WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
And how to confirm or disprove this ideas, one at a time. The cows are getting thirsty. . .
Livestock Water Tank
- Thread starter Wayne72
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In my experience the BarBarA will not freeze up if install correctly. That experience is over 15 years and down to -25F with the BarBarA drinker. No experience with other types.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
An equipotential bonding grid under the cows where they stand to drink tied into the water would mask the problem and allow the cows to drink.
The problem is this might be considered a fix and the problem never discovered.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
The first thing I would do is to inspect the service grounding to make sure it is adequate.
Then I would turn off the service disconnect, then lift the neutral coming from the meterbase to the service disconnect and check for voltage between this conductor and the neutral bar where it was lifted. If you have the 14 volts there, then IMO the PoCo has a deteriorating neutral nearby, or you may be on a SWER or there is a SWER nearby.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
Also, check for current on the GEC both with the main power on and with the main power off.
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
I would hope the OP does at least some of these tests and tries some of these candidate solutions. It might stop the tail-chasing.
But first recognize that you are pursuing something that looks like a tail.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If removing the EGC from the cord connection fixes the problem, it is 100% proof that the panel ground voltage is not the same as the local earth voltage at the tank. It is only reason for this that needs to be explored IF simply leaving the EGC open is not considered an acceptable solution.
(It should not be acceptable because it will probably not allow a hard ground fault at the tank to trip a non-GFCI breaker).
A neutral isolator installed by POCO may be the only practical solution. But even this may not be specced to tolerate a 14+ volt neutral offset.
(It should not be acceptable because it will probably not allow a hard ground fault at the tank to trip a non-GFCI breaker).
A neutral isolator installed by POCO may be the only practical solution. But even this may not be specced to tolerate a 14+ volt neutral offset.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
If the circuit was GFCI protected, would you let it go w/no EGC? I think I might, ... maybe.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Code wise it is a no no. Theory wise somewhat OK, might be better yet if an ungrounded source.
Best thing in this atmosphere is probably still a grounded source but one that is isolated from the MGN system that supplies it, maybe even with 60-0-60 volt source and no neural loading.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
Larry changed my mind on that. GFCI doesn't work very well on an ungrounded source.
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
It should work for ungrounded loads. Unless they changed it, the toroid inside only knows leaving and returning currents.
It seems to me all the worms are out the can by now and the OP is trying to find out what they mean. They all squirming at once.
I think that sometimes as each worm comes out you should torture as much info out of that worm as you conveniently can, but the test equipment for this deep dive may be costly and the calcs may be lengthy.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
That's not what I meant. We were talking about ungrounded sources. For a GFCI to work properly, there needs to be a parallel path (the ground that is referenced to neutral in the grounded source) for stray current back to the source.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
It works just fine. First ground fault does nothing but create a ground reference, it don't need to trip at this point as there is no stray current flowing. Should there be a second ground fault it will still result in current flowing outside the protected conductors and will result in voltage sensed by the CT in the GFCI and trip it.
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
I had to draw this one out.
IMO, if an ungrounded generator, H & N, supplies a GFCI, and if the current leaving and returning is different, then the GFCI will trip.
If the generator is capacitively coupled to the earth, some of the lost current will come back to it.
There will be very little lost current if it goes into the metal appliance shell and the shell is not grounded but is capacitively coupled to earth.
If it's 240 center tapped and the GFCI is working on 120v, I don't know what to think, yet.
The fine print is a killer.
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
I stand corrected. Even diagrams sometime let me down.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
You will have to draw that one up for me to agree with you. Since the first and second fault are from conductors that are from the GFCI, there is no outside of the protected conductor path. Having a grounded source allows detection of a fault of either hot or grounded conductor.
WasGSOHM
Senior Member
- Location
- Montgomery County MD
- Occupation
- EE
Now I think that an ungrounded 120vac source can't pass current through a person standing barefoot on concrete and touching the H lead.
In this case the H lead of the generator would now read 0 vac with respect to ground and the N lead would read 120vac.
The person becomes the ground conductor and passing capacitive current probably too small to feel. The current would increase as the generator is brought closer to the earth.
I never messed with an ungrounded AC source more than 12v or so. Pepco has cleaned up their act considerably on this power loss account and has cut down a lot of tree branches.
Ball park, you pay $1 per watt, 20 kilobucks for 20 kw, installed price, around here.
In this case the H lead of the generator would now read 0 vac with respect to ground and the N lead would read 120vac.
The person becomes the ground conductor and passing capacitive current probably too small to feel. The current would increase as the generator is brought closer to the earth.
I never messed with an ungrounded AC source more than 12v or so. Pepco has cleaned up their act considerably on this power loss account and has cut down a lot of tree branches.
Ball park, you pay $1 per watt, 20 kilobucks for 20 kw, installed price, around here.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
Hey Wayne, what's going on?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
fault between "hot" and "neutral" won't trip the GFCI even on a grounded system. Current that isn't flowing back through the GFCI is what is needed to trip it. With ungrounded system there can't be ground fault current until there is a ground reference - which is what happens with the first fault.
Yes if low level fault current is entirely on the load side of the GFCI you have condition that the device sees as a load and not a fault, but your risk of shock/electrocution generally is lowered in those applications as well.
oldsparky52
Senior Member
- Location
- Wilmington, NC USA
I agree with what you are saying. W/out a grounded source, it takes 2 faults for a shock hazard. Chances are that 1st fault is after the GFP and if it is, the GFCI will not see the 2nd fault as a problem. You would need a path for current that does not go back to the GFCI in order to trip it. So, if you had 2 faults after the GFCI, the GFCI will not work.
This is all theory, because almost ALL of what we work on is a grounded source. Grounded multiple times (which is part of some of the problems we have with NEV).
At least this is how I understand it. Maybe Larry will stop by and offer support.
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