Workshop/office power, prep for later years

[Daman2971985]

Hi all,

Im a recent home owner, and have a long term plan to build a building at the back of the garden (about 20 meters long garden). Consumer unit is at front of house and an awkward position so routing the armoured cable will be almost impossible once everything is decorated.

The workshop won't be happening for a good few years (need to save up!!), but currently my ceilings are down so I thought I should consider doing prep work now to save smashing up ceilings down the line.

Basically I'm thinking of putting in flexible conduit from the consumer unit to the back of my house with a draw cord ready for the eventual sparky.

The question is would a draw cord even work for amoured cable (would be a little less than 10meters of conduit). And if so, what diameter of conduit would be sensible (I'm assuming a 40amp trip)?

 

[flameport]

Draw cord as supplied with the duct will work for any cable. It's used to draw in a much more substantial rope, and that rope is then used to pull the cable in.
50mm diameter minimum, larger if possible. Ideally no bends, but make them as shallow/gentle as possible if there are any.

 

[plugwash]

In the UK we generally make a distinction between conduits and ducts.

Conduits are designed to be joined to electrical enclosures and are normally used with single wires. Common sizes range from 20mm to 32mm. Too small to reasonablly pull a SWA through.

Ducts are much larger and are designed to have cables including armoured cables pulled through them. They are normally run underground and usually do not run all the way to the final electrical enclosure. Sizes tend to start at 50mm and go up from there.

The problem I see with your plan is that is running a duct through a house is likely to be difficult. Most joists are likely too small for drilling a 50mm hole to be acceptable. bends in ducts should also be swept with a large radius

 

[Daman2971985]

Thank you both for your replies, that's helped a lot! Looks like my plans of future proofing were flawed!

Youre right though, the runs would need to be between joists (and through one) and down the walls, can't imagine I could get a shallow bend at either end and a 50mm hole in the joist in question would be too big anyway.

As an alternative, could I run a cable from just outside the consumer unit to a box on the back wall of the house? That way in the years to come a sparky could just connect that cable into the consumer unit and join on a length of armoured to run the length of the garden?

 

[ktuludays]

I was

Thank you both for your replies, that's helped a lot! Looks like my plans of future proofing were flawed!

Youre right though, the runs would need to be between joists (and through one) and down the walls, can't imagine I could get a shallow bend at either end and a 50mm hole in the joist in question would be too big anyway.

As an alternative, could I run a cable from just outside the consumer unit to a box on the back wall of the house? That way in the years to come a sparky could just connect that cable into the consumer unit and join on a length of armoured to run the length of the garden?

That's what I would do. Engage with a spark to ensure what you do is ok with them and get the cable with spare at each end to allow for termination sat in place now.

 

[Notch7]

As an alternative, could I run a cable from just outside the consumer unit to a box on the back wall of the house? That way in the years to come a sparky could just connect that cable into the consumer unit and join on a length of armoured to run the length of the garden

That was my thought when I saw this thread.

Run some twin and Earth to the rear of the house and stick it in a suitable enclosure.

make sure you use a big enough cable and if necessary a separate Earth - twin and Earth always has a much smaller Earth cable, maybe insufficient for exporting. You could a 3 core cable maybe hituff

 

[plugwash]

Personally I would advise using SWA even for the internal part of the run. that way you avoid any need for RCD protection of the cable.

 

[cdbe]

I ran a surplus length of 6mm cooker cable from my CU at the front of my house to a JB at the back and from there about 20m of heavy duty SWA to my garage (with a proprietary resin joiner about 2/3 the way up). Can't quite remember what I did with the earthing/sheathing but my electrician relative said it was "acceptable".

At my last house, some years ago, I had a 30-40m length of 2.5mm T&E from house to garage buried in a hose pipe! My electrician at that time told me to put a plug on the end and call it an extension lead. Worked fine but the lights in the house used to dim a bit when I used my welder.