Cooker Wiring

[imroberts]

At the moment I have the following:

- Above the worktop a cooker switch and socket. This is wired to the fusebox with 6mm cable
- From the cooker switch a hob (rated at 5.2kW) is connected, again with 6mm cable, via a cooker outlet behind the oven
- From the socket an oven (rated at 2kW) connected via a 13A plug

Now from my understanding all of this is perfectly safe, adequate, and within regulations.

My question:

I'm replacing the oven and hob, both rated as above, so can be wired up the same as above.

However, I would rather not have the oven on a mains plug with the cable going through the worktop, as it looks messy. Ideally, I would like a 13A spur running from the cooker switch, to power the oven.

i.e.
Switch
|-----> Hob
|------> 13A fused spur ---> Oven

In practice, however, this would mean on the switched part of the cooker switch, I would need to run 2 6mm cables off, one running direct to the hob and one to the 13A spur...

1. Is it considered acceptable practice to "force" 2 6mm cables into such a switch, or into the cooker outlet behind the oven? If not then fair enough, I understand

2. Theoretically this circuit from the fusebox could be running 5.2kW (hob) + 13A (socket) + 13A (spur) i.e. 48.6A. I know in practice this is never going to happen, but again would it be considered acceptable practice?

3. What would YOU do, given the current wiring configuration?

 

[luminaire]

You could take a spur from your kitchen socket circuit to use for your oven. Or if it is run on a ring include it as part of the ring circuit.
Don't try spurring off the kichen socket.
Leave the hob on the CCU.

 

[Albert]

If the oven is 2kW, you can connect it to the ring via a spur and a single socket/connection unit under the work top, you do not need 6mmsq for this oven.

IMO the best way to do it is to connect the oven on a separate circuit with 6mmsq cable and a cooker control unit, the reason is that if in the future you would like to change the oven you will not be limited because of the cable size, unfortunately this is not always possible.

I do not know where did you get the 48.6A from, in total without taking diversity in cosideration 5.2kW+2kW=7.2kW divide by 230V = 31.3A.

Yes you can supply both from the same control unit, which will allow you to connect 2x 6mmsq wires.
these will mean that you will have to pull from the control unit one cable to the cooker and one to the hob, I wouldsuggest to use connection boxes to termenate the appliences.

 

[imroberts]

You could take a spur from your kitchen socket circuit to use for your oven. Or if it is run on a ring include it as part of the ring circuit.
Don't try spurring off the kichen socket.
Leave the hob on the CCU.

I'd thought of taking a spur off the ring main, but there is no wiring I can get to easily near to the oven. Nearest is the extractor fan but that is already a spur off the ring main so I don't really want to use that

 

[imroberts]

If the oven is 2kW, you can connect it to the ring via a spur and a single socket/connection unit under the work top, you do not need 6mmsq for this oven.

Reason I said I would use 6mm cable for the oven is because the wiring upto the 13A fused spur is only protected by the fusebox, and the circuit is possibly rated higher than is suitable for 2.5mm cable. Or is this not relevant if the 2.5mm cable is running to a 13A fuse?

Likewise with the above, at the moment the hob circuit is running on 6mm cable from fusebox to switch, 6mm from switch to cable outlet, then 6mm to the hob. My new hob states 2.5mm (or higher) cable should be used. Again is it safe to replace the cabling from the outlet to the hob with 2.5mm, or should I keep this connected with 6mm for the above reasons?

 

[Steve]

Keep the cables at 6mm where you can, if they will fit.

For the oven, I'd fit a socket next to the cooker outlet, and wire it into the outlet. This way the whole lot can be isolated from the cooker switch.

 

[Albert]

Firstly there is nothing wrong with using a bigger cable, it is not always convenient. In this case it seems that 6mmsq will be the most reasonable.

Reason I said I would use 6mm cable for the oven is because the wiring upto the 13A fused spur is only protected by the fusebox, and the circuit is possibly rated higher than is suitable for 2.5mm cable. Or is this not relevant if the 2.5mm cable is running to a 13A fuse?

The protecting fuse/MCB is before the cable, nearer to the fuse box.
If the fuse in the box is not more than 20A you can use 2.5mmsq cable.
The main idea is that the cable should be able to carry the load (appliance) and the fuse to protect the cable, this is done by making sure that the carrying capacity of the cable is suitable for the load and the fuse is the same value or smaller.

 

[imroberts]

Keep the cables at 6mm where you can, if they will fit.

