Wylex Oven Connection

[vonsworld]

I have recently been doing some renovation work on my kitchen and have noticed that the dedicated cable from the Wylex fusebox to my single oven is using 2.5mm cable which I believe is rated 26amp. That's fine because the single oven is only 10amp, but the fuse in the box is 30amp.

Is that a mistake or what you would expect to find?

Presumably I should change the fuse for a yellow 20 amp Wylex fuse?

 

[EFLImpudence]

Are you sure it is 2.5 square mm. wire?

Is it a rewireable fuse?

 

[vonsworld]

I'll check the cable later to make sure, it looks like standard ring main cable. Yes it is a rewireable fuse.

Obviously I couldn't have a double oven running on this cable, but the current single Bosch oven is only 10 amp.

 

[EFLImpudence]

I'll check the cable later to make sure, it looks like standard ring main cable. Yes it is a rewireable fuse.

Ok.

In that case then, assuming the cable is not running through thermal insulation or the like, then a 20A rewireable fuse would be fitted as a matter of course.

Obviously I couldn't have a double oven running on this cable, but the current single Bosch oven is only 10 amp.

However - there are allowances for cooking appliance circuits, such as the omission of overload protection because a cooker cannot cause an overload and -

what we call diversity because not all the elements will be on at once even when all turned on (probably not applicable to a 10A appliance).


So, technically what you have is probably satisfactory.

Of course someone might have put 20A or 15A fuse wire in the 30A holder.

 

[flameport]

Presumably I should change the fuse for a yellow 20 amp Wylex fuse?

No. Rewirable 20A fuses cannot be used with 2.5mm cable.

A cartridge fuse or circuit breaker might be suitable, but changing devices in an obsolete fusebox will achieve very little.
If you want a higher rated circuit for a double oven or cooker, then a new circuit is required, and a new consumer unit to go with it.

 

[EFLImpudence]

No. Rewirable 20A fuses cannot be used with 2.5mm cable.

Are you saying that because of the very small excess in the derated value?

 

[EFLImpudence]

And:

No. Rewirable 20A fuses cannot be used with 2.5mm cable.

Presumably they can where the omission of overload protection conditions are met.

 

[flameport]

Rewireable fuses have a much higher fusing factor, typically around 2, and cable ratings based on those for circuit breakers must be reduced accordingly.
Assuming best case for 2.5mm² at 27A with a circuit breaker factor of 1.45, that's only 19.6A, which rather obviously is less than 20.
Although it's a small difference, it's below 20A.

Omission of overload is not appropriate for an installed circuit where the appliance at the end of it is undefined.
Even if it was a known item incapable of overload, it still depends on other factors, it's certainly not guaranteed.

 

[chivers67]

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