Question about voltage in U.S. house built in 1890

[niemand]

Most of the electrical outlets in this house is the 2-slot type with one slot wider than the other. I plugged in a grounded extension to a 3-slot outlet (valid grounded). I have a digital voltmeter set to AC volts, the black probe inserted into the ground of the extension, and the red probe inserted into the narrow slot of the 2-prong outlet. The reading I got was 62 V. The reading I got when I put the red lead into the wider slot of the 2-prong outlet was 59 V. Why not 120 V (the U.S. standard household voltage)?

When I measured only the 2-slot outlet (i.e., inserted one probe into the narrow slot and the other probe into the wider slot of the same 2-slot outlet), the meter read 120 V.

[bdunham7]

What does your service panel or fusebox look like?  Unless this has wiring from the 1920's that hasn't been updated, something isn't right.  The neutral (the large slot side) should be bonded to ground at the service panel.  I'd suspect you don't actually have real grounds and perhaps your system isn't actually ground referenced (this would be extremely unusual in the US).

[BlownUpCapacitor]

The electrical wiring in that house is not ground referenced, meaning neutral is not connected to ground; that's a big no no.

[Whales]

The electrical wiring in that house is not ground referenced, meaning neutral is not connected to ground; that's a big no no.

It sounds more like the ground wiring is not ground referenced.  The neutral wiring may or may not be grounded.

If a house full of appliances has its ground wiring disconnected and floating: measuring the ground wiring to be halfway between active & neutral sounds like a plausible symptom.

I recommend you get a sparky to check this out niemand. They'll have the tools and skills to diagnose the problem quickly. 

Out of curiosity I'd love to see pictures of your fuse boards, BUT, given what you have described any metal cased appliances in your house may be unsafe to touch.  Even the metal cased fuse boxes might be UNSAFE to touch or open.  Could also just be a high-impedance phantom voltage, but don't take the risk.

[BrokenYugo]

Pretty typical in a place like this you'll find people have added 3 prong sockets to the 2 wire circuits, leaving the ground floating (this is acceptable if a GFCI is used and marked appropriately) or worse yet connected to neutral to give a "bootleg ground" those are illegal for good reason and should be removed if found.

Assume nothing with power in old houses, you can often find a different era of hacked up old wiring in every room. Sockets with live/neutral reversed are also dirt common.

[niemand]

What does your service panel or fusebox look like?  Unless this has wiring from the 1920's that hasn't been updated, something isn't right.  The neutral (the large slot side) should be bonded to ground at the service panel.  I'd suspect you don't actually have real grounds and perhaps your system isn't actually ground referenced (this would be extremely unusual in the US).

The service panel is on the side of the house. Just circuit breakers; no fuses. What should I be looking for?

[niemand]

The 3-slot outlets were tested to have valid ground with this.

[niemand]

[...]
I recommend you get a sparky to check this out niemand. They'll have the tools and skills to diagnose the problem quickly. 
[...]

What's a "sparky"?

[wasedadoc]

[...]
I recommend you get a sparky to check this out niemand. They'll have the tools and skills to diagnose the problem quickly. 
[...]

What's a "sparky"?

A colloquial term for an electrician.

[bdunham7]

The service panel is on the side of the house. Just circuit breakers; no fuses. What should I be looking for?

Start by taking that cover off so you can see the wiring inside and post a good photo of that.  Carefully, of course.  Is there a grounding rod nearby?

The 3-slot outlets were tested to have valid ground with this.

With the voltage readings you are seeing, I would expect all 3 lights to be on at least dimly.  Try measuring from the ground of your socket to a plumbing pipe.

[Whales]

(Attachment Link)
The 3-slot outlets were tested to have valid ground with this.

Do not trust those testers, they make assumptions.  If your testing with a multimeter revealed the ground wiring voltages to be strange then maintain suspicion.

[coromonadalix]

same here,  see a master electician NOW   and get everything sorted out    and put an earth rod in the ground .... if there is not

As insurance(s) side  if it was done by an master electrician, and anything bad happens  you'll be covered, if "they learn" you did some job yourself,  you may end with more problems

dont play god please

[BrokenYugo]

A 3 light tester only works correctly on single faults, making them mostly useless, it's just 3 neons and 3 resistors. Dangerous compound issues can read all good, e.g. hot-ground reversal+bootleg ground will give a full pass.

[niemand]

[...]
Start by taking that cover off so you can see the wiring inside and post a good photo of that.  Carefully, of course.  Is there a grounding rod nearby?
[...]

Perhaps this thick painted wire is the grounding rod:

[bdunham7]

Can you take a zoomed-out photo so we can see the entire installation including the other boxes nearby?  I'm not seeing any ground wires in the box.  The bus bar where the white wires are going to should be the neutral/ground bond.  There's one big black wire going to that bar at the top, where does that come from?

