Circuit breaker for new belling oven incorrect. Should it be changed to 20Amps or 32Amps?

[Jenny tully]

Dear all,

I recently bought a new under counter belling bi70fp oven. 4.5kw at 240v. I have a circuit breaker on the main switchboard for the oven at 40Amps. I was told this needs changing to a 20Amps.

The specification on the oven stated 32Amps.

I am confused to the advice. What is the consequence if I install the oven and keep the 40Amps circuit breaker. Or should I change it to 32Amps or 20Amps?

Appreciate any advice.
Jenny

 

[Marvo]

The circuit breaker is there to protect the circuit from being damaged by overloading and it is sized according to the current carrying capacity of the wiring between the CU and the socket.

If an appliance or its trailing cable needs additional protection this would usually be in the form of a fuse in the plug or in a fused connection point or in the appliance itself so I'm not sure why you've been given advice to reduce the size of the circuit breaker.

 

[Midwest]

I note the manufacturers instruction manual, gives a minimum size 'mains lead 'size, i.e. Follow that and Marvo's advice, and you won't have a problem. I'd use a piece of 2.5mm heat resistant flex, myself.

 

[Wilko]

Hi - here's the link to your user manual and a pic of the electrical installation instructions for your model. https://www.belling.co.uk/media/664346/bi70fp-handbook03-12-2012.pdf
Reading this, the manufacturer does not require the MCB to be 32A, so you don't need to change it just to suit the oven.

 

[Marvo]

To be honest Jenny I'd strongly recommend you give your favourite sparky a call to come and install this unit, it's on a fairly powerful circuit by domestic standards and a bit outside of the realms of DIY. Some basic testing should be done before it's powered up because if there's any mistakes or latent faults there could well be a pretty large bang resulting in both you and your surrounding neighbours being without power or possibility of electric shock / damage to the appliance.

 

[Deleted account]

By our cable calcs yes 2.5mm cable with 20A mcb, it could possibly be a 16A mcb, but installation instructions over ride our calcs if it is as safe or safer.
So yes the 4mm with 32A mcb may be what is required.
However as marv suggested get a spark to confirm this as it is a bit on the powerful side of a normal domestic oven.

 

[rolyberkin]

The oven literature states it is a direct connection and what breaker will depend on what size cable you have feeding your current oven, the current rating of this appliance needs a minimum 4mm cable (as recommended by the manufacturer) As others have recommended get an electrician in. To answer your question should you leave a 40amp mcb in place and the cable is not capable of handling that current, under fault conditions you risk a fire.

 

[Midwest]

As Marvo stated, ocpd is there to protect the final circuit, nothing to do with the oven or its 'mains lead'. As the oven has a fixed maximum load, as long as the lead can carry that maximum load, then everything is cushty. All this talk about changing mcb is irrelevant.