stray voltage levels in saltwater aquarium

[jamey]

I know this is an old thread, but I just discovered a similar situation in my salt water system. My system is 2 tanks, 75Gal and 125Gal, sharing a 35Gal sump. The 75Gal was integrated into my setup about 3 weeks ago. Last weekend for the first time I felt a stinging when touching the water surface while standing on a carpeted concrete slab floor with bare feet, with a small cut on my finger. Turn everything off, and the stinging was gone. I narrowed the source down to my pumps, 4 Hydor powerheads, a Mag 1800 Return, and a Reef Octo Skimmer with a Bubble Blaster pump. My Snap On Vantage automotive volt meter ($3000 new) showed 28 Volts, positive lead in the water, negative to ground receptacle. Unplug the pumps one at a time, and the voltage dissapates little by little, along with the stinging sensation. My hands are cut up all of the time, so my curiousity is why is this happening all of the sudden. Even with just the skimmer running, I feel something. I want to believe that it is the very recent addition of Kalkwasser to my gravity fed ATO, causing something in my water chemistry to make me feel the stray voltage, that was most likely always there. Or maybe the Kalkwasser is making the water more conductive.
Anyway, here is the most interesting part, and I can't figure out the reason for it. If I split the loads, 4 power heads plugged into one receptacle, and the return pump along with the skimmer plugged into a different receptacle on a completely different house circuit, voltage drops from 28 Volts down to 1.4Volts! No more stinging. Unplug either one, half the voltage is back, 14Volts, and so is the stinging. Its like splitting the circuits is making the magnetic fields from the pumps cancel out each other.
Any ideas?
Also wanted to add, with 28 Volts in the water, my Ammeter, capable of DC Milliamps only, showed no current at all. Inconclusive because it is a DC meter, but worth mentioning

 

[Ingy]

sounds like a potential grounding issue. When you switched to the other circuit you brought in a better ground terminal. try switching all 4 pumps to the other circuit and see if the problem disappates completely.

 

[jamey]

Total of 6 pumps. Switch them all to either circuit/receptacle, 28 Volts, Split them up either way, 1.4 Volts. Disconnect any pump on either side makes the voltage creep up, like upseting the balance. Also has to be different circuits on different breakers to drop the voltage to 1.4 Volts
I kind of like having them split up, so if one GFCI trips, I will still have some circulation until the problem is fixed, but still very curious why it is acting the way it is.

 

[jeffaquarius]

Have you checked your electrical outlet (receptacle) if it has a good ground? If you get some voltage reading between the ground (round) and the neutral (larger flat) on outlet you have a grounding problem. The voltage difference between larger hole and round hole in outlet (smaller hole as common when measuring) must be close to zero volt. Check also your grounding probe if it has good conductivity (must be less than 1 ohm). They are sometime covered with algae and what not.

 

[kdpuffer]

I don't know if it is a grounding issue so much as an issue with your neutral line. Your ground and neutral are actually connected to the same point in the panel. The way most pumps are wired (hydor I know for sure) they don't have a ground prong so a grounding issue isn't likely. If you do a continuity test on your neutral (white wire) to ground (either bare copper or green wire) you should have continuity, if you don't then it's most likely an issue on the neutral. If you have continuity with alot of resistance (ohms) then there is a loose or bad connection somewhere. Another thing to look at is hot neutral reverse, I actually had this on a receptacle in my basement that I found after transferring everything into my 90g. Unfortunately I had all my tools at work so I had to figure it out the hard way- hand in water, zap, ouch that's not it. As far as your voltage dropping by switching to a different circuit that is most likely the induction canceling itself out due to the phase differential. Also if your having the same issue on the other circuit it's possible there is a loose connection on your main neutral line or main ground in the panel. In the panel your ground and neutral are actually connected.

 

[kdpuffer]

I forgot to add that it's also possible (not likely give the number of pumps) that the winding insulation on your pumps is degraded. Like I said not likely but I do have one pump at home that has that issue. Everytime my ATO kicked in it would energize my my main tank through the water it was pumping in. If my hand was in the tank at the time I would eliminate the need to grab a coffee.

 

[jeffaquarius]

I don't know if it is a grounding issue so much as an issue with your neutral line. Your ground and neutral are actually connected to the same point in the panel. The way most pumps are wired (hydor I know for sure) they don't have a ground prong so a grounding issue isn't likely. If you do a continuity test on your neutral (white wire) to ground (either bare copper or green wire) you should have continuity, if you don't then it's most likely an issue on the neutral. If you have continuity with alot of resistance (ohms) then there is a loose or bad connection somewhere. Another thing to look at is hot neutral reverse, I actually had this on a receptacle in my basement that I found after transferring everything into my 90g. Unfortunately I had all my tools at work so I had to figure it out the hard way- hand in water, zap, ouch that's not it. As far as your voltage dropping by switching to a different circuit that is most likely the induction canceling itself out due to the phase differential. Also if your having the same issue on the other circuit it's possible there is a loose connection on your main neutral line or main ground in the panel. In the panel your ground and neutral are actually connected.

