Hob and Oven wiring help?

[jAYISME]

Hi guys
Long time lurking but first time posting!. Thought i'd sign up.

So i've currently got a freestanding cooker which is fed off a cooker switch above the worktop. Its hard wired in. I am removing it and getting new worktops, a new hob (got that) and a single oven (need to get that).

My old cooker was hard wired in, but next to that theres a regular 3 pin plug socket which is on the cooker MCB as well. Its rated at 32a and 6mm cabling.

My new hob is 7.2kw, 6500w, 28.1a. It of course needs to be hard wired in where the existing cooker is. Which is fine.

The question i have is, when i get a new oven. Say it be 4kw, can i hard wire it into the same socket as the hob?. I regularly use all 4 rings and the oven at one go if that makes any difference?. Also, the same question if i was to get a 4kw 13a plugged oven, can i plug that into the socket on the same circuit and again be able to safely use all 4 rings on the hob and the oven at once?.

On another thread i noticed that someone advised to get a fused unswitched spur for the oven.

Advice please?.

 

[ericmark]

4 kW is well over 13A so no can't plug it in, but you can get cooker connection units so both can be connected to the 32A supply.

 

[EFLImpudence]

The question i have is, when i get a new oven. Say it be 4kw, can i hard wire it into the same socket as the hob?... can i plug that into the socket on the same circuit and again be able to safely use all 4 rings on the hob and the oven at once?.

You can hard-wire it to the same place as the hob - where the cooker is now - but it won't be with a plug.

 

[jAYISME]

I know 3kw and below ovens come with plugs.

All the ones im looking at require hard wiring. Apart from a Bosch oven which had a kettle lead.

I guess i didn't make it clear with my question.

I just wanted to know if i could hard wire both to the same 32a socket and use both full blast without a problem?. IF the oven i opt for has a plug on it, then could i do exactly the same ie.. Hob hard wired and oven plugged to the same cooker switch/mcb.

I read up you can do this if under 15kw. Not sure how true that is.

 

[EFLImpudence]

I just wanted to know if i could hard wire both to the same 32a socket and use both full blast without a problem?.

Yes you can hard wire them to the same place - the place where the cooker is wired - but it won't be a socket and plug.

I read up you can do this if under 15kw. Not sure how true that is.

It is true.

 

[jAYISME]

Yes you can hard wire them to the same place - the place where the cooker is wired - but it won't be a socket and plug.


It is true.

Thanks.

One other thing, my Hob is 28.1a and the oven im currently looking to buy is 16a. Total 44.1a. Sorry to confirm again, but that is ok on a 32a circuit? Correct?.

Sorry for being a n00b!

 

[EFLImpudence]

Yes, that's 10kW.

Even though you may turn everything on at the same time (actually one after the other) they will all cycle on and off with their thermostats so not use that amount overall.

 

[jAYISME]

Yes, that's 10kW.

Even though you may turn everything on at the same time (actually one after the other) they will all cycle on and off with their thermostats so not use that amount overall.

Good point, thanks again.

 

[jAYISME]

SOrry to bug you all again.

I've found another single oven i may purchase. But it comes with a plug. So if i purchase this, i need to remove the plug and hard wire it into the outlet with the hob right?.

 

[ban-all-sheds]

4 kW is well over 13A so no can't plug it in, but you can get cooker connection units so both can be connected to the 32A supply.

OOI, why are we quite happy with using diversity to calculate Ib when considering the In of the device in the CU, but not the device in the plug?

 

[ericmark]

OOI, why are we quite happy with using diversity to calculate Ib when considering the In of the device in the CU, but not the device in the plug?

You know jolly well why. With the British plug system the supply is to many plugs, and we use cable which could be overloaded, although using a plug and socket may be OK with some circuits, not with all. My dads house had a 15A socket connected to a 15 amp fuse for the immersion heater the plug and socket was to allow a plumber to remove and refit an immersion heater without involving an electrician. It was still a dedicated supply.

You could have similar with an oven, still a dedicated supply, the plug and socket is just for ease of maintenance, that's OK, but without working out the current draw through each leg of a ring, it is advised you don't draw over 2 kW and clearly 4 kW is well over the top.

With 4 area hot plate one may consider all 4 will not run together, but with a two element oven then both may well be on together, I know with my stand alone oven using some of the 12 options as to where heat comes from it can draw 20 amps for just the oven. And that 20 amp will be there at start up for around 20 minutes before the simmer stats start the mark/space regulation patten.

In the consumer unit we still have an incoming fuse, OK DNO fuse but still there, also there may be 12 MCB's and if you add 4 x 6 + 2 x 16 + 4 x 32 etc it may = 184 amp but if the lights only take 2 amp even if the MCB is rated 6 amp then we only add it up as 2 amp, so not the same as adding three 2 kW elements together as they will take 6 kW (26A).

 

[ban-all-sheds]

You know jolly well why.

No I don't.

With the British plug system the supply is to many plugs, and we use cable which could be overloaded, although using a plug and socket may be OK with some circuits, not with all.

Fused plugs do nothing to prevent a circuit cable being overloaded.

You could have similar with an oven, still a dedicated supply, the plug and socket is just for ease of maintenance, that's OK, but without working out the current draw through each leg of a ring, it is advised you don't draw over 2 kW and clearly 4 kW is well over the top.

But a 4kW (at 230V) oven is a 12.2A load.

so not the same as adding three 2 kW elements together as they will take 6 kW (26A).

A cooking appliance with three 2kW elements is considered to draw 15A.

 

[ericmark]

4 kW = 4000 Watt and when I went to school watts = volts x amps x power factor correction. So to transpose amps = watts / (volts x power factor correction) and power factor correction can't be above unity so 4000/230 = 17.39130435 amps if power factor is less than unity that goes up not down. So at least 17 amp. This is just simple maths, OK you could have a volt drop which would result in the watts not being 4000, but one really should calculate using the nominal voltage.

 

[ban-all-sheds]

Are you being deliberately obtuse?

A 4kW cooking appliance is considered to draw 12.2A.

You know, as in (17.39130435 -10) x 0.3 + 10.

 

[JohnW2]

OOI, why are we quite happy with using diversity to calculate Ib when considering the In of the device in the CU, but not the device in the plug?

I've often wondered that - it's a good question.

I suspect that the main reason probably is that people are concerned not about the protection (essentially based on average currents) but, rather, about the ability of a BS1363 plug/socket to cope with an 'instantaneous' (i.e. short-term) current which may at times be considerably more than 13A.

Kind Regards, John