What size cable and fuses?

[Andrewr4]

I'm adding a 2kw downflow bathroom heater. We have a 6mm cable that powered the old electric shower under the floorboards in a junction box so I plan to use that for the heater as it's easier to access than any socket cables. This cable isn't used for anything else.

I'm going to run a cable under a few more floorboards and then up the wall to the heater location.

I'm planning on using 2.5mm twin and earth cable connected to the 6mm cable at one end and a switched FCU at the other. Then the same size cable to the heater from the FCU.

My questions:

1) Is 2.5mm sufficient and is T&E ok?
2) What size fuse should be in the FCU? Presumably 13A?
3) What size circuit breaker should be used at the consumer unit as I suspect it's quite a large one currently that was used for the old shower?

Thanks for your help!

 

[OwainDIYer]

1) Yes, and T&E okay provided the circuit is protected by an RCD. Connection from the FCU would usually be by flex, or from a flex outlet plate adjacent to the heater if the FCU is elsewhere.
2) Yes
3) As it will be protecting the 2.5mm it should be 20A unless you can show that the 2.5mm is adequately protected by whatever's protecting the 6mm.

The junction box must be accessible for maintenance. Under floorboards is acceptable if there's an access hatch, but not if it's covered with fixed floorcovering.

The FCU must be located appropriately for the zones in the bathroom.

Unless ALL the circuits in the bathroom are RCD protected you will have to install equipotential bonding. This may already be in place if the shower was wired to 16th Edition.

 

[Taylortwocities]

And notifiable work. See WIKI for details....

 

[Andrewr4]

Thanks for the replies.

Is 1.5mm T&E also sufficient with a 16amp circuit breaker?

Thanks again

 

[EFLImpudence]

Yes, as long as it does not run through thermal insulation.

 

[securespark]

And notifiable work. See WIKI for details....

If you wait till April it is not notifiable if outside the zones.

 

[EFLImpudence]

And notifiable work. See WIKI for details....

If you wait till April it is not notifiable if outside the zones.

It's not now if outside the zones.