You are absolutely correct that ground and neutral are connected at the same point at the panel. Therefore, the voltage difference between them with respect to the hot wire should be zero. That only happens when there is no load. However, since your neutral conducts current while your ground wire does not, that explain why they should not be equal because of the voltage drop on the neutral wire. If you notice the more load or pumps you connect the higher voltage reading you get. Simple explanation is you have high resistance or bad connection on your neutral wire. High resistance may be due to the distance and size of wire from the electrical panel. It could also be due to defective extension cord or power strip. The ground probe for tank should take care of this stray voltage if you have a good ground at the outlet where you connect this grounding probe.

 

[jeffaquarius]

My Snap On Vantage automotive volt meter ($3000 new) showed 28 Volts, positive lead in the water, negative to ground receptacle.

Some DC voltmeter can pick up AC volts but are not accurate readings. The 24 volts on your DC snap on meter could actually be twice as that (48vac). You definitely need to have a good grounding probe in your tank to prevent shock when touching your water. It is not a good idea to have 2 separate circuits from panel to power your pumps. Good thing you might only have one pump with stray voltage. If you have two pumps with same problem connected to different circuits, guess what? You will fry everything on your tank. The reason why you are getting lower reading is probably because one pump happens to be plugged in reversed where the hot side becomes the neutral and thus would act as your grounding probe.

 

[jamey]

Just to clarify, meter was in AC mode when testing the 28 Volts measured. I do not have a grounding probe, and I am hesitant to use one after reading this:
Aquarium Grounding Probes
I have tested the receptacles with one of those cheap circuit testers from Home Depot, but will bring the meter home again and test the ground, and nuetral circuits, as well as checking for reversed hot and nuetral wires.
Can you clarify why using two different GFCI protected circuits would be a hazard?
Thanks

 

[jamey]

I am assuming that using two different circuits gives the potential to leak 240 Volts if there are failures on both sides? To those who are using ground probes, how many volts did you have in your tank before grounding, and have you noticed any behavior changes in your livestock?

 

[jamey]

Meter was set to AC Volts btw. 28 Volts

 

[jamey]

Have you checked your electrical outlet (receptacle) if it has a good ground? If you get some voltage reading between the ground (round) and the neutral (larger flat) on outlet you have a grounding problem. The voltage difference between larger hole and round hole in outlet (smaller hole as common when measuring) must be close to zero volt. Check also your grounding probe if it has good conductivity (must be less than 1 ohm). They are sometime covered with algae and what not.

Ok, I did these checks, with a good AC voltmeter, and everything checked out ok. 0 Volts between the ground and Neutral, and 0 Ohms. Also confirmed that the larger hole on the receptacle is the Neutral.
So I am assuming that I have had stray induced voltage in my tank this whole time from the pumps, and I am just noticing it now for one reason or another. I am switching everything back to the same circuit (Thanks Jaffaquarius for the wake up call) Can I just live with the stray voltage for now, and turn the pumps off when servicing? Never had a problem with the livestock in the 20 months it's been running. Everything seems to be healthy and thriving.

 

[jeffaquarius]

I am satisfied 100% with what this author is saying about the Ground Probe
Aquarium Grounding Probes
For me the primary purpose of having a Ground Probe in my tank is to eliminate the electrical hazard for myself and not for the fish. Now it is up to you to choose and decide which is more important, is it your life or your fish. A GFCI (Ground Fault Circuit Interrupter) is a good idea and I might have to put one too. You don't need to have a Ground Probe if you have GFCI. You need not worry for it to trip when you are not around because it will never happen. As long as your water is not grounded it will not trip. The reason is because GFCI is looking for unbalance current between Neutral and Hot to trip. Unbalance occurs when some current leaks to Ground. Therefore, it will only trip when the water is grounded by your body and if there exist an excessive stray voltage from your pumps and heaters. Or you can put your Ground Probe only when servicing your tank.

 

[jamey]

Ok, so I confirmed that the two receptacles I was using were on different hot legs. Measure the voltage between the two and it was around 270 Volts on my meter. Now everything is back on the same leg, and I'm back to 28Volts Stray Voltage.
Thinking about ground probes now.
Would it still be dangerous if I split the loads like before, dropped the stray/induced voltage down to 1.4V, and used ground probes, so if something went wrong the GFCI's would trip, eliminating the danger of exposing the water to 240 Volts. This way I would only be discharging 1.4Volts rather than 28Volts through the ground probes when things are normal. Just a thought.
I absolutely do not want to stress the fish, but I don't want to get electrocuted either.

