10mm shower cable

[D4N1EL]

Thanks for all the replies and confusion.

The other half picked the shower, the 9.5kw shower was on sale and cheaper then the 8.5kw shower. We ended up getting the 9.5kw shower instead.

In terms of using the shower, will that extra KW even be noticeable?

 

[EFLImpudence]

Well, it will make a slight difference but you won't know what the 8.5 would have been like.

 

[Iggifer]

10mm² is often used as a submain supply for a whole flat.

Nevermind submains, I suspect there's a fair few DNO cables that are 10mm² equivalent split con. They only install 16mm² on a new 80A supply now and you're very lucky to get a 100A supply out of WPD 'round here.

 

[deadshort]

My submains, 4mm ish singles! (with tape).

DSView media item 97788

 

[SUNRAY]

Do/did you ever see (or install) 16mm² cables in shower circuits?

Kind Regards, John

Yes of course:-

 

[EFLImpudence]

As I said, don't install it under the insulation.

 

[SUNRAY]

As I said, don't install it under the insulation.

Don't always get that option, besides sometimes the cost difference is too small to worry about.

 

[chappers]

Well, it will make a slight difference but you won't know what the 8.5 would have been like.

Exactly ! Some 8kW will outperform much higher rated models as with most things there are showers and showers and it's not always just about the numbers

 

[PrenticeBoyofDerry]

Hi,

The cable currently runs from my fuse board (not connected) along the top of my kitchen wall in some white trunking, up through the ceiling/bathroom floor into the loft to the area the new switch will be, then another wire from where the switch will be over the ceiling and down the wall to where the shower will be.

And how does the cable get from bathroom floor void to loft?
There are permitted safe zones to follow for cable that is buried in walls. Also for bathrooms and newly buried cable, there are consideration to be taken, to comply to the requirements of RCD protection.

 

[StephenStephen]

I'm not an electrician, and I think this has been made clear already, but anyway - my understanding is that it is fine to have a cable which has a larger diameter than you need. It's only if the cable is too small that it is a problem

 

[PrenticeBoyofDerry]

my understanding is that it is fine to have a cable which has a larger diameter than you need. It's only if the cable is too small that it is a problem

Untitled

• PrenticeBoyofDerry
• 31 Aug 2013
• 3

 

[sparkwright]

I've never seen a shower fed by 16mm t+e either.

But assuming the length of run is going to be considerable, it probably means there is no nearby consumer unit.

With that in mind, I would perhaps run the 16mm cable to a new small consumer unit close to the bathroom, and, via an appropriate MCB, run 10mm to the shower switch and then 10mm to the shower, avoiding thermal insulation.

Anything rather than trying to fit 16mm to a shower pull switch.

 

[Adam_151]

Designers who specify stupid cable sizes (because as EFLI says, they are skinning the cat in the wrong way) are generally invited to make themselves available to attend site when second fixing is happening to assist, normally there is a bit of mumbling and backtracking and a more sensible design appears

 

[JohnW2]

Exactly ! Some 8kW will outperform much higher rated models as with most things there are showers and showers and it's not always just about the numbers

I guess it depends upon what you mean by 'outperform'. You can't change the laws of physics, so a given amount of electrical power will produce heat at the same rate (hence same temperature rise at a given flow rate) with any shower. However, the perception of 'how good' a shower is will depend on a number of factors, such as the flow rate and spray pattern etc.

Kind Regards, John

 

[JohnW2]

I've never seen a shower fed by 16mm t+e either. ... But assuming the length of run is going to be considerable, it probably means there is no nearby consumer unit.

I'm not so sure about that - I doubt that length of the cable is often relevant. Even if one is concerned about voltage drop (and I personally don't see why one really needs to be, in the case of a shower circuit), as the figures Sunray posted illustrate, VD is not going to be the limiting factor. His figures, using a very unfavourable installation method, require 16mm² because of CCC considerations. The cable run could be more than three times greater than he postulated without even the regs' guidance on VD being exceeded.

With that in mind, I would perhaps run the 16mm cable to a new small consumer unit close to the bathroom, and, via an appropriate MCB, run 10mm to the shower switch and then 10mm to the shower, avoiding thermal insulation. ... Anything rather than trying to fit 16mm to a shower pull switch.

Yes, if one really had to use 16mm², then to reduce the CSA of the feed to the pull switch would be highly desirable. However, if, as you said, one avoided insulation for that last shower run, one wouldn't need a 'small CU' (with MCB) - a junction box or suchlike would be adequate.

Kind Regards, John