5 ms·

Do US plugs actually spark? I thought that was something you just saw in movies.

by qntm 16y ago

fluidcruft 16y ago
I see sparks regularly. Usually when the vacuum cable gets yanked from the wall while vacuuming (tripping, too short).
jacquesm 16y ago
Yes, they do. Sometimes they'll even spark when they're just sitting there with something plugged in. There is a mechanical/electrical machining process called spark erosion aka electrical discharge machining. Every time you have a spark a tiny bit of the metal of both contacts evaporates. Of course that's when you want it to happen, in sockets with plugged in loads you really don't want it to happen. Over time this process accelerates and it has been the cause of many house fires in the US. The fact that such sockets are placed in walls made of mostly wood placed right next to an upright stud does not help either. Sometimes they're so bad you can actually smell the ozone.
- ars 16y ago
  Everything sparks - it's not unique to american plugs. In the UK the contact is just deeper so you can't see it. If anything UK plugs spark more because the voltage is higher. And sparks are not the cause of many house fires, you just made that up. The sparks are harmless, and I've never seen a plug with erosion on it. Just because you can do it doesn't mean it actually happens.
  - jacquesm 16y ago
    No, I did not make that up, and I did not mean 'sparks on insertion' I meant 'sparks while inserted', though 'sparks on insertion' is not good either for your socket. American plugs spark (much) more frequently and strongly than their equivalent UK/EU plugs because the spring pressure from the side contacts is insufficient to maintain good contact over the lifetime of an installation, especially if the plugs are also worn. The fact that typically the current is twice as high doesn't help either (though if you get zapped it's less of a problem than in 230V installations, the US uses a balanced 110 system for most residential circuits where only a few receptacles which are of a different design have both sides of the step-down transformer outside of the house running to them). The UK/EU plugs are of a much more solid construction than the American ones, as are the wallsockets they go in to. I've seen US sockets that made an audible buzz while operating and get extremely hot (hot enough to melt the plastic). Not good. The usual way in which it gets to this state is that a socket has been overloaded a couple of times, or heavy load is plugged in or removed while switched on, the contacts have corroded or have some soot build up on them and then the resistance increases enough to start a runaway process that ends with the socket failing altogether or with the socket getting so hot that the plastic outside cover will start to melt. At that point all bets are off, especially in houses that are mostly constructed from wooden sticks instead of brick or concrete. Another cause of trouble like this is that there was a short period when due to the supply issues with copper electrical wire made of aluminum was tried in residential installations in the US. These required special fixtures so the wire would not come lose as the aluminum compressed over time thus shrinking away from the contact and causing an airgap and thus sparking. This kind of wiring is no longer 'code' and if you have such wiring it wouldn't harm to periodically tighten up on the screws to ensure good contact. Aluminum oxide build-up compounds this problem. People always blame 'short circuits' for electrical fires, but most of the time this is nonsense, since the breaker will almost always instantly trip in a short circuit situation. That's what they're designed to do. Half shorts (shorts that are of a resistance low enough to cause significant heat build-up and high enough not to cause the breaker to trip) and faulty contacts (intermittent contacts, sparks and thus heat) are a much more frequent cause of fire. Another big cause of fire is counterfeit junk hitting the market and do-it-yourself types that don't know the difference using this to wire up that extra socket for a space-heater in the attic.
    - ars 16y ago
      You must deal mainly with very old poorly maintained houses (rentals?), because all those problems do not exist in normal outlets. You have soot on your contacts???? Corrosion? Did it rain inside your house? NEVER tighten aluminium contacts! You will cause exactly those problems that you describe. If there is a problem with it you need to remove it, apply the anti-oxidant paste and reinstall. But aluminium to the contacts is very rare in america these days, where it does exists it's usually been pigtailed with copper.
      - jacquesm 16y ago
        > You must deal mainly with very old poorly maintained houses (rentals?), because all those problems do not exist in normal outlets. Rural areas, farmhouses, but one building I lived in in Toronto had a problem (a bad one) with one of the sockets and it was a fairly recent upgrade from what I remember. > You have soot on your contacts???? Corrosion? Did it rain inside your house? No, simply an installation from the 70's still operating in 2005. There are millions like that. And I don't live there anymore, I'm back Europe now. > NEVER tighten aluminium contacts! Not over-tighten, tighten. You should do it to the proper torque (there are special tools for that). > But aluminium to the contacts is very rare in america these days, where it does exists it's usually been pigtailed with copper. Yes, that's the slightly newer method, also since outlawed (and used as a way to fix problems). The biggest problem I think with the alu wiring was not even that it could not work, but that people would use it with the wrong connectors, the al specific sockets were pretty pricey. The only place where I know that aluminum is still used in residential wiring is on the entrance wire from the pole to the transformer, usually that's a very tricky connector that uses wedges to make the contact. If I found myself in a house with aluminum wiring I'd probably rewire the whole thing just for safety. Costly (especially with the US system which staples cables to studs) but worth the peace of mind.
        ars 16y ago
        No, I mean don't tighten it at all! Not unless you open it and add anti-oxidant. If you tighten it you break the air seal, and allow it to oxidize, and aluminium oxide does not conduct. The correct installation uses anti-oxidant to seal it, then you tighten it enough to crack the aluminum oxide, and the anti-oxidant protects it. If you tighten it without fresh anti-oxidant you are creating a hazard. And pig tails are not outlawed - quite the opposite, they are the recommended way to handle aluminium wiring.
makmanalp 16y ago
Yup, happens all the time.
jlees 16y ago
Unfortunately yes. As a Brit living in America, every time I have to deal with a plug socket I feel ever so slightly like I'm about to electrocute myself. Sure, the big bulky plugs are a pain to carry around, but at least I felt safe using them.

