“never plug extension cords into extension cords” is probably the most common piece of electrical related advice I’ve ever heard. But if you have, say, 2 x 2m long extension cords, and you plug one into the other, why is that considered a lot more unsafe than just using a single 4 or 5 meter cord?
Does it just boil down to that extra connection creating another opportunity for the prongs to slip out and cause a spark or short circuit? Or is there something else happening there?
For that matter - why aren’t super long extension cords (50 or more meters) considered unsafe? Does that also just come down to a matter of only having 2 connections versus 4 or more on a daisy chained cord?
Followup stupid question: is whatever causes piggybacked extension cords to be considered unsafe actually that dangerous, or is it the sort of thing that gets parroted around and misconstrued/blown out of proportion? On a scale from “smoking 20 packs of cigarettes a day” to “stubbing your toe on a really heavy piece of furniture”, how dangerous would you subjectively rate daisy chaining extension cords, assuming it was only 1 hop (2 extension cords, no more), and was kept under 5 or 10 metres?
I’m sure there’s probably somebody bashing their head against a wall at these questions, but I’m not trying to be ignorant, I’m just curious. Thank you for tolerating my stupid questions
If you need a ton of outlets, but your total load is under say 200w, is there any harm it? Or in my case, two extension cords separately plugged into a UPS that is plugged into the outlet.
On a scale from “smoking 20 packs of cigarettes a day” to “stubbing your toe on a really heavy piece of furniture”, how dangerous would you subjectively rate daisy chaining extension cords
As dangerous as one extension cord of their combined length. Don’t forget to verify that every cord rating is above load rating. I recommend to use at least same rating as circuit breaker or get extension cord with circuit breaker built in and never decrease rating down the line without circuit breaker before it, so even if you somehow overload it, there will be protection from it.
AND NEVER COIL OR THERMALY INSULATE! Cords rely on convection for heat dissipation, and spooling and insulating reduces it, thus increasing insulation temperature until it melts and spontaneously combusts. This applies to extension cords in general.
Because this is the Internet, I’ll be pedantic and say the interface where each cord plugs into the next probably adds some resistance as well.
So, 50 cords 1 ft each plugged into each other would have a higher resistance than the same wire at a single 50ft length.
I doubt it really matters in the practical terms of your answer and the question being asked though.
*insert technically correct*
I would also like to hear an expert opinion on this. Never really made sense to me either, but it also doesn’t sound unreasonable.
It increases the risk of electrical overload and overheating as it adds more resistance to the circuit.
Thanks for the response! Would you mind going a bit more in depth about that please? I could understand increasing the risk of overload if you were to daisychain power boards, as they add more power points to the circuit than it was designed for. But extension cords (at least in my experience) only have 2 ends - one with a single plug receptacle, and the other that plugs into a power point
Is it the actual connection between the two that adds more resistance to it? If it were the wiring, then wouldn’t that also pose a problem for longer extension cords?
In either case, what sort of resistance add are we talking about (feel free to pick random lengths of examples make it easier to explain)?
I don’t think what they said is actually a problem, it’s just a back-justification for the original trope. Daisy chaining them and strictly sticking to only the few appliances that would fit in one extension strip is fine. But that’s complicated to explain, it’s better to just tell people not to do it rather than expect them to understand what’s going on
A couple things that can happen…
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plugging in too many appliances over several daisy chained power strips trips the circuit breaker because too much current is being drawn
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if the country you live in has lax electrical safety standards then, yes, perhaps you can overload the daisy chain without tripping the main circuit which would lead to overheating
When the breaker trips then the fundamental issue is unlikely to be present. But to be able to push enough current to cause it to break the connection needs to have a sufficiently low resistance. If that gets too high it will never break, even if you short the cables. And that will result in a fire, because the protection does not work anymore. That is the dangerous part.
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The longer the cable, the thicker (heavier gauge) it needs to be to carry the same current without burning up. One extension cord is rated to carry the current it alone is able to carry. Put two of those in series, and both of them together are able to carry less current than either one by itself. This is how fires start.
I wonder what kind of safety margin is calculated into these…
Admittedly I’ve seen some wildly different shielding or thickness in my time
For extension cords? Pretty much nothing. They can be dangerous all by themselves. You have an outlet on a 15A circuit. You can plug all sorts of things into that outlet all at the same time, especially if you’re daisy chaining cords and adapters. The sum total of current from all those things can be less than 15A, so the circuit breaker never trips, but more than what your mess of extension cords can handle. Even worse, if it’s just a little more than the extension cords can handle, you might not notice right away, and then you’ll come home later to a pile of smoldering ash.
