There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
There is a reason for USB-C extensions not to be part of the standard. They can be bothersome in the best case and dangerous in the worst.
Going to take a wild guess and say the same reason you shouldn’t chain extension cords. USB can carry over 200w these days.
what if I don’t know that either
It all depends on current draw vs wire size over distance.
No, that’s not the reason at all. The actual reason is a phenomenon called “loop impedance”, which increases exponentially with each additional plug connection you chain together, regardless of the wire guage and distance of the extension
Too high loop impedance can cause your RCD to no longer trigger if you accidentally touch an exposed live connection, which is a major electrocution risk
Are you referring to AS/NZS 3000? I’ve never come across that here in the states, that’s some interesting reading and makes perfect sense.
On the practical side without engineering calculations, daisychaining extension cords will simply exacerbate voltage drop, which coupled with increased line resistance, will just cause increased current draw and increased thermal dissipation on the cord (those cords everyone’s dad has where the outer jacket is shrunk to hell against the internal wires), and poor reactance of (especially motor driven) equipment. This can be alleviated by using thicker cords (eg #10), but it still has limitations over excessive distance. A small battery charger will probably continue to work, whereas a table saw will have problems.
On the safety side, even sticking your finger on the load terminal of a 20a breaker will not trip it, even barefoot, as the human body doesn’t draw enough current, it just zaps the hell out of you. OCPDs are typically designed for system and equipment protection. GFCIs are more effective at protecting a person, but only if the current deviates to a different ground path. As far as I can tell from preliminary reading, the purpose of calculating loop impedance is determining the effectiveness of the grounding (earthing) conductor in relation to distance from the actual transformer. In a real world scenario, this is more going to be say if a cord were to be cut or equipment faults to ground, and whether the impedance exceeds the physical limitations of the wire to trip the breaker (or fuse).
Chaining regular extension cords isn’t a problem by itself, connecting too many things in parallel and exceeding the rated max is a problem (and chaining extension cords “just” increase the risk that ordinary people will decide to connect more than they should, especially because the lowest rated cable in the chain sets the total limit)
The issue of chaining extension cords is that you can physically plug a 10 amp extension cord into a 30 amp cord. If you don’t know what amps the device will pull, the 10 amp cord can overheat.
It’s an almost identical problem to USB c.
Why in the everloving would your electrical code allow sales of extension cords that can’t withstand the whole of the plug/socket rating. If it’s an adapter from a higher amperage plug to lower amperage socket you need a fuse.
The short answer is rating changed. We got more and more devices that required higher amperage ratings. So we went from 110 (which was what most homes were rated for in the 50’s) to 120. But if you happened to have an old extension cord lying around in your basement from before the change etc you absolutely could overload it.
The real problem though is that some devices you might use an extension cord for (lets say a welder because I know from experience those require more power than a standard 20’ extension cord puts out), require a certain gauge of wire to carry that power. If that wire is too small or the power source is insufficient, it’s likely no electricity will flow (without flaws in the circuit).
There are various kinds of extension cords made for various uses. Longer = more money, fused = more money, larger wire = more money. More insulation/weather proof plugs = more money.
You probably don’t need a big beefy extension cord for the lamp in the hallway. But you might need it for your weedwacker.
But if, say you hooked up an outlet dedicated for something like a washer/dryer. And you used the correct extension cord to connect to that outlet. Now let’s say you attach an older extension cord or power strip to that extension cord. One that doesn’t have an internal breaker to trip (there’s definitely a fair number that didn’t, back in the day). It would be an astronomically bad idea to attach your welder (or any high draw device) to that circuit. You absolutely can and will let the smoke out of your wires and where there is smoke there is fire.
110/120 is the voltage. That’s irrelevant to the amperage, which is somewhat standardized as 15a on normal outlets and 20a on kitchen or garage outlets.
Extension cords do not have fuses/circuit breakers. That’s found in some power strips but it’s neither required nor necessary with proper use.
