Oven Wiring

[imroberts]

Soon to be replacing an electric oven and ceramic hob... getting an electrician in to check over my work and issue a certificate anyway, and want to be sure I've done everything correctly

Quite a few questions I'm afraid...

1. Most cooker switches are 45A.

(a) Am I right in thinking the full rating is only applicable if it is fused with 45A and wired with 10mm cable?
(b) If it is wired with 6mm cable it should be fused at 32A?

2. Assuming 45A fuse and 10mm cable,

(a) I'm fairly safe to use the full 45A if it's just a switch?
(b) I'm assuming under the same assumptions if its a combined switch and 13A socket I can wire a maximum of 32A to the cooker switch?

3. What is the maximum power I can wire up to such a circuit? By my maths the maximum would be 45A x 230V = 10350W... same with a shower circuit... is this correct?

 

[Adam_151]

Soon to be replacing an electric oven and ceramic hob... getting an electrician in to check over my work and issue a certificate anyway, and want to be sure I've done everything correctly

Have you found an electrician prepared to do this?

1. Most cooker switches are 45A.

(a) Am I right in thinking the full rating is only applicable if it is fused with 45A and wired with 10mm cable?
(b) If it is wired with 6mm cable it should be fused at 32A?

Seems right, but arkward way of putting it, the cable must be able to carry a current at least equal to the rating of the protective device for the way in which its installed (a cable bunched with other in loft insulation can carry a lot less than one just clipped up a wall), and the same goes for switchgear; you cant put a 20A switch on a 45A circuit, but no problems with a 45A switch on a 20A circuit as long as the terminals are suitable for the cable sizes involved

2. Assuming 45A fuse and 10mm cable,
(a) I'm fairly safe to use the full 45A if it's just a switch?
(b) I'm assuming under the same assumptions if its a combined switch and 13A socket I can wire a maximum of 32A to the cooker switch?

Never seen it written down anywhere, but I generally beleieve a combined cooker isolator and socket shouldn't be on a circuit rated at greater than 32A (I'm sure the BS document for the device in question would clear it up if you are that bothered) also remember if it has a socket you have to consider how likely it is someone will use it to power the lawnmower etc, and RCD as neccessary!

3. What is the maximum power I can wire up to such a circuit? By my maths the maximum would be 45A x 230V = 10350W... same with a shower circuit... is this correct?

You can apply diversity to cooker circuits, its 10A + 30% of whats left + and extra 5A if there is a socket. It takes into account that you are not always going to have everything on at once, and even if you do, the rings will be comming in and out on the thermostat. You cant apply diversity to a shower because thats run at full power all the time (unless you switch it to half heat summer eco mode), contary to popular belief the dial that controls temperature just restricts water flow though the heat exchanger

 

[luminaire]

1(a) cookers are rated taking diversity into accout, then the size of the MCB is dependent upon the demand.

1(b) tThe size of cable is also dependent on demand, length of cable and how it is routed. I.e. through insulation etc.

Your electrician will be able to work all this out for you.