running armoured cable to shed - connection?

JohnB47

I'm planning to buy 25m of armoured cable to run from the house to a garden shed. I'm planning to run ordinary 2.5 twin and earth from the consumer unit (its own circuit breaker), under the floor and through a vent grill. At that point I want to connect the 2.5 to the armoured cable (2.5mm three core armoured).
Has anyone any advice on how to connect the two together? I was thinking of a weatherproof enclosure fastened to the wall outside. But there's also the in-line connector type, which I could use just inside the house. Any thoughts, also, on how to stop water coming in through the grill, where the cable exits? Maybe drilling right through the wall would be better (standard cavity wall) and fit an enclosure there with silicon gunge to seal it to the wall (with a screw or two too).
Any advice welcome.

knightstyle

Standard plastic connection box, Cable gland for the SWA with earthing washer and plastic cover plus a connection block inside the box.  Bring the 2.5mm t/e in the back of the box and silicone the back of the box before fixing it to the wall.

Belenus

Can you run the armoured cable in one length all the way from the Consumer Unit to the shed and avoid a connection?

Is that more expensive perhaps or more difficult to run under the floor?

Or too thick to connect directly to the consumer unit?

Is your consumer unit on an outside wall. You could drill through there and run most of the length outside.

JohnB47

A 25m length of armoured cable would do me to the side of the house. To go straight to the consumer unit - in the hall on the other side of the house from the side passage (and long garden wall that I want to run the cable along) I would need to go for a 50m drum - twice the price.
So I think I'll take knightstyles advice. I'll drill a hole through the wall and fit a waterproof connection box outside. The problem is, after much searching, I can't find a connection box cable gland that accepts 13.2 mm cable dia. Most seem to go up to 12mm.
I'm thinking of buying this cable:
https://www.screwfix.com/p/prysmian-6943x-grey-3-core-2-5mm-armoured-cable-25m-coil/38769#product_additional_details_container
I wonder if Screwfix will sell a suitable box and gland - I've looked at their boxes and they don't quote what size of cable they suit. Looks like I'll have to go to the store and have a chat.

adonis

What about somewhere like TLC,

https://www.tlc-direct.co.uk/

they should be more knowledgeable than screwfix.

fenwick458

I'd just use armoued all the way there. yes 50m is twice the price of 25m, but are you somehow obtaining 2.5mm T&E for free from somewhere? and what about the cost of the joint box and the time take to connect it all up?
2.5 SWA £1.20/metre for 50m is £60
2.5 SWA for 25m is £30, plus £13.25 for 25m of 2.5 T&E at 0.53p/metre
joint box materials could cost £3-4 depending on what you get...
so you are looking at saving about £13, plus you have to wire up a joint box also
If I have to join armored cables, I'd use a 20mm Galv through box. fasten the CP's to the box, and use 2 x through crimps for the L & N. use a 20S CW gland for the SWA, and a 20mm compression gland for the t&E. plus lid and gasket.

Belenus

Can you not buy the exact length of armoured cable that you need rather than a 50 metre drum?

A few years ago I bought the length I needed, 13 metres from memory. A local electrical supplier sold whatever length you require.

JohnB47

Thanks for the great ideas everyone. I have some 2.5 T&W left over from jobs in te past. I was just trying to save a few bob by running it inside the house and jointing it to the SWA outside. I see that if I buy 30m of SWA from TLC Direct (30 meters would need no joint) it would cost £40.05 They have a place near me, so I could collect. As for usage, it is really just for lights, a jigsaw, a log splitter and occasional vacuuming. Nothing too heavy. I've been doing that for years, using an extension lead connected up when I need it. Not really sure if I should go for heavier cable.

I've just used TLCs calculator and it shows that, if I used 30 metres of 2.5 SWA 3 core, I could go to 4Kw with a voltage drop of 8.35 volts (3.6 percent) max current cable load 17.4 to 31 Amp. That is way above what I need now and what I'm likely to need in future.

Thanks again everyone.

Just another thought. If I use SWA all the way, I'll have to drill quite a large hole through the wall - more expense for a large long masonery drill bit. (Screwfix quote their cable as 13.2mm dia, so I'd need, say, a 16mm bit - around £7 depending on length). Then, as it comes out of the wall, I'm planning for it to go down and underground across the side path before going up and along the rear of the fence posts. I'm assuming that this cable doesn't bend much, so how is it going to look coming out of the wall - a big loop sticking out? Or maybe drill below path level and bring it straight out. I could do that. It would be well below the dpc and into a void under the floor inside - just need to seal the hole well.

Risteard

JohnB47 said:

Thanks for the great ideas everyone. I have some 2.5 T&W left over from jobs in te past. I was just trying to save a few bob by running it inside the house and jointing it to the SWA outside. I see that if I buy 30m of SWA from TLC Direct (30 meters would need no joint) it would cost £40.05 They have a place near me, so I could collect. As for usage, it is really just for lights, a jigsaw, a log splitter and occasional vacuuming. Nothing too heavy. I've been doing that for years, using an extension lead connected up when I need it. Not really sure if I should go for heavier cable.

I've just used TLCs calculator and it shows that, if I used 30 metres of 2.5 SWA 3 core, I could go to 4Kw with a voltage drop of 8.35 volts (3.6 percent) max current cable load 17.4 to 31 Amp. That is way above what I need now and what I'm likely to need in future.

Thanks again everyone.

You shouldn't select 3 core - that will presume that it's a three-phase supply. You should select 2 core.

Also lighting is advised to be restricted to 3% volt drop.

Also the cable should not be run through a vent.

You should be getting an Electrician to do this for you - it's not a DIY job. You probably don't even know how to gland/terminate SWA cable.

Homer_home

JohnB47 said:

Thanks for the great ideas everyone. I have some 2.5 T&W left over from jobs in te past. I was just trying to save a few bob by running it inside the house and jointing it to the SWA outside. I see that if I buy 30m of SWA from TLC Direct (30 meters would need no joint) it would cost £40.05 They have a place near me, so I could collect. As for usage, it is really just for lights, a jigsaw, a log splitter and occasional vacuuming. Nothing too heavy. I've been doing that for years, using an extension lead connected up when I need it. Not really sure if I should go for heavier cable.

I've just used TLCs calculator and it shows that, if I used 30 metres of 2.5 SWA 3 core, I could go to 4Kw with a voltage drop of 8.35 volts (3.6 percent) max current cable load 17.4 to 31 Amp. That is way above what I need now and what I'm likely to need in future.

Thanks again everyone.

Just another thought. If I use SWA all the way, I'll have to drill quite a large hole through the wall - more expense for a large long masonery drill bit. (Screwfix quote their cable as 13.2mm dia, so I'd need, say, a 16mm bit - around £7 depending on length). Then, as it comes out of the wall, I'm planning for it to go down and underground across the side path before going up and along the rear of the fence posts. I'm assuming that this cable doesn't bend much, so how is it going to look coming out of the wall - a big loop sticking out? Or maybe drill below path level and bring it straight out. I could do that. It would be well below the dpc and into a void under the floor inside - just need to seal the hole well.

You do know what you are planning to do is notifiable work dont you?

FreeBear

Risteard said:  You should be getting an Electrician to do this for you - it's not a DIY job.

Ignoring the "DIY" bit, a new circuit, especially outside, should be signed off either by a competent registered electrician or by building control.

If you can, I'd suggest drilling a hole through the wall - £7 for a long drill bit isn't a huge expense, and will make for a neater job.