Pulling in cable - how hard can it be?

At last! I have a weekend free of pulling cables. :-)

16 mm² x 1 is just doable, but I am not sure that I would risk it for a live cable. x 3 is impossible, so I ended up with 6 + 6 + 4 for the lives. The dead tests are perfect.

The up the ladder - down the ladder - move the ladder - up the ladder - down the ladder, etc. bit is unavoidable, but the best bit is that I seem to have lost 3 lbs in 3 weeks. :-):-)

Hello, Chris. Wow... I've lost a few draw wires', in my time! VIR... you sometimes feel they will never unstick, (if that's a word), but, oh the joy of sparking!

far s I can remember... I just used the plastic draw wire to pull in a stranded single, for the BIG push, or pull.

All the best! Tom

Oddly, the part reel of "extra flexible panel wire" I have, that is really pretty much the same as UK 'tri-rated' quotes a bend radius of 6 times the OD - larger than the coarser stranded stuff. But that may well be based on repeated flexing rather than one-time installation - it can certainly be bent quite  easily about a much tighter curve than that.

Mike.

It is going to have to be Plan B. As Graham's diagrams show, the insulated cables appear to have plenty of room. OSG is not explicit, but perhaps it does allow for the thicker walls of (some) PVC conduit.

Here is my effort: with 3 x 16 mm² cables, they might be expected to fall under gravity into one of the two positions below. Vertical runs will slump together to some extent.

If we substitute 3 x 6 mm² for the live conductors, there still seems to be plenty of room and the 7 strands of the 16 mm² conductor have now become 21. Granted the bends tend to be squashed a little, but the smaller cables should be able to fit around the larger one more easily.

I think that I have got the scale correct, but just in case, here is some real conduit and cable.

I can probably manage with 2 x 6 mm² for the live conductors. Table 4D1A gives 41 A for each, but multiply by a factor of 0.8 per Table 4C1 and that gives 65.6 A, which is fine on a 63 A MCB.

Frankly, I don't intend to get anywhere near 63 A, whcih would cost about £4.50/hour or £110 per day!!!

mapj1 said:

but having stripped back the T+E the bend radii of the exposed tails ought to be similar to conduit cable singles - if not then someone has been pratting with the laws of physics again ;-)

Yes, if the material and class of conductor, thickness of the insulation, and the insulating material, are the same.

To confirm, this would be the case for 6, 10 and 16 sq mm 6192Y and 6193Y to BS 6004, compared with the same csa of H07V-R to BS EN 50525-2-31.

but having stripped back the T+E the bend radii of the exposed tails ought to be similar to conduit cable singles - if not then someone has been pratting with the laws of physics again ;-)

Mike

mapj1 said:

Well, Eland list 16m2 as having a min bend radius of 4 times the over insulation cable

Agreed ... as I posted earlier here: engx.theiet.org/.../136412

mapj1 said:

Actually I wonder how many folk over bend 10mm2 in shower switches etc

Interesting ... although to be technically very pedantic, difference vs 1c is that the bend radius is usually given for the cable, not the conductor. So, perhaps an oversight on the cable manufacturer's part (although this ought to be pre-empted by the switchgear or accessory manufacturer, because in any case the product may be served by singles in containment)?

Well, Eland list 16m2 as having a min bend radius of 4 times the over insulation cable dia, so 4 * 7mm  =28mm, so you really should be forming around a 56 mm or larger diameter mandrel - or the size of a  2 inch pipe in old money. I presume you have got at least  6 inch boxes?

Actually I wonder how many folk over bend 10mm2 in shower switches etc- there the rule is 3 times the overall diameter so 6mm*3=18mm or a 36mm diameter loop.

Mike

Hm! The hardest bit, which in fact may be attempting the impossible, is dressing the loops of cable into the BESA boxes. I am not sure that my thumbs are strong enough.

Given what I know now, I would have gone for three-phase and may still have to if I am not happy with the IR testing.

You live and learn!

Hi Chris,

After going through the replies from the thread, here's my take:

1. Teamwork Makes the Dream Work: Simon and AJJewsbury are spot on. Whenever possible, get someone else on the other end. Pulling in thick cables can be a two-person job. It's all about the balance between feeding and pulling.

2. Conduit Size and Bends: Broadgage and Sergio got a point about the conduit size. But I get your point about space constraints. Sometimes, the ideal solution isn't always practical. Too many bends and even the recommended sizes can become a chore.

3. Alternative Methods: Andy's idea about threading individual lengths of conduit over the cables is clever. It's a workaround, but it might just do the trick in tricky situations.

4. Materials and Techniques: WHJohnson suggested SWA. While it may not have been ideal for your situation, it's good to have options. Mike and Tom shared some wild stories. Sometimes, unconventional methods can be lifesavers - like Tom's use of lard or fairy liquid, and Mike's coax inside a nylon 'suzie' pipe.

5. The Third Cable Conundrum: As you and Graham highlighted, the third cable sliding between the other two can be tricky. The twists, the bends – it's a whole other beast.

6. Bending Challenges: Mapj1 and gkenyon provided insights about the cut-off distance and bending challenges, especially when dealing with rigid cables.

7. Patience Is Key: Your comment about patience hits the nail on the head. It's a tough job, and it's all about taking it step by step. As you rightly said, demonstrating that the job is possible is what counts in the end.

Yes, the OSG might give guidelines, real-world scenarios can throw you a curveball. 

take it easy on yourself! It's a tough job, and sometimes, it's just going to be a grind.

Cheers,