Cooker ratings and kWh / kW, options for 32Amp circuit

[converse]

We are replacing a standalone cooker with an unknown rating, the short cable to the wall is 6mm.

The circuit is fused at 32A which would suggest a max rating of between 7000 and 7680 Watts depending on whether you use 220 and 240V in your calc,

All the ceramic hob cookers are way above this at 10kW or higher, so that is obviously no go, as this is a temporary new cooker before we move house so don't want walls chasing out for new fat cables (fuse box is about as far away from the kitchen as you could imagine, kitchen is fully tiled.

So I assume this limits us to either a dual-fuel gas hob/electric oven (we have a gas connection behind the cooker), or perhaps a old style solid hot plate which is no more than 7kW (which I can't seem to find anywhere, all appear 9kW or higher)?

Currently all the sites I'm reviewing list the oven power as a consumption figure kWh rather than just rating W/kW, is that a direct conversion is a oven which is rated a 1kWh equiv to a rating of 1kW? I presume that with a gas hob, the oven is only going to be a minor current draw and nothing above 3000ish Watts - am I correct in my assumptions?

(edited for typo)

 

[OwainDIYer]

You can use diversity on the assumption that not all the parts of the cooker will be operated at the same time, and even if they are for short periods they will be switching on and off on their own thermostats.

IEE Guidance to 16th Edition Regs states that for households:

10 A + 30% balance + 5 A for socket (if provided)

http://www.tlc-direct.co.uk/Book/6.5.2.htm

However you have to decide whether diversity can be applied; in a large house where it is likely that a lot of entertaining with complex menus will be done it's more likely that the cooker loading will be higher.

The kWh rating depends on how well-insulated the oven is and is the energy used to keep it warm for one hour; in a well-insulated oven the element should be on for the initial heating up and should not be needed much thereafter. The actual rating of the element will probably be several times higher.

For most general domestic purposes a 32A circuit will be fine for an ordinary 4-ring 2-oven cooker.

 

[converse]

You can use diversity on the assumption that not all the parts of the cooker will be operated at the same time, and even if they are for short periods they will be switching on and off on their own thermostats.

IEE Guidance to 16th Edition Regs states that for households:

10 A + 30% balance + 5 A for socket (if provided)

http://www.tlc-direct.co.uk/Book/6.5.2.htm

However you have to decide whether diversity can be applied; in a large house where it is likely that a lot of entertaining with complex menus will be done it's more likely that the cooker loading will be higher.

The kWh rating depends on how well-insulated the oven is and is the energy used to keep it warm for one hour; in a well-insulated oven the element should be on for the initial heating up and should not be needed much thereafter. The actual rating of the element will probably be several times higher.

For most general domestic purposes a 32A circuit will be fine for an ordinary 4-ring 2-oven cooker.

Thank-you so much OwainDIYer v helpful. I did think the likelihood of everything being powered at once remote, but I don't want a wall cable overheating and causing a fire. It's on a modern circuit breaker in a modern fuse box, but only the downstairs socket circuit is RCD protected with a reset, the cooker and other circuits are just modern circuit-breaker fuse types.

So on that assumption would it be safe to go ahead with a 10.7kW ceramic hob/oven? (As even all the solid hotplates versions seem to be still 9kW+ and we loathe hotplates).

By my calcs I know that (the cooker we like, Hotpoint HAE60) has 2 x 1800W rings and 2 x 1200W rings (totalling 6kW) and although not in the spec sheet, the two ovens and grill must make up the remainder 4.7KW (as the oven in total is rated 10.7).

Using the Diversity calc (thanks again, link is excellent), this would give a total of 20.5A + say 5A for the socket [which we never use] giving a total of 25.5A, well under the 32A circuit.

I've also checked the manual download and this suggests "The cooker must be connected to a min. rating of 32A and a minimum contact
clearance of 3mm. The power supply cable should have a conductor size of 6mm2, minimum." This all is exactly what we have currently.

It would be extremely rare we'd be entertaining and using all the elements at once (never would the grill be on in that situ either), as we have a combo microwave we use as a small oven all the time (on a totally separate circuit too!)

Sound OK to go ahead?

 

[ban-all-sheds]

Currently all the sites I'm reviewing list the oven power as a consumption figure kWh rather than just rating W/kW, is that a direct conversion is a oven which is rated a 1kWh equiv to a rating of 1kW?

No - it's a figure for the total amount of energy the oven needs to do some standardised job (used to be heating a brick to a certain temperature and keeping it there for a certain time).

Allows you to compare one oven with another so you can see which will be the cheapest way to heat up your bricks.

Tells you nothing about how much current each draws - as an example of the difference between kW and kWh, a 100W light bulb left burning 24 hours per day will use 30% more energy than a 10 minutes under a 10.8kW shower.

 

[ban-all-sheds]

I did think the likelihood of everything being powered at once remote, but I don't want a wall cable overheating and causing a fire.

As long as the cable size is correct for the MCB rating it can't.

Sound OK to go ahead?

Yup.

 

[converse]

Thank you all so much for your replies - much appreciated Checked everything twice, MCB is correct rating cable is, so the order has been placed.