Ever wondered why extension leads have two power or current ratings? In this video, we uncoil the truth by ignoring the manufacturer's instructions.
Using a plug-in electric vehicle charger as an example, we'll show you the potential dangers of disregarding power ratings.
This question was raised following our review of the Marcaddy retractable extension cords.
👉 • Retractable Cable Lead...
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00:00 Why do extension leads have two power ratings.
00:46 Charging an electric vehicle with an extension lead
01:24 Extension lead thermal overload
02:04 Calculating the power loss in the extension lead
02:55 Thermal trip works!
03:16 Removing the thermal cutout
03:46 Meltdown
04:48 Extension lead teardown!
05:44 Cable grouping factors
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#extensionlead #extensioncord #evcharging
This question was raised following our review of the Marcaddy retractable extension cords. 👉kzhead.info/sun/ktaOgdx6fWhniGg/bejne.html
Have dropped comments before on sparkies channels about grouping factors.... such as putting all the T&E cables for example in a single 50 x 50 plastic trunk to a CU when they are moved/relaced with them rammed in and no air gaps between them. The same applies inside consumer units/distro panels - cable ties to group stuff together may look good, but it goes against the regs for grouping Reeled extension cables are especially bad for this but this proves why you should have one with a thermal cut out as a lot of end users won't appreciate that they have to uncoil it..
The instructions always say not to use when coiled up. People need to read the instructions.
I always wondered why those cables have had that rating difference, is the heat of the on top layer o wound cable, amazing... this question took 15years to be answer for me
Appreciate this video, great demonstration!
We had a power cut a couple of months ago which could of easily turned into our neighbors house being a live inferno. Plugged 2 2500w dimplex heaters into a 3500w rated extention lead. Luckily I was there to unplug it and give him a big rist slap but my god it was warm.
No thermal trip?
@@efixx Nope, his dads old 80's masterplug lead.
@@megatronskneecap Presumably with a special fuse as well?
@@yngndrw. yup.
Part of my job requires testing portable appliances in specific commercial buildings open to the Public. The number of times you see things like a Kettle, Fridge and Microwave plugged into the same extension cable is amazing. Sometimes it's a kettle, toaster & coffee machine, sometimes it's 4 high powered devices on one extension lead, sometimes it's multiple chained extension leads. Lots of people have NO idea what's unsafe. Our family also found a fuse which had either fuse wire or just some wire soldered across the terminals by my Grandfather, likely in the early to mid stages of his dementia. He also decided to cut the phone cable in the corner of the desk with some scissors. Quite why he did that we don't know, but he had been diagnosed by then.
Years ago we used really long 2 core extension leads to run garden tools, always wondered if you shorted the far end would the current be great enough, 25+A, to clear the fuse before the whole cable went up in smoke.
A mate and me were doing some wallpaper stripping at his new house about 20 years ago - as we moved up the stairs we needed an extension that we (foolishly) both plugged our respective strippers in to - we wondered what the plastic smell was after a while and the reel was practically about to melt itself together - it was partly coiled - the most ironic thing was that we were both fresh out of uni with E&E degrees 🤦♂️ Lesson learnt - I am super conscientious about any extension whenever I see any kind of load above 1kW on it 😬
Good video had someone use my lead and had a wallpaper remover plugged in wound up
I had one of these about 20 years ago . Old lady used if for her 3KW kettle . The flex was only .75 mm. No thermo cut out and she had a 13 A fuse in the plug top . She wondered why it wouldn’t pull out the plastic housing . It had melted in a solid block
sounds like a close call!
I'm not sure that anyone who needs this explaining to them should be watching this channel.
1000’s of new electricians join this industry every year
This is why I've always fully unwound extension leads before use, doesn't matter what load I'm putting on it. I also try to use the correct length extension for the distance required so I don't end up with a big loose coil of cable on the floor.
Top Tip 💪
I’m having a meltdown watching this 😂 nice one.
