Getting cables thro flex conduit ?

[Spinny]

I have some 20mm flexible conduit running in the ceiling space to rooflights for led lighting.

Finding pushing a cable or fish tape down and it just seems to get stuck wherever there is a curve or bend in the flexible conduit !

 

Any tips for overcoming this ?

Should I replace with something else - smooth walled ?

 

(didn't expect this and was using the conduit to facilitate easy cable replacement in the future)

[Nickfromwales]

Roll up some cotton wool and tie on to 6lb fishing line. Then suck it through with a hoover. Then tie the fish wire to that, then use the fish wire to pull cables in. 
 

Use silicone spray and pull a dead fish wire in the same time you pull the required cables in, to make retro fitting easier. 

[JohnMo]

You would normally pre plan and have a pull cord in the conduit prior to install. 

 

You may find it easier starting one end or other end depending where the bend is. You can get electrician Flexi rods for doing cables

[Kelvin]

You suggest the conduit you’ve used is replaceable so if that’s easy to do then replace it with smooth wall. If not then all of the above. I found mixed success using a vacuum if the conduit is quite narrow. Taping up the end of the cable and applying a lubricant to it has generally always worked for me. Failing that I also have a fish tape wire puller that I used to get a cable across a ceiling at a friend’s house. 

[Spinny]

Thanks all...

 

I do have a lan cable through each flexi conduit already. But when I used it to try and pull the 2 24V cables through (plus another pull cable in tow), it all still got stuck. It only seems to take a fairly large radius 90 degree bend or a slight 'S' bend to cause problems. It seems surprising that this stuff is sold and seemingly used so much when the ribbing on it seems like a real problem.

 

Is there any danger to the cable sheaths from a silicone lubricant ?

 

 

if I tape up and silicone should I be aiming for a particular shape - I guess a shape wider than the rib width by 3 times perhaps ? Surprising they done sell some sort of rolling ball end to attach which would revolve as it is pushed around corners. (I claim that patent).

 

[andyscotland]

It can also help to do it as a two person operation - one applying fairly constant tension on the draw wire/cord (good job for a teenager if you have one 🤣) and one pushing the cable in at the other end. I've found that reduces the tendency for it to poke into a ridge on the bend rather than going round. Make sure both the push and pull are directly in line with the end of the conduit opening to at least eliminate the friction at those points.

[Kelvin]

I only use the corrugated stuff for straight runs, short runs, or if it’s easy to access which has all been in the garage or outside.

 

You want the taped end to be rounded and smooth so it doesn’t catch. I personally wouldn’t use silicone lubricant. I bought some water based cable pulling lubricant because we had several large cables to pull through some tight bends. Any water based lubricant will be ok (Boots is your friend or the bathroom cupboard maybe 😉) 

[Onoff]

I've had my lad 3D print plastic  "shuttles" that we tie brick line to and suck through with a hoover. Similarly I've cut a square of plastic carrier bag, popped a hole through the centre and stuck the line to the plastic with a bit of duct tape. 

[-rick-]

2 hours ago, Spinny said:

if I tape up and silicone should I be aiming for a particular shape - I guess a shape wider than the rib width by 3 times perhaps ? Surprising they done sell some sort of rolling ball end to attach which would revolve as it is pushed around corners. (I claim that patent).

 

 

Show us a photo of what you have? If I were doing it I would look to space each additional cable quite a way away from the the previous join. Bundling them all together will make for an inflexible section.

 

Are you using stranded or solid core cable?

[Spinny]

Here is a photo of 1 run, I have flexi conduit running to 3 roof lights with a box placed adjacent to the rooflight - as in this one you can see the box on the right.

Sparky put the flexi in with a lan cable stuck through it.

I am running 2 cables for each rooflight - both 4 core 0.75mm cables because I am going to put two LED strips into one plaster-in alu profile around each rooflight. 1 cob addressable 24V RGB and 1 cob addressable 24V CCT. (Yes strictly I only need 3 core cable, but a spare core seemed ok as a reserve). So ultimately I need 2 cables and a pull wire running through each 20mm black flexi conduit run. Really don't want to be pulling the ceiling down if a new cable has to be run to a rooflight.

 

No doubt I can find a way to get the cables through in one way or another, especially as I have access to the conduit until it is boarded over. But it being tough to get through worries me for future fishing through.

 

Worst conduit has 2 90 degree turns to make - two horizontally and then one vertically to escape into the electrical cupboard.

[-rick-]

I meant show us a photo of the cable bundle you are trying to pull, especially the lead in (where you tape together cables).

 

Are these cables sold or stranded? In any case, sounds like a lot to stuff down a 20mm conduit in the best conditions.

 

Can you share the 4 core cable between the two strips. Vcc, Gnd, Sgl1, Sgl2? Obviously the Vcc/Gnd would have to take twice the current?

 

 

[-rick-]

More thoughts:

 

Can you tie the conduit to something straight to get rid of those bends at the joists? They really aren't helping. Really want the conduit to be very straight until it turns the corner.

 

A Stranded CAT5 cable would be much easier to pull than that chunky CAT6.

