I am not electrically savvy. Quite the opposite.

I have this simple one-light voltage detector,


I had an issue with a specialty appliance not working, when it had worked fine plugged into a different outlet. When I checked the outlet, the detector lit up on all 3 wires. The one it worked on checked out normal-the tester lit on the short/hot orifice and not on the other 2.

I tripped the breaker off and the light still lit up on all 3 wires, but much fainter. I shut off the main breaker and examined the outlet.

I found that the ground was not hooked up to the outlet, so I hooked it up and tried again. I had the same result-tester lights on all 3 wires, and still lights much more dimly when the circuit breaker is turned off. But there's no significant voltage there...it can't power anything up.

What's going on? I found other odd things. The outlet where the appliance worked fine and tested fine, also lit the tester dimly on all 3 wires when that circuit was turned off. How can that be, when it tested fine with the breaker on? These 2 outlets are on a different circuits.

 

A non contact test pen has ONLY one purpose...... to tell you if dangerous voltage is in the area where testing. Your pen has informed you that you have high voltage in the area you are testing. It cannot tell you that you are missing the neutral there which is why all the wiring shows hot.

You need a basic analog meter or a two lead voltage tester for troubleshooting.
A simple $10-15 meter from the home improvement stores is all you need.

 

What do you mean by the appliance worked fine when plugged into one receptacle and did not work fine plugged into another receptacle? Describe the incorrect behavior.

 

Non-contact testers can light up without true voltage due to induced voltage and other anomalies.

I find a neon tester is a great and inexpensive testing method and will answer most of your questions.
https://www.homedepot.com/p/Power-Ge...2060/203744891

 

I have an analog meter. I don't know off the top of my head how to use it to figure this out.

The appliance is a tempered water bath. It will not work without proper ground. It circulated fine but the heating element didn't function on the ungrounded outlet. I didn't try it after grounding the outlet, because of the apparent lingering voltage even with the breaker off. I didn't know if I should trust that circuit.

What is "induced voltage"? Why was the good circuit showing voltage on all 3 wires with the breaker off when it tested fine with it on?

Your pen has informed you that you have high voltage in the area you are testing. It cannot tell you that you are missing the neutral there which is why all the wiring shows hot.

I don't think I understand, except for the fact that it tests for voltage.

 

What I have experienced as a DIY'er lines up with what Zorfdt wrote. If you have a long runs of cable laying next to each other (as you might in a house where multiple cables are run together to a room a fair distance from the panel), you can turn the breaker for one cable off, and still detect voltage via a non-contact sniffer. That voltage is induced by the live cable next to the non-energized cable. As you note, it's not going to power anything, which is what that test light @Zorfdt linked would demonstrate. With my Klein NCV sniffer, I've learned to distinguish between real and phantom voltage - on this sniffer, when I'm on a hot wire, the sniffer will light all the way up and have a steady tone. When it's just phantom voltage, fewer lights, and beeping. And if I have any doubt whatsoever, I'll use my meter to confirm before touching the wires.

As PJmax said, you want to use your meter. Check voltage between hot and neutral (120), between hot and ground (120), and between neutral and ground (0). That will give you (and us) a better idea of what is going on.

 

I set my multimeter for 500 ac v. The scale goes from 1 to 10. When I test hot to neutral I get about 2.4.

Hot to ground it wiggles but no reading.
Neutral to ground it wiggles but no reading.

By wiggle I mean I just barely see it move


On the "good" outlet where the appliance worked, I get 2.4 on hot to neutral AND on hot to ground.

 

What you need to debug, is to determine the ability of the wiring to deliver power. Neon lights, voltage detectors, electronic voltmeters, and wet fingers are not the correct tools for the job. Use a 25 Watt incandescent light bulb. It will easily and cheaply get you in the ballpark for determining if the circuit can deliver power. And, that is what you want to know, NOT how much voltage is "present".

 

I don't follow that at all. The outlet delivers power. Please explain.

I think I need to do one more test with the meter to see if polarity is reversed. I know when I bought the house many years ago the inspector said a couple outlets were reversed in the garage. This room sits above the garage and is on the same breaker.

