Livewire

Mandy\'s avatar

Fox can be a literal tool…

Fox\'s avatar

This is an exaggeration.
I leave the live wire capped until just before I start working with it. πŸ™‚
One day I will actually get zapped doing this. It still hasn’t happened.

To: The Actually Squad:
I’ve already pointed out to Mandy that extended, in-wall electrical runs in houses tend to be solid copper, not stranded.

Fox\'s avatar


SAFETY NOTICE:
This is another example of “Do what I say, not what I do.”
And I say:
Turn off the damn electricity.

My understanding has always been: “The volts don’t matter; the amps kill you.”
“Well how many amp–”
“As low as 0.1amps”

This doesn’t mean high-voltage (greater than 500v) isn’t more dangerous; it is. It’ll cook your insides.
What this means is that 110/220 can still easily cause massive injury or stop your heart if you slip up for even a second.

Fox’s Comment On:
BORING STUFF! FACTS! SCIENCE! WHY ELECTRONS KILL YOU!
It’s not that they don’t like you. In fact, they’re attracted to you!
But they’re just using you to get where they want.

38 comments on “Livewire

  1. I was about to write that is difficult to get seriously harmed by touching a live wire, and how many times my dad has done it purposedly to check if a connection is working as intended, but after a long wikipedia session on electric standards, I guess that I know nothing about how electricity works on the US (split-phase, really!?).

    Given that, I can only say that THHN cable is intended for in-wall instalations and is stranded (and a nightmare to connect).

    1. Split phase is just single phase with a center tap on the transformer. Typically, only one half of the split will be present in a box like the one he’s working on, which means you’re right, serious harm is unlikely. It’s only ~120 volts. So long as you’re insulated from ground, anyway

    2. THHN cable can be stranded or solid; it just refers to the nylon coating around the cable.
      Unless you’re doing something rather specialized, most wires you encounter will be THHN.
      T – thermoplastic, N – Nylon (e.g., PVC)
      HH – High heat resistance
      W – Water resistance
      HW – Heat and water resistance (Many are also THHN rated)

      The only other of mention is XHHN, which is just a more durable/resistant/expensive nylon.

      1. X is for Crosslinked Polyethylene (XLPE) insulation, which is better exposed outside, like the “Bronco Wire” Aerial Drop Wire from the power pole to the house. https://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet34

        Or the underground from the property line to your house. NOTE: If this is after your house main disconnect feeding to the barn and outbuildings, you need Quadplex drop or 4-wire underground – separate neutral and ground.
        It’s far better where exposed to sunlight, XLPE doesn’t have the 2-layer Thermoplastic and outside Nylon sheath that the sun gets to.

        And yes, THHN is usually triple rated THWN and MTW – Machine Tool Wire for internal wiring on appliances.

  2. *flashbacks to exploding pliers*

    …Turns out I turned off the wrong breaker.

    1. Been there, as a kid. It was someone else who said they’d turned off the breaker, and I was using a pair of diagonal cutters on the line.
      Thankfully, they were insulated.

      +1 to Fox being paranoid, untrusting and cynical

      I’ve never managed to get anyone to agree to let me experience an actual flashbang (yet) but cutting that line caused a small explosion that curiously provided enough light and noise that I can only assume simulates the same effects of sensory-overload caused by flashbangs. I will never forget that moment of being both unharmed & unelectrified, yet after the blue flash I was completely unable to move, or even think. I still remember the terrible pattern on that crappy carpet, the plastic trim and the color of the wall; one second that frame existed, the next there was a blue flash, half a second of darkness, and that same frame slowly fading back into view because I simply couldn’t move so it all got burned into my brain.

      The diagonal cutters were not so lucky. The 15 amps are basically a plasma cutter at that point. I assume the missing steel is what turned into the energy I witnessed.

      1. From the other room: “What the hell was that noise?!”
        “…that was me cutting the line you said you’d turned off. You flipped the wrong breaker. Conveniently, it should be easy to identify the correct one now, as it’ll be the only one in there that’s tripped itself.”

  3. My dad’s electrified the plumbing. Twice. He’s no longer allowed to do electrical work.

    Good luck!

    1. OK, I’m curious: What scenario permits this? Ya know, besides improper grounding. GFCI are required for all outlets near water, so I’m guessing exhaust fan or switches.

