Understanding Stray Voltage

[BertZegers]

See "step potential".

The way to prevent stray voltage in barns is to make sure there are no potential differences. You have to connect every conductor (water line, vacuum line, steel construction) that has the risk to carry a potential to a central point. This central point is also connected to the ground rod. Every electrical equipment that is used is also connected to ground through the ground wire.
It is important to connect the rebar/mesh in the concrete floor/foundation and steel constructions with the central point. A stray voltage is no longer a problem because it is impossible to have a potential difference. ( the voltage on the cows front and rear legs will always be the same ) even a lightning strike causes no potential difference. This is code in Europe. In addition: the whole barn is protected by Ground Fault Interrupters with a 0.03 Amp sensitivity. The 0.03 Amp GFI will not trip "all the time" because only plastic enclosures are used. The ground rod resistance in the "ground" circuit is not allowed to be higher than 50 ohms, so the fault voltage on metal parts will never be higher than 25 volts for a maximum of 0.02 seconds.
The 25 volts in barns is half of what is allowed in homes. The rationale for this is that animals don't wear footware and cannot communicate danger. By the way, the 0.03 GFI prevents a lot of barn fires!
The biggest problem in preventing stray voltage in barns is that the barn is built without anticipating stray voltage.

 

[MossRoad]

So, just to be clear.

You can't bond the neutral and electrical ground at the sub panel. And I am guessing that it's a safety concern that if you broke the neutral, the ground conductor. would assume that role.

So taking things one step farther. If a device in the barn had neutral and electrical ground tied together, that would be the same as it being bonded at the panel, but would not cause the problems being experienced. Or?

Yes.

The neutral and ground are bonded at the MAIN panel. From that point on, in all sub-panels, they are isolated.

Glad you found your problem.

 

[MossRoad]

Troubleshooting 101 - cut the problem in half.

That is, turn off your main panel and see if the problem persists.
If yes, then you got big problems. :laughing:
If no, then turn it back on and shut off half the breakers and see if the problem persists.
If yes, the problem is in the half that are still on.
If no, the problem is in the half you turned off.
Proceed with turning off half the breakers left in the problem group.
Repeat till the problem circuit is isolated.

On a 40 breaker panel the most you'd have to do is 20, 10, 5, 3, 2,1..... so 6 tests to isolate down to the problem circuit.

At least, that's what I've been doing for years on situations like this.

 

[Tractor Seabee]

I see no mention of the most simple test; stick a outlet checker in each receptacle section and see what the lights show. An open neutral can cause your symptoms. Is your metal building, both skin and frame grounded? It is a huge antenna/receptor of stray currents in the air from something you have no control over. Do you have the required GFCIs for each circuit and/or outlet? They should trip. Have you sunk a ground rod close to the water receptacle and tested between the water and the ground with the heater in it. What happens when you disconnect the heater? Comb every appliance, equipment, and lights in and on the barn looking for something miss-wired. Fluorescent and other HID lights can do strange things. Animals can detect minute voltages that we cannot.

Ron

 

[RNeumann]

So, just to be clear.

You can't bond the neutral and electrical ground at the sub panel. And I am guessing that it's a safety concern that if you broke the neutral, the ground conductor. would assume that role.

So taking things one step farther. If a device in the barn had neutral and electrical ground tied together, that would be the same as it being bonded at the panel, but would not cause the problems being experienced. Or?

They are separated to help with diagnosis. They are all bonded at the main and the the utility doesn’t have both.

With the power to the panel off. Check for voltage on the ground and neutral. If you see voltage on either pull that wire from the panel and see if it still has voltage. If it does the issue is toward the house.

From what I’ve skimmed from you so far it’s either a bad appliance on the house panel or the wires coming to the barn have an issue. Those are my SWAGs. Both of those issues are diagnosed by pulling (in the barn panel) the ground wire coming from the house.

