terminating swa

[Stephen]

Hello,

A previous owner has buried some SWA to take power from the house to the garage. Whilst doing some gardening, I found a metal junction box buried in the soil. It looks like it is coated in some sort of "lard"; I presume to keep moisture out and to prevent rusting but it looks on its last legs.

The cable runs to the far corner of the garage; I think if I ran the existing cable to the nearest corner, I would not need a join and I could do away with the box.

I have found the wiki very useful to learn about swa.

I am unsure: should the SWA bend through almost ninety degrees as it enters or leaves a building? That's what the current set-up is like but that seems quite a bend to me. Would it be better to run the swa up to a junction box on the wall, like this:

and from that take some T&E inside?

Thanks, Stephen.

[Huge]

FWIW (I am not an electrician), I have done it both ways. The latter after having done it the former way, once(!).

[Tim Watts]

The bend radius of SWA of the smaller sizes, IIRC, is something like 6 times the outside diameter.

As for boxes - yes, it's a good idea. But beware of the armour earthing. It's not sufficient to clamp the wire lug (banjo) under the nut up against plastic as the plastic will give, resulting in an unreliable joint.

You can use:

or switch to a metal box like:

Some of the plastic boxes do have an optional metal reinforcing bar available for SWA joints too.

[John Rumm]

Its not ideal, but you can do it as long as the bend is not too tight. You can mitigate it a bit by drilling the hole at a downwards angle as well. Stops moisture tracking the cable through the wall, and reduces the bend required.

Yup, that is the better option. I sometimes use those (and the piranha nuts that Tim linked to), or if its a socket circuit, then sometimes use an outside socket surface mounted as a termination point:

There is a 20mm knockout on the underside of the backbox that you can take a SWA into nicely.

Yup, that's the normal approach. However in some cases (say a submain to an outbuilding, where you are exporting a TN-C-S equipotential zone, you will need another larger equipotential bonding conductor as well.

See:

[Stephen]

Thanks. I like the look of the aluminium box you have linked to; I had not considered that the plastic would be too flexible.

What is the group's opinion on the blade runner tool? I thought it might be useful for a newbie like me, yet TLC seem to have them as clearance, which makes me wonder if they are not very popular/not very good?

Thanks, Stephen.

[Tim Watts]

I have done SWA exactly once.

It's not hard - run the outer sheath with a stanley knife and pull back a mm or 2.

Use a junior hacksaw to run around the groove and cut part way into the strands (not all the way). Remove sheath. Flex each armour wire until it snaps off.

Run stanley knife around lower down and strip next ring of sheath - and then proceed to the main core cable.

Obviously - a couple of dry runs on scrap with the gland on a table will let you work out the stripping lenghts of each component.

[John Rumm]

I have one, and they are ok... I suspect that many will conclude there are other ways of doing it, and so not bother. IME they work better than trying to use a normal pipe cutter. Hacksaw is fairly easy for larger SWA, and side cutters ok for small ones.

[ARW]

There is a reason for that;-)

Anything over 70mm?

Junior hacksaw for that.

I assume the OP means this

IMHO probably one of the best tools I have ever owned but with only one caveat. I have done several hundred cuts with my bladerunner (and replacement blades) and all on 4mm or less SWA - I got my monies worth due to the number of SWA terminations I have done. For anyone going to do less than 50 SWA terminations then forget it.

[Stephen]

Yes, that's the one. I think it was recommended/mentioned in the wiki page about SWA. I don't mind paying £20 for a tool that will be used once if it will make it easier or give me a better result.

Thanks, Stephen.

[The Nomad]

Looks like a pipe cutter to me ...

Avpx

[John Rumm]

Its very similar, except the cutting wheel is replaced with a short section of hacksaw blade, which is rather better at cutting the steel wires. You can use a normal pipe cutter on small SWAs, but you have to do it up very tight, and it takes quite some time to get enough of a nick in the armour wires to be able to snap them off.

[tony sayer]

In article , Stephen scribeth thus

Looks the same as a copper 15-22 mm pipe cutter that does!.

[Richard Conway]

Having just done 12 SWA terminations as part of my brewery build I can attest that using a pipe cutting tool works pretty well. I simply used it to cut the sheath and mark the steel armour which I then trimmed using side cutters. Saved a fair bit of time and the joints were perfect.

The biggest tip I can give you is to remember to put the sheath and gland bits on the cable before trimming it - I forgot on more than one ant it's very difficult getting them all on once you've got the strands of armour sticking out!

[Tim Watts]

That 1970s rubber plug moment :)

[John Rumm]

Or a carefully made up and heatshrunk set cof connections to a DIN plug on the end of a cable with miniature co-ax enclosed.

[tony sayer]

That sounds a very good DIY project, can you tell us more?...

[Adam Funk]

It's sad but true!

[damduck-egg]

Should he be shy in case the netpolice think he is spamming putting his name plus Brewer into google brought up this.

G.Harman

[Stephen]

+1

[Stephen]

I think some cutting device might be preferable to a hacksaw because at least I would cut a nice circular cut rather than risk the two ends not lining up!

I do have pipe cutters but the "doughnut" style ones that are fixed for 15mm and 22mm, so not suitable for this purpose.

I am not sure whether to buy the proper tool for the job: the blade runner, which will only be used for this, or buy a pipe cutter for the same cost, which I could use on pipes afterwards?

John's comments suggest a pipe cutter will work but not as well. I guess because the blade is designed for softer copper rather than stronger steel?

Thanks, Stephen.