oven wiring

[Fred]

Hi,

My kitchen redecoration continues at a very slow pace! I am about to build the new oven housing. I have removed the oven from its old cupboard and found the wiring was a bit of a bodge. Some 6mm^2 T&E came from the wall into a choc block and into the other side of this another length of T&E ran to the oven.

I was going to ask why it is called choc block, but I wonder if I have just worked it out. Is it because you have a strip of connectors and then snap of three blocks (or however many you want), like you would do with a big bar of chocolate?

Anyway, back to the kitchen, I have tried to tidy things up by replacing the choc blocks with a proper cooker connection unit:

I was a bit surprised at the wiring instructions for this as the wire that enters the top of the box has to connect to the terminals at the bottom and the wire from the bottom has to connect to the terminals at the top. Why is this? I thought that tight bends in cable was a bad idea? Why not top-top and bottom-bottom?

I've also fitted a switch:

I realised after I had fitted it that I have put the "output" on the terminals labeled "mains in". Does this make any difference? I didn't notice the legend on the switch at the time and now they have been cut to length, it would be a hassle to move them. There is not a neon on the switch, so does it make any difference which terminals are "input" and "load"? I wouldn't have thought so but I'm not an expert, so I thought it best to ask here.

Finally, the oven is rated 4.2kW (IIRC). Do I do as was before, and used 6mm^2 T&E to connect to the connection unit or should it be flex? I am thinking that properly it should be flex (like my hob is) but OTOH once installed, it will be rarely moved, so perhaps T&E can be used for convenience?

I see TLC sell some 4mm^2 flex:

would that be best?

I notice that my new hob has five cores: two for the live connection, two for neutral, and one for earth.

TIA

[charles]

also, they used to be brown.

[John Rumm]

Yup, pretty much...

Does it not depend on which way up or down the wall the supply cable is coming?

Can't see it will make any difference, and you won't usually be switching it under load.

It ought to be high temperature flex, however there are many many out there wired in T&E.

This would be better:

Sometimes you find some that can be wired three phase as well as single as well.

[sm_jamieson]

The manual on mine said use 6mm TWE. I suspect most ovens for built-in use are well insulated at the back and the fanned vent is at the front. However I had made sure the connection box was low down and the connection panel on the oven was on the bottom corner, so the cable never went near the hotter parts of the oven. Simon.

[Fred]

I followed the instructions on the sheet enclosed with the fitting and it said the cable coming from the consumer unit that enters at the top, should connect at the bottom and the cable from the oven, entering at the bottom, must connect at the top. Perhaps it is to stop the wires falling out but it did seem odd to me because it involves bending wires, which I thought was a bad thing?

That's true. Would switching under load make a difference? I would think it would arc no matter which terminals the wires were connected to?

Thanks, I was of course forgetting that the hob is 7kW and the oven is 4kW, so the cable for the oven does not need to be as thick as that for the hob. I suppose in theory one could use 2.5mm^2 T&E but I guess 6mm^2 gets used because it is at hand after being sued to run the radial to the oven.

Thanks again.

[John Rumm]

Indeed - I can't see any real electrical reason for there being a difference. There may be mechanical ones for preference one way or another.

You could always give the manufacturers tech support people a ring if you want reassurance.

Yup, its common to wire the circuit as far as the isolator in 6mm^2 T&E from a 32A MCB. Then a number of options are available depending on the connection layout required. Some (smaller / single) ovens for example need a 13A socket, others will required hard wiring.