Don’t chain extension cords.
Nailed it in far fewer words than me.
Another bit of explanation I just thought of –
Think of an incandescent light bulb. It has a filament. You run electricity through the filament and it heats up enough to glow, producing light to see by. It does that because the thin filament has high resistance; it resists allowing current to flow through it.
Any piece of conductive material will do the same thing if you put enough current through it. Even an extension cord. It will heat up enough to glow. Being an extension cord, it will then melt the insulation and dramatically increase the likelihood of setting something on fire.
And because the wire gauge is less than the wiring in the wall the breaker won’t trip before it reaches the point where it’s overloaded either.
This is primarily a concern because extension cords aren’t fused, and there’s no control over how they are routed.
Most wiring in your walls come after a circuit breaker and are designed to allow for a certain amount of heating. The electrician follows a code that guarantees that the circuit breaker will trip before there’s any possibility of too much heat. This table indicates a higher ampacity rating for higher temperature ratings.
Now most extension cords are made cheaper by using lower gauge than the wiring in your walls. The general assumption is that they’re spread out, so the heat has no way to build up, and you won’t be plugging them permanently into something drawing the peak 15A allowed by the circuit breaker.
If you were to pile up a 100 foot extension cable and plug in a hairdryer, you’d probably start a fire. If it was all spread out, likely your hair dryer would just receive less than the 120V it’s expecting, and it wouldn’t get very hot.
Ironically, dinky christmas lights make very safe extension cords because they’re fused inside the plug.
This is incorrect. I need to increase gauge for voltage drop. Overloading the cable via length can only happen if I have a motor or other magnetic load at the end. A motor will try to draw it’s designed wattage regardless of voltage. A wire of a given ampacity will handle that many amps regardless of the length of the conductor. The relationship is power = voltage x current and voltage = current x resistance for single phase. The fire concern on extension cords tied together indoors is you have 100% strung that shit through a doorway or window, which is a code violation. You are going to pinch it and burn your shit down. all outdoor plugs are gfci these days and on site i can have 4 or 5 extension cords tied together. i only get 109 volts at the end but a heater is a resistive load. Doesnt matter for that application.
It’s obvious you know more or less all there is to know about this topic. So much so that I suspect you have trouble explaining it to laypersons like me because it’s difficult for you to determine which parts of your knowledge are obvious common knowledge and which parts are specialist knowledge.
The super simple explanation is that the wires are too small. The water hose analogy breaks down fairly quickly, but I’ll try using it. Imagine a garden hose, with a regular nozzle on the end. But it’s not a perfect world, and our hose doesn’t transfer all the water that goes into it. Think of this as ten pinprick holes along every meter of hose. If we have ten meters of hose, that’s fine, we only need to turn on the tap a little bit to get a decent spray out of the nozzle, and a little bit will dribble out these holes. Now let’s join another hose on. We lose more water to leakage, so to get the same amount of water out of our nozzle, we have to turn on the tap more, giving it a bit more water flow. Now, our pinprick holes are not just dribbling, they’re flowing freely. Now let’s take it to the extreme- we join a thousand garden hoses together, all leaking a little bit. We have to turn the tap on A Lot More, and suddenly our pinpricks are spraying a serious amount of water everywhere. Now imagine we use a bigger hose. Let’s take it to the extreme again and say it’s a big stormwater pipe. But the key part here is that it has the same amount of holes, ten pinpricks per meter. This way, we can get heaps more water down that pipe, more than enough to give that water nozzle everything it wants. Also, because our pressure can remain low, those pinpricks are only leaking a little bit, not spraying everywhere. This is getting pretty wordy and unwieldy to type out on my phone, so I’ll try and bring it into the real world a bit more. An electrical load, like a motor (say a compressor in a fridge, a circular saw, etc) is like to our nozzle. It will pull more current (amps, or water flow) to maintain the same amount of power output (water coming out of the nozzle). As we get a longer conductor, the voltage drop (pressure reduction due to water lost to the pinpricks) gets larger, and our voltage at the end of a conductor gets lower. Power = voltage * current, so if that voltage is lower, to get the same power we need more current. More current means more heating. More heat in a small cable means melting. Physics has a way out for us, thankfully! The thicker a cable is, the less voltage drop it has, kind of like our stormwater pipe. So the voltage remains at a normal level at the motor, and consequently the motor draws a normal amount of current. This is why longer extensions are generally a lot thicker than shorter ones. If you’re interested in the math, let me know, it’s actually pretty fascinating, and ties into why long distance power lines are all super high voltage, among many other things. The basic equations are also not too hard to work with.
