Diversity and the resilience of circuit protection.

ebee: 
 

Well i looked at the OP`s 94KW and thought “what?”.

I added it (assuming I understood correctly) and got 21.1KW.

I think the age old calculation for cookers holds pretty good in a normal domestic setting and I have no problem with it.

But surely it was designed for up to say 13KW or maybe 15KW ish sort of max load.

A traditional cooker had an oven, a grill, a hob of say 4 rings plus occasional use of a kettle perhaps.

If, in a modern kitchen, this is all taken care of by separate appliances then I see no need to adjust that calculation.

Where the OP states 6 appliances and the enhanced chances of using all together for some time then I think it might be prudent to tweak the calc a little bit.

In fact the sensible spread of arranging to two circuits rather than one might be appropriate.

Anyway back to the calc.

21.1 KW is 87.916A if we take 240 as the voltage considered might have been used as the manufacturer`s advert rather than the so called 230V nominal.

Take 10A leaves 77.916A .

30% of 77.916 A is 23.375A .

Add back on the 10A and we gets 33.375A.

If you want to multiply that by 240/230 then you might feel that 34.826A be more appropriate.

Either way you get to the very high end (or exceed it) of the well tried standard equation and you might decide a better “fix” might be the first 12A and 35% of the remainder be given a thought or some such tweaking.

There are some on here who will have graphs/charts/research to hand who will probably come up with a better solution (or indeed might say the old formula still holds good).

I take DaveZ`s comment about some Electricians not understanding diversity. but add caution, two reasons for it 1/ the cct in question and 2/ modern trends such as higher power electric showers, car chargers to name but two when we are loading a total installation loading might be in order.

It`s the age old chestnut of One house 100 sockets on one 32A circuit is often OK.

If we make it spread around to 2 or 3 circuits then the total load will not increase but however the max permissible load might well do. For one family living in a house this is never a problem but if , for a time, you temporarily have two or three families living in a house (example over a christmas break perhaps) then you might need to consider things a bit more.

I got my tin hat on now , waiting to be shot down ?

Many multi storied houses in multiple occupation originally designed for just one family can nowadays be occupied by many families and also single people, living full time in every room. A good chance of overloading there.

I saw the above in Milton Keynes where three story houses were let out to many tenants all sharing the facilities. No real maintenance or upgrading was carried out on the original electrics to cover the greater use and loading.

Z.

ebee: 
 

Well i looked at the OP`s 94KW and thought “what?”.

I added it (assuming I understood correctly) and got 21.1KW.

I think the age old calculation for cookers holds pretty good in a normal domestic setting and I have no problem with it.

But surely it was designed for up to say 13KW or maybe 15KW ish sort of max load.

A traditional cooker had an oven, a grill, a hob of say 4 rings plus occasional use of a kettle perhaps.

If, in a modern kitchen, this is all taken care of by separate appliances then I see no need to adjust that calculation.

Where the OP states 6 appliances and the enhanced chances of using all together for some time then I think it might be prudent to tweak the calc a little bit.

In fact the sensible spread of arranging to two circuits rather than one might be appropriate.

Anyway back to the calc.

21.1 KW is 87.916A if we take 240 as the voltage considered might have been used as the manufacturer`s advert rather than the so called 230V nominal.

Take 10A leaves 77.916A .

30% of 77.916 A is 23.375A .

Add back on the 10A and we gets 33.375A.

If you want to multiply that by 240/230 then you might feel that 34.826A be more appropriate.

Either way you get to the very high end (or exceed it) of the well tried standard equation and you might decide a better “fix” might be the first 12A and 35% of the remainder be given a thought or some such tweaking.

There are some on here who will have graphs/charts/research to hand who will probably come up with a better solution (or indeed might say the old formula still holds good).

I take DaveZ`s comment about some Electricians not understanding diversity. but add caution, two reasons for it 1/ the cct in question and 2/ modern trends such as higher power electric showers, car chargers to name but two when we are loading a total installation loading might be in order.

It`s the age old chestnut of One house 100 sockets on one 32A circuit is often OK.

If we make it spread around to 2 or 3 circuits then the total load will not increase but however the max permissible load might well do. For one family living in a house this is never a problem but if , for a time, you temporarily have two or three families living in a house (example over a christmas break perhaps) then you might need to consider things a bit more.

I got my tin hat on now , waiting to be shot down ?

Many multi storied houses in multiple occupation originally designed for just one family can nowadays be occupied by many families and also single people, living full time in every room. A good chance of overloading there.

I saw the above in Milton Keynes where three story houses were let out to many tenants all sharing the facilities. No real maintenance or upgrading was carried out on the original electrics to cover the greater use and loading.

Z.