Given the difficulty of pulling SWA through anything but smooth wall ducting, I'd bury the SWA direct and run the duct in the same trench and use that for comms alone.
The exception might be to run fibre in the same duct as SWA - depends on the relative price of a couple of cheap transceivers vs extra duct. Doesn't help the phone though.
Ages ago I came across this:
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's the genuine ducting - but hell, it costs (nearly £4/m)
50mm waste pipe is much cheaper - the only issue is forming bends in it that aren't sharp. Hot air gun perhaps.
Is that a complete no-no? Can I use high voltage isolators at either end? Ethernet magnetics are designed to withstand substantial primary-secondary voltages.
For the OP, there are methods of using power cable as the netork medium, Homeplug?
For a 20m run, use 2.5mm armoured cable from your local TLC. Unless you're welding, in which case 4mm. They also have an on-line calculator to assess voltage drop when loaded. From TLC (and similar) armoured cable is cheaper than you'd think, although it's an indecent price from the retail sheds.
Use the right glands. Ideally buy an armoured cable cutter (like a pipe cutter) as it's a fiddly job, otherwise let the sparky do it or do it with a hacksaw, but carefully. It's also often often a good idea to terminate the armoured cable conveniently at a small box just inside the shed / house, then cable from there with something more flexible.
20mm plastic conduit internally is cheap and easy, worth the effort compared to cable clips onto timber.
I wouldn't bother with phone or network cabling, as wireless is easy enough these days. You might consider wiring in an alarm though? I'd lay this in plastic pipe in a separate low-voltage duct, but still use direct-laid armoured cable for the mains.
Surely SWA is adequately protected to allow it to be run in proximity to anything? However, cat5 would need some mechanical protection in a duct of that size shared with SWA, Flexible conduit would do for that.
Is it true when using SWA? You can put signal cable next to mains if there is a physical spacer, i.e. a bit of plastic. SWA has insulation surrounded by insulation surrounded by wire armour and another layer of insulation. That makes it far better separated than it needs to be.
Stick a few cat5es in there too, and maybe a hose or rigid waste pipe as well to enable future cable to be added. Cost peanuts, and you'll kick yourself later if you dont.
Cat5e? This is for a shed! I'm just looking for an alternative to an extension lead.
Earthing depends on construction, any incoming services, any class-1 tools outside (or inside on concrete floor really). So it is possible the spark will want to TT the shed with a local earth tod, however using 3-core over 2-core is little different.
Cable installation.
- Duct - "perforated land drain" of 80-100-110mm.
- Burial depth - Suitable for ground usage, which means 450mm unless cultivated whereupon 600mm+ is better.
- Trench clearing - Clear trench of stones even if you use a duct
- Trench preparation - Base layer of riverwashed sand, duct or cable
- Trench infill - Drop in duct or cable, cover with 150mm of riverwashed sand
- Marking tape - yellow "electricity cable below" tape, splash of sand, fill in
Ebay do suitable black duct, 25m of 80mm is £18 plus delivery. The proper duct is called "twinwall" which has a smooth inside and is going to cost you over £100. You must keep bends very long to facilitate drawing in of the cable. Pick up some polypropylene rope - feed it through the duct via a vacuum cleaner & cloth or flexible cable-rod.
TLC Direct do yellow electricity marking tape, as well as suitable SWA cable & CW glands.
If you lay the duct in advance, take a few digital photo's of a tape- measure on top showing the depth and route. That way there is little concern about the spark signing work off (if he is bothered, most are too trashed from trying to carry immovable 10mm FTE reels to want to go digging a 20m trench in a garden without a mini-digger, dynamite etc).
I'll just use a bit of drain pipe to get across the patio part of the route so I can get on with that.
There's nothing wrong with any of those approach that I'm aware of, in the context of SWA, though if there is, I'm happy to have a regs reference.
The SWA doesn't need RCD protection in its own right (other than that that may be required by having a TT earth provision on the supply). Other parts of the same circuit might need RCD protection if they are concealed etc.
The shed does, at least absolutely on the socket circuits and possibly on the lighting if the wiring is concealed but not mechanically protected etc (though it's arguable a good idea anyway, being in a possibly damp location).
The disadvantage with having it at the house end is that when your angle grinder trips the RCD, you're possibly left in the dark holding it.
However, if you follow some of the options in the Wiring Matters Guide, this is exactly what will happen. It's not an absolute - just something to consider.
Arguably the ways from "best" to "worst" might go (with none actually being "wrong" AFAICT):
0) 2 completely independent RCBO feeds from house to shed, one lighting and one sockets. Local DP isolators in shed.
1) Non RCD distribution circuit to shed, two RCBOs in shed plus main isolator, feeding separate lighting and socket circuits (the mini CU).
2) Single circuit (not shared) RCD protected feed from house, sub fusing (eg FCU) for lights in shed.
3) Shared RCD covering multiple circuits feeding MCB then shed, then as 2)
I numbered the first one as 0) as it's not exactly a standard solution, but I'm doing it. It offers the greatest resistance against spurious trips on the lighting circuit.
No one does it because it means 2 cables to the shed. However, rather than actually adding an extra circuit, this will be part of a more general outside lighting circuit that was to exist (gatepost light, lawnmower shed light etc) anyway. So I can blow my socket circuit away, and still have lights. DP isolators in the shed in one enclosure to give a clear means of isolation of all local circuits.
1) is arguably the next best as it protects the lighting from spurious tripping due socket circuit RCD tripping. But if you overload or short the socket circuits, you will almost certainly open the breaker at the house too.
2) The most common scenario.
3) Probably quite common. Most likely to cause inconvenience, but not fundamentally unsafe.
(Debate is welcome - that's only my opinion)
You mean PME?
Well, that one causes infinite arguments - just have a look at teh IET forums. I believe that you are supposed to consult with the DNO. No one of course does in a domestic situation. Otherwise, it has much to do with whether you have exposed metalwork which may reference other earth zones - eg metal water pipes between buildings, or metal framed buildings in contact with the local ground.
Even if you have a TN-S supply, the DNO might convert it to TN-C-S (PME) randomly one day or you might suffer from the same sort of issues if the DNO's local network is MEN. Or they might say in writing you have TN-S but you actually have TN-C-S (that happened to me - EDF wrote TN-S in black and white, but the fuse puller chappie said that was bollocks as soon as he's looked in the cutout. I'd had my suspicions due to the L-E impedance measuring the same as the L-N impedance and both being very low.
I think, for a wooden or masonry shed 20m away, I wouldn't bother too much. Notice I said "I". It's not something I think the OP should do on my say so, but I plan to do exactly so myself. I merely raised it as an "issue" to consider, but I'm happy to have a conflab about it.
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