 

[coobie]

I am trying to help a neighbor. The cattle were not drinking from a pail with an approved heater. I gave him another brand new heater, same thing. I measured some voltage, from the ground of the receptacle to some tin on the shack leading into the barn.

I installed a temporary cheater plug, removing the ground and for the time being, the animals drank from the pail.

I noticed there was no ground rod at the barn. The barn is fed underground from a house panel a hundred yards away.

We installed a ten foot ground rod at the barn. I was shocked (pun intended) to still see 7 volts between electrical ground and the tin on the building. That tin is apparently in good contact with Earth Ground.

I understand electrical stuff, and have tried reading up on tingle voltage and stray voltage, but I really don't understand what's happening. Or how to correct it. There are Reactor Filters, which are apparently now seldom used anymore and hence no longer made by Hammond, but I understand that even less.

Have his local power company come out and do a stray voltage test.In my area they are free.

 

[GregbkH]

The most recent NEC requires that any sub-panels have the neutrals isolated and the only place where the neutrals and the grounds are connected is at the first is connection point (which is generally your primary breaker panel).
Hence, per the current NEC you should have two hots, a neutral and a ground going from the main panel to any and also panels including sub-panels in remote buildings.

Aaron Z

This guy is correct. All sub panels in out buildings fed from your main service panel shall have separate neutral and ground terminals not connected (bonded) to each other. All sub panels in out buildings shall have at least 2 ground rods or equivalent as well.

Master electrician

 

[BHD]

my understanding,

at one time the statement considered true, was electricity finds the path of least resistance,
the true statement is it will find all paths.

the neutral is a current carrying conductor, (that is in common with the ground) it caries current just like the hots in the panel, same voltages and amps,

the reason why the neutrals and grounds are separated, is so the ground does not become a current carrying conductor,

but the reason grounds all connected in the newer NEC, is to create a ground plane of equal potential,

say you have number of panels, and there all separate ground and bonded to the natural, do to changes in the earth, and resistance in the wires, you will find different potentials, if all the grounds/earths are bonded, then you make a net, of equal potentials,

according to the NEC, all metal is to be bonded, and then bonded to the earth as well, if a building has any utilities or water lines it is to be grounded and the panel is to treated a sub panel, (a 4 wire system),

most older farms, have a meter pole and usually it is a distribution pole or point, as well, and each buildings electrical is treated as it own main panel, in most instances the NEC today requires a 4 wire system, in it distribution system on a private place,

one can have stray voltage from power lines, as they are grounded as well, and there can be leakage or a path from power lines many miles a way traveling under the earth back to the point of distribution or the point of generation, and at times it can be a cause of stray voltage, by placing the ground rods and making ground plane that stray voltage is then equalized, in that area,

livestock barns under current code are to be built with a wire mesh that is embedded with the concrete floors that are bonded to ground, and any metal in the buildings, to make a equalized plane, same with swimming pools. all water lines and utilities are to be bonded as well, as they can create an unequal potentials,


(in the case of this discussion, with ground and neutral being bonded, and a stray voltage was created,

I would reinspect the ground wire for secure connections working clear throughout the electrical system, as more than likely there is some point of resistance to shunt the current back through the ground/earth,

(back in the 70's when the ground prong was introduced many a receptacle was what was called a boot leg ground where the neutrals was ran to the ground prong as well, or if a line was extended the ground was connected to the neutral. (since it was not understood by many, the thought was if the ground/earth was connected at the main panel and or meter, (in there thinking it was the equivalent to the same thing, so why not just connect it downstream in the system (there all going to the same place),

the ground does two things one makes a ground potential that is equal to the neutral, and second it give a place to drain off excess current so there is not an unequal potentials, and sometimes even will trip a breaker if there is a direct short, (many times does not happen because of resistance in the earth/soils),

the ground is there (example), if your dryer sitting on a concrete floor, (concrete conducts nearly as well as the earth does, may better), and say the dryer is on rubber feet, something shorts out to the frame of the machine, the frame of that dryer is now the same as the hot side of the power line, 120 volts, you walk up bear footed and open up the door of the dryer, you will get bit a good one as you just became the ground line, now if it is grounded properly the ground will drain off the voltage protecting you or you loved ones, and in a situation like this most likely pop the breaker as it will follow the grounding wire back and over load the breaker,

the problem with the ground/earth and the neutral being connected, is if a fault is found in the neutral line it will make the ground/earth in to a current conducting line, thus possibly creating the stray voltage problem discussed here,

