Armoured cable?

[Trw144]

Can anyone tell me if I still need to use armoured cable for outdoor lighting if it's going in a duct? Seems expensive overkill to me?

 

On a similar note, if I m using armoured cable, can I install it without a duct?

 

lighting will be mains voltage.

[jfb]

pretty sure you can use armoured without trunking - but I am not an electrician! 

Needs to be a certain depth and covered by a bit of plastic warning tape I believe.

[curlewhouse]

If you do a search this has been asked about on a few forums. for some bizarre reason, armoured cable questions seems to meet with real hostility! I had noticed that when searching and then I posted a question about the size required on a DIY forum and the vitriol from a couple of people was astounding! (I actually blocked them so I don't have to read the snide remarks)  I think it's some professional electricians getting protective about people doing their own work (even if it's being properly certified). Which is odd as my father was a professional electrician and certainly was not like that, so it's not an "electricians" thing.  My own understanding is that you MUST use armoured cable.  But you will find the definitive answer as regards the regulations HERE

[Crofter]

The supply to my house (built in the 70s) is not ducted, but then again it doesn't have warning tape either, and is six inches under the lawn

[Jeremy Harris]

You do not need to ALWAYS use armoured cable outside, even underground.  Look at your mains incomer - I'll bet it's just a bit of coaxial power cable, half the diameter of a bit of SWA and a good deal cheaper too.

 

There are other outdoor rated cables available that are a lot cheaper and easier to terminate than SWA, and that can be run in a protective duct, or pinned to a wall, or provided with another form of suitable protection (cable conduit can be useful for protecting external cables in some locations and keeping it looking neat).

 

SWA is a PITA to use, because of the challenges in terminating it (it has to be terminated with an SWA gland, and they are not the most user-friendly things ever invented).  For cables run outside or underground in a protected environment (like a duct or conduit) then you can use NYY-J cable (see here: https://www.tlc-direct.co.uk/Main_Index/Cable_Index/NYY/index.html )  Not a great deal cheaper than SWA, but a heck of a lot easier to use!

Edited January 21, 2017 by JSHarris

[ProDave]

The electricians on this forum are a bit more friendly and will try to help.

 

You definitely can bury SWA direct in the ground, that's what it was designed for. And terminating it in glands is not particularly difficult, but I guess I have had plenty of practice.

 

The concentric cable that the DNO's use is not recognised in the wiring regs (they have different regs to work to). And in any case it's only a 2 core cable.  There is a variation on that, split concentric, where half the outer cores are bare, to be used as the earth, and the other half are sleeved, to be used as neutral but that does not strictly meet the requrements for direct burying.
 

[PeterW]

2 minutes ago, ProDave said:

The concentric cable that the DNO's use is not recognised in the wiring regs (they have different regs to work to)  And in any case it's only a 2 core cable.  There is a variation on that, split concentric, where half the outer cores are bare, to be used as the earth, and the other half are sleeved, to be used as neutral but that does not strictly meed the requrements for direct burying.

 

Funny that as I was watching them do the install last week - and live jointing the new breach joint - and it seemed quite "thin" compared to the 25mm²  stuff I will end up using to do the rest of the run from the gate to the house.

 

And SWA is lovely - especially when the glands have nice sharp edges....

[Steptoe]

2 hours ago, JSHarris said:

You do not need to ALWAYS use armoured cable outside, even underground.  Look at your mains incomer - I'll bet it's just a bit of coaxial power cable, half the diameter of a bit of SWA and a good deal cheaper too.

 

There are other outdoor rated cables available that are a lot cheaper and easier to terminate than SWA, and that can be run in a protective duct, or pinned to a wall, or provided with another form of suitable protection (cable conduit can be useful for protecting external cables in some locations and keeping it looking neat).

 

SWA is a PITA to use, because of the challenges in terminating it (it has to be terminated with an SWA gland, and they are not the most user-friendly things ever invented).  For cables run outside or underground in a protected environment (like a duct or conduit) then you can use NYY-J cable (see here: https://www.tlc-direct.co.uk/Main_Index/Cable_Index/NYY/index.html )  Not a great deal cheaper than SWA, but a heck of a lot easier to use!

Co axial power cable, LMFAO,!  