 

[jeffaquarius]

Remember about the birds setting on a high tension wire and the reason why they are not affected by the 35 kilovolts? It is because there is no current flowing in the air or in their body. Current will only flow if you provide a path between 2 points with different potential (volts). The same thing applies in the stray voltage in your tank. That 28 vac you are measuring in your tank with respect to ground is a stand still voltage and no current flowing. It is a false notion that it affects your fish. As stated on that link you posted, it is the other way around. Once you have that Ground Probe in the water, you have just provided a path for that stray voltage to flow to ground. It is still not advisable to have 2 different circuits in your tank. I don't believe either that a current flowing in the water will affect your fish for the simple reason that salt water has more conductance compared to the flesh of fish therefore the current will just flow thru the water not through the fish. High Tension Electricians use Ground Probe so they can touch the wire which may still have some stray voltage in it. Therefore, I suggest you do the same thing. Just use the Ground Probe when maintaining your tank or have a GFCI so you don't have to worry about forgetting to put your Ground Probe.

 

[jeffaquarius]

Would it still be dangerous if I split the loads like before, dropped the stray/induced voltage down to 1.4V, and used ground probes, so if something went wrong the GFCI's would trip, eliminating the danger of exposing the water to 240 Volts.

If you are willing to use 2 GFCI for your set up then yes you can. You don't need a Ground Probe when you have GFCI. Another caution, if you use Ground Probe only with 2 circuits in your tank, the stray voltage may be cancelling out with respect to ground but not inside your tank. You now have 2 different potentials and current may be flowing inside your tank without you knowing it.

 

[jamey]

Another caution, if you use Ground Probe only with 2 circuits in your tank, the stray voltage may be cancelling out with respect to ground but not inside your tank. You now have 2 different potentials and current may be flowing inside your tank without you knowing it.

Excellent point. Your advise is well taken. Thanks!

 

[jeffaquarius]

Found this:

Stray voltage is an induced voltage caused by a spinning magnet (impeller for example) that is submerged in saltwater. To put it simply, a submerged pump with a spinning impeller acts as a small generator. Stray (induced) voltage has low to no current behind it and is easily handled by a ground probe. Many pumps with two prong plugs will cause stray voltage due to the lack of a grounding shield like the 3 prong pumps have.

Leaking or shorting voltage is caused by a failing item like a heater or pump. This voltage has A/C current that is being supplied by the wall socket. This type of voltage is dangerous and cannot be fixed by a ground probe. In this case, a ground probe completes the circuit and causes a bigger problem.



And this:


Aquarium Grounding Probes

It seems that there is little current involved and most of the voltage is induced by the pump impeller actions and from any two wire immersed devices you might have.
But it also seems to me a probe isn't a bad idea, as a GFCI will detect and trip any significant current, the probe will keep the seawater at the same ground potential (voltage) as the house wiring has. But in the end, no one thinks even my 34 volts is a big deal on all the posts I have studied so far.

Sorry Greg but I have to disagree with the idea that the stray voltage is coming from the motor. If it is, how would you explain the stray voltage from the heater when there is no motor on it? It actually comes from the electrical insulation of your equipment submerge in the water. Plastic and rubber are non conductive but they do have dielectric capacitance. Even space has some dielectric capacitance but very minute. AC will pass thru capacitors but DC does not. This explains why the more equipment and length of wires submerged in the water the higher your stray voltage reading becomes. Use DC motors and heaters and I guarantee you will not have any stray voltage in your tank. Not practical though. Just get a GFCI and case close.

 

[Gregcoyote]

I throw away a cheap pump at least one a year. The two wire kind with no ground. Had one almost fry me a few weeks ago. The pumps can leak or cause inductive voltages as mentioned above, in the tank. Some ph probes can also leak a small amount of current. It's almost impossible to get to zero if you have several pumps actually in the tank because of the effects of induction. The only exception are the expensive wave makers that keep the motor section on the outside of the tank.

 

[jeffaquarius]

This same issue was discussed in another thread and I was demonstrating where it is coming from.
http://www.aquariumadvice.com/forums/f11/tank-temp-has-been-steady-rising-262552-2.html
However, there is another way of proving this with more convincing result. Remove the Grounding Prove first if you have one. Using a good digital voltmeter, measure the existing stray voltage in your tank and record it for reference. Then submerge the remaining electrical cord of one of your power heads that is running except the plug of course. Measure again the new stray voltage reading and you will notice it is higher than the previous reading. My 26 vac went up to 28 vac which increased by 2 volts. I'm in the US and I have 120 vac power for my equipment. This explains exactly where the stray voltage is coming from. The more equipment and electrical wire submerged, the higher your stray voltage becomes. No need to throw away those power heads if you have GFCI.
You can avoid getting a shock from stray voltage by laying a rubber matting on the floor where you stand when working in the tank.