Running power to my shed, but trying to avoid a big trench

[Eric The Viking]

I've got 40mm waste pipe buried in the same trench with a pull string, ready to run some cat 5, CCTV leads and a doorbell/phone extension. Getting under the brick flower bed which delineates a 2 foot change in level was fun! I used a bit of downpipe fitted with a T-handle to bore down at 45 degrees, like a cheese taster!

Clever stuff!

As I said though, use braided draw-tape (rope/string) or be prepared to have a lot of tangling up going on. And try as much as poss to unroll off a cable drum, rather than pull off the side of the drum - anything that gets twists out before you send it into the duct.

I'd pull at least two at once to start with, too, as that reduces the risk of twisting up.

 

[jackjohnsonuk]

How about some pictures of the problem?
Theoretically a 25mm2 external diameter cable should have a a bend over about 450mm(ish) based on some old rules of thumb - So probably wouldn't stick tight enough to the building to be viable

 

[AJB Temple]

Why can't armoured be attached to a fence?

British rail near us have just run about 100m of armoured (several lots) on brackets above ground in one of their car parks. It is on the public parking side.

DIY sheds frequently run cables in exposed trunking trays. The new Notcutts garden centre and restaurant near Tunbridge Wells is largely cabled this way.

My Part P electrician has just passed 4mm cable to an outbuilding that is mostly secured to a wire fence. I didn't install it (was done a few years ago by former owner) but he did not feel it was either unsafe or breached regs. It is after all armoured. There are numerous guidelines but not much of it seems to be enshrined in law. The key thing is not to do things that are unsafe. A well routed visible cable above ground may be safer than an invisible cable underground in some circumstances?

 

[Bm101]

Don't know if it would work but I was just wondering about pushing armoured cable through pipes. Had a thought that maybe you could cut a cross in a tennis ball, shove the cable end into it and duct tape it up. Your ball acts as a buffer to any pipe joins etc that could catch a cable end. Bit similar to the old wheeled drain rods. Obviously it's only got a chance of working with armoured or heavy duty cable. Just a thought.

 

[MusicMan]

Just a point - the armoured cable required is very expensive. So even if you can bend it to the radius needed, it's going to be costly to take a more devious route than the shortest.

Keith

 

[AJB Temple]

For the short runs contemplated the differential cost of armoured is small. It is readily available on line. I just (yesterday) bought 120 metres of 16mm 3 core which came to £450 delivered including VAT. This is very heavy cable and we are only looking at £3.75 a metre inc. (you will pay more for shorter lengths but not massively more). An extra few metres will be irrelevant. It would have been £160 for 4mm 3 core armoured which will be sufficient in many cases with low voltage drop and not much demand. On-line prices vary by as much as double. Shop around.

 

[Racers]

Don't know if it would work but I was just wondering about pushing armoured cable through pipes. Had a thought that maybe you could cut a cross in a tennis ball, shove the cable end into it and duct tape it up. Your ball acts as a buffer to any pipe joins etc that could catch a cable end. Bit similar to the old wheeled drain rods. Obviously it's only got a chance of working with armoured or heavy duty cable. Just a thought.

Pushing cables doesn't work the friction between the cable and duct increases as you push and the cable kinks and rubs against the sides, pulling will straighten the cable reducing the friction.

Pete

 

[Wuffles]

Don't know if it would work but I was just wondering about pushing armoured cable through pipes. Had a thought that maybe you could cut a cross in a tennis ball, shove the cable end into it and duct tape it up. Your ball acts as a buffer to any pipe joins etc that could catch a cable end. Bit similar to the old wheeled drain rods. Obviously it's only got a chance of working with armoured or heavy duty cable. Just a thought.

Pushing cables doesn't work the friction between the cable and duct increases as you push and the cable kinks and rubs against the sides, pulling will straighten the cable reducing the friction.

Pete

Unless you can put a wave into the pipe that's enclosing the wire, which in this instance you can't. For reference, when trying to get a wire into some conduit, pushing, as you pointed out, it'll fail pretty quickly as it just jams.

However, fix one end of the conduit, with a brick or something, pull it taught and put a sideways wave into it, it eats the cable up and pulls itself through.

Just in case that was of any use to anyone ever, thought I'd leave it here.

Try it, it's fun. I do it all the time when trying to get cat5 cable to outbuildings at my place. You know, it's a hobby and I'm not hurting anyone.

 

[Racers]

You can blow string down with a compressor, or rope with a bigger compressor1

Pete

 

[Wuffles]

You can blow string down with a compressor, or rope with a bigger compressor1

Pete

Did that with a ping pong ball once on the end of some thin gauge rope. Worked a charm.

 

[woodshavings]

I have armoured cable clipped to the garden fence to the 'shop.
John

 

[m1ke_a]

Thanks for the inputs guys.

Have had 3 sparks out to price up the work. Interesting to get different interpretations from "yeah it's your garden, you can do what you like and I'll just bung a MCB in the house CU" to the more considered "a switched fuse at the house end would be one option", "have you thought about inserting a small piece of conduit between the front door frame for future?" and "BTW the new amendment 3 regs may mean some design tweaks"

I'm definitely leaning towards the two who spent more time discussing the options and pointing out little details!

I was initially leaning towards a 40a total load and using 10mm SWA. One of the sparks thought that pretty high and two said 10mm is going to be fun to work with!

Shed has 3 fluo lights and the maximum I'd be running in there is a 1/2" table router, bandsaw, circ saw, workshop vac, some chargers and an oil rad. Obviously only the lights, vac and one tool at a time would be in operation so the continuous load wouldn't be too high (would it?)

According to http://tinyurl.com/zs5ulrk 40m of 3 core 6mm SWA = 7000w / 30.4A

Have since come across reels of flex ducting - http://tinyurl.com/jn3j8zr so that covers protecting the cable (and thanks for the tips about pulling cable).

On the patio, I have to cross a foul drain, I'll be going alongside out incoming water main somewhere and could also cross a bit of the gas main so I'd rather not try moles or mechanical digging! - The gas board got their mole stuck when they renewed the gas and had to close part of the main road to dig it out! :lol: