Cooker circuit question

The kitchen in my newly-(almost) completed extension has a (professionally installed) 45A radial cooker circuit which currently terminates in a junction box. I don't intend to install a cooker but I do need to power an electric domino hob and a fridge-freezer close to where the box is situated. Is there any reason why I can't take two 2.5mm cables from the junction box via two switches to two sockets, to do so?

Many thanks.

Reply to
Bert Coules
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If the junction box is before/instead of a cooker control unit, no.

If the jb is downstream of a cooker control unit, when someone switches the cooker control unit off, they'll turn the fridge off.

If the cooker circuit trips, you might not notice as quickly as loss of a general power circuit.

This is useful for splitting cooker cables

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Owain

Reply to
spuorgelgoog

Owain,

Thanks for that; there is no cooker control unit, just the junction box.

Reply to
Bert Coules

The fridge should certainly have its own fused spur, with a proper isolating switch, e.g.:

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If the hob is wired with suitable cable/flex for 45A *and* the makers of the hob specify that a 45A supply is ok you could use a standard cooker switch (which would be useful if you ever put an oven in), otherwise same as above.

The main criteria are to protect the cable to the appliance by limiting fault current and to make servicing easy and safe by having separate isolation switches for the two appliances. Just having a standard plug would appear to work for the above, but a suitable socket to both accommodate 45A wire and safely switch 45A does not exist.

Reply to
Roger Hayter

The hob is specified as 230V 2900W and is fitted with what appears to be a standard flexible 3-core cable. It came from a previous kitchen where, as I recall, it was plugged into an ordinary 32A socket located behind the cabinet. I was intending to use a conventional cooker switch with 2.5mm cable to a cooker connector and the hob's own cable thereafter.

Reply to
Bert Coules

Yes. But change the MCB to a 20 amp one.

Reply to
Dave Plowman (News)

2.5mm2 is not rated for a 45A circuit!

It would be fine if he de-rated the breaker.

Reply to
dennis

I just checked. Despite the fact that the circuit is labelled "cooker" and wired with what I think is 6mm cable, the breaker installed is a 32A model identical with those on the ring circuits.

Reply to
Bert Coules

A 32 amp MCB would also do if the 2.5mm cable is a reasonably short spur running to a single socket or twin socket. (It's even shown in Appendix

15 to BS7671:2008 which I've had to show a doubter.)

I don't know if the adiabatic equation would stretch to 45A!

Reply to
Robin

You shouldn't do that. The 2.5mm^2 cable, the flex and the hob will then only be protected by a 45A MCB. If you don't want to plug the hob into the socket on the cooker switch (and you probably don't as it would look untidy) it needs it's own 13A spur. How you actually connect the isolating switch to the 45A circuit is a mystery to me, as you probably can't connect sufficiently big cable into the switch input - perhaps someone will tell us.

Reply to
Roger Hayter

But if is going to wire in the hob directly without a plug he needs either a 10A MCB, which probably woudln't be enough, or at most a 16A MCB, which might well be bigger then the hob is rated for; a 13A fused spur would be desirable.

Reply to
Roger Hayter

What if I did use a plug and socket for the hob connection? That's what was done (not by me) in my old kitchen.

Reply to
Bert Coules

On reflection, if you want to connect this circuit to a cooker switch it would be a lot better to leave it otherwise unused and take a spur off an adjacent ring main to a socket for the fridge and a fused spur switch for the hob. Ideally these should be two separate spurs, but one might do if they are not too long.

If you are going to use the original circuit you probably need to use a smaller MCB (absolute minimum 32A) and a plug for the fridge and definitely a fused 13A spur for the hob if you don't want it on a plug. The danger it seems to me is someone in the future changes it back to a

45A MCB for a cooker without removing these spurs they will not be properly protected.
Reply to
Roger Hayter

How often do cooker circuits trip?

And what are you probably doing if it does trip?

I'll bet it's something that you would notice:-)

Reply to
ARW

That's their problem.

If they cannot spot a couple of 2.5mm T&E cables from the junction box they connect the cooker into then they should not be doing the job.

Reply to
ARW

There are no equations if it was changed to a 20A or 32A MCB:-)

Reply to
ARW

oven elements can short to their sheath

Reply to
charles

Then the experts (see Robin's post in this thread) reckon a short spur of 2.5mm^2 from your cooker switch or the junction box to a socket will be ok provided you have no bigger than a 32A MCB.

Reply to
Roger Hayter

I checked back through the thread and found that, just after I posted the question. Thanks for reinforcing it, and to Robin and all the others who responded. Much appreciated.

Reply to
Bert Coules

No reckon, it's a fact.

Reply to
ARW

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