6mm cable with 9.8kw shower

[try1]

I have 6mm cable running to my shower, it's approx a 10m cable run. It runs from mains under the stairs into bathroom thro solid wall and behind tiles in bathroom for about 2m. I have a 45amp MCB unsure about a RCD. Will this cable etc accocmodate the load from a Mira sport 9.8kw shower. I know I should use 10mm cable but rewiring unfortunately is not an option at moment. Thanks

 

[securespark]

Who fitted the shower?

Why did they fit it if they were unsure whether the existing cable was suitable?

 

[securespark]

It is difficult to say whether the cable is satisfactory because we don't know whether the cable is grouped with others, whether it is run in trunking at all, whether it is running through loft insulation etc...

If the latter two, forget it. Trunking or conduit drops 6mm² down to 38A.

Loft insulation can halve a cable's current-carrying capacity.

 

[flameport]

If the cable is surface clipped or buried in plaster for the entire length, then it is suitable (but only just).
Any other method of installation is not acceptable.

What is the problem with installing a new cable?

 

[try1]

The cable is surface clipped for entire length, save for 1 metre between bottom of stair and bathroom, where although still surface clipped, but has piece of plastic trunking covering it. It is plastered/tiled in bathroom only. (the problem area)
It does not come in to contact with any insulation.

 

[try1]

Bathroom is fully tiled and would require ripping load of tiles off to connect 10mm cable at shower end (Mrs will kill me) or putting trunking in to hide surface cable, (not an option). Bathroom has concrete floors also so can't even go under. Mega frustrating

 

[securespark]

Technically, the cable is not sufficient to carry the load.

 

[try1]

'technically'

does this infer there is also a practical answer, albeit maybe not the best or should I really just replace the existing one with the same KW and hope she wants to redecorate soon....

 

[LiamPope]

If you could loose the meter of plastic trunking (either have it clipped to surface and visible if acceptable, or sink it into the wall) so that it could be truly considered 'clipped direct', then i would be OK. It's that run within plastic trunking that de-rates it to about 5A lower than it needs to be.

Hmmm how about running a cooling system in the trunking with the cable

 

[try1]

if it means being able to upgrade to better shower, removing length of trunking will be acceptable regardless of the grief..

 

[barera]

If you could loose the meter of plastic trunking (either have it clipped to surface and visible if acceptable, or sink it into the wall) so that it could be truly considered 'clipped direct', then i would be OK. It's that run within plastic trunking that de-rates it to about 5A lower than it needs to be.

Hmmm how about running a cooling system in the trunking with the cable

convince me that a one meter section of trunking really makes a difference!

 

[RF Lighting]

Prove that it doesn't

 

[LiamPope]

convince me that a one meter section of trunking really makes a difference!

You could have 100 miles of cable. If a single mm of it can't dissipate heat faster than it gains it through resistive heating it'll overheat at that point. The whole cable has to be de-rated to protect the most vulnerable section. It makes no difference how short that vulnerable section is compared to the total length of the cable.

Liam

 

[Steve]

I have a length of trunking from the top of my electric shower to the ceiling - was in the same predicament as the OP.

Managed to use 10mm² cable with trunking. The old 6mm was behind tiles. Trunking carries the cable back down the wall into the floor.

 

[sparkybird]

Obviously you'll be testing that 6mm cable before you install the new shower, eh?