I hope I made this as clear as mud,

 

[MossRoad]

I am trying to help a neighbor. The cattle were not drinking from a pail with an approved heater. I gave him another brand new heater, same thing. I measured some voltage, from the ground of the receptacle to some tin on the shack leading into the barn.

I installed a temporary cheater plug, removing the ground and for the time being, the animals drank from the pail.

I noticed there was no ground rod at the barn. The barn is fed underground from a house panel a hundred yards away.

We installed a ten foot ground rod at the barn. I was shocked (pun intended) to still see 7 volts between electrical ground and the tin on the building. That tin is apparently in good contact with Earth Ground.

I understand electrical stuff, and have tried reading up on tingle voltage and stray voltage, but I really don't understand what's happening. Or how to correct it. There are Reactor Filters, which are apparently now seldom used anymore and hence no longer made by Hammond, but I understand that even less.

So did the garage door opener solve this issue, or was it a separate issue?

 

[Industrial Toys]

Thanks for the help. I have been away and need to sit down and read the posts.

 

[MossRoad]

Don't use a metal chair.....

 

[GLyford]

So did the garage door opener solve this issue, or was it a separate issue?

That was Doofy talking about a similar experience, not Industrial Toys. (Post 36)

 

[Doofy]

I tried an electric freeze-proof bucket for an outside malamute. The bucket worked okay for a year then she stopped drinking from it because it was shocking her. I couldn't feel it when I'd stick my hand in. I've heard of the same problems with freeze-proof bird baths.

 

[hawkeye08]

I've had two incidents where I got bit.

First one was a farm where I grew up, taking a shower got bit when my foot touched the drain. I learned to keep my feet away from drain while showing. It would come and go, we finally figured it out, it only happened when one of the irrigation pumps was running (about 1/4 mile from house, pumping from pond filled by irrigation district. Turns out the insulation had rubbed off the large wires in metal conduit buried between the pump and its panel. That was so much fun to dig up (by hand) and fix. But no more shock when showing.

Second one was when we lived in 1952 travel trailer while we were building our current house back in 1993. The skin of the trailer was hot, my Mom was the first to get bit, the rest of us did not have an issue until one night I went outside barefoot to get dog in. Bare feet on concrete pad touching trailer side, it was a good bite for sure. Turned off power to trailer immediately and started troubleshooting in the morning. We found a hot wire from kitchen fan intermittently touching the metal housing.

We have an RV post about 100' from main panel, both have neutral and ground bonded and both have ground rods. This was done per inspector in 1993. I have been told all sub panels should not have neutral and ground bonded.

A question for those in the know,

Should a portable generator used to power a travel trailer have a ground rod? Should neutral and ground be bonded on generator? How about if used to power some things in house during a power outage (using extension cords, not tied into main panel)?

It will be interesting to see how this turns out for Industrial Toys

 

[MossRoad]

That was Doofy talking about a similar experience, not Industrial Toys. (Post 36)

Thanks, I blame the mixup on my hearing....

 

[Industrial Toys]

Actually the current in the neutral can approach zero if the current in the two legs are equal.

We aren't under the NEC but I am curious about the single point ground matter as another topic.

I will first locate that fencer.

I would then take some readings at the house just to see if the problem exists there too. If it is present, I may take off the conductors to the barn and see if the problem goes away. If not, I would probably suggest he call the Utility.

For context, it is a hundred year old barn, with sketchy wiring. The house is as old, but with 70s and newer wiring.

