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This question already has an answer here:

I have a desktop computer and a lot of external hard disk cases. I coiled all cables to make them organized and easy to clean. But an electrician told me; if you are using a cable, coiling (wrapping) cables is wrong. It could damage your computer, electronic devices, etc. You should un-wrap cables of devices if you want to use them. So;

Are there any bad effects of coiling electrical cables?

Note: I found this on a Stack Exchange site, but still I'm not sure enough: Physics of Coiled Cables

A quick answer that I learned; If cable is long and power usage will be high (up to 200 W), don't use a coiled cable. It melt and start a fire.

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marked as duplicate by Dmitry Grigoryev, Nick Alexeev Sep 28 '18 at 0:45

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    \$\begingroup\$ Unless they heat up so much you can feel it, I wouldn’t think twice about this. \$\endgroup\$ – winny Sep 27 '18 at 9:57
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    \$\begingroup\$ Data cables less than 3 meters? Not a problem. It's different if you go long lengths in an industrial setting or don't roll out the electrical wire on a reel. Those reels have a tendency to start burning if you load them on the loads the wires are designed for. \$\endgroup\$ – Mast Sep 27 '18 at 10:53
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    \$\begingroup\$ What cables are we talking about? Mains power? USB? Both together? \$\endgroup\$ – jcaron Sep 27 '18 at 10:54
  • \$\begingroup\$ @jcaron All cables. Because my wife wants to see them ordered & clean :) - My pc has 1000W psu + ( 2 x 24'' lcd monitors ) + 5 harddisks. And they are all powered up by 8-Way Extension with 6 Meter Cable. \$\endgroup\$ – Lost_In_Library Sep 27 '18 at 10:56
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    \$\begingroup\$ Use a shorter cable if that would be sufficient and put the rest in a cabletray of sorts. \$\endgroup\$ – Mast Sep 27 '18 at 11:09
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In the article that you linked to, it says in one of the answers,

The most notorious feature of loaded coiled cables is that they potentially generate a lot of heat in a tight space. In most cases it's not an issue, but at high load with little cooling such a coil could be a fire hazard.

And I actually have first hand experience with this. There was this extension cord (50 or 100 feet) that was wrapped around a spool, which I needed to power a small room heater. Still it was a 1500W heater which draws over half of what the outlet could deliver. Which means that it easily qualifies as a high load.

Lucky ending to the story: I could smell the insulation melting which led me to discover the danger and pulled the plug before it caught fire!

(I would have posted as a comment, but my rep < 50 Thought the OP really should have this info)

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  • \$\begingroup\$ Thanks for the ansywer. So, as summary, Can we say(?); "If cable is too long and power usage will be high (up to 1500W), don't use coiled cable, it could be melted and start a fire".. \$\endgroup\$ – Lost_In_Library Sep 27 '18 at 10:45
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    \$\begingroup\$ Yes, but I would specify an even lower limit, don't coil up the wires if the power is above 200 W. Also see my answer. \$\endgroup\$ – Bimpelrekkie Sep 27 '18 at 10:47
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    \$\begingroup\$ Were you using an appropriately sized extension cable for your load? I'm sure the self-contact and close proximity only makes the issue worse; but 1500W is also a pretty big load. Just quickly looking up some numbers, I could see that easily being too high current for the cable when using a 50 ft. or 100 ft. cord. \$\endgroup\$ – JMac Sep 27 '18 at 18:49
  • \$\begingroup\$ @JMac Thanks for the heads up, I didn't know that the ampacity for extension cords is less lengths >50ft. I found what I think is a good reference on the subject: stayonline.com/product-resources/reference-circuit-ampacity.asp It has been over 30 years, but my memory is of an orange "back yard" extension cord which are usually 16AWG or 14AWG I'm quite sure the heater was 1500W, so from a 120V outlet, that's 12.5A. From the chart I linked to, a 16AWG 50 ft cord is rated 13A (that's cutting it close!), but 100 ft cord is rated at 10A (oops!) Anyway, thanks again for the tip \$\endgroup\$ – i0oklng 1lke c0nfus10n Sep 28 '18 at 0:15
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Is there any bad effects of coiling electrical cables ?

That depends on the cirumstances.

The electrician is correct for the part of electrical engineering that he (probably) deals with. And that is high-power devices (more than say 200 Watt) running on mains (AC) voltage. With high power devices, large currents flow and these large currents through mains wires cause the cable to warm up. That's OK if the cable has enough "breathing space". If you coil up the cable that might not be the case. Especially in devices like these:

enter image description here

the heat cannot escape if you do not completely unwind all the cable.

If you would only be using this for powering one low power device like a radio or a phone charger, the heat generated will be of no concern, you can leave the cable rolled up.

But if you use it to power a 300 W floodlight and/or a lawnmower and/or a toaster then you do need to unroll the cable completely so that any generated heat can escape into the air.

Fortunately for you USB and nearly all computer cables cables are quite low power so coiling them up is no issue at all.

As winny commented: feel the cables wjhen they have been in use for a while. If you cannot feel that they are getting warm, then there is no issue.

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  • \$\begingroup\$ My desktop pc has 1000W psu + 2 x 24'' lcd monitors + 5 harddisks. And they are all powered up by 8-Way Extension with 6 Meter Cable. After reading your answer so it could be an issue, I need to unplug them :( Thanks for your answer. \$\endgroup\$ – Lost_In_Library Sep 27 '18 at 10:54
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    \$\begingroup\$ @Lost_In_Library Yes, definitely unroll (not unplug) that. That's way over what I'd consider a safe amount of power over a safe amount of reeled cable. \$\endgroup\$ – Mast Sep 27 '18 at 10:58
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    \$\begingroup\$ Indeed, for your AC cables I would also advice to unroll them. Not that it's that unsafe at the moment, a 1000 W PSU only consumes 1000 W if you have many high power graphics cards in your CPU running at full power. You would hear (fan noise) and feel (the warm air) that. But you're near the edge so better be safe and give the cables some room to breathe. \$\endgroup\$ – Bimpelrekkie Sep 27 '18 at 11:18
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    \$\begingroup\$ I can't even imagine the monstrous air conditioner you must have to compensate that kilowatt space heater of a PC. \$\endgroup\$ – MindS1 Sep 27 '18 at 12:48
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    \$\begingroup\$ @Lost_In_Library: For that power, I'd recommend plugging the computer directly into a wall outlet rather than into a power bar. Power bars are fine for lots ot low-power loads. \$\endgroup\$ – Peter Bennett Sep 27 '18 at 15:37
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I don't think the other answers are correct in stating that the heat is the only issue, though it is the biggest. I came into my office one Monday morning and found that the door had been forced open by the fire department who had put out a fire in the server room where someone had used a coiled cable to power a server - it had been like that for weeks but updates running on the server caused the power use to be higher for a sustained period of time.

However, power going through a coiled cable will also create a more concentrated electromagnetic field which can cause other problems. The most frequent problem I've experienced caused by this is a distortion in a CRT monitor caused by the power cable being coiled at the back of it, but others would be possible.

For example a long USB cable coiled with a long power cable could result in a significant voltage being induced in the USB cable, potentially destroying the USB port and/or peripheral.

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  • \$\begingroup\$ Thank you very much for sharing your experiences. I upvoted your answer. \$\endgroup\$ – Lost_In_Library Sep 27 '18 at 14:14

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