I had this many years ago when I worked in a shared office, the office next door went into 'blackout' so I unplugged everything, reset the trip and one by one plugged in every item until it tripped, it turned out that somebody had a heater under their desk attached to a coiled extension lead that had literally melted because of the current load. Needless to say they didn't do that again!
Extension leads in offices should be banned IMHO. I frequently confiscated underdesk heaters as a works sparky.
Good demonstration, shows how dangerous it is not to fully unwind. The best bet is to a get a waterproof extension cable instead. Oh and the cable connected to the car is called a 3 pin Type 2 cable, nothing to do with old people.
The plug in chargers are often known as granny cables. The one used as relatives tend to have EV chargers.
What about using extension cord with pressure water wash ? Some says dont use it with karcher
Shouldn’t be a problem if you use a waterproof one with good quality cable and fully uncoil the lead.,
@@efixx Thank you
called to a customer who smelled buring. told her to switch off the electics at the box. go to her about 30 mins later and after a nose about, found that her bedroom fan heater was run via a similar extension lead, no themal cutout. took out of circuit and posted up the house, tested all circults all ok. back to extension lead, took it apart and, hmm think she cut the electics just in time,. the inside of the plastic case had melted. as had most of the the cable which was black (used to be orange). hope showing her the inside of the extension lead stopped her using any more of them.
Powerful lesson 👍
Might share this on one of my EV groups. 🤨
the one thing that the cheaper extension leads have that really is annoying is that they say they have a 13a plug but in small writing the max load unwound is 10a as they have used 1mm2 cable why dont they make it clear that 10a max. i see these used all the time for high loads.
Do they fuse the 1mm2 ones at 10A?
@@efixx yes they do fuse them at 10A.
Was that ‘granny’ lead actually 13a? Most if not all are usually 10amp. The car did say 8mph when charging so I would say it was a 10amp one. Same result though.
Agree that most of the car manufacturer supplied ones are 10A, but this one we found does indeed draw the full 13A we've got a video coming soon which explores the cost of the power loss and in that video we measure the power.
@@efixx I try and steer people away from the 13a ones on the various EV groups I’m in. They are just going to plug them into any old socket, which is bad enough with a 10a one. It seems to be cost over safety. They don’t want to payout for a dedicated EV socket designed for the load. Most of these people are using them at their own homes daily not just for visiting friends. 8+ hours every night in a standard £2 B&Q socket. No thanks! I’ll share your video when it’s out on the groups. Hopefully it’ll make them think about it.
What caused the lead to melt? You fiddling with the safety stuff is what 😂 But a good example of how things can go wrong
Forcing the problem along 😃
always take all the cable out from the extension reel before using it and don't plug in more power then it can handle.
Pleased the old canard of inductive load wasn't brought up in the video. Because both conductors coil together and have counterflowing current, a wound extension lead is a bifilar non-inductive winding and so has negligible inductance no matter how long. The effect is exactly as described in the video, a purely resistive effect from so much conductor in an enclosed space.
Agree - Some of the other viewers are still wanting to push out the old canard!
@@efixx It's been a common myth in the events industry for decades and the trouble is it gets propagated to new people coming into the industry, it's like banging your head against a brick wall explaining it.
Induction has an effect as well
There is negligible inductance in a coiled cable as the L&N currents/magnetic fields cancel each other out, the heating is purely resistive NOT inductive.
Inductive loading isn't just imaginary maths! It is real, but not in the resistive sense! :) I've seen this happen to people who use extension cables in reels, rolled up, or in a plastic barrel... Lots of smoke, and heat!
There is negligible inductance in a coiled cable as the L&N currents/magnetic fields cancel each other out, the heating is purely resistive NOT inductive.
wound up it is a large coil, with an AC load, so there is inductance and not just DC resistance.
The inductance is minimal as the line and neutral are wound together so the return current is following exactly the same path.
My old boss would take any of these he found in the building out of service (you can always make use of the flex and plug) an approach the new one doesn't take, but I would...
