weird electrical fault

[James Baker SD]

I do most of my own wiring in the shop and feel OK with what I do. But I have a weird problem in the outside outlets (original with house) that totally confuses me as to what is happening.

My main panel outside has two GFI circuits lableled "outdoor outlets". I do not exactly know which outlet is on which breaker, but we have outlets around the house, some in the overhang controlled by light sensors and a few scattered in the garden for Christmas lights (that's what the house blueprints say) and have an additional on/off switch indoors.

Outlet closest to panel is controlled by lower breaker, shows 125V between hot and neural (narrow plug, wide plug respectively), 125V between hot and ground, and 0.1 between neutral and ground. So far so good I think. Next outlet in the chain is the same. Third outlet in chain behaves weirdly. If I throw the lower GFI breaker, it reads 0V everywhere. Put the breaker back on and it show nearly 0v between hot and netural, 125V from ground to either hot or neutral. Sure looks like a short, but not bad enough to trip the breaker.
Now the strange part, if I throw the upper GFI breaker to off, then outlet three seems fine, voltages just like outlets 1 and 2. I asssume some other outlets somewhere will be completely off now, but I do not have a map of which outdoor outlets are on which breaker. Seems that the upper breaker (which apparently does not control these 3 outlets) somehow manages to interfere with some and not all the outlets on the adjacent breaker (hence I would assume it uses the other 120V branch).

The house was built in 1975 and the wiring is a nightmare, but I do not see how what I am observing is explained.

[Patrick McCarthy]

So, am I correct in understanding that you have an energized "ground"? (green or, more likely, bare copper in the romex?)

[James Baker SD]

seems more to me that I have an energized neutral as I get 0V from hot to neutral, but 120V from hot to ground and 120V neutral to ground and ONLY in that one outlet, not the others on the breaker.

[Jeff Duncan]

I'm going to suggest tracking all your outlets first. Then when you have all the outlets that are on the 3 lines your tracking, I think maybe you'll find something plugged into it that's wired wrong. This is a fairly easy task, if you haven't done it before I'll outline an easy way for the DIY'r to do it, if you have, then ignore the following…...First step is to get yourself a helper. Now give that person a small portable electronic device. Now shut off all the breakers that you believe are in the area of the ones your testing save for one. You need to have that one circuit live. Have the second person go around and plug the device into every outlet making notes of which ones are live. Also check any light switches in the area. You have now mapped out that circuit! Repeat for additional circuits until you tracked as much as you need to. You can also do this on your own with a radio, it just takes a lot longer

By having a map of all your outlets you can check each one to see if you can find the problem yourself. And even if you don't and end up needing an electrician, it's still very beneficial to know what breaker controls what in the house

good luck,
JeffD

[Jeff Duncan]

Hmmm, I just re-read your last post, have you pulled that one receptacle to see if it's wired correctly? Still strange that shutting off the other circuit would affect it?

JeffD

[Joseph Tarantino]

I'm going to suggest tracking all your outlets first. Then when you have all the outlets that are on the 3 lines your tracking, I think maybe you'll find something plugged into it that's wired wrong. This is a fairly easy task, if you haven't done it before I'll outline an easy way for the DIY'r to do it, if you have, then ignore the following…...First step is to get yourself a helper. Now give that person a small portable electronic device. Now shut off all the breakers that you believe are in the area of the ones your testing save for one. You need to have that one circuit live. Have the second person go around and plug the device into every outlet making notes of which ones are live. Also check any light switches in the area. You have now mapped out that circuit! Repeat for additional circuits until you tracked as much as you need to. You can also do this on your own with a radio, it just takes a lot longer

By having a map of all your outlets you can check each one to see if you can find the problem yourself. And even if you don't and end up needing an electrician, it's still very beneficial to know what breaker controls what in the house

good luck,
JeffD

+1. great suggestion. did it at my house and it makes sorting out issues, de-energizing appliances/light/plugs really easy. doesn't take long. interesting how many homeowners don't do it, or for that matter, have so little knowledge about how the various systems that make a house work actually operate.

[Dick Mahany]

I had a strange problem in my wiring, although I think it was different than what you are describing. My house was built in 1974 (SF Bay Area code). I had a circuit that began acting up and was fed with a GFI. Intermittent at first, then part of the circuit stopped working all together. The root cause turned out to be that at copper crimp used in one box to connect 3 hots had apparently overheated due to poor contact (they used crimps rather than wire nuts). This resulted in the wires overheating and burning the insulation back about 3" on each conductor. Eventually the connection failed and shorted.

I only found it when I mapped the entire breaker panel to each and every outlet and switch in the house. A local electrician told me that he's seen plenty of bad crimps that began failing after 30 yrs or more. I agree with the suggestions on mapping the entire house to track each and every circuit. Once that is done, then a complete examination of every box in the questionable circuit can be done. I was sick when I finally uncovered the fault and saw the burned wires..............could have been a disaster had I not caught it in time.

