Stray voltage?

[MHG]

So the sps in my frag tank are fine, but my zoas and tourch are dying... All parameters are within spec... Same as my DT ... So today I took my volt meter and checked both tanks. DT is fine... Less than zero volts.... Frag tank has 53 volts. Unplugging items lowers is a
Title for each item. Return, heater, skimmer and circulation pumps are the biggest....

Now I have my sub panel right next to my frag tank. It tales two circuits for a
L the stuff in my frag tank... I moved everything to one and it's better but still close to 20 volts...



I am debating a ground probe... But I would rather not.. Some say don't, some say the stray causes no issues.... Replacing all my new pumps with new pumps is likely not gonna fix anything....

 

[mc-cro]

why would you rather not use a grounding probe?

 

[reefincredible]

This is funny because I had the same issue a few years ago with my 40g breeder SPS tank. Everytime I stuck my hand in the tank I got shocked. I used a voltmeter also and it dropped with every device that was unplugged, which is scary. Turned out the highest voltage leak was the heater, but the Koralias leaked quite a bit as well.

As far as the fish, I've argued that with an electrician. I say stray voltage is bad, IMO. He says the fish aren't grounded so it wont harm them. I argued that I wasn't grounded either, but I was barefoot on a humid day on carpet over a concrete foundation so apparently I was.

I'll always use a grounding probe.

 

[MHG]

why would you rather not use a grounding probe?

while I know quite a bit about electricity and the flow of electrons, there are enough people on RC saying a probe can kill you it is creating doubt.... While I disagree with them as I know electricity always seeks a ground and that if there is one provided it is not going to choose my ungrounded body over a ground probe. I still second guess it....

This is funny because I had the same issue a few years ago with my 40g breeder SPS tank. Everytime I stuck my hand in the tank I got shocked. I used a voltmeter also and it dropped with every device that was unplugged, which is scary. Turned out the highest voltage leak was the heater, but the Koralias leaked quite a bit as well.

As far as the fish, I've argued that with an electrician. I say stray voltage is bad, IMO. He says the fish aren't grounded so it wont harm them. I argued that I wasn't grounded either, but I was barefoot on a humid day on carpet over a concrete foundation so apparently I was.

I'll always use a grounding probe.

Well that electrician should look at the damage caused to boats in a marina by stray voltage....one boat with a bad ground will rot the anodes off the boat next to it to nothing. Even if that boat is not connected to shore power (not grounded)...

 

[mc-cro]

I have never heard that a grounding probe can kill you? if anything its the opposite, as you stated. I have had a lot of tank set ups, and a lot of electrical failures over the years. I would never even consider setting up a tank with out a GFI and a grounding probe. When you have a lot of pumps and other electrical devices in salt water, its not uncommon to have stray voltage. although to me 53v is not stray voltage, thats a problem.

(just because people here on RC parrot the same statement doesn't make it a fact, that is one of my really big rants about this place, so much bad information is thrown around so often people just assume they are facts)

 

[MHG]

Sorry my dislexia... 35 volts... Not 53.... You can find a ton of posts on RC where people are claiming a ground probe can kill you....

Anyway, my heater seems to be the biggest culprit, but all of my components seem to be adding to the problem....

 

[jcolley]

Sorry my dislexia... 35 volts... Not 53.... You can find a ton of posts on RC where people are claiming a ground probe can kill you....

I would challenge any of them to prove that using equations. Or a Kirkhov's Voltage or Current loop even. Nodal analysis? Anyone?

The purpose of a ground probe is to provide a safe return path for stray voltage. That way you don't become the return path.

Current prefers the path of least resistance; that's why it's called resistance. Which do you think has more restance, you or a wire? The human body has around 300 Ohms resistance under worst-case conditions. The wire has less than 1 Ohm. Both of those are assumed dry, so lower both when in contact with saltwater.

If voltage is present in the water, a hazard is present. The ground probe provides a safer path for the hazard to travel than you.

If the Underwriters Laboratories (UL) felt ground leads provided a hazard instead of mitigating them, do you think they would mandate their inclusion in certain categories of sumbersible electrical equipment?

 

[reefincredible]

I am a contractor and do HVAC work, and I don't understand how a grounding probe is bad. Electricity inherently wants to find ground. It, like water, will follow the path of least resistance. You can touch live wires if you are properly insulated. I've worked with Dominion VA power during construction and the linesman will sometimes stand on insulating mats when moving wires around in boxes.

Electricity scares the hell out of me but a grounding probe gives the current the path it's looking for.

 

[MHG]

It's a myth that is perpetuated buy guys who don't understand electron flow.... Just like people who say "you don't get shocked in a car during a lightening storm because the car has rubber tires and is grounded".......nooooo it is isolated......not grounded....

 

[MHG]

Just like people wo say don't drink RO/DI water... Why the hell not.....spectra pure makes millions on RO/DI systems for drinking....

 

[Kaosinnyc1]

grounding probe is a PROVEN means to eliminate stray voltage

 

[garydan]

I'd like to also point out that the entire concept of "stray voltage" is a myth...

When most people are talking "stray voltage" they're talking what their volt meter is telling them when they measure voltage of the tank relative to ground. Well, guess what, our volt meters are incapable of measuring voltage of a salt water tank, unless you have an electrical short.

If you have a short, the volt meter gives you a real number. If you do not have a short, then the number your volt meter is giving you us worse than useless... That's why it changes for every single item you plug in and unplug.

If you're interested, here's an article on why volt meters can't be used to measure a floating wire, which is what your tank is when you don't have a short: http://www.nema.org/stds/eng-bulletins/upload/Bulletin-88.pdf

So, ignore voltage, move the dial on your meter to measure current, and measure the current to ground. If it's 0, you're good. If it's > 0, then you have an electrical short.

