correct MCBRCBO for immersion?

[kudos1uk]

I currently have a 40amp MCB fitted in my CU for my immersion heater.

I don't use the immersion heater as I use gas so its only a back-up.

I'm changing the MCB's for RCBO's because I'm having an exstension built and need to bring them upto code.

I thought an immersion was normally fitted with a 16amp fuse? Should I get a 16amp RCBO keep it at 40amp?

Many thanks.

 

[RF Lighting]

What is the rating of the immersion heater in watts or kW?

What makes you think you need to do and remedial work to a circuit which I'm presuming is not affected by the construction of your extention?

 

[kudos1uk]

What is the rating of the immersion heater in watts or kW?

What makes you think you need to do and remedial work to a circuit which I'm presuming is not affected by the construction of your extension?

It's a 2.7kW heater.

Its only a small extension, enlarging the living room and adding a single bedroom and bathroom upstairs. The upstairs & downstairs lighting and socket circuits will be extended.

I will be first fixing but my electrician wants to see all wires before I cover anything and said I would need RCD protection to the extended circuits RCBO's are the easiest option to achive this.

Only 3 circuits are not affected by the extension (shed's, Shower & Immersion), it's just made sense to me to upgrade these MCB's while I was at it.

 

[RF Lighting]

Oh ok, fair enough.

Can your electrician not advise you on the apropriate sized RCBO?

I'm suprised he isn't supplying the parts. I certainly would.

He will be able to buy them cheaper than you, and can fit his prefered brand.

Oh, and a 16A RCBO should be fine for an immersion heater that size.