This is junior highschool level stuff. Not a vector or phasor in sight.
Your school taught anything at all about electricity? Mine sure didn’t.
My high school had a lot of vocational courses. I took auto shop, construction, welding, and small engine mechanics. Several of those covered electricity.
Do you mean inductive load rather than magnetic load? Or are all inductive loads attributed to electromagnets?
Edit: also, don’t like… a lot of appliances create inductive loads?
Most inductive loads are motors. I used the term magnetic rather than inductive in the Hope of making my response less jargon filled and more intelligible. Very generally speaking inductance is the magnetic portion of the circuit or more technically it would the contribution to the circuit that causes the wave form to lag. That is specific to an AC circuit.
Isn’t the added cable resistance small enough to not cause issues so soon? In case you just chain a few ( < 10 ) together.
It’s not just the cable resistance, but the added resistance at each connection point. Since the plugs aren’t the same piece of metal, just touching.
It’s going to be down to the gauge of the wire and if it’s rated for hard usage. There would be no difference if the 4m cable was the same gauge and insulation type as two 2m cables connected by cord and plug. You couldn’t say how dangerous it is specifically without calculating the load, wire ampacity, ambient temperature, insulation type, distance, and on and on so it’s general advice to prevent fires from overheating wires.
The smart answer: it can start a fire, don’t do it.
The honest answer: I’ve done it a zillion times and never started a fire. I buy heavy 12 and 10 gauge cords and only chain them to power things that don’t require a lot of amps, like LED lights.
When in doubt, a plug-in power meter is an option you can use to help monitor the situation. Plugs that draw a lot of amps can get warm, even when not using an extension cord. Also, it’s not uncommon for a device to pull a lot of amps on initial power-up, and then settle down to a lower draw.
I have an RV with 2x 10 gauge, 50’ extensions running power to it. I have a built-to-purpose coverat the connection point. Its fine and safe enough. Just keep slack at the connection. It cant be under pull stress.
Check the neutral pin at the pedestal and the connection. After a few months running an AC unit, it’ll be char broiled somewhere along the way.
I think it is partly a US specific problem as the quality of the extension cords really suck. Meanwhile in Eurpoe (or at least in Germany) the extension cords actually use the same wire grade as your in wall wires, so there is a basically no difference in using daisy chained extension cords versus different wall outlets (as long as the outlets are in the same curcuit)
The wires in your wall usually have 1.5 mm^2 while the extension cables have 0.75 mm^2 cross section.
I mean it is hard to find out if they are the exact same, since power strips often don’t specify it, but from handling both I’d say they are pretty much the same…
The cable specification is usually written into or molded onto the outer insulation, at least in Europe / EU.
Yep, came here to write the same. We have 240V and not 120V like the US. To power the same appliance in the US you have double the Ampere and therefore higher risk of fire (correct me if I’m wrong)
I strongly disagree… We just have higher standards regarding power wires. Since we have more voltage running through the wires we need tougher ones, but that is what regulation is for
So the higher Ampere doesn’t require thicker cables? Genuinely asking. The higher standards and regulations are absolutely part of why you don’t hear this rule here.
Its higher voltage,but yes It does. However the higher standards take care of that, so you don’t have too weak power cables available
Yes, as US uses an voltage of 120 V, the current drawn by a load is approximately double the current drawn by the same load in EU with 230 V. Thus the wires used in Europe only need approximately half the cross section compared to US. However, the insulation of the wires needs to be of higher standard.
Not necessarily exactly the same wires, but all rated for 16A, so the circuit beaker will trip long before any wire gets a chance to heat up
I’m not an electrician, but I recall that this video explains it pretty well (along with other interesting things): https://www.youtube.com/watch?v=K_q-xnYRugQ
Here’s another good example: https://www.youtube.com/watch?v=4cp28hIMP94
Stacking 283(!) double mains adapters and measuring the voltage drop. Because it’s not just the cable, each plug/socket adds additional resistance.