      1. Back when all pipes were metal ones, most building codes let you use the plumbing for your electrical ground*. As PVC became more common, that was not longer allowed, because there was no guarantee that some future plumber might lift the ground connection by replacing a metal pipe with a plastic one. If some amateur electrician later got their wires crossed, because of the floating ground, there wouldn’t be any current to trip the breaker/GFCI until someone got zapped by their faucet.

        I don’t actually know if this is what happened to Lutris’s dad, I’m just putting it out there as a possibility.

        *And, in some places, actually encouraged you to do so. The idea was that the home piping was connected to miles of underground metal pipe, making it a much better ground than a 6-foot (or whatever) rod.

  4. Dad got real upset the time he got a little jolt working on a light switch and I snorted a laugh. πŸ™‚

  5. So… Who want’s to tell me the difference betwixt solid copper and stranded? How does it make a difference?

    1. Electrons prefer to go on the surface of a conductor, instead of on the core: with stranded wire you have more surface with the same diameter, allowing to transmit more power on thin cables. Also, they are more flexible and elastic (returning to their initial shape instead of becoming curved).

    2. For the purposes of this explanation, unless otherwise specified, assume we’re discussing standard 14 awg (gauge) cable for interior, residential, electrical work. (IRC code req. for typical 15a circuits)
      Obligatory note: I am not an electrician

      • Installation: Solid wire retains its shape and supports its own weight so it won’t spool up like stranded wire will. This is useful running through walls and between joists in existing homes–you can ‘push’ solid copper. Trying to do the same with stranded can be…well, ever heard the term ‘pushing rope’?
      • Expense: Copper is extruded or drawn into wire. Stranded wire requires more effort to create as it has to be drawn into a smaller amount, then twisted together.
      • Fatigue: if you repeatedly bend wires they will eventually break. This is why most electrical cords designed to have any interaction with end-users are nearly always stranded copper, as it’s more flexible by design, and also able to survive more bends before breaking. Circuits running to fixtures or outlets don’t move, so they will use less expensive, solid copper that’s easier to install.
      • Connections: Using solid copper, you know if your connection is strong–there’s only one possible point holding onto the end. With stranded lines and cheap connectors, the entire surface area may not be making contact, which can be a ‘Bad Thing’.
      • Diameter: ‘Gauge’ is how we measure the size of a wire. The numbers go down as the wires get smaller because, at least originally, that’s how many times the wire had to be drawn (stretched) through the machine to reduce its diameter. Gauge (AWG anyway) was originally created based on solid wire. Stranded wire of equal gauge will always be slightly larger in diameter to its solid counterpart due to the unavoidable gaps between the strands.
      • Corrosion: If the wire isn’t jacketed, stranded wires will suffer more corrosion due to increased surface area. Only really applicable in electrical circuits when dealing with ground wires.

      You may also hear some talk about phenomenon called the skin effect and the proximity effect, especially in reference to solid vs. stranded. There seems to be some confusion regarding the differences between what most think of when we say ‘stranded’ cable and cable that can actually counter those phenomenon. When most say ‘stranded’, we’re referring to what you’ll find when you go to any hardware store: multiple strands of bare copper–run in parallel, twisted or braided–of a diameter slightly larger than a solid wire of equal gauge.
      The following is very important: In regards to the skin effect and proximity effect, the stranded wire I just described functions the same as a solid wire.

      The skin and proximity effects are only present in AC electricity–DC is unaffected because it does not alternate. This alternating causes something called ‘back EMF’, which is strongest at the center of the wire(s). It’s an opposing magnetic field, which the electrons don’t like, as it creates resistance. As such, the electricity travels where it exists the least: the physical surface of the wire. Now it can’t all run right on the surface, so it does have a ‘depth’ it goes, literally called the skin-depth. As the electricity can not make full use of the solid wire, somewhere it got misconstrued that having multiple strands in contact with one another will counter this, which isn’t the case. One solution to save money is actually to use a hollow pipe, but those tend not to flex very well.
      Proximity effect happens when two insulated AC wires are placed next to one another. While they’ve back EMF inside the cable, they also generate an EMF around the cable itself. When two cables are placed next to one another, the EMF generated from both simply push back into the cables, and the electrons ‘run away’ from that area, because it’s now harder to travel through it. The end result is that there’s now even less area for the electricity to flow through without encountering resistance, so you’ve effectively lessened the total theoretical amperage the cable can transfer…before the insulation starts to melt.

      The only wire I’m aware of that can counter skin and proximity effects are litz wire, which are multiple, individually-jacketed strands in specific patterns, potentially in recursive layers. I suspect this is where the idea that ‘stranded wire’ can reduce skin effect: someone heard that litz wire is stranded, but didn’t catch all the other requirements.

