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Old 09-18-2017, 07:37 PM   #21
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That's what he said. Some people throw parts at a problem until it goes away. True troubleshooters and far and few between.

I'm a little confused about pulling grounds off and such. The first thing I would have done is kill the power at the dock panel. The second would be to kill the power feeding it. It breaks the problem up and eliminates bigger parts that way.

Yes but first I had to determine what was going on there,takes a little time to finally realize that the problem 4 volts between the water and the dock.Thats the first thing you would have to do.Now that Ive thought it out with your help the first thing Im going to to is check the feeder. thanks
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Old 09-18-2017, 07:41 PM   #22
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Originally Posted by hardworkingstiff View Post
My guess (since I don't have a meter and on site) is there is a difference of potential between the PoCo neutral and the water. When you ground the neutral at the service disconnect, you energize the ground around the rod to the voltage on the PoCo neutral.

The water may be a parallel path back to the PoCo distribution (maybe back to the nearest substation). A degrading neutral in the PoCo distribution could cause enough resistance for the water to be a more noticeable parallel path for the PoCo neutral current.

If this is the case, you won't get it fixed (the PoCo will fight you), you can only treat the symptom. The way you treat the symptom is to drive some ground rods near the water and reference the ground conductor in the feeder to the dock panel.

Doing this sucks because if the PoCo does have a developing problem this will mask it and allow it to get worse.

You know this type of problem is why we have the equipotential bonding system at swimming pools, right?
And around AG buildings. The cows feel it before a human will. And it's more times than not a poco neutral issue.
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Old 09-18-2017, 07:48 PM   #23
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thanks hardworking ,

I remember a similar problem about 20 years ago, The people were swimming by a submersible lake pump and feeling electric fields around the pump.I remember bringing the pump into the boat and getting 90 volts between the shaft and the aluminum boat frame with the pump power turned off.It did not go away until I separated the grounds at the pump disconnect .That particular issue was the pocos problem so i cant remember what but I assume a loose neutral connection of what you just described.
My memory seems blank out crucial details
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Old 09-18-2017, 08:12 PM   #24
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Just make sure it's not leakage on your feeder before you call the PoCo. I would contact the PoCo to give them a chance to fix it (but I doubt they will).
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Old 09-18-2017, 09:53 PM   #25
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Wherever metal meets water the FIRST thing you have to do is make sure that you don't have cathodic// battery action.

This entails killing ALL AC power and then re-testing.


AC with a DC bias will come off as AC in a T5-600 or T5-1000 meter...

Which I would NEVER use in such a case.

You want a Simpson analogue meter.

These DON'T sample -- and are extremely polarity sensitive.

I've lost track of how many e-men have lost their tails chasing DMM readings.

DMMs are FAST -- but CAN'T reveal weird circuit faults.

Analogue meters are SCALE versions of the circuit under test.

That's why you MUST have an analogue -- high sensitivity -- meter in your tool suite.

It WON'T sample, it won't average, it won't compensate for the wrong polarity.


ANY TIME water craft are involved, one HAS to worry about cathodic action -- coming or going.

That has to be eliminated FIRST.

I've lost track of the e-men that thought they had it figured out -- only to find at the end that they had issues with the cathodic protection system. Heck, they didn't even know it existed. Nothing about it. Their brain was wired to AC.

EVERY TIME I read about trivial voltages and water craft -- I worry that DC current is involved.

IT, VDC, MUST be eliminated as a factor STRAIGHT OFF.

Only then can you proceed with AC issues.

A T5-600 is WAY too crude to trust with such low voltages.

It's designed// engineered for 120 VAC and stuff like that.

NOT 3 VDC.

That's down around the limit of its range.

NEVER trust ANY test instrument at the limit of its range.

BTW, you really need a megger.

Master Electricians are WELL aware of how test instruments can lead you astray.

(Always a risk at the extreme range of the device -- DC corn fused with AC Volts -- etc. )

Noobs take ALL such readings as Gospel.

Last edited by telsa; 09-18-2017 at 10:01 PM.
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Old 09-18-2017, 09:56 PM   #26
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And...

How many times do I have to post it ?

DMM SAMPLE readings. You are always looking at a digital display of averaged samles.

Analogue meters MIMIC readings.

Hence, the term, ANALOGUE.

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Old 09-18-2017, 10:01 PM   #27
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I definitely will check the easy stuff first before replacing the 10-3 uf,couple of j-boxes along the way I should at least be isolate the bad section as there is a couple of splices located in above ground pvc j-boxes.
I would check those Jboxes first to make sure those splices are good.

if so I know you mention you lifted the EGC off at the subpanel if I did read it right ? if so go back to the main panel and look very carefully on the ground connection at the main panel.

If that place did have electric water heater that can throw ya in the loop if the element is half way toasted. ( that is one of few source you will find it some case.)

Use the anlog meter not the digital verison due you can see exctally what you are hitting on stray voltage espcally that low a voltage.

some case you may have to use ampmeter to clamp up that feeder conductor to see how much current it drawing.,,
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Old 09-19-2017, 12:26 AM   #28
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If the POCO MGN is at a potential that far from remote ground there is a serious problem with the metallic neutral. If 4V is low enough that POCO will not correct it they can install a neutral isolator. This separates the secondary neutral from the MGN with a semiconductor stack that will withstand, for example, 6V RMS but will break down and conduct if there is a high voltage fault needing a fault clearing path.
They work, allowing the customer end GES to hold their neutral close to remote earth (and the lake water.)
The POCO problem also implies that there is a 4V or greater step potential near the ground rod at their pole, but without the water to provide a path through skin resistance it is probably not noticeable.

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Old 09-19-2017, 06:12 AM   #29
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The POCO problem also implies that there is a 4V or greater step potential near the ground rod at their pole, ....
I'm not sure I agree with that statement, but it might be that I just don't understand why you are saying that. Care to elaborate (for my education)?
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Old 09-19-2017, 05:38 PM   #30
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I am not saying just replace the feeder, chasing a short can be lessened if you have a live feed to work from, If disconnecting feed to sub panel shows its cleared then it is down line. Since every splice has to be disconnected any way just check as you go. I don't know the layout but I would also see if there is a distribution box or small trans. supplied by PoCo, in the area. Had two deaths in pools from leaking feeders on their side this year in my area in resort hotels. Down side is they won't believe you till you have absolute proof. It's never their fault. Been there done that. Old systems fail but not the PoCo's they last forever. Installations are only as good as the person who installs them.
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