OK to downrate CCU fuse to meet oven specs?

[tomsavage]

I'm about to install a new electric oven (AEG B2100-4). The rating on the oven itself is 3.0kw, which by my calculations would draw about 13A.

The manual specifies connection via: "Cooker Control Circuit, 2.5mm2 PVC T&E, fuse - min:15A max:20A". It also says "It is necessary that you install a double pole swtich between the oven and the electrical supply with a minimum gap of 3mm between the switch contacts"

I plan to use this switch which although being overkill on the current rating, is the neatest Logic Plus switch with a 3mm gap that I can find.

What worries me a little is the fuse specification. The oven is to be installed on the cooker radial, which currently has a 30A fuse in the CCU. To meet with the manual's "15-20A" requirement, I guess this involves using a lower rated fuse in the CCU. The radial also feeds the cooker hood (through a 5A fuse) and the hob ignition (through a 3A fuse). So I guess I would like reassurance that replacing the 30A CCU fuse with a 20A will be a safe and compliant way to protect this circuit.

Thanks in advance.

 

[JohnD]

An alternative method would be to fit a Fused Switched Connection Unit. this is the same size but incorporates a 13A fuse cartridge.

Yet another alternative would be to replace the cooker connector block with an unswitched socket, and connect the oven using a flexible cord and a 13A fused plug.

 

[tomsavage]

Thanks for those suggestions. I'd originally had in mind using a 13A plug, and had in fact expected the oven to come with one. However, does the 3.0kw rating mean that I shouldn't use a standard plug? The manual does after all specify a minimum 15A fuse. Or is this not strictly necessary?

 

[JohnD]

15A fuse (or MCB) assumes it is fed on a Radial Circuit (not a fused plug). Most people in foreign countries do not have the benefit of our wonderful 13A plug system.

A 13A fuse is ample for a 3kW appliance (3,000 watts divided by 240 volts is 12.5 Amps)

 

[slippyr4]

A 13A fuse is ample for a 3kW appliance (3,000 watts divided by 240 volts is 12.5 Amps)

But 3000 watts divided by our nominal 230V is 13.04 A

 

[JohnD]

hee hee

 

[tomsavage]

Thanks again. I shall go the 13A plug route, and if the fuse blows at any point I can think again.

 

[tomsavage]

connect the oven using a flexible cord and a 13A fused plug.

One final question: is there a specific kind of flex I should use? Does it need to be heatproof, etc?

 

[slippyr4]

connect the oven using a flexible cord and a 13A fused plug.

One final question: is there a specific kind of flex I should use? Does it need to be heatproof, etc?

You ought to use a 2.5mm^2 flex. You can get this at a proper electrical supplier, not usually a diy shed. Commonly used for immersion heaters.

 

[RF Lighting]

why 2.5mm² flex?

1.5mm² is rated at 16A.

More than enough for a 3kW oven.

 

[securespark]

It should say in the manual what cable spec is.

See Wiki for decoder.

 

[tomsavage]

Sorry to post another question, but...

If I am now going to use a 13A plug to connect the oven, then presumably I don't need to use the hefty 32A switch that I mentioned earlier:

...and can instead use a 20A DP switch such as this:

...even though the oven manual actually specifies a switch with a 3mm contact gap. Surely if it's on a 13A plug then this is pointless? Or am I missing something?

 

[RF Lighting]

The 20A DP switch will have a 3mm seperation gap, but as you have a plugtop which can be removed this is not really an issue anymore.

 

[securespark]

The 20A DP switch will have a 3mm seperation gap, but as you have a plugtop which can be removed this is not really an issue anymore.

Assuming it is accessible to pull out!!

 

[JohnD]

IMO it is best practice to have a DP switch above the worktop, feeding the 13A unswitched socket below.

In the event of a fault, or a fat fire, or for servicing, you need the switch to be readily accessible and in plain view.