Cooker and hob...1 feed or 2?

[EFLImpudence]

bsr:

Induction hobs are advertised as more efficient than ordinary hobs, therefore they must use less electricity overall.

It is true that this might not affect initial current but it can hardly be more than conventional hobs.


The diversity calculations have been used for decades with no problem.


There have been a few posters lately saying, in effect, "Yeah that might be so and within the regulations but I just don't like it" - it makes no difference whether you like it or not.

 

[JohnW2]

bsr: ... Induction hobs are advertised as more efficient than ordinary hobs, therefore they must use less electricity overall. .... It is true that this might not affect initial current but it can hardly be more than conventional hobs.

Yes, as you will have seen, I effectively questioned that. If induction rings required a greater amount of initial continuous energy use when switched on from cold than do conventional rings, it's hard to see in what sense they could be regarded as 'more efficient'

The diversity calculations have been used for decades with no problem.

That is true but, to be fair, it's not impossible that the calculations would be less appropriate for some 'new technology' - but, as above, I would expect that to be the case (in a 'worrying direction') only if the 'new technology' were less efficient than the old one.

There have been a few posters lately saying, in effect, "Yeah that might be so and within the regulations but I just don't like it" - it makes no difference whether you like it or not.

It certainly makes no difference in terms of compliance with the regulations, although it becomes a bit more complicated if (as sometimes is the case) the regulations 'do not make sense' (at least, to us)!

Kind Regards, John

 

[EFLImpudence]

That is true but, to be fair, it's not impossible that the calculations would be less appropriate for some 'new technology' - but, as above, I would expect that to be the case (in a 'worrying direction') only if the 'new technology' were less efficient than the old one.

It would also mean that the Wattage ratings were more than stated.

It certainly makes no difference in terms of compliance with the regulations, although it becomes a bit more complicated if (as sometimes is the case) the regulations 'do not make sense' (at least, to us)!

Ah yes, but what I had in mind, and the things about which it was said, were standard procedures - like diversity and the classic Winston's socket on light circuits.

 

[JohnW2]

It would also mean that the Wattage ratings were more than stated.

The 'wattage ratings' are just the totted-up totals if everything was drawing its maximum current simultaneously, aren't they? Typical/average energy consumption 'in-service' is a very different matter.

Ah yes, but what I had in mind, and the things about which it was said, were standard procedures - like diversity and the classic Winston's socket on light circuits.

Sure, but those are cases in which the regulation (or 'guidance', in the case of diversity) 'makes sense' to us!

However, for example, as I recently said to winston in relation to the (what we all seem to agree is) nonsense of Table 52.3, if we want to comply with the regulations then we simply have to 'live with them', as they are, even if we think that they make no sense - and nothing is gained by repeatedly moaning about them (to anyone other than JPEL/64).

Kind Regards, John

 

[EFLImpudence]

The 'wattage ratings' are just the totted-up totals if everything was drawing its maximum current simultaneously, aren't they?

Well, yes, but a 2kW induction hob cannot draw more at switch-on than a 2kW conventional ring - otherwise it would be more than 2kW, wouldn't it?

 

[JohnW2]

Well, yes, but a 2kW induction hob cannot draw more at switch-on than a 2kW conventional ring - otherwise it would be more than 2kW, wouldn't it?

Yes, of course, but the OP says that his induction hob is "11.7 kW". Assuming it has 4 'rings', that is just under 3 kW per 'ring', which I think is more than the average conventional one, isn't it? Edit: it was actually 7.2 kW (hence 1.8 kW per ruing for 4 rings), not 11.7 kW - so please see subsequent post for consequences of correcting this. My apologies!

However, this again begs the question about 'efficiency'. If the induction hob is 'more efficient', why does it require higher-powered rings?

Kind Regards, John

 

[EFLImpudence]

Yes, of course, but the OP says that his induction hob is "11.7 kW". Assuming it has 4 'rings', that is just under 3 kW per 'ring', which I think is more than the average conventional one, isn't it?

Oh, I see what you mean.
So, yes, but it is not more than an 11.7kW conventional one.
Whatever it is, it is still subject to the same diversity calculations.

However, this again begs the question about 'efficiency'. If the induction hob is 'more efficient', why does it require higher-powered rings?

I don't know.

 

[EFLImpudence]

Hi, I'm looking to get a new cooker (4.4kw) and induction hob (7.2kw) installed.

 

[JohnW2]

Hi, I'm looking to get a new cooker (4.4kw) and induction hob (7.2kw) installed.