Do US plugs actually spark? I thought that was something you just saw in movies.

by qntm 16y ago

Do US plugs actually spark? I thought that was something you just saw in movies.

fluidcruft 16y ago

I see sparks regularly. Usually when the vacuum cable gets yanked from the wall while vacuuming (tripping, too short).

jacquesm 16y ago

Yes, they do. Sometimes they'll even spark when they're just sitting there with something plugged in. There is a mechanical/electrical machining process called spark erosion aka electrical discharge machining. Every time you have a spark a tiny bit of the metal of both contacts evaporates. Of course that's when you want it to happen, in sockets with plugged in loads you really don't want it to happen. Over time this process accelerates and it has been the cause of many house fires in the US. The fact that such sockets are placed in walls made of mostly wood placed right next to an upright stud does not help either. Sometimes they're so bad you can actually smell the ozone.

ars 16y ago
Everything sparks - it's not unique to american plugs. In the UK the contact is just deeper so you can't see it. If anything UK plugs spark more because the voltage is higher. And sparks are not the cause of many house fires, you just made that up. The sparks are harmless, and I've never seen a plug with erosion on it. Just because you can do it doesn't mean it actually happens.
- jacquesm 16y ago
  No, I did not make that up, and I did not mean 'sparks on insertion' I meant 'sparks while inserted', though 'sparks on insertion' is not good either for your socket. American plugs spark (much) more frequently and strongly than their equivalent UK/EU plugs because the spring pressure from the side contacts is insufficient to maintain good contact over the lifetime of an installation, especially if the plugs are also worn. The fact that typically the current is twice as high doesn't help either (though if you get zapped it's less of a problem than in 230V installations, the US uses a balanced 110 system for most residential circuits where only a few receptacles which are of a different design have both sides of the step-down transformer outside of the house running to them). The UK/EU plugs are of a much more solid construction than the American ones, as are the wallsockets they go in to. I've seen US sockets that made an audible buzz while operating and get extremely hot (hot enough to melt the plastic). Not good. The usual way in which it gets to this state is that a socket has been overloaded a couple of times, or heavy load is plugged in or removed while switched on, the contacts have corroded or have some soot build up on them and then the resistance increases enough to start a runaway process that ends with the socket failing altogether or with the socket getting so hot that the plastic outside cover will start to melt. At that point all bets are off, especially in houses that are mostly constructed from wooden sticks instead of brick or concrete. Another cause of trouble like this is that there was a short period when due to the supply issues with copper electrical wire made of aluminum was tried in residential installations in the US. These required special fixtures so the wire would not come lose as the aluminum compressed over time thus shrinking away from the contact and causing an airgap and thus sparking. This kind of wiring is no longer 'code' and if you have such wiring it wouldn't harm to periodically tighten up on the screws to ensure good contact. Aluminum oxide build-up compounds this problem. People always blame 'short circuits' for electrical fires, but most of the time this is nonsense, since the breaker will almost always instantly trip in a short circuit situation. That's what they're designed to do. Half shorts (shorts that are of a resistance low enough to cause significant heat build-up and high enough not to cause the breaker to trip) and faulty contacts (intermittent contacts, sparks and thus heat) are a much more frequent cause of fire. Another big cause of fire is counterfeit junk hitting the market and do-it-yourself types that don't know the difference using this to wire up that extra socket for a space-heater in the attic.
  - ars 16y ago
    You must deal mainly with very old poorly maintained houses (rentals?), because all those problems do not exist in normal outlets. You have soot on your contacts???? Corrosion? Did it rain inside your house? NEVER tighten aluminium contacts! You will cause exactly those problems that you describe. If there is a problem with it you need to remove it, apply the anti-oxidant paste and reinstall. But aluminium to the contacts is very rare in america these days, where it does exists it's usually been pigtailed with copper.
    - jacquesm 16y ago
      > You must deal mainly with very old poorly maintained houses (rentals?), because all those problems do not exist in normal outlets. Rural areas, farmhouses, but one building I lived in in Toronto had a problem (a bad one) with one of the sockets and it was a fairly recent upgrade from what I remember. > You have soot on your contacts???? Corrosion? Did it rain inside your house? No, simply an installation from the 70's still operating in 2005. There are millions like that. And I don't live there anymore, I'm back Europe now. > NEVER tighten aluminium contacts! Not over-tighten, tighten. You should do it to the proper torque (there are special tools for that). > But aluminium to the contacts is very rare in america these days, where it does exists it's usually been pigtailed with copper. Yes, that's the slightly newer method, also since outlawed (and used as a way to fix problems). The biggest problem I think with the alu wiring was not even that it could not work, but that people would use it with the wrong connectors, the al specific sockets were pretty pricey. The only place where I know that aluminum is still used in residential wiring is on the entrance wire from the pole to the transformer, usually that's a very tricky connector that uses wedges to make the contact. If I found myself in a house with aluminum wiring I'd probably rewire the whole thing just for safety. Costly (especially with the US system which staples cables to studs) but worth the peace of mind.
      - ars 16y ago
        No, I mean don't tighten it at all! Not unless you open it and add anti-oxidant. If you tighten it you break the air seal, and allow it to oxidize, and aluminium oxide does not conduct. The correct installation uses anti-oxidant to seal it, then you tighten it enough to crack the aluminum oxide, and the anti-oxidant protects it. If you tighten it without fresh anti-oxidant you are creating a hazard. And pig tails are not outlawed - quite the opposite, they are the recommended way to handle aluminium wiring.

makmanalp 16y ago

Yup, happens all the time.

jlees 16y ago

Unfortunately yes. As a Brit living in America, every time I have to deal with a plug socket I feel ever so slightly like I'm about to electrocute myself. Sure, the big bulky plugs are a pain to carry around, but at least I felt safe using them.