4 ms·

Such as a gun is always loaded, my take is electricity is always dangerous. Even professionals can get into accidents, moreover us uneducated plebs.

ChrisMarshallNY 4y ago
I remember watching some electricians rewiring some stuff at my old workplace. We were moving into a new office, and had to have some light switches changed for the new zone. The electrician popped open the switch plates, yanked out the old switches, clipped the wires, stripped the wires, wired up the new switches, and screwed everything back together. It was all live (like 300 volt live), as the lights turned on (queue spark), as he wired the new switches. He was not wearing gloves. It was all barehanded. It was quick, though. Took, like, a minute.
- mikestew 4y ago
  It obviously can be done, and I've heard folks more experienced than I say "all ya gotta do...", and I'll admit that I might have even wired a switch/outlet myself without flipping the breaker. And a pro could probably get away with it for a long time. But it just sounds like something that is one distraction away from a bad day.
  - aaronmdjones 4y ago
    In the UK, as far as the Health & Safety Executive goes, who are the people who will be hauling you up in court if your screwups cause injury or death, they go to great lengths to discourage working live if at all possible. That said, it is sometimes necessary. I've replaced a circuit protective device in a live electrical panel in a commercial setting before. As you point out, avoiding distraction is a very important factor. That means no chit-chat, no-one overlooking and critiquing what you're doing, noise to a minimum, all of the tools you'll need prepared up-front, etc.
- foobarian 4y ago
  Meh, for 120V or 220V worst can happen is you get a little shock or trip the breakers. I don't bother shutting off power to household circuits either. I heard from HV vets that one acquires a habit of keeping one hand in the back pocket when working on substations, industrial installations, and such. :-) Not sure where there would be 300V for light switches/fixtures though. Some bespoke factory setup?
  - ChrisMarshallNY 4y ago
    The lights were using some higher voltage. The Operations Manager mentioned it to me, while the work was being done. Apparently, it's standard. Something like 320 volts (don't remember the exact number). I had not heard of it, beforehand.
    - aaronmdjones 4y ago
      230V AC is the RMS (root mean square) voltage; if you rectify it to DC, it comes out to 325V. Put another way, the /highest/ absolute potential difference between line and neutral in a 230VAC system is 325V.
jimnotgym 4y ago
Every electrician I have met, has had some kind of shock in their career. Mostly it is a small induced current issue, which can easily kill you if it knocks you off a ladder....
- fendy3002 4y ago
  No matter how many times I see someone changing computer parts while the power is still connected, if I'm doing it I always unplug the power then pressing the power button to ensure it's unpowered
  - aaronmdjones 4y ago
    You won't get hurt working on a live computer unless your power supply is dangerously engineered (stick to well known named brands) or wide open (don't open it up unless it's been unplugged and sitting on a shelf for months) for the same reasons pointed out elsewhere in these comments; the voltage simply isn't high enough. It won't even induce a perceptible amount of current (unless you do something stupid like stick your tongue on it), much less a harmful amount. You'd be surprised at all the stuff you can get away with on a live computer. For example, did you know that AHCI (SATA) and PCIe (and thus NVMe) are both hot-pluggable and hot-swappable? ... and that you can hotswap RAM (with a cooperating motherboard and OS) and even CPUs (on multi-socket boards)?
    - fendy3002 4y ago
      Hdd or ssd are hot swappable? thats cool, thanks for sharing. as for ram I have tried it once and it freeze the pc, I forgot if I have another plugged in or not though.
      - SV_BubbleTime 4y ago
        Sata is hotswappable. IDE was not. And I believe m.2 would be if the connector was designed a little different, because that’s all u.2 is. Compact Flash Express is, but again, that’s NVMe and splitting hairs between u.2. Typically on hot swappable devices it’s been common to make the ground pins a little longer than the rest, ensuring that those will make contact first. The issue with hot swappable devices aside from a sharp initial draw is “grounding” the circuit to an IO pin before real ground is made. Most default low potential IO pins won’t enjoy taking the full load of the device while the ground plane is missing connection. Oddly to me, many new PC BIOS ship with SATA hot swapping disabled. IDK why. You can plug the drive in it’ll spin up, but no data transfer will happen until you reboot. Safe, just ineffective. I recently had to learn this the hard way.

