# 4.2Kw Oven install

#### mrbiscuit

Hi All,
Can someone clear up some confusion for me please?

I'd like to install a 4.2 Kw oven and grill.

I calculate that this will pull a maximum of 17.5 amps.

As I understand it (...and I'm willing to be corrected), 2.5 mm twin and earth is rated at 27 amps in conditions where it is clipped and un-insulated.

With a 10 metre radial and a 20 amp MCB, would it be OK to use 2.5 mm?

I ask because often I see online suggestions for larger cable sizes, when it seems that 2.5 would be more than suitable.

Hopefully someone can elucidate for me.
...And yes, I know this work is notifiable, and it has been.

Thanks,
Richard.

Although 32A MCB and 6mm² cable is a standard cooker circuit which could accommodate any cooking appliances you might want to have in a domestic situation.

Actually 4mm² cable is sufficient for 32A but people still use 6mm² because people used to have to use 6mm² so people still use 6mm² because they do.

Nothing else will be on this circuit. The hob is on separate radial.
So although 32A MCB and 6 mm cable are standard, do I break and rules or risk safety by using the 2.5 and 20A MCB?

So although 32A MCB and 6 mm cable are standard, do I break and rules or risk safety by using the 2.5 and 20A MCB?
No, it is fine.

Is your hob circuit the standard 32A/6mm²(or 4mm²)?
You might be able to just connect the oven to that circuit and save having to notify.

The hob is 32A/6mm, but the oven and hob are on different sides of the kitchen.

No, it is fine. ... Is your hob circuit the standard 32A/6mm²(or 4mm²)? .... You might be able to just connect the oven to that circuit and save having to notify.
Indeed. In fact, I'd go further and say that connecting both oven and hob (or an 'integrated {oven+hob} cooker') to a 32A (6mm² or 4mm²) circuit is probably 'the norm', with it being pretty (very?) unusual to find separate dedicated circuits for oven and hob.

Kind Regards, John

Ah, I see - so am I allowed to take a connection from the hob and run cable from it round the kitchen to the oven socket?
I'm looking to see if there are dedicated sockets that allow this...

Ah, I see - so am I allowed to take a connection from the hob and run cable from it round the kitchen to the oven socket?
Exactly - and, provided you are in England (not Wales) that would not be notifiable, since you would merely be extending an existing circuit. Installing a 'new circuit' (from the CU) is one of the very few things which remains notifiable in England.
I'm looking to see if there are dedicated sockets that allow this...
Flameport has indicated the usual way of doing this.

Kind Regards, John

Thank you all.
I very much appreciate you guys taking the time to help me out.

Thank you all.
I very much appreciate you guys taking the time to help me out.

If you mean because the circuit's OPD will be 32A, then I would refer the OP to previous discussions about this - I'm certainly not going to get involved in a repetition of all that.

The 4.2kW (peak instantaneous) load obviously does not, per se, require 4mm² cable in the absence of faults (allowing for diversity, 1.5mm² might well be adequate), so it all comes down as to whether one thinks it likely that the oven will result in an 'overload' (as opposed to 'fault') current.

Kind Regards, John

If you mean because the circuit's OPD will be 32A, then I would refer the OP to previous discussions about this...

Kind Regards, John

... An OPD is only there to protect the cable...
Kind Regards, John

An OPD is only there to protect the cable.
Indeed, and over-current protection of the cable is not required at all if the nature of the load is such that it is "unlikely" to result in an overload current (provided there is adequate fault protection).

Kind Regards, John

Indeed, and over-current protection of the cable is not required at all if the nature of the load is such that it is "unlikely" to result in an overload current (provided there is adequate fault protection).

Kind Regards, John
And when the unlikely event happens and the cable overheats and fails, does one say "Oh dear me I wonder why that happened" or even "I wonder why there are horrible smelly fumes in my kitchen?"

Alternatively does one think ahead and say "For a few pounds more, that can't happen."

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