What causes this

[threeputt]

I live in a house I bought 49 years ago. It was built in 1958. My electrical panel was upgraded to a 125 amp about 15 years ago. I had the old fuse type. Most wiring is the older two wire. I had some wires updated that could be got to easy as I have a full basement. The clothes drier in basement was upgraded as was where we plugged in the washing machine. The electrician also cut a hole in my floor and added a grounded outlet to where I plug in my computer and monitor .

The question I have is when I was checking in a spare room in the basement tonight I noticed I got a strange reading using my meter as shown in picture. Is this safe ?

I just never checked it until tonight. There are a total of four like this in this room and one more. Two out of the three outlets were showing volts of 53 to 54 volts and the one was 2.7 volts when putting the red lead of meter on hot side of outlet and just touching black lead to the outside of outlet cover which is metal by the way. One actually showed around 80 volts when testing like this. We very rare use this room . For now I turned off the breakers to these two rooms. I used these outlets tonight and they worked . Do they need replacing ? wondering what would cause this ?

I know I have read where people just put a GFIC on first outlet from panel instead of rewiring the entire house. For now I would like to know how I can fix these outlets if there is a fix. How would I know which one is at the end ? I think I read where you can use a tool to find out but I don't remember what it was called.

 

[fitter30]

Checking both sides of the outlet should be 120vac. The outlet box doesn't have ground attach to it.

 

[Zeke]

I think he wants to know the potential. Could be inducted voltage or could be a leak. But with only the box and NM cable....

 

[BreeStephany]

The reason you have less than 120V between the case and hot is because while there is some level of path to a ground, there is a stronger resistance which is causing voltage drop.

At a main disconnect on a modern service, the grounding conductor (earth) and grounded conductor (neutral) are bonded, which is why on a properly grounded installation, you will read 120V between ground and hot. If there are grounding conductors in the box, they may not be properly terminated to the metal parts of the enclosure or may have a loose connection elsewhere down the line.

The boxes you are showing appear to be CMU blocks, so they are technically somewhat of a path to ground, but a poor path to ground and definitely not within the resistance range necessary for an effective grounding path, in addition, they do not have a good bond to the grounded conductor (neutral) at your main disconnect so there is a bit of resistance in the electrical path between these conductors.

Another possibility could that you have somewhat of a short between a neutral conductor and the metal housing on these receptacles, which would also allow for a return path to produce voltage when you test between the metal surface of the box and hot, and because it is a short, it would produce some level of resistance creating a poor path, but nonetheless, a path to ground for you to produce a voltage between the hot and the metal enclosure.

To make the installation as safe as possible without running new conductors, the use of a GFCI receptacle on the circuit at the first receptacle in the circuit would be ideal. This can also be accomplished through a GFCI breaker. This will ensure that ground faults existing on the load side of the GFCI device cannot occur, as the device will detect a difference on current between the line and neutral conductors and trip the circuit.

To make the installation as safe as possible, I would highly recommend running new conductors with a proper grounding conductor.

Just my two cents.

 

[Stuff]

It appears to be in the basement so should have GFCI for safety. Using a GFCI breaker is more expensive than a receptacle but then you don't have to figure out which is the first receptacle on the run.

 

[alfredeneuman]

It's a High Impedance meter. High Impedance meters read "phantom" voltages where is none.

 

[KenC]

Earlier answers are correct. No 'real' ground in the old wiring, just whatever the Concrete Blocks will carry. And meter reading ghost voltages. Your comment about GFCIs is right on. Only problem can be finding the first recpt on a circuit. Sometimes wire routing doesn't go where you would expect. GFCI breakers are more expensive, but can be easier.

GFCI solution is Highly recommended.

 

[threeputt]

Thanks for all the replies. Outlets are now GFCI protected. So far no trips. Learned something about meters and phantom voltage. I like the green light on the new GFCI.