Can I use a 4mm T&E for a 7.5Kw shower?

[louis butler]

The cable is installed in 3 metres of trunking, 3 metres clipped direct, and 5metres in the joist space with no insulation,

 

[westward10]

You rate the cable for the worst installation method with regard to its current carrying capacity, that would be the trunking. Being contained in trunking reduces its current carrying capacity to below that required for a 7.5kw shower.

 

[Dave OCD]

It would also be false economy as you can be certain that someone will want to replace it with a higher rated unit in the future. For the length of run and cost why not use 10mm and perhaps a 9.5kW shower which will perform a lot better in the middle of winter when the incoming water is really cold.

 

[Dustydazzler]

As a minimum I would run 6mm in for a domestic hot water shower

 

[louis butler]

Yeah I did think it should be a 6mm minimum but this was wired by somebody else so this cable was already in place, so should i have to say to the customer that the cable needs upgrading,
Thanks

 

[James]

The cable is installed in 3 metres of trunking, 3 metres clipped direct, and 5metres in the joist space with no insulation,

Sounds like a fairly easy run to replace the cable.
if you are going to put your name on the certificate, make sure that it is compliment otherwise it will always be a nagging doubt in your mind that some day it will come back and bite you.

 

[telectrix]

It would also be false economy as you can be certain that someone will want to replace it with a higher rated unit in the future. For the length of run and cost why not use 10mm and perhaps a 9.5kW shower which will perform a lot better in the middle of winter when the incoming water is really cold.

water is not much colder in winter. 18" down in the ground temp. is fairly constant all year round. at about 10degrees.

 

[Intoelectrics]

Yeah I did think it should be a 6mm minimum but this was wired by somebody else so this cable was already in place, so should i have to say to the customer that the cable needs upgrading,
Thanks

I would personally recommend to the customer that the cable requires upgrading as it was incorrectly rated for the installation method in the first place. However, rather than a scaremongering approach, I would focus on the benefits such as the possibility of a larger rated shower unit, like Dave OCD suggested.

 

[louis butler]

I would personally recommend to the customer that the cable requires upgrading as it was incorrectly rated for the installation method in the first place. However, rather than a scaremongering approach, I would focus on the benefits such as the possibility of a larger rated shower unit, like Dave OCD suggested.

Ok will do, thanks

 

[Mikegh]

water is not much colder in winter. 18" down in the ground temp. is fairly constant all year round. at about 10degrees.

If you're using the pumped type the water in the attic is colder in winter

Not sure how common the pumped is the UK ,I think they're mostly mains fed ?