A little knowledge and all that, ,,,,,

Concentric, or split concentric will not be within BS7671 for a domestic install unless you use a deviation and can justify it meets or exceeds BS7671, so not really a DIY job,

SWA can be buried direct if trenched, and bedded correctly,

NYY cables and all other forms of armoured flex and Hi-Tuff need to be glanded correctly, which is no easier (or harder) than SWA tbh, but, very very few people ever gland any of these cables correctly,

also, if you have a PME supply, you MUST have permission from the DNO if you wish to use their earth outside the equipotential zone, I've never once heard of them grant it,

 

You can always wing it, lots of people do, but it would only takes the one fatality to be at your own place. 

 

[PeterW]

8 hours ago, Steptoe said:

A little knowledge and all that, ,,,,,

Concentric, or split concentric will not be within BS7671 for a domestic install unless you use a deviation and can justify it meets or exceeds BS7671, so not really a DIY job,

 

I think that's the point we've all made though - coax or concentric cables (same cable structure, different terminology) is used by the DNO up to the incomer fuse at which point it is then a domestic installation onward from the meter. 

 

Post the incomer fuse you are then into a domestic set of rules on cable which are more about do as I say not as I do ..!

 

Like all things, it's the detail in the connections that is key and earthing of SWA is one of those areas it's recognized there are issues hence the use of products such as the Piranha earth connectors. 

[Steptoe]

5 hours ago, PeterW said:

 

I think that's the point we've all made though - coax or concentric cables (same cable structure, different terminology) is used by the DNO up to the incomer fuse at which point it is then a domestic installation onward from the meter. 

 

Post the incomer fuse you are then into a domestic set of rules on cable which are more about do as I say not as I do ..!

 

Like all things, it's the detail in the connections that is key and earthing of SWA is one of those areas it's recognized there are issues hence the use of products such as the Piranha earth connectors. 

Piranha nuts still require the gland to be made off in the same way, they are really useful for glanding into a non metallic box though, where a normal gland and nut is of no use. 

Its also very common to see the wrong type of glands used, and glands made off incorrectly. Even by so called electricians, the amount of times I've saw BW 's used when it should have been CW (IP rated) , and also quite often CW made off incorrectly, 

External supplies really do require a decent understanding of earthing and how to terminate the proper cables properly, its not really a diy job IMHO , beyond perhaps installing the cable as instructed by your electrician.

[Trw144]

Many thanks for al your input on this. I had the armoured cable and ducting so (for this element at least) I would put the armoured cable into the duct.

 

However, looking at the cable, it looks a bit of a pig to work with. Therefore my next question, I have a couple of patio up lights that will most likely be 12/24v - therefore can I use a non armoured but outdoor cable for this element (still ducted)?

[Onoff]

Get a Bladerunner, it's a doddle:

 

Basically a pipe cutter with 1/2" of junior hacksaw blade in place of the cutting wheel.

 

I’ve seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhauser gate. All those moments will be lost in time... like tears in rain...

 

 

[Jeremy Harris]

Anyone tried a decent pipe cutter?

 

I have sheath strippers, etc, and up till now have always just trimmed the outer sheath back, used a sharpie to measure the cut point on the armour wires, wiggled the inner core around in a cone-like motion to neatly get the armour wires clear, then trimmed around the armour with a pair of sharp, double action, side cutters.  Does a very neat and tidy job, but is a bit of a faff.

 

So, looking at that tool, what happens if you ran a pipe cutter around the outer sheath, right where you want the armour wires trimmed, so that it scored the wires, then removed the excess sheath and broke the wires, as in that video.  Then use a standard sheath trimmer to trim the sheath back the right distance back from the cut armour and cleanly removed the sheath (and I have to say my adjustable sheath cutter, with its sharp blade does a MUCH neater job of cutting the sheath than that tool does).  From then on, it's assemble as normal, ideally with a Pirana nut rather than the  banjo and crap nut the glands often come with.

 

I may have a go with a pipe cutter and sharp blade tomorrow on a bit of scrap SWA and see if it scores the wires enough to get them to break cleanly.  If it does, I'm going to kicking myself, very hard, for not thinking if this before, all the more so because I have a pretty expensive pipe cutter, that was one of the best investments I made, and if it can do this job as well then it'll be a real bonus.  Also, I can't help thinking that a very sharp, hard, pipe cutter wheel may score the armour wires more cleanly than a bit of junior hacksaw blade, although I may be wrong.

Edited January 24, 2017 by JSHarris
typo - "od" when I meant "of"

[joe90]

I remember watching an electrician deal with the armour by using a half round file to file/ score the wires with the corner of the file  then simply snap them off, I was impressed how neat it was and the wires remained flat with the cable.

[ProDave]

Why make it complicated.