Resistance increases over longer distance cable, and increased load from appliances. (Especially don’t with american electrics, they aren’t fused so the wire can overheat and set fire to the surroundings.)
To clarify a bit, the benefit of the UK system isn’t the end device having a fuse, but the cable itself having a fuse.
In the US the setup would be something like
- Wall has 20A wiring.
- Electrical panel has 20A fuse to avoid the wire in the wall from overheating.
- Extension cord is designed for 10A
- You plug in 2 10A devices to the extension cord.
- The wall wiring is fine, it can take 20A.
- The circuit breaker doesn’t trip as it is also 20A.
- The extension cord overheats and starts a fire.
In the UK the 10A extension cord will have its own 10A fuse in the plug. So when you turn on the two 10A devices the fuse in the extension cord will blow and prevent the extension cord from overheating.
Bold of you to assume that the wall outlet would have a 20a breaker. Most don’t, unless they’re in a kitchen.
But you’re right about the resistance. Also, most extension cords are undersized for the loads they pull, they’re commonly made with 16 or even 18awg wire, further increasing resistance (which translates to heat).
Source: am electrician in US
The circuit power doesn’t matter for the example. I was just picking easy numbers. You can have the same problem as long as the rating of the extension cord is less than the circuit breaker. (And as you pointed that out this is a very common case due to the frequently low rating of extension cords.)
I’m not trying to be ignorant, I’m just curious.
I think you’re in the right community! Don’t let anyone tell you to shy away from asking curious questions. (well, unless the question is also bigoted, illegal, baiting, sealioning, or otherwise disingenuous)
I’m not an electrician in any jurisdiction, but one answer for why two 2-meter (~6 ft) extension cords in series is inadvisable compared to a single 4 meter cord is that it’s not an apples-to-apples comparison. Longer cords necessarily have to be built differently than shorter cords, not only because of electrical codes (eg the NEC in USA) or product safety specs (eg UL, CSA) but also being well-designed for their expected use. There’s also the human aspect, which all good designs must account for as well.
Here in the USA, common extension cord lengths are ~2 m (6 ft), ~7.5 m (25 ft), ~15 m (50 ft), and ~30 m (100 ft). Of those cords, the common wire gauge used might be 18 AWG (~1 mm^2), 14 AWG (~2 mm^2), 16 AWG (~1.5 mm^2), and 12 AWG (~3.5 mm^2). I’ve intentionally rounded the metric units so they’re more analogous to common wire gauges outside the USA. Finally, the insulation used can be anything from “thin, indoor only” to “heavy, abrasion and sunlight resistant”. And while the USA technically has a boat-load of AC connectors, the grand majority will use the standard 2-pin or 3-pin 120v connector, formally known as NEMA 1-15 and NEMA 5-15 respectively. What this means is that chaining extension cords is both possible and somewhat common. The problem is one of mismatched designs.
From a cursory search on the website of a major USA home improvement store, the smallest wire gauge used for a 100 ft cable is 16 AWG. The largest is 10 AWG (nb: smaller numbers mean bigger wire). That thinner cable is marketed for outdoor use. The thicker cable indicates its use “indoor/outdoor” and for heavy-duty applications. It is also branded with a major power-tool company, which would be appropriate as power tools often draw high current.
Whereas looking at 6 ft extension cords, most are 16 AWG but a few were 18 AWG (thinner than 16) or 14 AWG (thicker). But I could not find any thicker cables than that, certainly nothing that uses 10 AWG (~6 mm^2). The “heavy duty” cables of this length also used only 16 AWG wire.
Because electrical resistance is additive in series, and because Ohm’s Law governs the voltage lost at the end of a cord, the use of insufficiently large conductors can cause voltage issues for high-current appliances. Appliances for USA-spec generally require 120 Volts +/- 10%, with utilities aiming to provide 120 Volts +/- 5% from the outlets. This means a “sufficient” power cord should not have a voltage drop of more than 6 volts, give or take. Of course, a high-current appliance will also cause a larger voltage drop than a low-current device, so we only consider the former case.
For a machine that draws 12 Amps attached to a 100 ft extension cord made of 18 AWG wire, the voltage drop would be 15 volts. This is bad for the machine, which now sees a lower voltage than expected. Had the cord been made of 12 AWG wire, the drop is an acceptable 3 volts.