And I can literally only reach my car with a welder if I use an extension cord…
The risk of daisy-chaining power strips is it become very easy to overload it, so yes, a circuit breaker would be nice as fire protection. 17 phone chargers would be fine but heating appliances will overload it fast. With no internal breaker, it’s easy to cause a fire with really cheap strips but, if life was ideal, they’d all be made to handle 20a loads like the receptacle in the wall.
The risk of daisy-chaining extension cords is the extra resistance incurred at each connection. There’s a varying amount form the imperfect contacts and a varying amount from pulling the cords apart over the time of device use. If you keep burning plugs with your yard care equipment, it’s probably not normal. It’s usually from partially unplugged cords trying to carry 10-20a across half the planned plug contact. You can readily buy 10-16 awg cords in 110v markets. It’s up to you to determine the appropriate gauge. In an ideal world, they’d all be 10awg. But we don’t have that, we have a world where you can actively choose to save money and increase risk.
Some extension cords absolutely do have circuit breakers, I know this because we use them at work for some of our heavy duty equipment. I also know for a fact that fused link extension cords were their predecessor and you can buy both on Amazon still so I know they exist.
Further I was not saying don’t use an extension cord with a welder. I was saying the correct gauged wire for that extension cord may be necessary to carry the load.
The point of bringing up 110 vs 120 volts was to point out that more voltage = more push. More push through a smaller circuit than is recommended means more heat.
Amperage is the draw, and it’s important because most devices are rated by draw rather than voltage, so what I said does make sense in that context. I wasn’t trying to say they were the same thing. The reason they’re rated in amperage is because the amperage is what kills you, and because thats what the safety devices are rated in. That’s how much of a draw they can withdtande before they break the circuit.
I was also pretty exhausted when I responded so my explanation barely makes sense even to me, but I do see where I was going with that. Have you ever seen one of those old brown extension cords with three outlets? They’re usually 2 prong (don’t have a third prong for ground). They also don’t have any of the fail-safes that new extension cords do have.
While I was not specifically talking about daisy-chaining power strips, I wanted to make it clear that even using multiple extension cords in a daisy-chain manner adds significant resistance to the circuit and with enough push and a big enough amperage appliance it absolutely is a fire hazard.
I’m not sure where you got that I said you shouldn’t use an extension cord with a welder. I was saying you don’t need an extension cord worthy of powering a welder safely in order to power a lamp. But a smaller lower rated extension cord that works for a small indoor appliance is not up to the task and would be dangerous to use with a welder without the proper protections.
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Yes, that is a risk. Don’t forget about voltage drop, though! A short extension is generally quite a thin conductor, and the thinner the cable, the more resistance you get in the cable itself.
The funny thing is the breaker only costs $0.01 to include, but could prevent a house fire. Crazy we don’t demand it in all of our cords
British cables are fused in the plug, and it’s a pain in the ass. I don’t see the problem with a breaker that just drops the whole circuit if something goes whoopsie.
That’s just rephrasing what I said. You can plug in too much for a single extension cord even if there’s no chaining. A chain “just” increase the risk.
Yes but I was emphasizing the parallels to the USB c problem.
In USBC if you use a 200 watt cable that has 200 watts going through it and then extend it with a 15 watt USB c cable, the 15 watt cable will over heat.
If you plug a 30 amp load into a 30 amp cable and then extend it with a 15 amp extension cord, you will get overheating on the 15 amp extension.
You could also just plug in the 10 amp cord and plug the device into it. The chaining doesn’t change anything here.
I feel one would have to work really hard, with really shitty extensions, with really high amp draws to cause a problem.
SOURCE: I’ve temp wired some nutso shit.
Yeah, I think in this case there’s a lot more tiny conductors sharing what can add up to pretty high current loads on PD connections. Adding extra connectors adding resistance to low (5-20v) voltage high current connections is adding an extra failure point and increasing resistance on the whole cable run.
Not inherently unsafe, but just not a good idea to promote because you know someone will try to run a 200w charging cable for 30m with like 5 connected cables.
I would hope that a device capable of pulling 200w from USB would be intelligent enough to detect the excessive voltage drop and error out or reduce the current.