Shower replacement

[Nooby83]

I have a Mira 8.5kw (@ 240v) shower that has broken. I want to replace it ideally with a matching powered unit, however I am unsure about the current wire. It appears to be 6mm² (although isn't labelled), and runs approx 10m total to the consumer unit (7m under floorboards, no insulation, and a 3m section in trunking), on a 40a MCB.
Normally I would assume I can replace like for like, but a lot of what I've read online recommends 10mm² or 16mm² for over 8kw.
Is this wiring safe enough or does it need upgrading?
Is replacing a shower unit like for like notifiable?
Thanks

 

[EFLImpudence]

I have a Mira 8.5kw (@ 240v) shower that has broken. I want to replace it ideally with a matching powered unit, however I am unsure about the current wire. It appears to be 6mm² (although isn't labelled), and runs approx 10m total to the consumer unit (7m under floorboards, no insulation, and a 3m section in trunking), on a 40a MCB.

Ok.

Normally I would assume I can replace like for like, but a lot of what I've read online recommends 10mm² or 16mm² for over 8kw.

Rubbish.

Is this wiring safe enough or does it need upgrading?

From your description it is fine.
9.5kW would be just over the limit because of the trunking but because of the short duration of showers I would say it would be alright,
but 8.5kW definitely alright.

Is replacing a shower unit like for like notifiable?

No.
There is no mention of "like for like" in the regulations; just "replacements" which are not notifiable.

 

[Nooby83]

Ok.


Rubbish.


From your description it is fine.
9.5kW would be just over the limit because of the trunking but because of the short duration of showers I would say it would be alright,
but 8.5kW definitely alright.


No.
There is no mention of "like for like" in the regulations; just "replacements" which are not notifiable.

Thanks. If you don't mind me asking 2 quick follow up questions please:

- You mentioned 9.5kW would be just over the limit: Would a 9kW @240v (8.3kW at 230v) be ok? It's surprisingly difficult to find an 8.5 that matches our previous unit for flow rate and I don't want to upset the Mrs. by getting a 'weaker' shower.

- to give a bit more detail, the under floorboards section of the wire is between 1st floor floorboards and ground floor plasterboard ceiling, mostly suspended in the middle of the void, occasionally next to other cables. Assuming that doesn't make a huge difference?

 

[EFLImpudence]

Yes, 9kW will be alright.

As I said I would not worry about a 9.5kW.
Whilst that is only just over, @ 230V & 8.74kW which technically we should use for design, it is acceptable.