I have been asked to have a look at proposed shower install. The bathroom is downstairs in a flat roofed single story extension. The only way to route the cable is to go outside onto the exterior wall. The run is approx 20m then drill back into the house for the shower switch.
I need to decide whether to use swa or plastic conduit.

Just had a look in App 3 at 4mm 90 degrees thermosetting swa is good for 49A. Having read the note it says that the switchgear etc must be suitably rating for the same temperature.

Can anyone advise on the easiest way to do this. I was surpised that 4mm seems to be adequate.....have I missed something?

Thanks.

The higher temperature rating of the 90 deg. cable allows it to pass more current. If it was limited to 70 degrees max, then the rated current for it would be lower.
Why SWA?
T+E, in trunking if need be,or covered in capping, would be far easier. 6mm may suffice, I'd be tempted to go for 10mm T+E anyway, as showers are only going top get more powerful - there were no 10.8kW showers a few years ago, now they are common, and the difference in price between 6 and 10mm is pretty small as an overall cost of fitting the shower.

As has been pointed out to me recently, 90deg thermosetting cables are only good for that rating if the corresponding switchgear is also rated for the same temperature. So it might be wise to use table 4D4A and upgrade the cable to 6 or 10mm2.

It gets worst with 4D1A and you would have to go with 10mm2 in 25mm2 conduit.

Legh

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Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

Plastic capping run on an external wall come on life can't possibly be that bad
If it's got to be external personally I'd galv tube it with appropriately sized cable for the load not for a future load that might or might not get used

MrP
plastic capping on an external wall what is the world comimg too

LOL, you galv tube it mate and let every man and his dog undercut you! Are you self employed?

Think you will find galv tube cheaper than plastic a better engineering solution less chance of a call back wont warp looks better wins in my books
Or would you go for the plastic capping
MrP
We all work for ourselves

Plastic capping exterior, haha

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Dougie
Power Plus Electrical.co.uk

My mission is to live as long as possible......so far so good!

Stock + die, cutting compound, end boxes, saddles, couplers, singles, labour etc etc

You wont win the job, its a domestic shower not a plant room!

Thanks Legh, looks like doing it in 6mm swa then. I was a bit unsure with the 90 degree thermosetting. Is the cable likely to get that hot with approx 40A flowing. If it doesn't get anywhere near that hot does it really matter if the switch gear is only rated at 70 degrees?

Whats the Ground floor construction of the house amd extension?

As a electrician you would carry this stuff in your van wouldn't you?
You still have to buy the bits in plastic and as crazy as it sounds s galv is cheaper than PVC
Plus a better engineering solution

You will never compete against bodgit and scarper who run the cable incased by capping

MrP

Just because its in my van, doesnt mean the client gets it for free!

Im not saying be rough, win the job by discussing options with the client.
If another guy prices to clip direct youve got no chance, another days work gone and the cupboards are already bare...

Quote;
As a electrician you would carry this stuff in your van wouldn't you?

You still have to buy the bits in plastic and as crazy as it sounds s galv is cheaper than PVC

Plus a better engineering solution



You will never compete against bodgit and scarper who run the cable incased by capping



MrP

As I see it. Its as much for fault conditions as its for normal running temperature. The assumed starting temperature at the time of the fault would be taken as 70deg rising to its maximum of 160deg. If the cable is running normally at a lower temperature then you have some leeway and protection against overheating. As well as the current and time limiting affect of the protective device.

Legh

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Why do we need Vernier Calipers when we have container ships?

http://www.leghrichardson.co.uk

"Science has overcome time and space. Well, Harvey has overcome not only time and space - but any objections."

Trunking, capping or 25mm metal conduit!.........
Capping surely?, trunking and capping allow an easier run, conduit with 10mm in boxes etc=nightmare, capping my bet tbh.

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Those who make no mistakes do very little work!!......

Could you run swa external, and convert to t and e on the inside.

I think capping outside would look rough.

Its going to be SWA all the way. Drill through wall from meter cupboard, 20mm galv end box on outside wall, SWA vertical to high level, then horizontal for 20m, drop down to height of shower switch, another galv end box, then through the wall for the switch.

Can't believe people would seriously consider doing this in capped T/E