ECN Forum Forums General Topics of the Trade General Discussion Area GFI Tripping

Right now I have 6"-7" of snow on top of everything. This may have to wait until spring.

I would check the GFI outlets and make sure that the supply is on the line side terminals not the load side.

Martin,


Let me say Welcome to the board. Don't be a stranger, we are all friendly around here. As for the GFI line/load side, I did that already. It would not be the first time that I was rushing and I screwed that up. Now a days with the new style, they have the tape over the Load side so that I don't make those mistakes anymore. ( At least I hope I don't)

Looks like this is the hot thread on GFCI's this winter which is always the time I get headaches beyond the ordinary because I start to run trough heaters.

Last year I went through agony with stray voltage problems unrelated to the GFCIs. This phenomenon has been around virtually forever but gets worse as buildout continues around us without substantial upgrades in the local grid. (Not ragging on the power company, I think it is a travesty that they have to provide us power in the sticks at the same price as in more densely populated areas. I'd rather be able to pay for a system that works than be stuck in a relationship with them where what they can charge me is limited so they scrape by doing the minimum. Rural electrification was one of those social programs that, if it was ever useful, has long outlived it. But, I digress . . . you better get used it it, that's my middle name.)

So, although I've occasionally seen animals react to trough heaters because of this stray voltage problem, I've been running them for 30 years here and never had trouble tripping GFCIs. (That was why I was doubly mystified by the stray voltage until I realized it was not straying between line and neutral which is the tripping monitor of a GFCI, but rather between neutral and ground.)

But this year, I started plugging in trough heaters in one location and get a loud buzz and then a trip. I'm not sure I have ever heard a GFCI buzz like that. Different GFCI unit from different manufacturer right next to this one on the opposite leg of the 240 connected to the same neutral all on the line side terminals in the box, so I move over and same result. So I plug something else - a hair dryer we keep for thawing stuff - into both of them and it works fine.

So I carry the trough heater to another installation and it works. However the variable is that I have a short (6 foot) extension cord in the location that keeps tripping. I didn't suspect the cord because it doesn't trip with just the cord plugged in, but I plugged the hair dryer into the cord and that causes a trip. So I go back and move the trough closer and low and behold, the thing works without the cord. Cord looks fine and dry, uncut, not old or cracked, but assume this means there is maybe a moisture related minor neutral to ground fault that isn't noticed until there is actually current flowing. This makes sense as I think about it, although not when yours frustrated truly was out in the field.

Now my wife reports that the sans extension cord installation tripped the breaker overnight, so I'm slogging out there momentarily. Not to undermine her logic skills but she infers this from some lights being off rather than from having taken a flashlight and actually checking the kill-o-watt that I keep installed at the trough heater so that we can monitor hours that its on, know that it is working and know if the power is out visually.

It may be that I left one of the other circuits off with all our testing yesterday and that is why the lights are off. But I'll fill in that blank in a half hour. Meantime, I think I have managed to talk myself through what is happening with the extension cord just in writing this out.

I guess the bottom line is, could we get a less sensitive GFCI that would provide some protection in these circumstances but eliminate this constant nuisance tripping in difficult circumstances. There were trough heaters long before their were GFCI, and maybe I don't spend enough time on farm forums, and/or maybe all the old timers with stories of dead cattle, horses and farmers killed by trough heaters gone critical just haven't made the net, but the cost benefit of this safety protection is starting to exceed its utility at the moment.

My other notion is just to try an airstone for a pond and see if that will keep the water open, but thats maybe a more appropriate discussion for a livestock forum, but figured a bunch of handy guys around here might have dealt with other stuff besides wire in their lives -- not that there's anything wrong with that . . . .


thanks,

brian

Brian,

I used to do electrical work for a farm in my town. We would use heater tape around the water pumps in order to get water to the live stock. When I worked near a dock on the lake, we used to use bubblers in order to keep the water from freezing around the dock. I am going to assume that an airstone is like a water bubbler. Maybe they make electric blankets to wrap around the trough to prevent the frozen water.

As for stray voltage, that would be a real hot topic around here. I have seen lots of problems with stray voltage around pools. Sometimes it was caused by pin hole leaks in the Power Co. (POCO) primary underground feeders.
We would get readings between 5-30 volts around a pool. Enough voltage so that you feel a tingle when you touch metal, the pool deck and had bare feet.

