| Electronics > Repair |
| Question about voltage in U.S. house built in 1890 |
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| BlownUpCapacitor:
Use a DMM to measure the potential of those boxes to ground. Should be near zero or under 10v. I wouldn't go touching those boxes if they are at an elevated voltage. |
| tooki:
--- Quote from: niemand on May 14, 2024, 01:39:11 pm --- (Attachment Link) The 3-slot outlets were tested to have valid ground with this. --- End quote --- Note that these do NOT actually prove the outlet is wired correctly with a proper ground: one thing slimeballs do is to fake the ground by bridging the ground and neutral terminals on the receptacle itself, with no actual ground. This is called a bootleg ground, and BrokenYugo mentioned them above. A tester will show it as correct, but it’s actually dangerous, and even worse if multiple outlets have been wired this way, but some with the line and neutral reversed. In that case, you can end up with a device housing (or cable shield) at 120V. Connect two “grounded” devices that on different outlets and you’ve got a dead short (for example, a TV and a DVD player). If you ever find an outlet with a bootleg ground, which is an attempt to deceive inspection, you must assume the entire electrical installation is unsafe until it’s been inspected by an electrician, whom you should give a heads-up about the bootleg ground so they know they’re dealing with a questionable installation. I randomly had a video about this very thing suggested to me the other day: |
| Stray Electron:
--- Quote from: bdunham7 on May 14, 2024, 06:06:57 pm ---Is this a townhome and the other meter is for the other owner/tenant? Those are two "main breakers" under the meters so that all makes sense, but there are still no ground wires anywhere so I've no idea how your outlets are getting grounded. That big, painted wire going into the ground probably goes to a ground rod of sorts and perhaps the wire going back into the house is cobbled into some sort of ground wire network going to the outlets, but that would be pretty hacked work. The only other possibility I can think of is that your house has conduit throughout and the ground bonding goes through that. I don't see any NM sheathed wires, so perhaps that is what they did, in which case you can pull the covers off your outlets and you should find a metal box that is grounded. Your bad ground at your 4-plex outlet could be due to a break in the conduit or a bad ground bond between the box and outlet ground terminal. --- End quote --- I agree, the two disconnects makes this look like it's duplex with both homes being fed by a two meters in a common box. FYI I'm pretty certain that the NEC doesn't allow houses to be grounded simply via the metal conduit. The joints are too unreliable. If the outlets are going to be grounded then they must be grounded via a wire. OTOH not every jurisdiction in the US requires compliance to all of the NEC, particularly in older homes so grounding may not be a requirement for the OP's house. OTOOH, under certain conditions the local authorities may require that the home be brought up to the current NEC requirements. So it depends. OP, I would follow Tooki's advice and pull out one of the outlets (after turning off the breaker and double checking that there is no power at the outlet) and physically looking at the wires connected to the outlet.. There should be three wires including a bare or green colored ground wire. But I think that you will find that the only wires are the black "Hot" leg and the White Neutral. |
| bdunham7:
--- Quote from: Stray Electron on May 14, 2024, 06:46:02 pm --- FYI I'm pretty certain that the NEC doesn't allow houses to be grounded simply via the metal conduit. The joints are too unreliable. If the outlets are going to be grounded then they must be grounded via a wire. --- End quote --- Conduit-as-ground used to be fairly common and I'm not sure the NEC actually prohibits it even today. However, typical modern practice would be to include a ground wire. Properly installed conduit does include fairly robust ground bonding devices and the failures I've seen have been either a bad job or a corrosive environment. In dairy barns, for example, regular NM was allowed even though it was exposed (typically not acceptable) because it was safer than conduit that would rust and separate. That installation doesn't look to be modern, it could easily be 60+ years old and it would have been a retrofit even then. |
| niemand:
--- Quote from: bdunham7 on May 14, 2024, 06:06:57 pm ---Is this a townhome and the other meter is for the other owner/tenant? [...] --- End quote --- Yes. |
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