Shall I ask my sparky to run a 6mm or 10mm cable ?

[tlogic]

Hi,

I am Currently in the process of building an extension and my builders will shortly be getting their electricians to commence the first fix electricals.
I've got an integrated double oven going in and a single oven and I just wanted to know if I should make sure they run either a 6mm or 10mm cable from the CU to both my ovens with a cooker switch?

The double oven is rated at 5.9kw and the fuse rating is 32amp.

The single oven rated at : 3.6kw and the fuse rating is 16amp.

What's more confusing the single oven I have chosen refers to a plug, so is it just plugged into a socket or will it need hardwiring?

link to oven


My qualified electrician will be doing this work for me not me.

Thanks

 

[littlespark]

4mm is adequate for 32A, and 2.5 for 16.

However, that’s very simplistic… you have to take into account length of run and any routing through insulation.

Your spark will be able to advise.

10mm or 6mm would be too much, though.


The plug on the single oven may just be bad translation on the instructions.
Does it physically have a plug fitted?

I wouldn’t think so at 3 and a bit kW

 

[davesparks]

I just wanted to know if I should make sure they run either a 6mm or 10mm cable from the CU to both my ovens with a cooker switch?

Neither, give the electrician the specifications of the appliances and let them calculate the cable size required.

 

[oscar21]

Don't try and feed multiple ovens off the same cable, you will end up with a consumer unit inside one of the cupboards.Much better to run one cable to each appliance whatever the sizes will be.

As for the cables requiring plugs etc I would go off the ratings on the appliance, a 3kW oven on a 13A plug will work technically but it wont be long before either the plug or socket burns out, if it was me I would put one of them on a 16A supply.

As for the labels on the appliance leads, Lamona/Howdens stuff comes with these and the oven flex's have a label on stating "DO NOT FIT A PLUG" good advice except they use the same flex for the gas hobs and that has the same label on it. there are probably loads of those hobs shoved straight into a 32A cooker supply round the country.

 

[Rockingit]

One thing which often (always?!) gets overlooked in these cases is the cost of energy losses in smaller -v- larger diameter cables over time. I vaguely recall that one of Lucien’s last posts on here ran through this from the viewpoint of car charging so I won’t repeat (and I’ll try to find and link) but the basic principle is the native amount of energy lost just in the cable itself which makes it sometimes worth the extra expense of going up a size for a better long term payback for higher load circuits.

 

[pc1966]

I think energy cost consideration made it in to the amendment 2 regs, but would need to check.

Generally speaking the cable cost, though not trivial, is small compared to the whole project and much less than the cost of future replacement if it proves too small for whatever reason. For that reason, and the energy usage cost over time, you might be better to go with a bigger cable than the minimum just in case.

As already covered, there is more to cable selection than just the load current. You have:

• Cable installation "method" which dictates thermal insulation and so current carrying capacity for a given size and temperature tolerance.
• If the cable is outdoors it needs to be UV-proof and/or protected against damage using duct or trunking (or armoured and suitable for some physical stress already)
• The overall length and current has to be considered to keep voltage drop within tolerable limits (and also power loss, above)
• The circuit characteristics and cable choice combined have to be designed for adequate fault and overload protection, this might also demand RCD protection for shock depending on cable type and if hidden and run less than 50mm from a wall surface (back to using SWA maybe...)

 

[pc1966]

Can to OP clarify if this extension is just another room on the side of the building (so multiple cables going through the walls for lights, sockets, etc, as for inside work) or a separate building with a run outside or buried?