So if you’re operating construction tools, it would be a terrible idea to use three random 6-ft cables, and you should instead use a single 25-ft cable. Even though it’s longer than you need, the fact is that most 25 ft cables use thicker conductors, which reduces the voltage drop overall.
But there’s also that peaky human factor. Sure, there would also be more connectors which could come loose, but the really pressing issue with daisy chained cords is when people do that indoors, because they only have light-duty 6 ft cables handy. And for that Christmas tree, they need to use attach three cables together to go beneath the hallway rug.
This is essentially the worst-case scenario: using thin conductor cords, with thin insulation, underneath very flammable household surfaces, which are also trodden upon by foot traffic. Every step on that cord weakens the insulation and fatigues the conductors. Over time, the conductor becomes thinner where it’s being fatigued, and this increases the voltage drop. An unfortunate result of a voltage drop is that it generates heat. For a cable which is uniformly thin, this heat is spread over the whole length. But for localized conductor damage, the heat is pin-point… directly under a flammable rug.
In the USA, some 3300 house fires started from an extension cord. Because these cords are not within the walls, they are usually beyond the control of often-strict building/electrical codes, something that’s been critiqued by a prominent YouTuber. The US CPSC even goes so far as to create memes to promote their messaging that space heaters – a common, high-current appliance – should not be used with extension cords or strips.
Of course, from an electrical perspective, even a ten-long chain of dinky extension cords would have no problem powering just a single LED night light. But it’s reasonable to ask: 1) is this just asking to be struck down by fate, 2) are there better alternatives like thicker/longer cords, and 3) why isn’t there an outlet where you need it?
(There’s also a scenario where too long or thin of an extension cord can cause a circuit breaker to fail to trip during a short circuit, but it’s fairly esoteric and this post is quite long now)
In short, the blanket recommendation to avoid daisy-chaining cords is to avoid the nasty and sometimes fatal results when that can go wrong, even with it might not always play out that way. There’s almost always something safer than can be done than daisy chaining.
+1 for technology connections video. Was going to post the same link.
First, I’m not an electrician, or anything even vaguely approaching one.
I’ve never heard that advice with extension cords, only power strips.
You could theoretically link enough extension cords together to cause problems, but it would need to be some extremely shit extension cords or a LOT of them. Resistance increases over distance, which in power cables manifests as them getting hotter. That isn’t a problem until all the sudden it is a problem.
For power strips, the main danger is that you’re potentially introducing more outlets than any of them are rated for. If you’re just using 2 3ft power bars to functionally make a 6ft cable that you’re only plugging a single thing into… you’re fine. Or at least I was, idk I did it for like a whole year. If you’re plugging 16 things into a single wall outlet via power strips you can trip the circuit breaker, or potentially much worse stuff can happen like things getting melty and starting a fire.
If you know enough of what you’re doing to math out the power draw+what your outlet/power strips are rated for you can pretty (afaik) safely daisy chain them if you wanna.
Yeah, there are two components here
- Adding extra length.
- Adding more outlets.
2 is the main problem, but you need a little of 1 to have it fail in an unsafe way (ie. not just tripping the circuit breaker).
If you just add a lot of extra outlets and plug lots of stuff in then you will simply trip the circuit breaker. (Assuming that everything is properly set up according to code.) In order to create a problem you need some extra wiring that is rated for less load than the wall wiring. (Now in practice every splitter has some amount of wiring, so these can be the same device, but most power bars are rated to be “fully used” or have a fuse internally). So the problem looks something like this:
- Have a 20A wall circuit.
- Plug a 10A extension cord into it.
- Plug a power bar or other splitter into the extension cord.
- Put enough devices into the splitter to generate 15A of current.
Now you are overloading the extension cord and risking fire.
Meanwhile landlords: "one 50 year old outlet should be enough for two bedrooms right?*
50 years old? Most of the landlords I’ve dealt with in my life consider 100 year old outlets to be perfectly sufficient, along with their carrying capacity and number in each room.
“ it was enough to power a lightbulb in 1925, so it should be perfectly sufficient for your needs with all of your TVs and computers and such.”
With one landlord, I actually had to call the city inspector into the building in order to verify that the power supply for each apartment fell beneath city requirements (it’s more complicated than this, but this is a simple explanation for casual readers). He spent the next three years doing everything in his power to get me out.
But the building got rewired pretty quickly after my report to the city. I even got compensation to stay in the hotel for a couple of days while they worked on my apartment.
