6mm imperial current rating

[JohnD]

View attachment 226162

what year was that "1.5 times rating" published?

 

[JohnW2]

what year was that "1.5 times rating" published?

... from the IEE Wiring Regs. 14th Edition, 1966

Kind Regards, John

 

[AndyPRK]

Lol.

Changed the cooker switch today and found the input cable smaller than the outgoing cable Still imperial.

I also noted wylex (Crabtree and Volex) don’t make 45A Mcbs


I’ll leave things alone

 

[AndyPRK]

Note to self.

New cooker limits total load to 31A

Each cooking element uses approx 10A

Fan in oven uses 2A
Dishwasher uses 8A

 

[ericmark]

My cooker 220 - 240 volt 50 Hz 10466 - 12455 watt and manufacturer recommends a 32 amp fuse. So 51 amp and 32 amp fuse, as in real terms you will not turn all on together.

Wylex fuse box first fuse some times can be over 30/32 amp some had a reinforced first fuse, but whole unit only 60 amp and although you can fit RCD protection as I did here in real terms today it would cost more than a new consumer unit to do, I only did that as at the time consumer units with built in RCD's were not made. I have items in my house which the manufacturer says should be RCD protected, I think most houses will with some item stipulate RCD protection, plus the problems using any plastic water pipes without RCD protection and fitting the earth bonds, the electrical safety council may say the old Wylex box can still be used but in real terms we all know it has reached end of life.

 

[JohnW2]

My cooker 220 - 240 volt 50 Hz 10466 - 12455 watt and manufacturer recommends a 32 amp fuse.

I suppose that (unless 25A 'fuses' {MCBs} are available for one's CU, that is fair enough in terms of the 'standard' (OSG) diversity calculations ...

If the 12,455 W relates to 240A, that works out as an after-diversity current load of about 22.6A (at 240V). If it relates to 230V, then the after-diversity current (at 230V) would be about 21.4A. In either case, those figures are slightly over 20A, so a 20A MCB would not be appropriate (although a 25A one, if available, would be).

Indeed, even 2.5mm² (Method C) cable protected by a 25A MCB would be compliant with regs.

Kind Regards, John

 

[ericmark]

Not sure if current goes up or down with voltage variation, with oven lower the voltage the lower the current, but that may not be true with hob, but that also raises another question, if an induction hob uses less energy to a halogen hob then clearly you done need a supply as big as you would for halogen as clearly cooking same food with less energy used, but the induction can heat food faster, but not for that long, and it has features like auto boil then simmer, so for a short time a induction can use more power, but over half an hour will clearly use less power. So should the same sums be used with halogen and induction?

 

[AndyPRK]

I have a 17th Ed board.

As it happens I fitted an induction cooker, and on full power it uses around 10A per ring (without power boost)

 

[EFLImpudence]

...but not all the time.

 

[JohnW2]

As it happens I fitted an induction cooker, and on full power it uses around 10A per ring (without power boost)

In terms of diversity, the important question is what would be the average current over a period of time (say 30 mins) if all of the rings were 'on full' simultaneously.

I believe that some induction hobs also limit the total (instantaneous) current that can be drawn at any point in time. Does yours?

Kind Regards, John

 

[JohnW2]

Not sure if current goes up or down with voltage variation, with oven lower the voltage the lower the current, but that may not be true with hob ...

I'm old fashioned and tend not to even think about induction hobs - but, in relation to them, you're quite probably correct - i.e. they might well act as 'constant power' loads, hence with a current that increases if voltage reduces. However, for any particular voltage that does not alter the diversity calculation.

Kind Regards, John

 

[AndyPRK]

Yes it does

 

[JohnW2]

Yes it does

What is the ceiling of instantaneous current draw that it allows?

Kind Regards, John

 

[AndyPRK]

As per previous post, 31A.
Oven has priority. And it reduces the hob heating.

 

[JohnW2]

As per previous post, 31A. Oven has priority. And it reduces the hob heating.

Ah, yes, apologies, I'd forgotten you'd mentioned that earlier.

I presume that the 31A figure is chosen so as to keep the maximum current below 32A. However, if one believes in the concept of diversity (which most people seem to with cooking appliances), that's probably not necessary. Diversity exists 'over time' as well as across different parts (e.g. rings/oven) of a cooking appliance, so there's no reason why the instantaneous peak current has to be limited to 32A to run off a 32A circuit.

Don't forget that (without any built-in 'current limiting') standard diversity calcs allow a cooking appliance with a theoretical peak current draw (e.g. initially, if everything were turned on from cold) of about 73A on a 32A circuit.

Kind Regards, John