 

Ability to deliver power is a function of both voltage and current potential. So, voltage is just one half of the equation. You cant measure current with a voltmeter. Basically, its that simple. Use an instrument that simulates a real load on the circuit. A 25Watt load won't test maximum current capability, but its many times better than a typical voltmeter.

 

There are outlet testers that can detect reversed polarity. Another option is if you have a known good outlet nearby (120V between hot and neutral/ground and 0V between neutral and ground) is to check voltage between the two outlets - hot to hot should be 0 if both circuits are on the same hot leg into the panel or 240 if the circuits are on different hot legs into panel, hot to other outlet neutral should be 120, so it will be easy to see if the polarity is reversed.

 

so is this incorrect then?

https://mrelectric.com/blog/how-to-u...test-an-outlet
Check if the wiring is reversed.
Place the red lead into the large slot and the black lead into small slot. If you get a reading, the wiring is reversed. This won’t affect simple equipment like lamps but can cause issues for more sophisticated appliances and electronics.

 

The easiest way to check for reversed wiring is to check from the large slot to ground.
There should be 0volts
Check from the small slot to ground should be 120vAC.

You should be measuring 120vAC. Not 2.4. That may mean you are just looking at the wrong scale.
Also since this is an analog meter..... there should be a lower setting closer to 120v like 250v.

 

Try it yourself on your known good outlet. You will get a reading. Does that mean the wiring on your known good outlet is reversed? No. It means that you are measuring voltage between the hot and neutral.

I think what they meant to say was if you read -120v instead of +120v.

 

He mentioned his scale reads from 1 to 10. So using the 500V AC setting, 2.4 would translate to 120V. But yeah, if a lower setting than 500 that is still greater than 120 is available, he should use that.

 

Well if I set the meter at 250 you can just double the readings. It still works out to 120 v

I don't know for certain whether any of my outlets are "correct". But as stated above when I test one I think is correct, I get

120 hot to neutral
120 hot to ground
nuthin neutral to ground

But on the questionable outlet I get nothing going hot to ground or neutral to ground so I suspect the ground is bad, even though I hooked it up at the outlet.

I also traced the wires and they come from an outlet in the garage that my inspector identified as reverse polarity when I bought the house long ago. However I don't think I can say for certain the outlet in question was wired the same, but it seems likely I'm dealing with a bad ground and likely reversed polarity too.

I'm having an electrician come in next week because I need to have my breaker panel replaced anyway.

 

If you have 120v across the slots then you are correct..... you are missing the ground.

 

Can you elaborate on this? Is there a ground wire in the romex that supplies the outlet? Or did you just connect a piece of wire between outlet and box (assuming it's a metal box)?

Assuming the outlet is fed by romex with a ground, if you look at this circuit's connection at the panel, is the ground wire connected to the panel's ground bar (or neutral bar if this is the main panel)?

 

Prior to starting this thread there was a ground wire at the romex (I had to look that word up) but it wasn't connected to the ground screw on the outlet. I then connected it.

I traced the romex back to the outlet in the garage that I know has reversed polarity. And I've traced from there back to another garage outlet that seems to be wired and grounded properly. I'll call these #1,2 and 3.

#3, the one that is wired properly based on multimeter tests, is wired through the interior wall but mounted on, not set flush in the wall. I presume that it is grounded at the breaker panel because it is grounded somewhere. The romex runs from #3 along the inside of the interior garage wall to the #2 outlet with reversed polarity, and then up the interior wall to #1 outlet in the room above the garage which is where this all started. Judging by the interior romex and reversed polarity Number 1 and 2 were probably added by a previous owner who reversed polarity and didn't ground them. I'm guessing I just need to switch the wires that exits #3 to correct the issues but I might just wait for the pro to come.

(yes I am the original poster...I have 2 computers and can only log into one account on each, and can't get them merged)

 

The lack of ground is a separate issue from reversed polarity. Reversed polarity is when you attach the hot (black) wire to the silver screw and the neutral (white) to the brass screw. That will make the wide plug prong hot instead of neutral, and vice versa for the narrow plug prong.

Lack of ground is your ground connection is not continuous back to the panel. If hot to neutral and hot to ground at outlet #3 are both 120V, then your ground is good between #3 and the panel. And you have romex with ground at outlet #1. So the problem is likely at outlet #3 (where the romex between # 3 and #2 may not be connected to ground at outlet #3) or at outlet #2.