For the oven, I'd fit a socket next to the cooker outlet, and wire it into the outlet. This way the whole lot can be isolated from the cooker switch.

Are you proposing the following then?

- Single 6mm cable from fusebox to cooker switch
- Single 6mm cable from cooker switch to outlet
- Two 6mm cables out of outlet, 1 to hob and 1 to 13A fused spur

 

[imroberts]

Firstly there is nothing wrong with using a bigger cable, it is not always convenient. In this case it seems that 6mmsq will be the most reasonable.

Reason I said I would use 6mm cable for the oven is because the wiring upto the 13A fused spur is only protected by the fusebox, and the circuit is possibly rated higher than is suitable for 2.5mm cable. Or is this not relevant if the 2.5mm cable is running to a 13A fuse?

The protecting fuse/MCB is before the cable, nearer to the fuse box.
If the fuse in the box is not more than 20A you can use 2.5mmsq cable.
The main idea is that the cable should be able to carry the load (appliance) and the fuse to protect the cable, this is done by making sure that the carrying capacity of the cable is suitable for the load and the fuse is the same value or smaller.

The fuse is more than 20A, indeed there is potential for the hob alone to take more than this.

Given this fact, would you recommend NOT using 2.5mm cable, even for the 13A spur?

 

[Steve]

Keep the cables at 6mm where you can, if they will fit.

For the oven, I'd fit a socket next to the cooker outlet, and wire it into the outlet. This way the whole lot can be isolated from the cooker switch.

Are you proposing the following then?

- Single 6mm cable from fusebox to cooker switch
- Single 6mm cable from cooker switch to outlet
- Two 6mm cables out of outlet, 1 to hob and 1 to 13A fused spur

Yes. However forget the fused spur. Use a single unswitched socket outlet. There will be a 13 amp fuse in the plug top. This will make servicing easier on the oven.

 

[imroberts]

Keep the cables at 6mm where you can, if they will fit.

For the oven, I'd fit a socket next to the cooker outlet, and wire it into the outlet. This way the whole lot can be isolated from the cooker switch.

Are you proposing the following then?

- Single 6mm cable from fusebox to cooker switch
- Single 6mm cable from cooker switch to outlet
- Two 6mm cables out of outlet, 1 to hob and 1 to 13A fused spur

Yes. However forget the fused spur. Use a single unswitched socket outlet. There will be a 13 amp fuse in the plug top. This will make servicing easier on the oven.

Sounds a good suggestion. Am I safe using 2.5mm for the two cables out of the outlet if two 6mm cables will not fit? Or should I find another solution if this is the case?

Also, the potential maximum current on the cooker circuit will be:

- 5.2kW for the hob (I know in reality it will never hit this)
- 2kW for the oven
- 3kW for a kettle plugged into the socket on the cooker switch

Is the circuit adequate for this?

 

[Steve]

If 6mm wont fit, use 4mm. 2.5 isnt enough where it is only protected by a 32 amp device.

 

[davelx]

If 6mm wont fit, use 4mm. 2.5 isnt enough where it is only protected by a 32 amp device.

It is if it's a single unfused spur off a ring final though!

Also consider 473-01-02 and 473-02-02 which I think would apply in the case of a single socket outlet adacent to the cooker connection plate and wired to it with a very short run of 2.5mm.

 

[imroberts]

If 6mm wont fit, use 4mm. 2.5 isnt enough where it is only protected by a 32 amp device.

It is if it's a single unfused spur off a ring final though!

Also consider 473-01-02 and 473-02-02 which I think would apply in the case of a single socket outlet adacent to the cooker connection plate and wired to it with a very short run of 2.5mm.

The hob, although rated at 5.2kW, recommends using 2.5mm cable (or greater).

I understand from your comment that 2.5mm IS safe for the 13A socket, despite this cable being protected only by a 32 amp device?

Would this logic also apply to the hob or would I need to use 4mm or 6mm?

 

[davelx]

The two reg I've cited allow you to reduce the current capacity of a circuit without inserting a lower rated protective device at the point of reduction, subject to certain conditions. Specifically in this case:

1) the distance between point of reduction and capacity and protective device (ie 13A fused plug) must be <3m

2) it is installed such as to minimise risk of fault current (ie keep it short, run directly between CCU and socket, buried in plaster or in steel conduit)

3) it is installed so as to minimise risk of fire or danger to persons - again, keep it short, run directly between CCU and socket, buried in plaster (or in steel conduit)

If you comply with the above, IMO 2.5 to the 13A skt. would be fine. Others may, of course, beg to differ. Aren't the regs fun