Also, this looks like a sub-panel, not a main service panel.  There's no main breaker.  Is there any other sort of accessible panel anywhere?  Where does the service entrance come from--overhead or underground?

[Stray Electron]

   Is that your main breaker panel or is it a sub-panel??


  In the 3rd and 4th pictures in post #13 you can see the Ground bus bar on the LH side of the box and there's nothing connected to it. It's mounted directly on the metal box so the box should be directly connected to Ground. That is IF the Ground wire was connected to the Ground Bus Bar, but from what I can tell nothing is connected to that bus bar.  The Neutral bus bar is on the RH of the box and is visible in photos 3, 4 and 5. Note that it is insulated from the metal box.

  If your house was wired to modern standards ALL of the ground contacts in ALL of your outlets should run directly back to that Ground Bus Bar and if it is your Main Panel then the bare ground wire that connects to your Ground Rod should also connect to it.

   The wire that you point out in photos 1 and 2 appears to be a ground wire but it's attached to a different box than that shown in photos 3, 4 and 5.  It's been painted over but it should a bare, solid copper wire and it should be clamped to a ground rod but some people merely shove them into the ground. You need to dig into the soil and see what's there.

  A agree with a previous poster, even though you have a three contact outlet I don't think that the ground contact in it is actually connected and the voltage that you're seeing from L1 to Ground is just from leakage. 

[Stray Electron]

Can you take a zoomed-out photo so we can see the entire installation including the other boxes nearby?  I'm not seeing any ground wires in the box.  The bus bar where the white wires are going to should be the neutral/ground bond.  There's one big black wire going to that bar at the top, where does that come from?

Also, this looks like a sub-panel, not a main service panel.  There's no main breaker.  Is there any other sort of accessible panel anywhere?  Where does the service entrance come from--overhead or underground?

  I agree, it looks like a sub panel.  You can follow the feed wires out through the hole in the lower left side of the box and in photo #1 you can see that that conduit feeds back to box #2.  The OP's "ground wire"? in photos 1 and 2 also goes into box #2.  But based just of these photos it's impossible tell if it's connected to anything.

   BTW not all houses in the US have a 'Main Breaker". Mine doesn't.  The incoming power lines directly feed the L1 and L2 bus bars.

    OP I will point out that unless a previous owner did some weird and illegal trickery somewhere in the wiring after it leaves the box, then none of the circuits coming from box #3 are grounded.  You can follow every wire in that box and and they all connect to the 3 incoming power lines or to the Neutral Bus Bar or to a circuit breaker so there are NO Ground wires anywhere on those circuits.

[niemand]

[...]
With the voltage readings you are seeing, I would expect all 3 lights to be on at least dimly.  Try measuring from the ground of your socket to a plumbing pipe.

The ground I have been using for this comes from this 4-outlet type receptacle that is being used by computers:

This is located right on the other side of the wall where the service panel is. All the original readings came from the bottom right outlet of this receptacle. The black plug on the upper left is an APC UPS system (Smart-UPS 1000) for computers and router. I don't have an extension long enough to reach plumbing pipe from here. (Behind the wall in the back is the kitchen where a 2-outlet receptacle is being used by the refrigerator and stove. I've been presuming that this is wired to the same ground as the 4-outlet one being used by the computers.)

Per your advice to get a reading from a plumbing pipe, I had to use the 2-receptacle GFCI outlet located in the bathroom, which is on the opposite end of the dwelling unit:

I used the ground slot from this with the black probe and got the correct 122 V when I inserted the red probe into the hot (narrow) slot on the ancient 2-slot outlet out in the hallway (the hot slot of both 2-slot outlets gave me 122 V; the neutral slots gave me 0 V). Touching the plumbing pipe with the red probe gave me 0.009 V; lifting away the probe gave me 5 V (perhaps due to capacitative coupling?). So it appears that this receptacle is properly grounded, whereas the 4-outlet receptacle being used by the computers is questionable.

[niemand]

Can you take a zoomed-out photo so we can see the entire installation including the other boxes nearby?  I'm not seeing any ground wires in the box.  The bus bar where the white wires are going to should be the neutral/ground bond.  There's one big black wire going to that bar at the top, where does that come from?

Also, this looks like a sub-panel, not a main service panel.  There's no main breaker.  Is there any other sort of accessible panel anywhere?  Where does the service entrance come from--overhead or underground?

I don't know how to tell a main from a sub panel.
Service entrance? Perhaps behind the wall? The 4-outlet receptacle I mentioned above is behind this wall about 5 ft to the right.

Other boxes nearby:



Main service panel perhaps (I can't open the long one with the wing nuts at the bottom of it):

[bdunham7]

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.

[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]

(Attachment Link)
The 3-slot outlets were tested to have valid ground with this.

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]

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.

   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]

   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. 

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]

Is this a townhome and the other meter is for the other owner/tenant? [...]

Yes.