ChrisMarshallNY 4y ago

I remember watching some electricians rewiring some stuff at my old workplace. We were moving into a new office, and had to have some light switches changed for the new zone. The electrician popped open the switch plates, yanked out the old switches, clipped the wires, stripped the wires, wired up the new switches, and screwed everything back together. It was all live (like 300 volt live), as the lights turned on (queue spark), as he wired the new switches. He was not wearing gloves. It was all barehanded. It was quick, though. Took, like, a minute.

mikestew 4y ago
It obviously can be done, and I've heard folks more experienced than I say "all ya gotta do...", and I'll admit that I might have even wired a switch/outlet myself without flipping the breaker. And a pro could probably get away with it for a long time. But it just sounds like something that is one distraction away from a bad day.
- aaronmdjones 4y ago
  In the UK, as far as the Health & Safety Executive goes, who are the people who will be hauling you up in court if your screwups cause injury or death, they go to great lengths to discourage working live if at all possible. That said, it is sometimes necessary. I've replaced a circuit protective device in a live electrical panel in a commercial setting before. As you point out, avoiding distraction is a very important factor. That means no chit-chat, no-one overlooking and critiquing what you're doing, noise to a minimum, all of the tools you'll need prepared up-front, etc.
foobarian 4y ago
Meh, for 120V or 220V worst can happen is you get a little shock or trip the breakers. I don't bother shutting off power to household circuits either. I heard from HV vets that one acquires a habit of keeping one hand in the back pocket when working on substations, industrial installations, and such. :-) Not sure where there would be 300V for light switches/fixtures though. Some bespoke factory setup?
- ChrisMarshallNY 4y ago
  The lights were using some higher voltage. The Operations Manager mentioned it to me, while the work was being done. Apparently, it's standard. Something like 320 volts (don't remember the exact number). I had not heard of it, beforehand.
  - aaronmdjones 4y ago
    230V AC is the RMS (root mean square) voltage; if you rectify it to DC, it comes out to 325V. Put another way, the /highest/ absolute potential difference between line and neutral in a 230VAC system is 325V.

jimnotgym 4y ago

Every electrician I have met, has had some kind of shock in their career. Mostly it is a small induced current issue, which can easily kill you if it knocks you off a ladder....

fendy3002 4y ago
No matter how many times I see someone changing computer parts while the power is still connected, if I'm doing it I always unplug the power then pressing the power button to ensure it's unpowered
- aaronmdjones 4y ago
  You won't get hurt working on a live computer unless your power supply is dangerously engineered (stick to well known named brands) or wide open (don't open it up unless it's been unplugged and sitting on a shelf for months) for the same reasons pointed out elsewhere in these comments; the voltage simply isn't high enough. It won't even induce a perceptible amount of current (unless you do something stupid like stick your tongue on it), much less a harmful amount. You'd be surprised at all the stuff you can get away with on a live computer. For example, did you know that AHCI (SATA) and PCIe (and thus NVMe) are both hot-pluggable and hot-swappable? ... and that you can hotswap RAM (with a cooperating motherboard and OS) and even CPUs (on multi-socket boards)?
  - fendy3002 4y ago
    Hdd or ssd are hot swappable? thats cool, thanks for sharing. as for ram I have tried it once and it freeze the pc, I forgot if I have another plugged in or not though.
    - SV_BubbleTime 4y ago
      Sata is hotswappable. IDE was not. And I believe m.2 would be if the connector was designed a little different, because that’s all u.2 is. Compact Flash Express is, but again, that’s NVMe and splitting hairs between u.2. Typically on hot swappable devices it’s been common to make the ground pins a little longer than the rest, ensuring that those will make contact first. The issue with hot swappable devices aside from a sharp initial draw is “grounding” the circuit to an IO pin before real ground is made. Most default low potential IO pins won’t enjoy taking the full load of the device while the ground plane is missing connection. Oddly to me, many new PC BIOS ship with SATA hot swapping disabled. IDK why. You can plug the drive in it’ll spin up, but no data transfer will happen until you reboot. Safe, just ineffective. I recently had to learn this the hard way.