As it is coiled up there is also inductive heating. As an apprentice in the 70's I saw a large steel sprung, and encased extension lead melt very quickly being used unwound.
There is negligible inductance in a coiled cable as the L&N currents/magnetic fields cancel each other out, the heating is purely resistive NOT inductive.
@@mfx1 Good point, I never thought about that. Must have been that it was such a large extension lead that caused the mealting. I had just assumed the metal casing and core, plus the big spring in the middle had also contributed. But what you say is quite right, never really thought about it that much.
I think those cord reels need a thermal fuse, PTC device, or disconnect. Too many people are simply unaware of the risk, and we can make them safer. Edit: a thermal safety at a *safe* level. It could even be made to detect when not fully unspooled.
A smart extension lead - next thing you'll be suggesting it has an app! 😆
I think your thermal camera needs calibrating or something, the infrared image is quite offset from the visible light image.
We’ll take a look at that - thanks
Looks like it was calibrated in 1970.
the closer you are to an object the more this effect happens due to the visible light and thermal being 2 separate cameras in different places, its not noticeable once an object is further away.
I have had a couple of issues with coiled extension leads. One when I was considerably younger than I am now, when I ran a 3kw fire without uncoiling the lead. I think more heat was generated in the lead than in the fire. It became one mass of melted plastic, no way would it unravel again. The other one was trying to run a small stick welder without fully unrolling the lead. It was only for 1 stick to quickly tack something together, but it wouldn't weld at all, I thought the rod was damp so stuck it in the oven to dry it out, but it was still rubbish. The penny finally dropped and when I unwound the whole lead the weld was fine. I think the coil was acting to upset the whole electrical circuit. I always unwind the whole lead these days.
Great insight 👍
Whos is Corsa E Joe?
🤔
Did Gordon trade his Tesla for a Vauxhall?
That's not a CE mark on the cutout, it doesn't meet the standards for the lettering, that's known as the "China Export" mark, if they couldn't be bothered to meet the requirements for just the lettering printed on the outside, would you trust it?
If youre a sparky, active, installing etc and you didnt know this consider learning more, please
The standard incident is to plug the tea urn at the village fete and not uncoil the extention lead. A big baby burco is 3Kw and will take 45 minutes to getup to a boil....
Burco boiler classic 🫖
It would have been more fun if you had allowed it to go through to full destruction and flames. Have you never seen photonic induction?
It was close but car finished charging
Too much heat...
What caused the extension real the melt ? You did Gordon by plugging it into another extension cord , you should never plug extensions into extensions . Good demonstration showing just what can happen when stupidity is in play. Try that again with out plugging it into another extension , and see what happens. Will make a difference? Great video as always Gordon .
Nope. The melting is because internal resistance of the cable that causes heat. And because of being coiled up, the heat gets trapped and accumulates leading up to the melting of the cable.
You still can’t plug an extension into an extension
That’s just a short converter between our 16A socket in the yard.
@@Dog-whisperer7494 That's nonsense Sean.
@@Dog-whisperer7494 can you explain your thinking. Other than volt drop
A come on, you should have left it for longer. we want to see flames... ;-)
Resistance is not a problem for coiled power lead It is reactance Basically coiled up power lead is a coil, it poses significant inductance Mind electric current causes electromagnetic field which causes electric current to flow , but this is opposite to original electric current This is problem
It's purely I2R losses - the line and neutral conductors following the same path cancel out any inductive effect.
But it's not the resistive power loading that is only causing the heating. The fact that the cable is wound up in a toroid will cause much more inductive loading and subsequent heating to occur.
It would be inductive only one core was wound around the reel, however the line and neutral follow the same path so the neutral return cancels out any inductive effect.
Who in their righthand would leave an extension coiled up 3specially pluugging in a car charger are we not sensible people on here
It’s in the folks on here you have to worry about. It’s those who don’t know!