“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

  • r00ty@kbin.life
    41·
    2 days ago

    I think a lot of people are mostly on the money here. It’s to do with resistance. Now, I’m not a qualified electrician, but I’m an amateur radio license holder and a lot of what you learn for that is applicable here.

    The main problem as many have said is resistance. This comes about from both the length of the conductors but also from every plug/socket connection adds resistance. Also in the case of the non extension socket multipliers, as you add more the weight bearing down would also likely start to make the connections less secure causing more resistance and possibly adding to the problem through arcing.

    Now the resistance alone on small loads likely wouldn’t be a huge problem. But if you had a large enough load (specifically at the end of the stacked connectors/extensions), or a fault that caused a larger than expected load the current would cause the resistance to generate heat.

    There’s a lot of ifs and maybes involved, but really why do it? There’s really no real world situation to need to have a dangerous amount of extensions like this though.

    For larger loads here in the UK there’s some very specific other concerns when dealing with ring mains. But really you’d need to do really weird/unusual things for that to become a problem.

    • Aqarius@lemmy.world
      3·
      2 days ago

      On the contrary, practically every single person in this thread that mentions resistance is talking precisely backwards. Higher resistance will not cause overheating. Except for certain motor loads, it will cause malfunction due to voltage drop. The actual fire hazard is the increased chance of faulty cable, faulty connection, and, inevitably, overloading.

      • r00ty@kbin.life
        2·
        2 days ago

        Resistance alone doesn’t cause heat. Drawing current through resistance causes heat at the point (or points) of resistance. Which is why I clarified that it’s not likely so much a problem on small loads.

        This is why resisters come in different physical sizes. Because they have differing abilities to dissipate power as heat.

        A good example is of dummy loads in radio use. Which needs to dissipate the power output of a radio. That can be anything from milliwatts to a kilowatt. Up to probably 50w they will have a basic heatsink. I’ve seen huge drums filled with oil as 50ohm resisters to handle up to a kilowatt of dissipation.