This, along with hotels that hide their only PowerPoint behind the bed but have 50 bloody phone jacks, are my pet peeves. But it kinda makes sense when you consider they were mostly built before the days of having a ton of devices in the bedroom. A lamp and alarm clock, maybe a TV if you’re well off, would’ve been perfectly fine for a lot of people
I once read a theory on an electricians forum about how the USA electrical code’s mandated maximum distance between adjacent outlets on a wall, coupled with the typical bedroom layout, as well as home builders trying to be as cheap as possible, led to only a single outlet being placed directly in the middle of the longest wall. This is also the most logical position for a bed, so the theory is that the bed pressing against the outlet over time was a contributing factor to electrical-related house fires.
I cannot find where I read that originally, and certainly the granularity of nationally-reported fire data is not sufficient to prove that theory. And while the electrical code’s distance requirements haven’t changed, more homes will now put enough outlets so the only one isn’t behind the bed.
The absolute worst is when the Word Documents are stashed away in some random drawer. Or when you find an Excel spreadsheet under the mattress!
I really wish my autocorrect would stop doing that. I can count on one hand the amount of times I’ve actually wanted to write “PowerPoint”. I couldn’t even count on 10 hands the amount of times it’s assumed I’m some kind of idiot that doesn’t know “PowerPoint” is a single word when I type “power point”
I like when it only autocorrects the second word. “I’m going to home Depot”
Not so awful, but it’s disappointing when you open the drawer expecting a Bible, but there’s only OneNote there.
Years ago, I used to play live music. We played in a lot of shitty dive bars. Thinking back on all the ancient decrepit plugs we used to power our instruments, amplifiers, and stage lights with…it’s a miracle we never started a fire. Nightmare fuel now that I’m older and a little bit wiser.
The longer the cord is the more resistance there is; ie the more electrical load on the circuit. As long as you are pulling less than what the circuit and cord is rated for, there isn’t an issue, you will just be wasting a little extra power from the extra resistance. The plugs themselves can also have a bit of extra resistance.
Two pieces of advice that will make the biggest difference:
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Keep the total length of all extension cables used as short as is reasonable. Don’t use a 20m cable when a 4m cable will do.
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Buy extension cords with higher wire gauges (higher wire thicknesses). A 12 gauge cable (4mm2) will provide notably less resistance than a 14 (2.5mm2) or 16 gauge cable (1.5mm2). The packaging will say what gauge it is. Note, I’m talking about the thickness of the metal itself, not the thickness of the extension cord as a whole. I have seen some very, very thick extension cords with absolute trash wires inside.
The more resistance there is, the less the electrical load is. Maximum electrical load would be a short circuit (near zero resistance, maximum current flow); minimum would be a cord or device with infinite resistance (no current flow).
Considering V=I*R and P=I^2 * R, increasing resistance will decrease current and this will decrease power.
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“never plug extension cords into extension cords” is probably the most common piece of electrical related advice I’ve ever heard.
Same reason power cables outside are fucking huge and the cord to your TV is tiny.
Electrical loss generates heat, so the longer the cable, the thicker it needs to be before that heat is too much.
Don’t forget a filament in an old school light bulb is just really thin wite. The thinner it is the less energy required to make it glow, which is why there’s like a 200 year old light bulb still going, it’s just a thick filament and very inefficient
So I’d never plug two of those rinky dink indoor extension cords together, it doesn’t take much length before it starts “glowing” like a light bulb filament, which happens at the plug and can burn a house down.
But…
Growing up doing rural construction with heavy gauge extension cords we never thought twice about hooking multiples up as long as it was just something quick for a few minutes at a time. Then never left it plugged into the source when not in use. You’d never do it for like a radio even because eventually it’s gonna heat up back at the aource.
Someone else already mentioned not pulling it right, we’d “doughnut” the connection so that if it did get yanked accidentally it wouldn’t unplug, but obviously it can’t be under constant stress even like that.
So many people here talk about the thickness needed of else it heats up. That is simply wrong. The heat is the same per length and is dissipated the same way with twice the length aka the temperature is the same*. The issue is that the short circuit current could drop below the value needed to actually pop the breaker, allowing for a ton of heat to be generated where it shouldn’t be. The same way a light bulb glows bright hot but does not trip the breaker etc., now just imagine the cable to be the glowing part.
*There is another issue if you do not lay them out, that the heat has nowhere to go. Causing coiled wires to have a far lower rating compared to when they are fully extended.