[-rick-]

Well this is stuck in my head for some reason so another thought: why not run all these cables outside the conduit? Leave the conduit for unexpected future need. No reason to pull out existing cables if future needs require something different, just add additional through the conduit.

[andyscotland]

26 minutes ago, Spinny said:

I am running 2 cables for each rooflight - both 4 core 0.75mm cables because I am going to put two LED strips into one plaster-in alu profile around each rooflight. 1 cob addressable 24V RGB and 1 cob addressable 24V CCT. (Yes strictly I only need 3 core cable, but a spare core seemed ok as a reserve). So ultimately I need 2 cables and a pull wire running through each 20mm black flexi conduit run. Really don't want to be pulling the ceiling down if a new cable has to be run to a rooflight.

 

Plus the existing network cable?

 

I agree with @-rick- that sounds quite a bit for 20mm with bends.

 

It won't be helping if they're 4 core sheathed - you'll be losing space to the sheath and also that makes it more rigid around bends. If the whole run is in conduit between boxes you could use singles, starting each one staggered after the other as @-rick- said.

[Spinny]

I will only use the led tapes one at a time. Either colour, or white, but the transformer, power switch and WLED controller will be in the electrical cupboard so two power leads do need to run to the rooflight. I could use one 6 core cable. But the 2 cables are around 5mm diameter so fit ok, the third white cable here is LAN and not needed, am going to replace it with something thinner as a pull wire.

 

I did run cables outside the 50mm conduit runs I have under my suspended heated floor to keep them free for future use, but not so feasible here with just one hole into the rooflight upstand - a hole now lined up with the adjacent box - the plan being to push any connector or soldered end back into the box.

 

I am wondering whether 20mm smooth walled conduit would be better, but never used it before - saw a spring for bending it - how does that work - do you heat it up with a hairdryer then bend it with the spring ?

 

Anybody else run cable to led strip in rooflights ?

[Mike]

Flexible conduit is used almost exclusively in Europe, so there's no problem with the concept. However the rule here in France is that they should be no more than 1/3 full by cross-sectional area. In other words, you need a bigger duct or more than one.

 

I'd pull no more than 2 LAN cables though a 25mm duct, for example.

[andyscotland]

1 hour ago, Spinny said:

I will only use the led tapes one at a time. Either colour, or white, but the transformer, power switch and WLED controller will be in the electrical cupboard so two power leads do need to run to the rooflight. I could use one 6 core cable. But the 2 cables are around 5mm diameter so fit ok, the third white cable here is LAN and not needed, am going to replace it with something thinner as a pull wire.

 

That does look relatively full to me. A 6 core cable will be even more rigid round bends I think.

 

Also as @-rick- mentioned that does look like you're trying to pull them as one big lump, it will be much easier if you spread out the point where each one joins onto the one before so that you get as much of a taper as you can. The thinner cable will help to lead the following cable round the bends and so on. 

 

1 hour ago, Spinny said:

I am wondering whether 20mm smooth walled conduit would be better, but never used it before - saw a spring for bending it - how does that work - do you heat it up with a hairdryer then bend it with the spring ?

 

Possibly, it will have fewer snag points on bends and obviously will sit dead straight in the sections where your flexi is dropping - but you can potentially solve those without swapping it all out. Also the smooth conduit might actually have more friction along the length (the cable is in contact with the wall all the way, unlike flexi where 50% is on a ridge and 50% over a valley) so might not end up much different.

 

For bending you don't need a heat gun (and can easily over melt it that way), just insert spring, rub up and down the outside with a rag a bit to gently warm it a little, then bend. Bend it slightly over the angle you want then you can ease it back to the exact angle as you fix it into place.

[-rick-]

12 hours ago, Spinny said:

I will only use the led tapes one at a time. Either colour, or white, but the transformer, power switch and WLED controller will be in the electrical cupboard so two power leads do need to run to the rooflight. I could use one 6 core cable. But the 2 cables are around 5mm diameter so fit ok, the third white cable here is LAN and not needed, am going to replace it with something thinner as a pull wire.

 

With addressable tape, AFAIK, you can set the output to 0% and get no light even though the strip is powered on. Obviously there will be some extra current draw, but I wouldn't be shocked if normal LED controllers leave the power on all the time anyway.

 

The 4 core cables you have are thinner than I was imagining and you have cat5e rather than chunky cat6. So overall the conduit is less stuffed than I thought but still given the awkward bends over the joists less is more.

 

@andyscotland repeated my point about spacing the joins. I suspect your 4-core cable is stranded (maybe labelled as flexible) which will make it easier to pull. That CAT5 cable is probably solid core. If you wanted to pull CAT5 through conduit then getting some stranded would likely make things easier. (Its usually used for patch leads).

 

As a complete aside, why did you choose addressable strips over normal ones? The added cost seems hard to jusitfy for me.

[joth]

12 hours ago, Spinny said:

Either colour, or white, but the transformer, power switch and WLED controller will be in the electrical cupboard so two power leads do need to run to the rooflight.

Be careful about the distance from WLED controller to the tape. As well as the usual voltage drop on a long line, it's also prone to interference. For example the WS2811 guideline is 10m maximum, but some people have problems even working within that