Electric oven and ceramic hob......... I know AGAIN

[mattyboy1982]

First of all just want to say thanks for any help in advance!

Now I've got an old cooker radial that starts on a 45amp cooker switch with socket. This is fed on 10mm2 cable that goes back to a 45amp mcb on the consumer unit. This has just been used to power an old gas hob ignition. Now the other half wants the kitchen done and a new built in electric oven and hob. The type she liked is a 6.5kw ceramic hob and a 3.6kw electric oven. My main question is can both these units be powered on this same feed?! Or will I have to pay a sparky to run a new separate feed so they each are powered independently?! If that's the case then think I'll stick with gas! But if not then the way I see it working is like this. Deep breath.....

10mm2 cable to 45amp cooker control unit. Then 6mm2 cable to dual box which will have a cooker outlet plate 1 side for the hob and a single unswitched socket on the other side to plug the oven into. From the cooker outlet plate would then be 4mm2 heat resistant cable to the hob. And 2.5mm2 heat resistant cable from the oven to a 13amp plug which would go into the socket!

Phew now go easy lads. That's my basic understanding and i'm just trying to get an idea of how big a job is ahead for my wallet!!

Cheers.

Matt.

 

[ColJack]

View media item 10929 View media item 10930

you'll have fun with trying to run a 15.6A oven off a 13A fuse..
the oven will need it's own 16A circuit..

electrics in a kitchen is notifiable under Part P... have a look at it in the wiki for more info..

 

[mattyboy1982]

Thanks for the quick reply and those pics r what I was thinking!

On to the oven and we were told in the shop that the oven had to be wired to a plug socket! Maybe I have got the oven kw wrong?! If not I'm guessing running both appliances directly from the same feed is a bad idea?! Even though the 10mm cable can handle both appliances?!

 

[ColJack]

the 10mm can, but what about the 2.5 cable to the oven that's fused at 45A then? that's a no-no..

ideally the hob cable should also be 6mm..

 

[mattyboy1982]

The 2.5mm would be fused at the 13amp plug. Although that looks like a no no! And your right 6mm would be better but it seems non existent in heat resistant form!!! Do you know where to get hold of it?!

 

[mattyboy1982]

Sorry ignore my reply I see what u meant now cuz obviously the 13 amp plug wouldn't be there anymore!! So is there any way around that? Cuz I'm not sure I have any space left in my consumer unit so that would be whole house re wired which is a massive job!!

 

[ColJack]

you could always use that 45A feed as a sub main and feed a small 2 way CU in the kitchen.. that way you can put in a 16A for the oven and a 32A for the hob..

alternatively, get a smaller oven

 

[LiamPope]

Check the manufacturers instructions for the oven. If they say it can be plugged into a 13A socket then it can (I guess maybe they've applied some diversity?). Then you could do as above. If not it might still be acceptable to use the same supply for both replacing the socket on the dual box for another cable outlet, if the oven does not need to be fused down. It will need 6mm cable though in this case (unless you apply diversity yourself and conclude you can change the MCB for a 32A, in which case you can use 4mm cable).

Liam

 

[mattyboy1982]

I've re checked the oven specs and it is 3.4kw and it says can be wired to a plug or wired directly to the main supply! But doesn't say which to do! Could I change the unswitched 13 amp socket for a switched 16amp fcu? Although I don't think that sounds right!!

 

[ColJack]

where are you planning to get this 16A fuse from?

it will be the euro spec.. they have unfused sockets over there and 16A radials..

 

[mattyboy1982]

I'm thinking the 2 way CU option sounds the easiest! Although this whole thing about the oven needing a plug is confusing! Surely the manufacturers should give clearer guidelines!! Any other options for me guys? Apart from a gas oven!!

 

[securespark]

Col: sorry to open up this whole debate again...

Weren't you in favour of using short lengths of smaller-csa cable in situations like this, provided the cable could carry the load demanded by the appliance attached to it?

What about 10mm² cable from the CU to a switch then onto a 60A JB, splitting to each appliance?

 

[LiamPope]

Isn't that essentially the same as going to the dual backbox, or a single backbox with one of those dual appliance outlet thingies?

How come this hob/oven install is any more taxing than the hundreds of other hob/oven threads we get on here? Surely it comes down to the manufacturers instructions (which the OP needs to be more specific about)? I mean, they are the bible when it comes to installing appliances, aren't they - if the MIs tell you to jump off a cliff, then you do (and sue them afterwards), right? If this thing is sold in England and the MIs say you can wire it to a plug, then surely you can wire it into a plug? The worst that can happen is you blow a 13A fuse if it really runs at its max rated power for long enough. If it says it can be hard wired and doesn't specifically say it needs fusing down, and doesn't imply fusing down by saying something like 'provide a 16A supply', then surely you can shove it on a cable outlet with the hob? Or am I missing something? Of course the mini 2-way CU idea is great and removes all doubt, but it may not be necessary.

 

[ColJack]

Col: sorry to open up this whole debate again...

Weren't you in favour of using short lengths of smaller-csa cable in situations like this, provided the cable could carry the load demanded by the appliance attached to it?

What about 10mm² cable from the CU to a switch then onto a 60A JB, splitting to each appliance?

yes I am, but I base that on there being a fuse downstream to protect the smaller cable by disconnecting the load before the cable was overloaded..

so to wire in 2.5mm to a socket from a 10mm 45A cooker circuit is fine because the 13A in the plug would protect the 2.5mm.. however, as he needs a 16A feed for his oven, and it's only the oven stats etc limiting the load, it's possible for a fault on the oven to overload the smaller cabe until the 45A breaker operates..

 

[mattyboy1982]

Ok guys thanks for all your help so far. Ive downloaded the instructions for the oven an dhob we are looking at and here they are word for word!

OVEN:
230v - 50hz. Output rating MAX 3400 W

If the appliance is not connected to the mains with a plug, a multi-pole isolator switch (with at least 3mm contact spacing) must be provided in order to satisfy safety regulations. The power cable H05 RR-F or H05VV-f min 1.5m, 1.5- 2.5mm² must be of sufficient length to be connected to the oven even if the oven stands on the floor in front of its built in cabinet. The oven is earthed by the earth terminal. If the oven is conncted to the mains with a plug this plug must remain acceessible after the oven is installed.

HOB:
230v - 50hz. Maximum connected load power 6.0kw
The hob is to be connected to the mains using a device that allows the appliance to be disconnected from the mains at all poles with a contact opening width of at least 3mm eg automatic line protecting cut out, earth leakage trips or fuse. A type H05SS-F (180°c) cable or one of a higher grade must be used as the mains connecting cable.

Talk about confusing! Where could i get the type H05SS-F cable from?!