Replacing a built in oven --- my assumptions

[zetland76]

Hi,

I am wanting to replace a built in oven that was installed more than 10 years ago. Looking behind the oven there is a substantial supply cable (hard to bend, possibly 30A) coming direct from the cooker box mounted just above the work surface. The cooker box is connected direct to the 30A trip in the consumer unit. The "cooker" cable goes to a round junction box behind the oven with two heavy duty (30A) exiting. One connected to the oven and one to the hob. It looks like the existing wiring is man enough to handle substantial currents.
There are 2 types of oven available, "hard-wired" and 13amp plug. I realise that cutting the plug off the latter type and wiring it into the junction box is a complete NO! NO! as in the event of a fault the 13amp cable would melt before the 30A trip went. However I am assuming than the "hard-wired" oven has no supplied cable but has screw terminals at the back where the existing 30A cable can be attached. (I'm hoping "hard-wired" does not mean an attached 13 amp cable with no plug that requires a qualified electrician to attach a plug after fitting the oven). Therefore connecting such an oven to the existing cable would mean "30A protection" exactly as it is now?

Regards Mike

 

[EFLImpudence]

There are 2 types of oven available, "hard-wired" and 13amp plug. I realise that cutting the plug off the latter type and wiring it into the junction box is a complete NO! NO! as in the event of a fault the 13amp cable would melt before the 30A trip went.

Half right
Ovens will not overload the cable so if the cable can cope with the fault current - a measurement will determine this - it will be fine.

However I am assuming than the "hard-wired" oven has no supplied cable but has screw terminals at the back where the existing 30A cable can be attached.

It may have a cable.

(I'm hoping "hard-wired" does not mean an attached 13 amp cable with no plug that requires a qualified electrician to attach a plug after fitting the oven). Therefore connecting such an oven to the existing cable would mean "30A protection" exactly as it is now?

No, if it could be supplied by a plug then it would have one

or

You can fit whatever cable will be adequate for the current.

 

[PrenticeBoyofDerry]

If you have a 30A supply and a cable that can deal with the current, then you have options!
Choose the oven you want/suits your requirements, then take it from there.

Out of interest what rating is the hob?

 

[ban-all-sheds]

Zetland - FYI - there is no such thing as a "30A cable".

http://www.batt.co.uk/upload/files/4d5.pdf

 

[Taylortwocities]

The "cooker" cable goes to a round junction box behind the oven with two heavy duty (30A) exiting.

Do away with this and fit a proper dual appliance connector plate.

 

[zetland76]

Thanks for all replies.
I take your point TTC but the picture of the dual appliance connector plate I looked at does not appear to have a fuse, so if I connect an oven which comes with a 13 amp cable to the 30 amp supply wouldn't I have a problem if say a 20A fault occurred on the oven. Or am I being too pedantic?

Mike

 

[EFLImpudence]

I take your point TTC but the picture of the dual appliance connector plate I looked at does not appear to have a fuse,

Of course it doesn't. It is just for connecting wires.

so if I connect an oven which comes with a 13 amp cable to the 30 amp supply

If it does then that will be the maximum current the oven can draw.

The 'supply' cannot force 30A down the cable if the oven only draws 13A.

wouldn't I have a problem if say a 20A fault occurred on the oven.

You cannot get a 20A fault.
A short circuit or fault to earth will be hundreds of amps. If the cable can cope with this (testing and calculation will confirm) for the split second until the fuse blows then all is well.

Or am I being too pedantic?

Not pedantic. You don't understand how it works.

 

[Steve]

What is the rating of your hob?

What is the rating of the NEW oven?

Or to put it more simply, does your hob have four electric rings? And is the new oven a single (where only one part of it can be used at once) or double (where you may have a grill and an oven running simultaneously)?

 

[seasickstevie]

The issue is: what does it state in the installation instructions that come with the oven?

If it says something about must be protected by 13amp fuse, then that's what you must do.

 

[ban-all-sheds]

I'd be more inclined to ask the maker to explain, and justify, why he has made an item of equipment which is so shoddy that it has to rely on external devices meant to protect the supply cable for protection of its own internals.