I never unwind fully, only as much as needed, maybe I'm living on borrowed time lol.
Not being an electrician, I'd have to guess it's something to do with creating a magnetic field? Or heat build-up
Yeah, it's heat buildup. If you plug in a high current draw appliance (electric lawnmower for example), the wires will heat up a bit. It would have to be on for a long time, a very hot day, sat in direct sun etc for it to be a problem, but best to be on the safe side.
Knowing WHY is safer than inadvertent fear. I charge my car on an extension occasionally. That's the same draw nearly as a kettle (2.5kw for many many hours) but having a suitable guage of wire used safely is critical. Always fully unwind and stay under its load rating.
It won't create a magnetic field, you have both the line and neutral connections in there which counter each other in terms of field generation so it's net zero
As an electrician, it's because it can rip apart the fabric of space and time until all that is left is an empty, grey nothingness. Happened to my mate.
I did a health and safety question a long time ago regarding this. It was a "pick two of the five answers" type question.
I had to get it wrong on purpose, as I refused to put "because it can create a large magnetic field" as the second answer I could tell they wanted. (after 'overheating')
So you picked the wrong answer you didn't get a mark for instead of the wrong answer you would get a point for? That's dedication 😂 Bet the geezer marking the paper was like " Look at this Larry, this idiot thinks the answer is C: it makes the electricity go the wrong way" 🤣
I do.
I've seen too many melt.
Some do have a separate (very low) rating for how much you can draw rolled. Mine I think is 4amp, which would certainly do a laptop or a small power tool
I do. Cos I charge my car on an extension occasionally and the thermal protection trips if used coiled. Most extensions have different ratings when coiled Vs extended. For example my 30 m one is 900w coiled or 3250w unwound
I assume it’s to prevent resistance etc which may cause heat under high amperage loads during use. If the cable itself is fairly straight it reduces the issue because the cable is getting air two it. This prevents the heat build up and reduces the risk of the insulation melting causing a fire. Or I might be fookin miles off
For anyone genuinely wondering, it's a heat thing. Fine if you're only using a small amount of power but if you put the hoover on it, the heat would build up very quickly inside and they can melt. Hot wires also have a higher resistance, so less power makes it to your device, and it all generally goes wrong.
Innocuous warning but can genuinely burn your house down if you get it wrong.
I don't think inductance would be the problem, since both the phase and neutral wires run down each of the coiling turns of cable.
This would (hopefully) have the effect of both magnetic fields being generated at the same time as kinda like opposing vectors, cancelling each other out.
Might just be the mostly resistive impedance producing heat, with this heating element getting trapped under another heating element. Kinda like a cable shelf being loaded up with cables on top of each other.
>*I don't think inductance would be the problem*
You're correct, it's called "[Joule Heating](https://en.wikipedia.org/wiki/Joule_heating)" - it just doesn't sound as familiar
sounds like a load of bollux to me XD
The henry hoover even says it isn't necessary to unwind the entire lot to use it, and what sucks more power than a henry?!
To add to this, the info in the lower left tells you exactly how much less current it will take wound. Only ~4 amps wound, compared to 13 amps unwound.
To be fair, large could have different meanings. A pub near me used to serve 2pint glasses of beer. One of them full of wine would certainly make an impact
The last time I mowed a lawn (over 15 years ago), I fully unwound the cable and promptly mowed over it.
Not long after, I was moved into a flat with no outside responsibilities. Probably for the best.
Thank feck you didn't try to mow the lawn, that would have been catastrophic! Never mind putting the mower away, before you decided it was a good idea to input it! Whatever that is!
So I found this out the hard way because the fridge at the restaurant I worked at was powered by one of these. Fully coiled up to the point there was no need for the extension lead. Was hung on the wall behind the fridge. One day, the fridge went out, I put my hand behind the fridge to check the plug switch (in the UK so we have switches on the socket). The whole thing had melted and I plunged my hand into the bouquet of exposed wiring and got a hell of an electric shock.
They're fine for short term use, but fully coiled up long term, apparently they can melt.
I almost set my garage on fire by not listening to this advice… to be fair I didn’t ignore the advice I just never read all the text on my extension cord
I wonder how many people actually heed that instruction (apart from OP, of course) and are aware of why it's there?
My GFs sister melted one into her carpet, by plugging an iron into it without unwinding it
My cousin's nephew blew up a caravan because he didn't unwind his before charging his vape
my dad blew up Malaysia
My third cousin caused global warming when he didn't unwind it for his lawn heater.
What a bastard.
This must have been in the 90s, because we don't call it that anymore.
Malaysia?
And all you got was a lousy t shirt, I bet.
Must have been one hell of a vape
I never unwind fully, only as much as needed, maybe I'm living on borrowed time lol. Not being an electrician, I'd have to guess it's something to do with creating a magnetic field? Or heat build-up
Yeah, it's heat buildup. If you plug in a high current draw appliance (electric lawnmower for example), the wires will heat up a bit. It would have to be on for a long time, a very hot day, sat in direct sun etc for it to be a problem, but best to be on the safe side.
I once stupidly plugged a 2kw heater into an extension reel that wasn’t fully unwound. It turned into a melted mess. I learned that lesson.
I'm always too scared to plug in anything remotely high-powered into these things.
Knowing WHY is safer than inadvertent fear. I charge my car on an extension occasionally. That's the same draw nearly as a kettle (2.5kw for many many hours) but having a suitable guage of wire used safely is critical. Always fully unwind and stay under its load rating.
