Terminating old SWA

[D.M.Chapman]

While fixing parentals washing machine last night (broken wire to motor it turns out) I had a look at the "damaged shed feed"

Turns out to be rather ropey...

3 core 2.5mm SWA running to shed. in shed it's joined with a terminal block to some T&E that's run into the back of a socket in the coal shed attached to the house.

This T&E is damaged, and needs replacing (that bit is simple :-))

Given I'll be sorting this, I want to improve the rest a bit.

Questions:

1) How do I terminate the SWA in the coal shed? Looking at toolstation I see the SWA gland kits but they offer "Small" or "Standard". What am I going to need to 3x2.5 SWA (OD of cable is just over 12mm)?.

2) What the best/easiest box to terminate the SWA in - I was assuming a metal box but I see plenty of plastic ones that look suitable. For example, would I be able to fit the SWA gland to this (or similar):

or

Alternatively,

looks good but is that designed for surface mounting (doesn't look like it). Whatever I terminate the SWA at will be screwed to a wooden joist in the roof of the coal shed, and likewise at the shed end (about 8 metres away).

3) Thinking of then wiring it into a switched fused outlet (instead of directly into the back of the socket as it currently is). If I were to run conduit (just the plastic stuff) then am I going to struggle to get T&E through this? I know the single cable is available, but only on rolls of 25m or more and I'll only be needing 3 m... If 2.5mm T&E through 20mm conduit isn't going to work, any reason I can't strip the T&E I have to provide singles to pull through the conduit?

Note: I'm not planning on changing the earthing (currently via one of the cores, and I'll add the currently unearthed armour to this as well), or anything more exotic that sorting out the dodgy termination of the SWA and providing a switch. Whole house is on a 30ma RCD so there is protection there - and AIUI, exporting earth 8m to a shed isn't likely to be a problem (I know, ought to test it properly but...).

It's only to run a flourescent tube in the shed a a socket for radio etc. Nothing major, dad has parkinsons so his days of playing with big powertools is gone (if nothing else, the electric motors have a habit of turning off his brain implants via his magnetic reed switch in his shoulder :-))

Cheers,

Darren

[Tim Watts]

On Tuesday 03 September 2013 09:57 D.M.Chapman wrote in uk.d-i-y:

Try this:

size-chart.html

I would say the 20mm "small" (20S) should do the job there:

If you use a pirana nut,

you can terminate in any reasonable junction box. I would only avoid surface mounted backboxes as they are a very hard and brittle plastic.

Or you can use the Wiska earth bar:

and the matching box:

That gives you the internal terminal bar and self sealing rubber exits for the T+E. Probably the easiest and neatest. Saw a load down the Highcliff (at Christchurch) Premier Inn the other day on external lighting posts. 2x SWA looping through and (presumably) a connection through the box back for the luminere. So they are clearly deemed good for external use.

That's actually a suggested method from the IET Wiring Matters magazine (readable online if you google).

2.5mm2 T+E will easily pull though 20mm round conduit even with several bends (OK you need to pull it though with a leader string, but I've done it several times).

Good. Unearthed armour is not compliant. Clearly put in by some fool who did not understand how SWA works!

Not likely to be a problem there.

[dom]

Yup, 20S SWA gland.

This is a nice box to mount an SWA gland, the covers pop out and are the correct size (used one a couple of weeks ago).

[spuorgelgoog]

Tinfoil waistcoat?

Owain

[ARW]

Terminate the SWA into

at the the house side if possible.

[D.M.Chapman]

Was planning on using one of those as the switch, yeah. Won't be able to terminate the SWA there though - it finished up at the roof. One of those with a blanking face plate would be perfect but they don't appear to exist.

Also, does that come with 20mm cut out for the gland fitting or would I need a 20mm hole saw as well?

Cheers,

Darren

[dom]

If you do, I bought one of these ages ago and it's proved its worth many times over:

(20mm standard backbox grommets and SWA glands)

[fred]

In article , D.M.Chapman writes

They have knockouts and are fine for terminating armour, plenty of room.

I see what you mean about

not being intended for surface mounting but I can't see any openings that would actually disqualify it for that use. Clearly not intended for a location where there's any wetness but as a DIYer I'd be happy to use it (my pref is for metal boxes in semi industrial locations :-).

[D.M.Chapman]

Pondering something like

for terminating at the remote end.

Given I would need to fuse the lights properly, by the time I've fitted a couple of fused spurs for the lighting (currently 1mm2 cable on a 13A fuse which isn't ideal *sigh*) it might as cheap (and easier) to fit a small CU on the end and a couple of small MCBs.

Darren

[fred]

In article , D.M.Chapman writes

Yep, that sounds like a good idea although maybe consider one with an RCD incomer so the socket will protected for outdoor use:

with 32A socket mcb with 16A socket mcb

If already RCD'd at the house end it would allow moving over to a non RCD position to save outside leakage tripping the house.

[D.M.Chapman]

I would, but the whole house is protected with a 30mA RCD already. Is there any real advantage in having another one? (or any real disadvantage).

Price wise, that second on is very tempting though...although appears to not actually exist in stock anywhere :)

There are no non-RCD positions. There are also no spare ways at all.

This started as a "can you replace the damaged T&E" and I'm keen to avoid ending up with a rewire :-)

Darren

[fred]

No benefit as you wont get any discrimination between the house and second RCD but it would mean you already have the bits if you decide to change the in-house connections at a later date (like after some damp in the shed trips the house RCD while your dad is on hols and he loses a freezer full of food[1]). No disadvantage I can think of.

Now showing as clearance. The other one only needs an extra 16A MCB so

2quid more. Maybe try CPC, they're free post on all online orders and usually cheap for this kind of stuff.

Understood.

[1] I only mention it as your posting history suggests a bit of a bad luck gene in the family ;-/

[D.M.Chapman]

Lol! I'm now wondering what I've posted in the past....

*goes to hit google*

Darren

[fred]

Sorry, for a moment I had you mixed up with Dave (unlucky with computers) Roberts (don't know why).

[dennis]