I'd check both #3 and #2. Remember, the ground wire needs a continuous path from each outlet back to the panel, so check that the ground wire in each romex entering an electrical box is connected to the other ground wires entering that box. Now that you know what you're looking for, you'll probably be able to spot the problem.

And while you're in those boxes, you can fix the reverse polarity. The hot (black) between outlet #3 and outlet #2 and between outlet #2 and outlet #1 should land on the brass screws of the outlets. The whites should land on the silver screws.

 

I know for a fact the #1 outlet is wired for correct polarity (black to hot/short, white to not/wide) but those wires must be reversed further down the line where they leave #3.


If hot to neutral and hot to ground at outlet #3 are both 120V, then your ground is good between #3 and the panel

Yes, it is. But the hot/neutral wires leaving #3 for #2 must be reversed right there at #3.

I think we are on the same page, just stating it slightly different. Pretty sure anyway lol...

 

Or they could be reversed at outlet #2.

I'd check #3 first, since we know everything up TO there is good. So start checking FROM there downstream.

 

Gotcha, yup thats the plan

 

A non contact voltage sensor requires an electric field for operation. Electric field exists anywhere there are two conductors with a potential difference between them. So in any dwelling electrically powered and electronic devices operating, there are countless electric fields being generated. Therefore it is easy to see how a non contact voltage sensor can yield false positives. False negatives are rare but do occur since the person holding the non contact voltage sensor provides a path to earth ground to complete the circuit which may not occur if the person is well insulated from earth ground. A 2 lead electrical tester/meter is the most reliable device for testing the presence/amount of voltage.

 

OK, I found the problems. The ground is not connected at #2, and the polarity is reversed there.

What is the proper way for me to hook the ground wires up at #2? The one coming from #3 and the breaker panel goes onto the green screw on the outlet, but that doesn't leave much room for the ground that will run upstairs to #1. Do I ground that one to the outlet box? That is how the ground leaves #3...but I don't want to assume that's the correct way...

 

Good job, mystery solved.

Edit: Updating because I misread this location as having a metal box.
Multiple ways to do it, but you don't want multiple wires under one screw. I'd remove the ground from #3 from the outlet's green screw and replace it with a short piece of ground wire. Then splice together 3 grounds:
1. ground from outlet #3
2. ground leaving for outlet #1
4. short ground wire under green screw at outlet #2

 

Only #1 is plastic outlet box, 2 and 3 are both metal.

But I think splicing in a ground wire at 2 will make my life easier because the ground was cut very short there, giving me limited space to work with. Can I use anything more flexible to splice than that heavy gauge romex ground wire, or does it have to be that?

 

You should use ground wire of the same gauge as the romex used in this circuit. So for example, if the romex on this circuit is 12g, you should use a piece of 12g ground wire. It used to be that romex would have smaller ground wire in it than the conductors, so 14-2 with ground might have 16g ground wire (rationale being that the ground wire isn't normally carrying current, it's just there for fault clearance), but the romex I see now has ground of same gauge as the conductors, so there might have been a NEC code change that prohibits downsizing the ground wire. Someone more knowledgeable about the code might chime in here.

Since outlet #2 uses a metal box, use short pieces of ground wire for the metal box's green screw and for outlet's green screw. Then splice together 4 ground wires - the 2 from the box and outlet, and the grounds from incoming and outgoing romex.

 

Understood, thank you. Going on the assumption that some ground is better than no ground I'm going to use 14 g for the short splice wires for now because its what I have, and I will talk to the electrician when he comes to estimate on a new breaker panel next week. If need be I will change it out. The romex is 12 g and the ground is certainly no smaller than 12.

 

Awesome...well, sort of. That #2 outlet where all the trouble was is up over an immobile workbench and right below a heavy shelf that is also immobile. After mucking around with it for 15 minutes I realized it was going to be almost impossible (for me) to rewire it there so I just took it out completely and spliced the romex so it goes straight to #1. I will figure out a plan for that outlet later, I don't really need it immediately because #3 is only 8 feet away and they make these things called extension cords. But my immediate problem is solved. My upstairs outlet is wired properly and my tempering bath works.