  6. Boring Stuff / Facts / Science about the dangers of electricity:

    Everyone is different and every scenario is different, but it always really boils down to whether or not the electricity decided you were the fastest way to get to its favorite, negatively-charged thing in the world: the world. Specifically, the Earth itself. The world’s safest electrician is one who can levitate.
    (And companies have actually repaired major power lines working from helicopters)
    Are you standing barefoot in a puddle of water? Where did you touch the wire? Ungloved, right hand? OK, electricity likes you cuz you’re an expressway to the ground along that side of your body. Not standing in water but your other, bare hand is leaning against a grounded, metal surface? Now you’ve a better chance of dying because the fastest way from one hand to the other is pretty damn close to your heart–a delicate piece of fleshy machinery that gets knocked out of whack when hit with electricity cuz it kinda relies on low-levels of that at certain intervals to keep itself ticking. Too much outside juice and it goes into ventricular fibrillation which means it starts quivering instead of pumping. This is commonly known as a heart attack.
    Even if it doesn’t cross your heart, your skin is a lousy conductor. This means it has high resistance. Resistance is great, as electricity likes to go where there’s the least resistance. The problem occurs when electricity decides–skin or not–you’re still the path of least resistance, and makes you its new racetrack. If enough is going through you, all that resistance in your skin means the electricity has to ‘fight’ to get through it. When electricity fights with something, that something heats up. In this example that ‘something’ is your skin. Again, everyone is different, but most skin will burn exposed to 110 degrees for a long period of time, or 170 degrees for less than a second. How fast it heats up is based on the amount of electricity is passing through and how much resistance your skin is providing. I’ll leave running through the plethora of scenarios that could cause major damage there to you, as most damage from standard household voltage isn’t enough to cause major burns to internal organs, just that big one on the outside of you. So since it’s based on time, you can just get away from the electricity, right? Maybe. Tasers actually operate on the same ‘let-go phenomenon’ caused by alternating current that forces muscles to contract, but prevent humans from releasing. It’s happens because the muscles that open your hand are weaker than those that close it. Makes sense, right? If you’re grasping something, you need more strength to hold it. If you’re letting something go, you just need enough force to move your fingers. The problem is that alternating current…well, alternates. And like your heart, the muscles in your fingers also respond to electricity, cuz that’s how we tell them to do stuff! So what happens when your hand gets hit by 110 volts of alternating current operating at 60Hz? Your hand muscles all get forced to operate at about a bazillion percent over capacity cuz they’re getting a bit more current than normal. And they’re getting forced to do this 60 times per second. (Cuz that’s what 60Hz means) And the flexor muscles that keep your hand closed are doing a better job than the extensors trying to open it at the same time, so you’ve clamped down on whatever you were holding. Now, were you holding a live electrical wire? If so, your life is about to get a lot more interesting–and potentially a lot shorter–because as discussed earlier, the longer your skin has to heat up, the worse the burn will become. It will be of absolutely no comfort to know that the burn where you contacted the source of electricity will likely be less severe than the one where it’s leaving your body. Yeah, electricity does damage a bit like a gunshot wound.

    Everything above illustrates why ground wires are so important: In the event something shorts out, electricity will always choose a copper line to the ground (hence the name of the wire) over you, given the option.

    1. I got to watch the Fix-High-Power-Lines-From-A-Helicopter trick from my bedroom window after hurricane Fran in 1996. Pretty cool. πŸ™‚

  7. Sometimes you have to work it Hot long enough to get it all open and make sure it’s “really most sincerely dead.” And by the time you get that far you might as well just leave it on.

  8. The amazing thing is that twice (!TWICE!) we’ve had to call 9-1-1 for the PROFESSIONAL ELECTRICIAN who was stupid enough NOT to turn off the power to the circuit he was working on and got zapped. Different guys, of course (or so I fervently hope).

  9. “The volts don’t matter; the amps kill you.”

    But the volts determine the amps. The amps are the volts divided by the resistance of the path.

    1. And the engine determines the type of fuel it uses, but it really doesn’t matter if it’s powered by diesel or gas if it collides with you, does it? What matters is whether or not it was traveling fast enough to kill you.

