New built-in oven installation problem

newforms80

Hi,

I'd bought a new Neff built-in oven (U16E74N3GB) and paid for installation from the company I bought it from online. The installer said he couldn't install it because the fuse breaker was rated at 40A and the oven only needs 20? He said the breaker would need to be replaced with a 20A version.

I don't know very much about ovens/electricity and would really appreciate some help from people that know more!

A few other companies online list it as a total 6.8kW load (and a few others with a 20A fuse rating). But, at 6800 watts / 230V comes out at 29A- so surely I'd need at least 30A?

zax47

There's the principle of Diversity to apply if the item (cooker{oven+hob} or multiple oven) has multiple heating elements - even of both/all in use then thermostatic control would mean they are not all consuming the maximum they can for all of the time.

The diversity calculation is: 10A plus 30% of the remainder of the load. 10A represents roughly 2.3kW, so in your case;

10A + 30% of ((6.8-2.3kW)/230) = 10A + (19.56*0.3) = 10A + 5.868A = ~16A. So 20A breaker is nearest best choice for protection.

Owain_Moneysaver

It may only need 20 amps but the question is whether the cable or flex supplying the oven is adequately protected by a 40 amp breaker.

As the oven is a fixed appliance unlikely to cause an overload fault, the only protection required is for short circuit. The manufacturer's installation instructions do not specify a lower rating for the protective device so you can assume the supplied cable can carry the full connected load of 29A, which should be suitable for 40A short circuit protection.

Therefore the oven should be safe connected to the 40A circuit.