 

Where you want to cut the armour, run round with a hacksaw through the sheath and part way through the armour.  Cut the sheath off to that point. Snap the remainder of the armour off there, already weakened by being cut part way through. Strip sheath back a little more and fan out the armour strands as above.

 

It really is not difficult. This method and using the blade runner as above result in all strands of the armour being exactly the same length, which is crucial to getting a good clamp in the gland.
 

[Jeremy Harris]

I'm definitely going to have a go with a pipe cutter tomorrow, just out of curiosity.  I'm afraid I probably can't produce a great video, of construction channel standards, but I'll see if I can have a go at making one, as if it works, then it'd be useful to know, as a lot of people probably already have pipe cutters.

[ProDave]

I tried a pipe cutter. all it did was deform the ends of the strands and push them into the inner sheath of the cable. the result was the ends of the strand sall curled over and near impossible to terminate.  that's why the hacksaw or blade runner cuts them without pressure.

 

(look at the inside of a copper pipe cut with a pipe cutter, it will be burred inwards to some extent)
 

[Steptoe]

Unfortunately @JSHarris a pipecutter will usually just try and crush and slightly deform the cable, 

the cable just pushing itself into an oval away from the blade as it rotates,

I'm not too good at describing stuff (proper English is a second language to me, I only learnt it at grammar school at the age of 11)

Fit your gland to the box/enclosure

Line your SWA up to it, and mark where you want the armour to be cut with some tape, this keeps it square when you move the cable

Cut the outer sheath with a junior hacksaw, keep cutting round and round until you are halfway through the armour strands,

Slice the outer sheath off with a knife,

Flex the strands in and out and they will snap off, just do 3or4 strands at a time

When all broke off, offer up your shroud, the wrong way round

Now take your knife again and cut the tip off tour shroud where it sits on the inner sheath

Turn shroud around and fit

Slide outer nut of gland over, not forgetting compression ring etc if its a CW, and inner ring if it has one, 

Cut back outer sheath just enough to give you enough armour to get a nice seat on gland body

Mark and remove inner sheath where it will enter enclosure, 1/4" inside is adequate, ensure inner sheath is kept intact throughout the gland body,

Remove inner sheath

Slide conductors and inner sheath through gland body

Line armour to gland, (it may help to five it a squeeze with some pipe pliers)

Slide nut up (and inner ring if required),

Start nut by HAND, very important you don't cross thread

Tighten nut with tool of choice

(Tighten compression gland if applicable, CW only)

Slide shroud over

 

Additional notes

If a metal enclosure : final tighten of inner nut , hammer and chisel usual method for most

If plastic enclosure, ensure you have fitted your piranha nut the right way round, then insert your grub screw and fly lead.

 

If you are fitting SWA to removable steel panels the earthing methods are up to yourself, too many differing opinions on how to do it. But I doubt many diy will be doing that

 

HTH.

 

 

 

 

[Jeremy Harris]

Right, that's tomorrows experiment cancelled, then!

[Onoff]

I tried the pipe cutter too, not good from memory. 

 

I will for a laugh try and fit a bit of hacksaw blade to a normal pipe cutter in place of the wheel. The Blade Runner uses junior hacksaw blades don't forget. So you have a thin but square blade that cuts a channel in the steel core effectively weakening it - more so than the V cut a pipe cutter does.  Makes a lovely "zinging" noise too.....

 

I'll take some close ups of mine with a decent camera.

 

(Mind I've used a giant Record pipe cutter for scaffold tube before. Saved getting a Hot Works Permit).

[PeterW]

37 minutes ago, Steptoe said:

 

If plastic enclosure, ensure you have fitted your piranha nut the right way round, then insert your grub screw and fly lead.

 

 

 

 

 

Quick question then ... seen the external (CW..?) glands came with two nuts not one and the picture on the bag showed one either side of the earth tab. 

 

Is that for insulated or plastic boxes in place of a piranha ..?? 

[Steptoe]

2 minutes ago, PeterW said:

 

Quick question then ... seen the external (CW..?) glands came with two nuts not one and the picture on the bag showed one either side of the earth tab. 

 

Is that for insulated or plastic boxes in place of a piranha ..?? 

Yes, and no, but don't use them, 

Its a catch 22, the only way to use a banjo properly with a plastic enclosure is to fit it outside the box, slide it onto the gland, tighten first nut up to it, fit gland, tighten 2nd nut, but 2nd nut will not stay tight, plastic creep, so you need the first nut to hold banjo tight to gland

Piranaha nuts are the answer, saves a load of faffing about.