electrician with stray voltage,go figure

[spamreefnew]

Let me start by saying that I am a master electrician,and have been for some time. Just for the fact that my return pump has been making noise I decided to check my tank for stray voltage. The results wear shocking (pardon the pun).
with one probe in the tank water and one to ground I was getting about 30VAC,with one probe to the house "hot" and one probe in tank water I get 75VAC!! Ok so I start unplugging things one by one,,,,unplug pump #1 still 75V,,,,unplug pump #2 STILL 75V,,,,unplug heater,STILLL 75V! Wait a second,,,there's nothing left to unplug!?!?!? Well there is one thing left,,one powerhead upstairs that I cant check right now because everyone is sleeping up there,but I will check it in the AM. I did the tests in my basement fish room/sump. But the thing that threw me for a loop was that I decided to hit the power switch on the power strip that feeds pumps 1&2 and the heater and the voltage dropped to about 10VDC??? I have no idea what to make of the readings,,,,how can I get voltage to the house "hot" AND to the house neutral from the same body of water? I do however find it very intresting that 75V plus 30V = 105V.........I will unplug EVERYTHING in the morning and test once more but I would relay like some ideas from you guys who are used to dealing with under water electrical theory :lol2:

 

[staindsoul]

The 75vac test is just showing you have a larger difference of potential. Because your going from a floating potential path to a ungrounded conductor. Go from your ungrounded conductor to a piece of wood on your floor or a piece of metal sitting on a chair sitting on your floor and you will see some random low voltage reading with a digital meter. You might even see a couple of volts with just a probe on the ungrounded conductor and the other probe in the air. Ignore that test. The same with the 10vac (I'm assuming you had a typo).

The 30vac from tank to grounding conductor MAY be a problem. Redo the tests from grounding conductor and tank unplugging everything including the other power head.

Edit: later in the paragraph you said the nuetral make sure you are using the grounding conductor on the recptacle for the test, not the nuetral. The nuetral as you know is only bonded at the panel or should be. You have return current traveling on that conductor and it would skew your test.

And by "floating possible path", I don't mean water. Haha. I mean some arbitrary conductive path that may be made up of multiple types of conductors.

 

[staindsoul]

got to thinking more about this, this morning. that 30vac is just more differnce of potential, between the ground and water. if your going to have a voltage leak it will be between 100 and 130 volts.

throw a gfi on your equipment, if you dont have one and let it be.

 

[spamreefnew]

I think I understand what you are saying. Guess I am just reading the "unbalanced" load due to the pumps? So I should get nothing from ground to tank water. I will re-test soon. I don't normally have to deal with this type of thing,,like you said we electricians just throw a GFI in there and forget about it I might just do that

 

[staindsoul]

its not the unbalanced load of the pumps. that voltage your reading is the POTENTIAL energy. take a non digital meter and try it, like a "wiggy" tester. you wont see anything.

its like i said about a digital meter with one probe in the air and one on the ungrounded conductor. you will read a volt or two. there is no voltge but a potential for that.

 

[spamreefnew]

I agree ,,however,,I ran all the tests with an analog meter with the same result..thoughts?

p.s. I installed a NEW GFCI and it did not trip.

 

[staindsoul]

awesome on the new gfi.

and the only thing i can think of is the analog meter is seeing the difference of potential, which you just said it did. they are old school and i havent tried them on that, i will dig one up from our shop and try it out. i was thinking a resistive meter like wiggy's because i tried to chase 80volts on a nuetral on a temporary trailer for a job with a digital meter for hours. finally pulled a old set of wiggy's out and it didnt seeing anything, i did verify the wiggys on a known live scource. a resistance meter wont register difference of potential. another way to think about dop is, you know you can grab a live circuit as long as you are not grounded. you dont feel a voltage but the potential is there i you ground yourself. same principle.

 

[BeanAnimal]

"stray voltage" is meaningless without being put into context with current. A voltage reading between the HOT and the TANK may indicate that the tank water is grounded or in contact with the neutral conductor may, albiet not very well (high resitance). This could be throug a pump shaft, or a partial fault in a device. Placing the meter between the tank and the ground/neutral and reading voltage would also make sense if the meter is a better earth path than the partial ground in the tank mentioned above. That said, it may be none of the above. You may find that switching the "HOT" leg you are testing from creates a a different reading. We can talk about several different possible "voltage" soruces, but again without a current measurement for context we can not draw any conclsusions.

 

[staindsoul]

with the gfi not tripping there is no current, or it is below .5ma. the trip rating of a gfi. or it isnt working, not as likely. there is no current.

edit: I believe we are saying the same thing bean, just differently. there is no current to reference, so there is no voltage, merely a potential.

 

[BeanAnimal]

Also remember, that if the fault is from HOT to NEUTRAL then the GFCI will not trip eiher (example: salt creep bridging the HOT and NEUTRAL blades of a plug in an outlet strip, or an ungrounded magdrive pump with exposed windings in an ungrounded tank).

 

[spamreefnew]

I understand now. thanks to all,and good points all. Yes after installing the gfi today I confirmed that there is nothing wrong,,in my mind any way