Ayep, stray voltage...

[Kizmar]

So... I determined that I have (had) stray voltage in my sump. By the process of elimination, I found the culprit to be the protein skimmer. I'm hoping since the skimmer pump is under a year old that Reef Dynamics will replace it at no cost (other than maybe shipping). We'll see.

The real reason I'm posting this is to talk about how I realized I had stray voltage...

This is a little beside the point, but a couple months (or less) ago I had tested the sump with a multimeter in efforts to troubleshoot the issues I had with a starfish dying in the sump. At the time I (don't think) there was rogue electric current in the water. So I think this issue just recently started, or slowly kept getting worse over the last few weeks. ...or it's been intermittent and I just caught it at the right time.

Anyway, how I noticed it... I was feeding the Peppermint Shrimp that are (now) in my refugium. When I stuck my fingers in to sink the pellets I felt a sharp pain where I had a couple tiny cuts. It surprised me so much that I jerked my hand out of the water. Of course, I had to do it again to see what exactly I just felt. I held a finger with a cut in the water long enough to tell it was electric current, not just saltwater on a little cut. When I put a finger that didn't have a cut in the water, I felt nothing.

Begin process of elimination:

1. Stick finger with cut in display tank with everything plugged in: no shock. Good, at least it's not affecting my display.
2. Unplug the heaters, stick cut finger in sump water: SHOCK!
3. Unplug the pumps, stick cut finger in sump water: SHOCK!
4. Unplug the skimmer pump, stick finger in sump water: no shock. Bingo!

I wouldn't have guessed a small cut would amplify stray voltage so much. As I mentioned, I felt nothing when dipping a finger without a cut in the water. It was a significant difference.

Hopefully I can get this resolved quickly because my skimmer is out of commission until I get a replacement pump.

 

[Kizmar]

I think I still have stray voltage, after all that typing.

Is there an expected amount when you have as many electronics running in the water?

Is anyone using a grounding probe? I'm trying to figure out if I need to worry about this.

 

[Amba]

We use so much electricity there is bound to be stray voltage. I would add a grounding probe anyway, they are only a couple bucks.

 

[Kizmar]

After some additional research and testing, I think what I'm dealing with is pretty normal. I just haven't been bare-foot sticking my hand in the water with a cut. Both of which intensify any sensation of stray voltage in the water.

I'll be ordering a grounding probe tonight though.

 

[RockStacker]

Even without electrical equipment running, saltwater in itself will have sufficient electrolytic properties to register on a voltmeter. However, there is normally not enough current to be of any safety concern.
Some students have tried building saltwater batteries and found that they need a lot of saltwater to even light up a single low power LED.
Induction by motors in the tank could also add more voltage to the equation, but again not that significant.

The issue is when you have a hot wire come into contact with the water.

I'll just reference this post instead of taking chunks out of it :)
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