      Amps are the volts divided by resistance. Volts are the amperage multiplied by the resistance. A wall outlet is 110 in the states. It’s 220 in Europe. Static electricity in your body can be 25,000 volts. But none of that matters nearly as much as the conditions that will put your heart into v-fib, which is based on the current, not the frequency voltage.

      1. If you double the voltage, you double the current that will flow through you when you touch it (assuming the same skin conditions). That’s why European sockets are more dangerous. I’m not making this up.

        Static shocks are less dangerous because they are brief, not because the instantaneous current is small (it’s actually very large). The charge built up is small due to your body’s low capacitance, so the current is only large for an instant before that charge is depleted.

        As for frequency, I didn’t mention it at all.

        1. It’s a little irritating having you try to lecture me on the subject when everything you’ve typed was already explained–at length–in my other comments on this comic. The meaning of the old phrase doesn’t seem to be sinking in, so let’s try this another way:
          Go try to find a chart depicting how many volts across your heart will put it into v-fib.
          Then tally up all the ones you find showing how many amps will put it into v-fib…

          …go on. I’ll wait.

  10. I remember hearing that the zap you can get from rugs (e. g.) are up toward 10 000 (TEN THOUSAND!) volts, but the amps are so low (0.0001 low?) it doesn’t really harm us.
    Anyone heard something similar or know something about this?

    1. 25,000. But I suspect it’s very low capacity (amp hours) and amperage (current) so you just get hurt a little. The spark you see is actually air transforming into the fourth-state of matter: plasma.

  11. Be careful with that. Or else, OMD’s Electricity with play in your head…

  12. Trimming trees around the hydro lines and the stories told in school and from other people who’ve ‘taken a poke’ you learn to give even 240V house service’s a healthy berth….I’ve watch a co-worker bounce his head off the live line in a 17kV circuit and not do a thing (insulated aerial lift and helmet)- and a mere 8kV three phase line turn a 2 inch branch into flames in about three seconds. Not one of my better days, but nobody got hurt and there was no fire damage to the lines, but it was a half panic to go grab an insulated pole so I could knock it away

  13. Working for a historic streetcar operator, I have experience working with 600v DC power. It’s all about whether you’re grounded or not. Most electric railways used insulated work platforms on their line cars. That permits the line workers to handle the wire while hot. When turning traction power on and off, the dispatcher had to use an insulated pole as the switches would become live once closed.

  14. Back in the mid-’90s, my family moved into a new house and my room was missing a lighting fixture, with dangling wires in its place. It was eventually rectified.

  15. I was at a relative’s house while he was doing some electrical work. He cut one of the wires, and *POW!* It was still live. Put a nice round hole in the edge of his wire-cutters; guessing they work nicely as wire-strippers now.

    I myself have developed somewhat of a ‘sensitivity’ to line voltage, due to getting mild (~60V) zaps from the metal case of an old tube radio when touching anything grounded (later found a ‘leaky’ capacitor across the line cord in said radio). This came in handy while doing some electrical work at a friend’s house. I was assured that the power had been turned off, and was about to loosen the terminal screw on the outlet I was replacing when I felt that familiar tingle in my hand just as screwdriver neared screw. “This outlet is still live!” We turned off the main breaker to the house, and I was able to complete the work without incident. Yes, I now use a multimeter to double-check for voltage on outlets and switches before working on them.

    I’ve gotten a few full-force line voltage shocks in my time, of course (no high voltage/B+ yet, thank goodness ***KNOCK ON WOOD***). Dumbest was while working on an old “hot chassis” tube radio in my basement, standing on the concrete floor while wearing socks. Touched the metal shaft of the volume control, got a mild shock. Figured the (non-polarized) plug was in backwards, so I reversed it, touched the control shaft again, and got a much STRONGER shock that time. Wearing shoes while working on electronics should be right up there as a rule with “don’t solder in shorts.”

      1. Yep, one of my many mutant powers, along with being able to (badly) play goofy music on junky keyboards. Still have yet to hear from Professor X, for some reason……….

  16. This actually reminds me of my dad. Not because my dad would do stupid things, but because I remember him ending up in the hospital for being electrocuted on the job more than once, and he always ended up being just fine. So when he got into an auto accident while on the job, I wasn’t worried at all. Long story short, I should have been worried.

    That was over half my life ago. I know people have an urge to say, “Oh, I’m so sorry” even to a complete stranger, but this was a long time ago. I like remembering my dad. He was a lot smarter and a lot wiser than I think anyone around him gave him credit for being.

    The same thing goes for my mom. I try and tell her, but I don’t think she believes me.

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