I used to wrestle with various techniques for keeping water lines open, but thank god I bought an exacavator and we have buried lines to half dozen hydrants around the farm. Every once in a rare while you can freeze one of those. I'm not even 100% sure I know how but I assume in the cases I've seen they might have had slight leak at the seat that exceeded the drainage capacity of the surrounding soil so you got a water level established up the hydrant, but maybe I'm overthinking this and it was just CTWT.



Right, an airstone is an aquarium and backyard pond aesthetic outlet for pumped air to do the bubbling. With fish, it oxygenates the water as well as keeping it from freezing if it is an outdoor fish pond. I don't know why there isn't more focus on this kind of device for water troughs. It may put the animals off, but I have found that the introduction of stray voltage (see below for more on that) from the standard trough heater approach is highly offputting to livestock - for obvious reasons, i.e. they tend to be well grounded unless you get them rubber horseshoes (mostly kidding although they make rubber boots that are substitute for standard metal horseshoes for riding. Of course, if the horses wore them in the fields this would pretty much frustrate the effectiveness of elecric fences, or you would have to run one or two ground strands as well as hot strands).

So back on the GFCI issue. I rechecked everything. The GFCI stayed on running the heater as long as I didn't use the suspect extension cord. I took the cord inside and warmed it up for 24 hours laying on the warm floor and hoped I might drive out any moisture that might be cause the tripping. My ohmmeter shows infinite resistance between all legs of the cord. But took it back out, plugged it in and it still trips as soon as I plug anything into it, despite the fact that these same appliances will run in the same GFCI without the cord. It is no great loss to need another 6' cord but I'm mystified as to how to really diagnose what the problem with the cord is if anyone has any ideas. The male end is a molded original. I shortened the cord and put a field installed female on it. Same cord was running these heaters last year without any tripping.



No underground feeders around here lighting up manhole covers and frying dogs, or the like. We're in the sticks. It's all overhead. But I did some fairly extensive research on this last year. The Stray voltage to which I refer is the relatively ubiquitous Neutral to Earth Voltage, i.e., the line loss or voltage drop between of the return to the substation - which is exacerbated in rural climes because of the distance to the substation and a grid that was sized based on electric demands before exurban buildout.

Because the voltage drop is based on current, it varies around here from about 3 volts at low usage times to as high as 7 or 8 volts when a lot of power is being drawn first thing in the morning and early evening.

This potential is introduced to the exterior of any grounded appliance because of the bonding of neutral to ground at the box. And more ground rods or pounding them deeper, etc. is marginally helpful. The one thing I learned about this, that is the most helpful analytical tool, is current takes all paths to ground relative to resistance, as opposed to my earlier misconception that it takes the easiest path.

If I had any doubt what horses were experiencing, I've had some good bouts myself running electric drills and angle grinders with diamond blades in concrete where we are using water as a lubricant and to control dust. We obviously run the tools on GFCIs but once everything is thoroughly misty, I can get some goddamn good, i.e. painful, tingles off the casing of the tools when I am grounded but this doesn't throw the GFCI.

This is because the same amount of current is going out the line and back the neutral as far as the GFCI measures. The current that is zapping me is the small but potent potential (guess that is redundant but for emphasis) between the neutral and the ground which is not measured by the GFCI.

This is a subject I really like to talk about but it is only tangentially related to GFCI. If there is a stray voltage thread here I'll try to stray onto it.

Brian

There are some faults that trip a GFI but don't show up at very low voltage, i.e. with a multimeter. This is where a megger gets really helpful, because its test voltage is much higher.

got it, of course. i usually think about voltage . . . eer amperage I mean when I think about it . . . as breaking down continuity. so you can test and get continuity on a circuity but apply load and the continuity breaks down at a corroded or loose connection somewhere.

and of course with very high voltages I think of faults -- , i.e continuity to ground as becoming more likely, but, of course, 110V is well more than the testing voltage on standard tester.

unfortunately the meggers are well more than I can spend to confirm that there is a fault at 110V on this $5 extension cord, so I guess I will have to accept that trying this on several GFCIs and getting the same result is definitive. unless and until I find a friend who has one, my mind is whirring on that. You see, I know this linesman . . .

thanks for the note

brian

For tingle voltage problems one of the solutions the local power co uses is a Ronk Block isolation device at the transformer. http://www.ronkelectrical.com/blocker.html

Regarding the GFI, I remember when I bought my Black and Decker electric lawnmower 5 years ago it came with a warning note that certain brands /model numbers of GFI's that were know to trip if thelawnmower was used.

They advised to change to a brand not on the list to prevent problems.