Whoops

Thanks for noticing that! I'm not sure where my 11.7 kW came from. I was presumably of thinking of the total of the two appliances (11.6 kW), but didn't even quite get that right! See my other responses regarding implications of this error!

Kind \regards, John

 

[JohnW2]

Oh, I see what you mean. So, yes, but it is not more than an 11.7kW conventional one.
Whatever it is, it is still subject to the same diversity calculations.

As per my error which you pointed out, it should have been 7.2 kW (i.e. 1.8 kW per ring for 4 rings), which may not be much different from a conventional one.

However, correcting that probably makes things a bit 'worse'. If the induction hob has similar power rings to conventional ones, if it used more 'initial energy' (hence perhaps requiring a different diversity calculation), that could presumably only be because the induction hob was less 'efficient' than the conventional one, couldn't it?

Kind Regards, John

 

[EFLImpudence]

As per my error which you pointed out, it should have been 7.2 kW (i.e. 1.8 kW per ring for 4 rings), which may not be much different from a conventional one.

Ok.

However, correcting that probably makes things a bit 'worse'. If the induction hob has similar power rings to conventional ones, if it used more 'initial energy' (hence perhaps requiring a different diversity calculation),

That is my point. How can it use more initial energy if it is the same Wattage?

that could presumably only be because the induction hob was less 'efficient' than the conventional one, couldn't it?

I don't understand that. They are said to be more efficient.
If it doesn't/can't use more power than its rating, it must depend on the time taken or more precise heating method.

Presumably, more efficient means it takes less time or less power to heat the pan/food to the required temperature rather than wasting energy heating the lump of metal of a conventional hob.

 

[JohnW2]

That is my point. How can it use more initial energy if it is the same Wattage?

'Wattage' is power, and energy is energy (power times time). If the suggestions that conventional diversity calculations may not be appropriate for an induction hob are correct, then, if the rings are of similar power to conventional ones, the only possibly reason (for conventional calculations being inappropriate) would be if the induction rings had to be powered for longer periods of time (for a longer proportion of clock time) to achieve the same ('cooking') result - which to my mind (and the minds of those who charge for electricity according to energy usage) would mean 'less efficient'.

I don't understand that. They are said to be more efficient.

As above, I don't understand it, either. If they were even 'as efficient', let alone 'more efficient', then conventional diversity calcs should still be applicable, shouldn't they?

Kind Regards, John

 

[EFLImpudence]

'Wattage' is power, and energy is energy (power times time). If the suggestions that conventional diversity calculations may not be appropriate for an induction hob are correct, then, if the rings are of similar power to conventional ones, the only possibly reason (for conventional calculations being inappropriate) would be if the induction rings had to be powered for longer periods of time (for a longer proportion of clock time) to achieve the same ('cooking') result - which to my mind (and the minds of those who charge for electricity according to energy usage) would mean 'less efficient'.

Not sure what you are arguing about.

Are you agreeing with me but pointing out that if I were wrong things would not be as I have stated?

As above, I don't understand it, either. If they were even 'as efficient', let alone 'more efficient', then conventional diversity calcs should still be applicable, shouldn't they?

Yes. They are.

It is obvious.

 

[JohnW2]

Not sure what you are arguing about. Are you agreeing with me but pointing out that if I were wrong things would not be as I have stated?

As you say, I think we are agreed. I replied "'Wattage' is power, and energy is energy (power times time) .... etc.", since I was a bit confused by your having written ...

How can it use more initial energy if it is the same Wattage?

I was trying to indicate (perhaps not clearly enough) that I didn't understand what you meant by "initial energy" - since 'energy' (as opposed to 'power') is measured over a period of time, and therefore can't really be 'initial'.

However, maybe my confusion resulted from the fact that I was taking your words too literally - and, as I said, I think we agree.

To summarise my position .... if the induction hob rings are of similar power to conventional ones, and if they are 'at least as efficient as' (or 'more efficient than') conventional rings, than the traditional/conventional diversity calcs must be 'at least as applicable'. Only if the induction hob were less efficient than a convention one might that not be the case.

Kind Regards, John

 

[EFLImpudence]

Ah, fair enough.

However, you did say it first:

However, correcting that probably makes things a bit 'worse'. If the induction hob has similar power rings to conventional ones, if it used more 'initial energy' (hence perhaps requiring a different diversity calculation), that could presumably only be because the induction hob was less 'efficient' than the conventional one, couldn't it?

To which I replied:

That is my point. How can it use more initial energy if it is the same Wattage?