 

[reefincredible]

I'd like to also point out that the entire concept of "stray voltage" is a myth...

When most people are talking "stray voltage" they're talking what their volt meter is telling them when they measure voltage of the tank relative to ground. Well, guess what, our volt meters are incapable of measuring voltage of a salt water tank, unless you have an electrical short.

If you have a short, the volt meter gives you a real number. If you do not have a short, then the number your volt meter is giving you us worse than useless... That's why it changes for every single item you plug in and unplug.

If you're interested, here's an article on why volt meters can't be used to measure a floating wire, which is what your tank is when you don't have a short: http://www.nema.org/stds/eng-bulletins/upload/Bulletin-88.pdf

That's pretty cool info

So, ignore voltage, move the dial on your meter to measure current, and measure the current to ground. If it's 0, you're good. If it's > 0, then you have an electrical short.

 

[dkeller_nc]

So, ignore voltage, move the dial on your meter to measure current, and measure the current to ground. If it's 0, you're good. If it's > 0, then you have an electrical short.

And, I'll add that if you've installed a grounding probe in your system, you may or may not be able to measure a current with your meter, either - it depends greatly on the model of the meter.

It is true that a grounding probe can provide a low-resistance path to ground in a reef tank, and that is exactly the problem. A grounding probe takes a voltage potential and turns it into a current actual.

 

[_shorty_]

And, I'll add that if you've installed a grounding probe in your system, you may or may not be able to measure a current with your meter, either - it depends greatly on the model of the meter.

It is true that a grounding probe can provide a low-resistance path to ground in a reef tank, and that is exactly the problem. A grounding probe takes a voltage potential and turns it into a current actual.

I was also suspecting you might need to remove the grounding probe before trying to measure current from the tank...

You are correct, but it sounds like you're saying a grounding probe is bad? If there's a short in the tank, there's a problem... period. In my logic, the grounding rod would not cause the problem, only help protect you from it. If you don't have a grounding probe, YOU become the vessel of turning that voltage potential into the current actual.

If i'm thinking correctly, I could see it as maybe a problem relative to safety of the inhabitants of the tank, but not so much for us.

I'd like to also point out that the entire concept of "stray voltage" is a myth...

When most people are talking "stray voltage" they're talking what their volt meter is telling them when they measure voltage of the tank relative to ground. Well, guess what, our volt meters are incapable of measuring voltage of a salt water tank, unless you have an electrical short.

If you have a short, the volt meter gives you a real number. If you do not have a short, then the number your volt meter is giving you us worse than useless... That's why it changes for every single item you plug in and unplug.

If you're interested, here's an article on why volt meters can't be used to measure a floating wire, which is what your tank is when you don't have a short: http://www.nema.org/stds/eng-bulletins/upload/Bulletin-88.pdf

So, ignore voltage, move the dial on your meter to measure current, and measure the current to ground. If it's 0, you're good. If it's > 0, then you have an electrical short.

Good stuff. thanks for posting.

 

[garydan]

Yes, you need isolate the tank to measure for current flow. If you have a path to ground and are measuring for current on another path to ground, you have what's called a "current divider", what you measure will depend on the resistances and amount of current flow between the paths.

To isolate your tank, you need to remove all paths to ground. If you have a titanium heater, it's also a ground probe, a chiller is too. I haven't personally measured, however what LobsterOfJustice encountered in this thread makes perfect sense. The manufacturers of the titanium heaters and chiller manufacturers are going to ground the frames of their product, to protect their own liability in the event of failure. Because the frames of their products are also in contact with the water, they are effectively ground probes whether you want one or not. So, if you have a titanium heater, or a chiller, you'll want to unplug them before measuring for a short.

The good side is, titanium heaters and chillers are unlikely to cause a short or voltage in the tank. Think of it this way, if either of these items fail there is a direct metal to metal path to ground inside the product. That path will be the lowest resistance path available.

Devils advocate for a second. If you have a ground probe, then yes you are providing a path to ground. If the current flowing to that ground path is less than the 15 or 20 amps necessary to blow your circuit breaker then it is dangerous. Why? Because it's going to generate heat somewhere, so there's a potential for a fire.

Whether you have a ground probe or not, use a GFI. It detects the current flow to ground and will cut power (technically it detects an imbalance between the hot and common wires). If you have a ground probe, then the GFI will pop when the short occurs. If you do not, then it'll pop when you put your hand in. If you have a short, there will be a current flow to ground eventually.

 

[JiveWalker]

I'm assuming all or your equipment is in the sump. You may be reading induced voltage from the wires to and the magnets in the equipment. Saltwater is conductive and the sump water is in close proximity to the wires/equipment compared to the display. Just a theory. Google induced voltage.

 

[jtrasap]

The outer titanium portion of a titanium heater is isolated from the rest of the heater. The portion that touches water is not grounded.

 

[garydan]

The outer titanium portion of a titanium heater is isolated from the rest of the heater. The portion that touches water is not grounded.

From an EE perspective, if I were building one I'd probably ground the whole frame, including the outer sleeve. I wouldn't be surprised if it varies from manufacturer to manufacturer though.

If someone is wondering how to find out whether or not it is (I don't have one to do this test with). On most volt meters they have a continuity setting, when it's in this mode if you touch the probes on the meter together it'll beep. Unplug the heater, and touch one end to the heater body and the other to the round ground pin on the plug. If it beeps, then your heater will act as a ground probe.

 

[jtrasap]

I agree there probably are some that are manufactured this way but I know the ones I've had weren't. I have a couple titanium heaters in a tote that will give you a nice jolt when in the water if you become the ground. I think the main concern with them is the seals giving out and water making it inside to the heating element.