External Cabling Requirements?

[Peter Ashby]

I have a power cable running to my garage (not installed by me). It comes off a secondary consumer unit, runs under the floor and then out through a hole punched in a vent, then up beside the downpipe, over the top of the gate and in under the roof gap (concrete sectional garage). The whole thing looks pretty kosher apart from the cable, it is standard internal grey 3-core (about 3mm I think). I want to upgrade this, partly so I can get it down from over the gate (problematic for carrying tall things in) and run it over the ground (well, along the front of the small step formed between the patio slabs and drive). Beavering around the sheds turns up armoured cable of various ratings including external but my understanding was that outside I should run cabling in trunking.

So can I replace the cable with this armoured cable or do I need to install trunking? if the latter can I get away with some plastic variety so I don't have to earth the metal stuff? and if so where do I buy it?

I sometimes wish the previous owner had buried it under the concrete slabs thus inhibiting me from doing anything about it ;-)

Peter

[nightjar]

Armoured cable can be run on its own. It is the indoor type of cable, as used in the existing installation, that needs to have extra protection. For that, I use black heavy duty 20mm round PVC conduit. There is also a cable called Hi-Tuf that can be used for external surface mounting, which is much easier to route than armoured cable. Personally, being a belt and braces man, I would use Hi-Tuf and also run that through conduit along the edge of the slabs, where it might expect to come in for more than the usual wear and tear.

Colin Bignell

[Peter Ashby]

I was looking at that this morning and I think I'll be able to excavate under the edge of the slab and recess the cable which should help that aspect. I was also thinking of putting a junction box in just inside the house wall since I don't see the point of running armoured cable all the way back to the cu.

Peter

[stefek.zaba]

Only the small disadvantages of it being another joint to potentially work loose, and of making cable-tracing a little less intuitive. For these reasons I kinda prefer HiTuF for visible external runs - nicer to work with where it comes into the CU, 'nearly' as resistant to likely mechanical damage in typical domestick situations. F'r example, as we redo the downstairs den I'll replace the existing 2.5mmsq T&E-with-HiTuf outside which runs to the nearly-attached garage with a single length of 6mmsq HiTuf, allowing an upgrade of the outgoing MCB from 20A to 32A with voltage drop well under relevant limitses - since the garage/wshop loads have noticeable switch-on surges and I want to be able to run the 2kW quartz heater, vac, and dust-making powertool without doing 'how close am I to 20A+ at this point' stuff in my head ;-)

Stefek

[T i m]

[T] I was looking at different 'tough' cable options and was offered what may of been 'HiTuf' as an 'as tough' alternative to armoured (black, round, fairly rigid and sounded like HiTuf from memory ..).

I asked if it would equally resist a hit from say a spade or fork and the guy said yes. He went and found a short length of the cable and piece of metal, put the cable on the counter and clumped it with the metal (I assume to demonstrate that it would take a blow from a spade)?

With the first blow he had nearly cut it in half ... I'll stick with armoured ;-)

All the best ..

T i m

[Lurch]

I must say I've heard this Hi-tuf recommended here and assumed it was the same as FP200 or Fire-tuf, I've never heard of Hi-tuf. If it is the same then it isn't really mechanically protected, it's fire alarm cable, basically flex, but mildly tougher. Maybe an example of Hi-tuf would help. ..

SJW A.C.S. Ltd.

[T i m]

[T] To me it looked 'like' armoured (silky deep black finish and quite 'stiff') but looking at the end it looked just like a thick sheathed flex? I can't even remember if the cores were solid or not (I'd assume they would be or multi stranded solid).

I found this ..

says

"Hituf multicore PVC cable is more robust than standard PVC sheathed cables and provides a quicker, more economical alternative for: General power, control and fixed wiring uses. Temporary wiring on open sites."

"Temporary wiring on open sites" dosen't sound like it would be the right thing for running power to a garage does it?

All the best ..

T i m

[nightjar]

HiTuf is a normally insulated round PVC cable, with an additional outer sheath of a much tougher plastic. The outer sheath protects against the degrading effects of UV light when surface mounted outdoors and it provides better mechanical protection than an ordinary cable. However, if you plan to bury a cable in too shallow a trench, where it might be vulnerable to spades or forks, then SWA is the stuff to use.

