Bunching excess cable

[watercooled]

Is it ok to bunch excess cable with a tie wrap like this:



just I've noticed on some extension leads it says you must fully unwind before use.

Thanks

[PeterStoba]

i've nevre had any problems doing this...

[watercooled]

OK thanks. I think the warning on extensions is because it can carry high voltage/current - the cables I bunched are 5/12v and a few mA.

[GoNz0]

extension reels cause a coil effect the way you looped them is fine.

if they get hot your doing it wrong

[piggin23]

If you coil an extension lead and place a high load on it (large hammer drill) you can heat up the cable and cause it to melt.
As for your desk this will not be a problem.
The problem you could have is coiling cables into a circle and placing a current through them can cause a magnetic field. This can the cause interference. ie in a radio
Better to use two cable ties and make it flat. Ensure you don't crush the cable down to much as you could damage the internal cores.

[watercooled]

Thank for all the replies everyone. I decided to tidy the cabling in my desk and bunching the cables together made it much easier (I was bored ). None of them are coiled, just folded like in the image. Why does the cable modem transformer have to be so big lol - the one that powers my router has the same output and is much smaller.

[peterb]

If you coil an extension lead and place a high load on it (large hammer drill) you can heat up the cable and cause it to melt.
As for your desk this will not be a problem.
The problem you could have is coiling cables into a circle and placing a current through them can cause a magnetic field. This can the cause interference. ie in a radio
Better to use two cable ties and make it flat. Ensure you don't crush the cable down to much as you could damage the internal cores.

Yes and no.

If you have a coil of wire on a reel, it prevents the inner turns from cooling - because of the lack of air flow. However on an AC cct, there are two cores, so the magnetic field cancels out (more or less) so there is no em radiation at all. The same is true of cables carrying DC. In the OP's case, the cables are low voltage, but still (relatively) high current, and the conductors being thinner will have a slightly higher resistance. However in practice bunching the cables like that will be quite safe.

[DJ_Enigma]

I always thought this was a no-no, but if not I'll do mine too

[Blaineoliver]

You can create a nice electromagnet using the coiled wires too, so be careful that its nothign high voltage/wattage such as an oven.

[watercooled]

Not strictly true with power cords, since the voltages in the two inner cables cancel each other out. You also need a ferrous core for making a magnet.

[peterb]

Not strictly true with power cords, since the voltages in the two inner cables cancel each other out. You also need a ferrous core for making a magnet.

To be pedantic, it is the current flowing in the conductors that creates the magnetic field, and ypou don't need a ferrous core you still get a magnetic field - but in a twin pair of conductors they pretty much cancel out (not quite as good as twisted pair of course - but the same principle)

[watercooled]

There would be a magnetic field but not much would be attracted to it, as the conductors aren't ferrous. Even so, there is a small magnetic field around anything that carries electricity, which is partly why non-contact voltage detectors work.

[Tagster]

As I used to work in a welding/engineering environment I can confirm that pretty much any electrical cable will produce a magnetic field (tho' fairly weak), you just got to look at all the metal fillings hugging the cables on the floor!

[watercooled]

It's true that any cable that carries a current has a magnetic field surrounding it - Fleming's left hand rule. Just when live/neutral run parallel the field is effectively cancelled out.

[Saracen]

You can get all sorts of weird effects from coiled cable, including magnetic fields and complex inductance effects. But in terms of extension leads, the reason for not coiling them is simple .... heat causes fires.

Cables have a resistance. Run lots of power through them and heat is generated .... whether coiled or not. But if you then coil them, you concentrate that heat in a small area, restrict the ability for it to dissipate and risk melted cables and an electrical fire.

It's that simple.

Yes, there's magnetic field effects, yes there's inductance changes and so forth, but all of a minuscule level. The reason for the rule about uncoiling extension cables is simply heat dissipation if you stick a heavy load on it.

Of course, if you're talking about other forms of cable, other effects come into play. If you're talking about RF down a coax transmission line, then the impedance effect can cause an imbalance, standing waves, reduction in transmitted power and even output stage damage in extreme cases. You also risking damage to the cable from kinks, and the airgap tends to be important.

If you're talking about unshielded data cables, crosstalk can reduce signal quality. If you're talking about cable carrying analog video signals, then you risk ghosting, but would probably be okay with audio signals as the frequency is that much lower.

In the case of watercooled's cable, does it feel like there's any heat in there? Personally, I very much doubt it, but of course, thin cable like that will heat uo that much quicker than heavy insulation. But it's also carrying a fraction of the power.

I suppose, if you're worried, instead of using three-inch loops, use six inch loops. That way, you spread out any heat that much more. But given the type of cable you have there, I can't see any problems being at all likely, even if theory says it's possible.

Incidentally, the fire risk from coiled mains extension cables IS real. Fire services DO get called out to fires caused this way. You'd no doubt not have a problem running a 60w inspection light from it for 5 minutes, but don't try it for any length of time with a 3KW electric fire ...... unless you want more heat than the electric fire is giving you.


Caveat: All IMHO, of course. I don't give electrical safety advice out.

[Stoo]

Nod, the high output device on extension cables advice is very sound - a chap at work's wife used an electrical heater on the end of a coiled one and wondered what the funny smell was - she'd managed to melt the cable into one mass - luckily the chap at work found it and turned it off before it shorted/caught fire..