Under current conditions, I am curious if I grounded the Tin to the rod, would the potential on the electrical ground diminish or would I liven up the tin? Maybe both!

I like a HOT shower but not like that. You don't remember all the cuts on your hands until you grab those handles.

 

[Tractor Seabee]

IT, Grounding the building metal skin is a code requirement. AS mentioned before it is highly accessible and the skin forms a huge antenna to collect stray currents flying around in the ether. If it is in this case correct term is bonded to the ground rod and ground conductor it then has the same potential, so no tingle.

Ron

 

[3Ts]

A similar situation: My shop had a problem with tingles. I did not notice it because I always wore boots or heavy soled shoes. My daughter came out one time barefoot and touched my (cast iron) table saw and jumped! I measured 56 volts to ground, but only when it was running! Turned out that, on the second floor, one of the outlets, when it was pushed in to the wall had the sharp end of the ground wire punctured the neutral insulation. Fixed that and all was good. The shop is on a different circuit than the 2nd floor, but off the same sub-panel.

 

[Belevolk]

Actually the current in the neutral can approach zero if the current in the two legs are equal.

We aren't under the NEC but I am curious about the single point ground matter as another topic.

I will first locate that fencer.

I would then take some readings at the house just to see if the problem exists there too. If it is present, I may take off the conductors to the barn and see if the problem goes away. If not, I would probably suggest he call the Utility.

For context, it is a hundred year old barn, with sketchy wiring. The house is as old, but with 70s and newer wiring.

Under current conditions, I am curious if I grounded the Tin to the rod, would the potential on the electrical ground diminish or would I liven up the tin? Maybe both!

I like a HOT shower but not like that. You don't remember all the cuts on your hands until you grab those handles.

The Canadian Elec Code is not all that much different than the NEC. Single point grounding is the accepted simple method of a grounded electrical system. There are ungrounded electrical systems, that is way different subject. There is a section in the Codes that allows for a supplemental grounding, how ever I have seen electrical engineers run afoul trying to use that section. Driving a ground rod at your remote building is a marginal idea. If this ground rod is connected to the ground coming from the service on your home you have just entered into supplemental grounding. Reason most do not use it is because the conductor between the barn and the elec service has to be the same size as the elect service ground, surely not a 10 awg like you have.
Having voltage between the ground rod and the building tells me that your building sub panel or load is leaking voltage. Your sub panel at the building should have the neutral and the ground isolated from each other. Shut off the power and use an ohm meter to be sure there is no connection. Quite common to have a screw in the neutral block that lands into the sheetmetal so the panel could be used as a service. You will need to lift one of the wires or you will read to your service and back. You should not get a reading, 0.00. Your sub panel should be bonded to the building. Bolting the sub panel to the building sheet metal should be good enough. Be sure that the neutral/grounded conductor has no connection to the ground at any of your loads.
The only thing I can think of that may be a issue is the conductors from the house. Romex is not rated to be underground even in conduit. Time and water will destroy the outer sheath and eventually work into the cable and cause problems. This can be tested by using a 1000 v megger, not an ohm meter. You test phase to phase, phase to neutral and ground, then ground to neutral. Circuit needs to be dead and removed from both ends for this test. Anything over a megohm would be satisfactory. Anything less, well that is a longer story. Might be time to consider a new feed. I do not remember all of this thread, did you test for voltage between the ground and neutral at the barn? We tested trailing cables in the mine at 5000v and wanted a gigohm of resistance. Voltages on those cables were either 4160 or 7200 ac

Grounding the tin to the ground rod is creating a difference of potential, very bad for living creatures especially horses.

 

[aczlan]

A question for those in the know,

Should a portable generator used to power a travel trailer have a ground rod? Should neutral and ground be bonded on generator? How about if used to power some things in house during a power outage (using extension cords, not tied into main panel)?

It will be interesting to see how this turns out for Industrial Toys

If it is connected just to the travel trailer, or to an extension cord, it is considered a separately derived system and would need to be bonded at the generator.

Aaron Z