Power and CAT5 Run for Garden Shed
- Thread starter Beebopper
- Start date
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No I won't be doing same duct for both, but thanks for the info on the up / down.
Still not sure what elec cable to use from the house, 2.5mm or 6mm?
The second electrician did, but the first one said 6mm² - hence I presume, the OP's question.
Kind Regards, John
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That's right John, I've found a chart on this site that cross references cable size to load and to my (very limited) knowledge on this I see it as 2.5mm, but obviously not 100% as I should be trusting the trade, but have two opinions!
It really all comes down to the load. You have said "a 1.5kw heater, lights (led) and computer equipment. Not much more, maybe a phone charger. 17m run". As the second electrician has said, for that load, 2.5mm² would be more than enough. However, the question arises as to what additional power requirements you might possibly have in the future. If you're "sure" that you will never need more, then fair enough. However, given the relatively small differential in cost between different sizes of SWA (and the great hassle of burying it!), I personally would be inclined to go for larger than 2.5mm² SWA for any sort of outhouse, to provide some degree of 'future proofing".
Kind Regards, John
Ok thanks for the honest advice John, much appreciated – for reference this is the chart I used to see what cable may be required:
//www.diynot.com/pages/el/el004.php
I’m not 100% sure if any further power requirements may be needed in the future, I suppose it could be possible - The outhouse is split into two sections, an office on side and shed the other. So there is nothing to say in 5 years for example I decide to get a machine to stick in the shed, maybe a wood saw or drill, unlikely but certainly not out of the question. The thing is, both sides are unlikely to be used at the same time, and also I have no idea how much load machinery takes?
Adding up the office side, if all was in use at once, lights, PC, heater etc it’s probably near 2kw in total (so allowing 2.5-3.0kw would be safe?). That chart above says 2.5mm goes up to 4.8kw.
I think the first sparky was using your train of thought, but second one looking at in reality what would be used. Maybe 4mm is a good compromise![/url]
//www.diynot.com/pages/el/el004.php
I’m not 100% sure if any further power requirements may be needed in the future, I suppose it could be possible - The outhouse is split into two sections, an office on side and shed the other. So there is nothing to say in 5 years for example I decide to get a machine to stick in the shed, maybe a wood saw or drill, unlikely but certainly not out of the question. The thing is, both sides are unlikely to be used at the same time, and also I have no idea how much load machinery takes?
Adding up the office side, if all was in use at once, lights, PC, heater etc it’s probably near 2kw in total (so allowing 2.5-3.0kw would be safe?). That chart above says 2.5mm goes up to 4.8kw.
I think the first sparky was using your train of thought, but second one looking at in reality what would be used. Maybe 4mm is a good compromise![/url]
Use this one:
http://www.batt.co.uk/upload/files/4d4a_copy1.pdf
Depends on the installation method, grouping factors, ambient temperature factors etc, and, of course, how long it is.
No cable has a rating which is absolute.
- //www.diynot.com/wiki/Electrics:MCBtoCable
- http://www.tlc-direct.co.uk/Book/4.3.1.htm (all subsections)
- http://www.tlc-direct.co.uk/Book/4.3.11.htm
- http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html <- Specify 2-core cable and PVC, even if that is not what you are using or it will make invalid assumptions.
The references above which are in italics are out of date. The principles are still valid, and you can absolutely learn valid things from them, but you will need to refer to the latest edition of the Wiring Regulations to get the correct data.
Indeed. However, the difference in price between 4mm² and 6mm² is so relatively small that I personally might well be tempted by the additional 'future-proofing' provided by the latter!
Kind Regards, John
Again thanks for all your help guys, I have in fact sourced another sparky who has ben really helpful and gone through the load / numbers with me and recommends 4mm cable. He's coming to install and sign off in the next week or so.
My responsibility is to sort the cat5 from the house to the shed, and he recommends it goes in conduit rather than clipped like the armoured SWA will be.
I am going to use 20mm conduit clipped to the house wall, then into some flexi conduit to go underground for 2m and up into the shed. Will also be feeding in a telephone line as well. Got a couple of questions though:
I will be using:
http://www.screwfix.com/p/tower-con...rch-_-SearchRec-_-Area2&_requestid=128503#_=p
1. Where the cat5 exits the house, how to I get a sealed connection to the conduit, do I use one of these and punch a hole in the back?:
http://www.screwfix.com/p/tower-1-way-terminal-box-25mm-black-pack-of-1/86534
2. How do I join the rigid conduit to the flexi? And should this be done above ground just before the flexi goes under the paving slabs? I have seen connecting adaptors, are these the ones to use?
I know that ban-all-sheds said the flexi stuff isn't suitable before, was that just for electrics or for all cables? Do I need the twin wall again for the cat5?
The sparky will be laying the armoured cable direct on sand and marked up appropriately.
Thanks...
My responsibility is to sort the cat5 from the house to the shed, and he recommends it goes in conduit rather than clipped like the armoured SWA will be.
I am going to use 20mm conduit clipped to the house wall, then into some flexi conduit to go underground for 2m and up into the shed. Will also be feeding in a telephone line as well. Got a couple of questions though:
I will be using:
http://www.screwfix.com/p/tower-con...rch-_-SearchRec-_-Area2&_requestid=128503#_=p
1. Where the cat5 exits the house, how to I get a sealed connection to the conduit, do I use one of these and punch a hole in the back?:
http://www.screwfix.com/p/tower-1-way-terminal-box-25mm-black-pack-of-1/86534
2. How do I join the rigid conduit to the flexi? And should this be done above ground just before the flexi goes under the paving slabs? I have seen connecting adaptors, are these the ones to use?
I know that ban-all-sheds said the flexi stuff isn't suitable before, was that just for electrics or for all cables? Do I need the twin wall again for the cat5?
The sparky will be laying the armoured cable direct on sand and marked up appropriately.
Thanks...
Fair enough.
If you're talking about flexible conduit with a corrugated interior, then pulling a significant length of any sort of cable through it can sometimes be 'fun', particularly around bends, because of the corrugations.
Kind Regards, John
The problem with 20mm flexible conduit is that the combination of its small size and non-smooth walls makes it very difficult to pull an armoured cable through. You were talking about 6mm² cable - the diameter of that is 17 - 17.5mm. There would be zero chance of pulling that through ribbed conduit which inside is 1mm wider, at best. Even smaller cables are likely to snag on bends.
Cat5 would not be such a problem, it's smaller and more flexible, but might still snag on bends. Why are you so keen to avoid using twin wall ducting?
Cat5 would not be such a problem, it's smaller and more flexible, but might still snag on bends. Why are you so keen to avoid using twin wall ducting?
It will only be the cat5 / telephone going through conduit and the run is approx. 2m, so not a great length to get it through. The reason I'm seeing if it is ok as I actually have a reel of it at home and thought I could use it, rather than getting something else. I do understand that it can be a pain in the arse though. But if twin wall is better for future use or longevity, then I won't cut corners as I don't want to dig up the slabs again in a hurry if I can help it. (It's only 2 slabs so not an entire driveway or anything).
I'm assuming the 20mm conduit (rigid) is fine, but how do I link that to the underground (either flexi or twin wall) and also how do I cleanly connect to the hole in the wall where it exits the house?
It seems that the idea of running teh SWA in ducting has gone out of the window:
Indeed. Although it would be OK for very short runs, I personally wouldn't want to pull a significant length of even Cat5 through a duct with internal corrugations, particularly if there were significant bends involved.
Kind Regards, John
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