybe I am the only person in the country to think this way.
Maybe I am the only person in the country to have experienced the problem.
Maybe I am not and all the others simply say 'it conforms to the regs' and ignore the damage when they encounter the problem.
Regardless of any of those scenarios I will not wire a 7.4KW appliance with a bit of 1.5mm² flex just because it may just be perfectly rated at the diverse current of the appliance.
If I found such appliance running on a 2.5mm² I'll automatically do a feel test to check for distortion such has been my personal experience.
I'll also breakout a previousely posted image: of a cable installed according to the regs
But it seems I'm the only person to be aware of such issues, not diversity in this case but still a cable running on an OCPD significantly larger that its CCC.
Yes, I don't know where I got 17A from, either for each lead or a cockup on the arithmetic front.
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I said it, thats what it works out to with diversity
Back to that 5 core cable, just noticed this circuit diagram in the manual:
Are you really supposed to re-do the separate Lives and Neutrals, and crimp them together as shown, before fixing into the cooker outlet plate !?? Or just put each pair, unjoined just as the 5 core cable was supplied, into the appropriate L and N terminals at the cooker outlet ?
Are you really supposed to re-do the separate Lives and Neutrals, and crimp them together as shown, before fixing into the cooker outlet plate !?? Or just put each pair, unjoined just as the 5 core cable was supplied, into the appropriate L and N terminals at the cooker outlet ?
You don’t need to crimp them.
It’s usually how it’s done when it leaves the factory though. (So maybe why it’s in the manual )
It’s usually how it’s done when it leaves the factory though. (So maybe why it’s in the manual )
That's not what we are talking about. We're talking about a situation in which the OPD is of an appropriate rating to protect the cable, but with the (after diversity) 'design current' (for both cable AND OPD) a lot lower than the theoretical 'maximum load' (absolutely everything 'on'simultaneously) that the appliance could represent.
For example, take a cooking appliance which represented a theoretical total load of 15 kW at 230V - just over 65A. Allowing for diversiity, that would be a current of about 26.6 A, hence fine with 4mm² cable or even (just) 2.5mm² Method C cable. However, the OPD would be a 32A one, hence not quite adequate to protect either 2.5mm² cable - so one would presumably use 4mm² cable (which would be adequately protected)
Probably none of those 'maybe's but, rather, the fact that you are talking about something different from the application of diversty. As above, there is nothing about the concept of diversity which allows (or makes it sensible for) an OPD to be used to 'protect' a cable whose CCC is less than the In of the OPD. As you say, the OPD is there primarily to protect the cable, and therefore must have an In appropriate for protecting the cable concerned.
Fair enough, but you could. Even if the 7.4 kW related to 230V (which t rarely would!) - that's only about 32A - which, after diversity, becomes about 16.6A - so fine with Method C 1.5mm² cable - and that cable,in turn,would be (just) adequately ;protected by a 20A OPD.
What was the CCC of the cable and what was the In of the OPD protecting it?
Since you say it was "according to regs", do I take it that the latter was no greater than the former? If that really was the case (and assuming no /'poor connections' etc.), yet the cable came to harm, you would appear to be questioning the correctness of the tabulated cable CCCs which we all use, all of the time. Are you sure that there were not any 'poor connections' in the equation?
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