Colin Bignell

[Dave Plowman]

Description on the TLC site.

[nightjar]

I normally put a rectangular junction box rated to IP68 on the oustide of the wall, with a piece of conduit running back through the wall for the cable from the house. That enables me to run the SWA straight down from the bottom of the box. SWA does not bend easily and that is much easier than running it through the wall and then down. If I were using Hi-Tuf, I would run it right back to the CU, if possible.

Colin Bignell

[Lurch]

Not the stuff I'd use, I think I've come across similar stuff before, just used it as heavy duty flex, not for replacement of armoured. ..

SJW A.C.S. Ltd.

[Peter Ashby]

Ok thanks for that, I'll have a better look at the situation and think about the corners. In the present situtation with the flex there are two

90degree bends but running it at ground level should remove those though there is a solid concrete pillar to consider.

Peter

[stefek.zaba]

That's about right: it's (more than mildly) tougher than ordinary T&E, UV resistant, suitable for clipping to the outside of 'ordinary' domestic/light-industrial property (e.g. for feeding a bunch of BS4343 sockets), but is *not* a replacement for SWA in situations where there's a serious risk of mechanical damage. It's tougher than Fire-tuf, with the jacket being designed to provide mechanical protection rather than resistance to fire (and LSH): stripping it requires nontrivial effort, as the construction goes: outer black jacket (not all that hard), inner white not-much-plasticiser-in-this-PVC-(if-that's-what-it-is), in which the 'normal' PVC-insulated cores are in turn embedded. For burying, HiTuf would need additional protection (a tough conduit). But HiTuf's a handy addition to the armoury ;-) of cable types.

Others have pointed you at the TLC website; if you want a spare foot or so, email me you physical address and I'll send you an offcut, in the unlikely event your usual trade counters look at you blankly when you mention the stuff next time you're in...

Stefek

[Dave Plowman]

Some flex - it doesn't bend easily. IIRC, it's not designed to be used where a flex is anyway - it's an outdoor version of TW&E as it were.

[Lurch]

It's all academical anyway, I never have, and probably never will use it. Useful to know what it is now though. ..

SJW A.C.S. Ltd.

[Lurch]

Probably more useful the diy'er where SWA would be a little trickier to terminate, being a proper (!?) sparky I don't find SWA difficult so doubtful I'll be using Hi-tuf.

The nearest I've used has been Armaflex. As I say I can't see me personally needing to use Hi-tuf. Thanks for the offer though. ..

SJW A.C.S. Ltd.

[Dave Plowman]

It's quite useful where you have to surface mount a cable outside, like along a wall where it will be seen - it's quite easy to make a neat job of, and rather less of an effort than Pyro, although more obtrusive.

[Peter Ashby]

Well my job is done with Pirelli 35A armoured cable. It was forced on me since tying up the old internal flex over the gate while I demolished the column shorted it and blew the house CU unit fuse, but not the fuses in the garage (a giveaway that one). So here I sit, aching and sore from sitting under the house in a space too small for me fitting a junction box, first attempt fails, screws too small, armed with some appropriate spax screws it is up. Then the old cable needs to be cut (all house power off, just in case) and cleaned back. That is two long crawls under the floor and careful over the barely supported gas pipe. Then it is enlarge the hole in the air brick to admit the armoured cable (pre stripped). So back under (now with a head torch) and attempt to connect them together in the junction box. A connection is made, but I can't get the top over the armoured and I have forgotted to sleeve the earth cable, sigh. So its out for some tape and a cable cutter for the armor wires to cut the cable back some more and slap on some tape. 45 min later and its done, so am I. But I have to run it into the garage, cut it, cut it back again and wire it into the garage cu.

After a long soak in the bath and tea, the fuse is put back together (after cleaning molten metal out first) and the power switched on, so far so good, into garage, switch on, no bang! turn on lights, let there be light! flick switch to make the sockets live, they work!

So I have the garage wired with armoured cable, but the gate post is languishing. Why do things always toke so much longer than you expect? Oh and it snowed on me while I was enlarging the air brick hole.

Peter