shower cable

[johnad]

How accurate is the TLC volt drop calculator
I was looking at the wiring for a shower I was possibly going to install
Not sure on the shower yet but looking at the bigger 10.5kw I went to the TLC
Calculator.
Twin and earth
Clipped to wall
Non-lighting
30 0C
1 side by side
10.5kw
230v
15metres
The result came up at 6mm (a little small I thought ?)
And just by altering the application to “above plasterboard with less than 100mm insulation” it then jumps to 16mm.
The cable will be clipped to exposed beams (old cottage) then across a small loft space (extension) to the bathroom pull switch about ½ in loft space and ½ clipped.
Is 6mm t&e about right for this cable run ????

 

[ricicle]

6mm² is just in for 10.5kW when the cable is clipped direct. Any other factors will probably push this to 10mm² and even 16mm² if insulation is involved.
(All off the top of my head as I havn't got any books to hand !)

 

[johnad]

Thanks for the quick response
In reality the shower would probably be smaller than 10.5kw
I was just looking at the worst case
If part of the cable run is across a loft space I assume I can just lay this over the insulation but will this contribute to the volt drop?

 

[securespark]

Just go for the worst case: that way, even if you don't plump for a large kW shower now, you can safely upgrade in the future without replacing the cable all over again.

 

[bongos]

If part of the cable run is across a loft space I assume I can just lay this over the insulation but will this contribute to the volt drop?

It won't contribute to volt drop but it will mean applying derating factors to the cable because of the presence of insualtion. It's this that will likely up the size of the supply cable.

 

[ricicle]

Only distance contributes to voltage drop (on smaller cables)
You need to keep the cable out of contact with any insulation

 

[johnad]

But is 6mm still in for that run or should I push it up to 10mm

 

[Aragorn84]

i would use 10mm as a minimum for any new shower installation.