[Bob Kalb]

Ground Fault Circuit Breakers are designed to operate on two wire circuits only. If the original wiring to your outdoor outlets was done utilizing a 3 wire circuit ( two hots & one neutral) and the GFI breakers were introduced later by someone unknowledgeable, that might be the problem. You might be getting a hotfeed through the neutral on one of the GFI's. You should check he incoming wiring at the panel to determine ifthat is the case.

[James Baker SD]

Ground Fault Circuit Breakers are designed to operate on two wire circuits only. If the original wiring to your outdoor outlets was done utilizing a 3 wire circuit ( two hots & one neutral) and the GFI breakers were introduced later by someone unknowledgeable, that might be the problem. You might be getting a hotfeed through the neutral on one of the GFI's. You should check he incoming wiring at the panel to determine ifthat is the case.

Bob, Can you explain a bit more? The outlets themselves have a receptacle for the ground pin. And most of them measure 120V from hot to ground pin so I assume the grounds are wired. Sounds like I have some work to do, mapping the outlets to breakers and checking wiring under the outlets. But I did not quite understand the part about GFI not designed for 3 wire circuit. The previous owner did a lot of work to this house, most of it incorrect :-(

[Bob Kalb]

Can you tell me the physical locations of the two GFI breakers in your panel. You refer to them as upper & lower. Are they adjacent to each other, or are they separated by other regular circuit breakers. I need to know to determine if they are fed from the same hot leg in the panel. I have come up with a possible answer to your problem if they are on the same power leg. If they are separated - by how many spaces. Starting at top of panel, 1st c/b is A, next below is B, third is A and so forth.

[James Baker SD]

Bob:

Most of the breakers control two circuits each, a two big breakers control only one and occupy two slots (subpanel inside house and oven). Starting at the top, the GFI are in slots C & D (two double breakers controlling 4 circuits above them). The GFIs control only one circuit each. They are the only 120V circuits which have a slot of their own. They are definitely adjacent locations so I assume on different hot legs, but I don't know that for sure since I haven't taken any breakers out to look at the panel architecture behind them. We also had a 12V transformer controller for garden lights plugged into that circuit that was misbehaving further from the panel than the outlets that alerted me to the problem. I unpluged that unit, so maybe it was part of the problem. What confuses me was seeing the neutral seemingly powered at one outlet of the circuit, but not at the other outlets. I measured them under no load (except for the Fluke) so maybe I have a very high resistance path at the particular outlet (spiders love to make their webs in the strangest places) that looks like a short with just a trickle of miliamps flowing, but isn't enough to trip the breaker far away. Right now I am not using the circuit so I have it off until I have time to understand what is happening.

[Bob Kalb]

James

Almost all panels nowadays use alternate buss positions in a vertical line, however there are some rare oldies that did not account for two pole circuits and put alternate buss left right. If you can get mfg & cat # of your panel I might be able to find spec sheets on it.
My possible solution only works if the GFI's are on the same buss.

[Jason Roehl]

Bob:

Most of the breakers control two circuits each, a two big breakers control only one and occupy two slots (subpanel inside house and oven). Starting at the top, the GFI are in slots C & D (two double breakers controlling 4 circuits above them). The GFIs control only one circuit each. They are the only 120V circuits which have a slot of their own. They are definitely adjacent locations so I assume on different hot legs, but I don't know that for sure since I haven't taken any breakers out to look at the panel architecture behind them. We also had a 12V transformer controller for garden lights plugged into that circuit that was misbehaving further from the panel than the outlets that alerted me to the problem. I unpluged that unit, so maybe it was part of the problem. What confuses me was seeing the neutral seemingly powered at one outlet of the circuit, but not at the other outlets. I measured them under no load (except for the Fluke) so maybe I have a very high resistance path at the particular outlet (spiders love to make their webs in the strangest places) that looks like a short with just a trickle of miliamps flowing, but isn't enough to trip the breaker far away. Right now I am not using the circuit so I have it off until I have time to understand what is happening.

Stick your voltmeter on the screws of the two adjacent breakers while they're on. If you measure 230-250V, they're on different legs. If you measure 0V, they're on the same leg.

[Roger Rayburn]

I'm in the camp of mapping out the circuits. If you don't have a helper, pick up a Circuit Detective from Harbor Freight, for example, it will help you identify what is where. Importantly, test every breaker on every outlet. I have read about one outlet being controlled by two breakers, with symptoms similar to yours. Verifying what every breaker controls is as important as verifying everything that a breaker DOESN'T control. Based on your symptoms, it would also be worthwhile to pick up one of those gizmos you plug into outlets that verifies correct wiring.

[James Baker SD]

Stick your voltmeter on the screws of the two adjacent breakers while they're on. If you measure 230-250V, they're on different legs. If you measure 0V, they're on the same leg.

Thanks for the tip. Just did it and I measure 244V. So back to square one in understanding what is happening.