Cable sizing

[shaky1105]

Ive been using tlc's cable calculator to size up a cable for a shower but there isn't an option to show cable being run inside an uninsulated stud wall ( 5M ) or underneath a floorboarded floor ( 3M ) in an unheated space.
Can I use the "clipped direct to a wall" with no insulation section or would it be better to use one of the "insulated wall" sections ?
The difference means using either 6mm or 10mm cable. and I have access to enough 6mm cable without having to buy any more.
The shower is a 9.5KW unit btw.

 

[flameport]

6mm cable will probably do, however it will be at it's limit, so there is no way a more powerful shower could be fitted in future.

10mm would the the sensible choice, as this would allow a replacement shower to be of a higher rating. 8m of 10mm cable isn't exactly going to cost a fortune anyway.

 

[planemad]

I would use 10mm anyway, future proof and will take the current without overload.

 

[shaky1105]

Thanks for the replies I can see your point about future-proofing. It's just that I do have about 11M OF 6mm T&E kicking about that I can use.
I don't want to make it unsafe though, that's why Ive asked here.

Thanks

 

[ColJack]

always install 10mm
showers get more powerfull so in a few years I expect we'll see 12.5 and 13.5KW showers as an option..
you say 9.5KW now but in 4-5 years when that's fubar you'll want another and odds are the missus will want a more powerfull one..

 

[riveralt]

Ive been using tlc's cable calculator to size up a cable for a shower but there isn't an option to show cable being run inside an uninsulated stud wall ( 5M ) or underneath a floorboarded floor ( 3M ) in an unheated space.
Can I use the "clipped direct to a wall" with no insulation section or would it be better to use one of the "insulated wall" sections ?
The difference means using either 6mm or 10mm cable. and I have access to enough 6mm cable without having to buy any more.
The shower is a 9.5KW unit btw.

This is classed as Reference method B - number 47 of Table 4A2 17th edition. Single core or multicore cable in a ceiling floor or suspended floor.

This gives a current carrying capacity(Iz) of 38Amps for 6mm2 cable and 52 Amps for 10mm2 cable.

9.5kw shower = 9500/230 = 41Amps -so you should use the 10mm2

 

[shaky1105]

Thank you very much to all that replied, looks like I'd better go get myself some 10mm then - hehe.
One more thing, if you don't mind of course. I don't really want to put the isolating switch in the roof of the bathroom, I'd rather have it somewhere not so noticeable. I was hoping that it would be OK to put the switch in the Gas Cupboard under the stairs.
I can't seem to find any regulations anywhere that point to any areas where the switch cannot be fitted and the local council are as about as useful as a chocolate fireguard.
Would this position be OK as long as it's clearly marked etc ?

 

[LoveRocket]

'fraid not Shakester - the DP switch is required as local isolation, so anyone working on the shower can see the switch.

How about above the bathroom door.


PS. If I'm wrong on this someone will politely point it out, so stand by before you take that as gospel.

 

[ColJack]

there's many opinions on here about what exactly the shower switch is for..
some say emergencies and demand that it be a pullcord with the cord in reach of the person in the shower, others say maintainence and can be a switch in the airing cupboard as long as the door to said cupboard is in the bathroom or lockable to prevent someone switching it back on..

 

[Taylortwocities]

It is good practice for everything to have an isolator provided close to the device. But I have yet to find a specific regulation (or guide) that says that one MUST be provided for an electric shower.

<Puts head back below the parapet>

 

[shaky1105]

How about above the bathroom door.

I take it you mean outside the bathroom itself ? If I understand correctly, the only electrical connections you can have in a bathroom are a shaver socket.

The ceiling is only 7'6" or have I mis-read the zones picture ??

 

[ban-all-sheds]

I don't know if you've misread the diagram of the zones, but it does look as if you might have misread what's allowed in each.

//www.diynot.com/wiki/electrics:bathroom-zones

 

[shaky1105]

I don't know if you've misread the diagram of the zones, but it does look as if you might have misread what's allowed in each.

Spot-on with that last comment. Now I've paid a little more attention I can see what I need.

Thanks

 

[Paul_C]

It is good practice for everything to have an isolator provided close to the device. But I have yet to find a specific regulation (or guide) that says that one MUST be provided for an electric shower.

<Puts head back below the parapet>

There used to be such a rule. Look back at regulations A.58 through A.61 in the 14th edition.

 

[Taylortwocities]

Aah yes, the 14th. Came out just before the relief of Mafeking so not relavent.
Can you find the equivalent in the 17th, otherwise there is no specific requirement.