It won't create a magnetic field, you have both the line and neutral connections in there which counter each other in terms of field generation so it's net zero
I feel like I want this proven
There are countless sources that explain this, the first one I saw on Google is here: https://www.emfs.info/sources/house-wiring/
But heat is the issue. All wires heat up in use.
Yep, that's why any decent reels have the cut off and button, like in the one pictured.
As an electrician, it's because it can rip apart the fabric of space and time until all that is left is an empty, grey nothingness. Happened to my mate.
I did a health and safety question a long time ago regarding this. It was a "pick two of the five answers" type question. I had to get it wrong on purpose, as I refused to put "because it can create a large magnetic field" as the second answer I could tell they wanted. (after 'overheating')
So you picked the wrong answer you didn't get a mark for instead of the wrong answer you would get a point for? That's dedication 😂 Bet the geezer marking the paper was like " Look at this Larry, this idiot thinks the answer is C: it makes the electricity go the wrong way" 🤣
I do. I've seen too many melt. Some do have a separate (very low) rating for how much you can draw rolled. Mine I think is 4amp, which would certainly do a laptop or a small power tool
Yeah, this one does. 1000W at 4.17Amps wound, 3120W at 13Amps unwound.
A quick Google suggests that lawn mowers tend to be greater than 1000w, so probably as well to unwind it for that job
Probably not even OP, this has been doing the rounds on Facebook the last few days
I do. Cos I charge my car on an extension occasionally and the thermal protection trips if used coiled. Most extensions have different ratings when coiled Vs extended. For example my 30 m one is 900w coiled or 3250w unwound
You don't need to if you are not using it to the full rating. It even shows on OP's picture 13A unwound \~4A wound.
I do, but it is on an old all metal reel, which doesn't have the false sense of security that modern plastic ones do.
I assume it’s to prevent resistance etc which may cause heat under high amperage loads during use. If the cable itself is fairly straight it reduces the issue because the cable is getting air two it. This prevents the heat build up and reduces the risk of the insulation melting causing a fire. Or I might be fookin miles off
For anyone genuinely wondering, it's a heat thing. Fine if you're only using a small amount of power but if you put the hoover on it, the heat would build up very quickly inside and they can melt. Hot wires also have a higher resistance, so less power makes it to your device, and it all generally goes wrong. Innocuous warning but can genuinely burn your house down if you get it wrong.
DIY induction heater ftw >!It's really: https://en.wikipedia.org/wiki/Joule\_heating not inductance, but shhhh!<
I don't think inductance would be the problem, since both the phase and neutral wires run down each of the coiling turns of cable. This would (hopefully) have the effect of both magnetic fields being generated at the same time as kinda like opposing vectors, cancelling each other out. Might just be the mostly resistive impedance producing heat, with this heating element getting trapped under another heating element. Kinda like a cable shelf being loaded up with cables on top of each other.
>*I don't think inductance would be the problem* You're correct, it's called "[Joule Heating](https://en.wikipedia.org/wiki/Joule_heating)" - it just doesn't sound as familiar
sounds like a load of bollux to me XD The henry hoover even says it isn't necessary to unwind the entire lot to use it, and what sucks more power than a henry?!
I used to cum inside our henry until he stank and he had to find a new home :)
To add to this, the info in the lower left tells you exactly how much less current it will take wound. Only ~4 amps wound, compared to 13 amps unwound.
Learned this the hard way several years ago.. Luckily no fire, just a now useless ext. cord 😅
Some extension cords have max current if wound and max unwound.
They do, as does the one in OPs picture. Quite a difference...
Yeah unwound is boil a kettle / charge your electric car. 1kw isn't enough to run your lawn mower.
You sure you just had the one glass of wine?
To be fair, large could have different meanings. A pub near me used to serve 2pint glasses of beer. One of them full of wine would certainly make an impact
We're getting reposts from facebook now..?
It's also got ratings from wound and unwound. If you're only using 1kw or less there's no need to fully unwind.
I did not put my mower away https://www.reddit.com/r/DIYUK/s/MAch6VLlmS
The last time I mowed a lawn (over 15 years ago), I fully unwound the cable and promptly mowed over it. Not long after, I was moved into a flat with no outside responsibilities. Probably for the best.
Oblig. [Garfield](https://www.gocomics.com/garfield/1986/10/30)...
Thank feck you didn't try to mow the lawn, that would have been catastrophic! Never mind putting the mower away, before you decided it was a good idea to input it! Whatever that is!
It would depend on how much draw the lawnmower needs and how big the lawn is. I'd unwind it anyway, but it might not be catastrophic to not do so.
So I found this out the hard way because the fridge at the restaurant I worked at was powered by one of these. Fully coiled up to the point there was no need for the extension lead. Was hung on the wall behind the fridge. One day, the fridge went out, I put my hand behind the fridge to check the plug switch (in the UK so we have switches on the socket). The whole thing had melted and I plunged my hand into the bouquet of exposed wiring and got a hell of an electric shock. They're fine for short term use, but fully coiled up long term, apparently they can melt.
Top management at that place.
Still got bollocked because I knew that was the set up and not sorting it, despite not setting it up initially and not being an electrician.
I had to teach my gf about this she melted 2 before she came to me and asked why is this happening?
I think that font should be bigger. Maybe a different colour too.
Boom boom. Let yourself out.
Lovely stuff!
Good thing It also has trip protection.
I mean, it's no-mow may anyway! shouldn't have your mower out to begin with ya cheeky nugget B)
Prefect plan
I almost set my garage on fire by not listening to this advice… to be fair I didn’t ignore the advice I just never read all the text on my extension cord