Hot/Ground Reversed

[larry4406]

1987 House that we moved into last year.

Came home last night and several light circuits are dead and the garage door opener outlet also was dead. Not sure exactly how this circuit is wired/branched.

Plugged a bug eye tester into the garage door opener outlet and it says hot/ground reversed (outlet is not a feed thru, junction somewhere else). Breaker did not trip. Black to ground is 120V, white to ground is 120V, black to white is 0V. Tripped the breaker and reset it but no change. Non-contact probe indicates power to several of the dead lights.

For about the past week+ have had on occasional flicker on the lights that are now dead. I had figured that was just a ballast going bad (kitchen fluorescent light flicker was most noticeable). About 3 weeks ago we had a bad lightening storm which fried my computer motherboard even though was plugged into a surge protector (we saw a white flash in the room and heard computer pop pop). Computer outlet not on the now affected circuit but that room's lights are.

From what I have read on the net, what I really have is an open neutral somewhere. None of the outlets in the house are back stabbed as I replaced all of them.

Am I now on a easter egg hunt tracing the entire circuit and checking every neutral junction? I have CB Circuit alert (non contact probe), bug eye tester, and a VOM. Nothing else to help chase the circuit (ie toner).

Currently, breaker is off and will attempt to address it this weekend and am looking for ideas.

 

[NLBUILDER]

You likely have an open/hi-impedance neutral connection at your service entrance or the utility end of your service. Call the power company and have them check first before you go any further. A open neutral at the service entrance can cause a lot of damage to 120Volt appliances.

 

[BillK]

About 3 weeks ago we had a bad lightening storm which fried my computer motherboard even though was plugged into a surge protector (we saw a white flash in the room and heard computer pop pop).

Larry,
That was exactly what I was thinking when I looked at your location. Those were some nasty storms and I bet something took a hit. I would probably start with the circuits in the room your computer is in.

 

[zmaxmotorsports]

Start at panel and work your way out.

 

[wyliesdiesels]

So this is only happening on one circuit?

Have u checked everything at your main service panel?

Did the PoCo do any line work in your area recently?

 

[Mustang51js]

Gonna go with a loose neutral

 

[homebuilt burner]

I have never heard of anything like this. How would you start to trouble shoot a loose neutral or poor connection on neutral???

 

[larry4406]

Only one circuit affected. My plan is to kill all circuits except the affected one. Then use non contact probe to chase circuit from panel to first device/junction via attic and check neutrals. Then proceed to the next and so on.

The 120v between white and ground blows me away and no tripped breaker. I'm thinking something arced and the white and black fused together.

No POCO work to my knowledge. Will check the panel. I do know the subject breaker is functioning proper with 120V from the lug to the ground/common bar.

 

[wyliesdiesels]

Only one circuit affected. My plan is to kill all circuits except the affected one. Then use non contact probe to chase circuit from panel to first device/junction via attic and check neutrals. Then proceed to the next and so on.

The 120v between white and ground blows me away and no tripped breaker. I'm thinking something arced and the white and black fused together.

No POCO work to my knowledge. Will check the panel. I do know the subject breaker is functioning proper with 120V from the lug to the ground/common bar.

Sounds like u may have lost the neutral connection to the panel and the neutral became energized. If thats the case, there would be no reason for the breaker to trip because theres no ground fault.

 

[Slowgsr]

I agree with the above.
Ever open a neutral and grab the side connected to the load? That's how you get power from neutral to ground and nothing from hot to neutral.

Your white and black did not arc and fuse together. Being a professional and seeing people who are quite handy and good at diy projects, new electrical is one thing if you've got direction but most troubleshooting and retrofit work should be left to a professional. As you can cause injury to yourself during troubleshooting if you don't know what your doing.

Go in your panel and check your neutral connections, if this is good you need to start opening all devices that are on the troubled circuit until you find the issue.

 

[larry4406]

Sounds like u may have lost the neutral connection to the panel and the neutral became energized. If thats the case, then the breaker wouldn't trip because there's no ground fault since there's no connection to the neutral bar...

And this is the answer...

Screw loose. Killed main, checked all screws, and relanded the neutral and back in business.

Thanks all.

 

[Slowgsr]

Feels good when you find the problem, and when you do find it it's usually obvious ��

 

[wyliesdiesels]

I agree with the above.
Ever open a neutral and grab the side connected to the load? That's how you get power from neutral to ground and nothing from hot to neutral.

Your white and black did not arc and fuse together. Being a professional and seeing people who are quite handy and good at diy projects, new electrical is one thing if you've got direction but most troubleshooting and retrofit work should be left to a professional. As you can cause injury to yourself during troubleshooting if you don't know what your doing.

Go in your panel and check your neutral connections, if this is good you need to start opening all devices that are on the troubled circuit until you find the issue.

Exactly. The 120v is fed through the device and onto the neutral wire..seen this happen many times...

And this is the answer...

Screw loose. Killed main, checked all screws, and relanded the neutral and back in business.

Thanks all.

Yup! A loose screw can cause a lot of havoc!

 

[larry4406]

Exactly. The 120v is fed through the device and onto the neutral wire..seen this happen many times...

In my case, this must have been thru the light bulb filaments on the lighting circuits that were still in the "on" position. No devices were plugged in to the two outlets that were on the affected circuit when I detected the 120V from white to ground..

 

[crucible]

I work in data centers, and we get infra-red (FLIR) testing done once a year on all our electric distribution connections looking for hot spots before anything becomes an issue. Any found connection that is relatively hot is rare, but it almost always is because of a loose connection/screw just like this, but on a larger scale.

Now if only FLIR units start becoming more affordable that us average Joe's can afford them.....but that still wouldn't change the fix-someone with tools tightening them down

 

[1Garageman]

WOW, that is scary! Glad you found the problem!!!

 

[Movover]

I work in data centers, and we get infra-red (FLIR) testing done once a year on all our electric distribution connections looking for hot spots before anything becomes an issue. Any found connection that is relatively hot is rare, but it almost always is because of a loose connection/screw just like this, but on a larger scale.

Now if only FLIR units start becoming more affordable that us average Joe's can afford them.....but that still wouldn't change the fix-someone with tools tightening them down

Its already out..

http://www.flir.com/flirone/display/?id=62909

I am waiting for the android version hopefully soon!