Stray current; is this much OK?

[erayk1]

So I have a few tanks at my place and I noticed today that my tang in my 220 was swimming around really quickly, doing this backwards nascar circuit around my rockwork. I measured the current in the tank and found I had 33 Volts going through it. I found the culprit (stealth heater) and took it out. Now I'm down to 1.3 Volts, is that OK? It made me think about my other tanks, so I tested them all. On another system, I had 114 Volts going through the tanks, and it's my best looking tank. Non of the inhabitants showed any signs of stress, but if I brushed my lights while in the tank, I got nailed (OUCH!). Again it was a #*$% stealth heater.:hammer: I unplugged that one and now I'm down to 5.6 Volts in that system, is that OK? I checked everything else and a few pumps are putting out like 1 volt each so I don't really want to replace them all if I don't have to. Any suggestions would be appreciated!!!

 

[kingfisher62]

I do not know about the voltage but if those were the stealth pro heaters there has been a recall. Return them for credit.

 

[erayk1]

They were actually the previous version of the stealth, still the same I will be returning them for credit because of their lifetime warranty. I personally will never buy another one of those things, I love the idea of them, just not worth all of the hassle everyone has with them...

 

[wickedfish]

How did you measure the stray electricity? I want to check my tank I have a lot of random things, you never know.

Thank you,

E,

 

[erayk1]

I used a multimeter, you can get analog or digital ones fairly cheap these days. I got a digital one for the precision for $20. It was definitely a "shocker" to see what I had going on in my tanks... Anyone else with experience with these matters?

 

[jeff@zina.com]

Now I'm down to 1.3 Volts, is that OK?

Stick your tongue on a AA battery to find out.

It'll be fine.

Jeff

 

[erayk1]

I know its around the same voltage as a battery, but is the other tank being around 6 volts to much?

 

[Floyd R Turbo]

It's not the volts that kill you, it's the amps. 24 milliamps will kill you.

 

[ambergris caye]

I took my dirty old stealth heaters to petsmart (no receipt, box, or even suction cups) and they gave me store credit towards a comparable heater. I spent $4.72 and received two new submersible fluvals, one 200w and one 300w for two old stealths (200W and 250W).

 

[erayk1]

I also took mine back to my LFS and got credit for replacements. Those fluval heaters seem promising so far.

 

[garydan]

just wondering, when you measure it, how are you measuring it?

relative to house ground? If you do that, then wouldn't you always get a voltage of 0 because your ground probe connects the salt water to your house ground? Saltwater is conductive so you're basically measuring voltage across a wire, which is always 0.

I guess you could disconnect your ground probe and measure from saltwater to ground, but then the house ground is tied into your neutral wire for the house, so theoretically you could see some (very small) voltage on the ground side that's not in the tank, but on your ground wire itself, depending on the quality of the grounding the house has. Voltage is always measured relative to something, so what you're measuring relative to is important.

I've seen some people measure voltage to "air" with the digital meters. It's really quite comical, because what they're seeing is electrical noise from treating the wire as an antenna, or tiny voltages created from nearby magnetic fields. The digital meters are sometimes too sensitive, giving what
you think is a reading but is really just some electrical noise.

I would think the best way to deal with stray voltage is to put a ground probe in and use a GFI breaker. If there is any power leaking through the water it'll go to ground from the pump/heater to the ground probe, causing the GFI to trip. GFI detects when power goes out of the hot wire and doesn't return through the common, and isn't that what stray voltage really is?

Just looking at this from the electrical engineering perspective (i have a degree in computer engineering, which is just a handful of classes away from an EE degree).

If you're worried about power leaking into the tank, make sure you have a GFI and ground probe.

 

[Floyd R Turbo]

If they already have a grounding probe in the tank, then of course they would see zero volts. You would not necessarily get zero volts to house ground if you didn't have a grounding probe, why else would you measure?

 

[lhope4000]

A GFI whether its a breaker or receptacle trips when there is a current imbalance between the hot and neutral, doesn't sense ground.

 

[Floyd R Turbo]

True, just a fault. I think that was posted here as an additional comment.

EDIT: you can have a stray voltage that is not a fault, so you need both protection systems in place

 

[garydan]

Ground and neutral are tied together in your box (go take a look)

I'm just saying that i believe much of what people are reading is "phantom voltage" due to the nature of the meters we use.

http://www.nema.org/stds/eng-bulletins/upload/Bulletin-88.pdf

If the tank isn't grounded or connected into the electrical system, then you're probably just measuring noise. Voltage is relative to something, and what you're measuring it relative to makes a difference. Take a look, there's instances where some people actually have a small voltage on their ground wire in the house, google it. So, are people making sure their "ground" is actually at 0? Even if it is at 0, then you're still going to be measuring "phantom voltage" due to the high impedence in the meter because the tank is effectively an open wire. There's no real power flowing, it's static electricity or other noise.

I think the only way to see if there is any real power leaking into the tank from equipment would be to put the meter into "amp" mode, not voltage mode. Connect the meter to ground and the tank to the other side of the meter. The meter then becomes part of the tank grounding system, giving you a stable base point to measure relative to. In this mode there is no high impedence, the meter is just a wire. If there is power leaking from any equipment, then the meter will measure the amps actually flowing to ground, not "phantom voltage" due to high impedences. I haven't tried this yet, but theoretically it makes more sense than trying to measure the voltage of a tank that's not grounded and is really just an open wire.

 

[garydan]

Ok, so put my money where my mouth is.

I have two meters, one is an expensive tektronix meter, the other is a cheap cen-tek meter from harbor freight. The voltage readings on them ranged from 100 (cen-tek) to 400 (tektronix) dc millivolts, both practically 0 AC volts but not actually 0, bouncing around .1. They're inconsistent with eachother and it's not a solid reading on either.

Now, i put the cen-tek meter in amp mode (the tektronix doesn't do amps). Low and behold, i'm seeing a solid 17 microamps consistent from the tank to ground. I look around, unplug a few things and it doesn't make a difference. Then i unplug the protien skimmer and bam, it drops right to solid 0. Plug and unplug in the skimmer a few times, solid reading every time. I wasn't aware of it, but clearly my skimmer pump is leaking some power.

With the protein skimmer unplugged i switched back to checking the voltages again, still reading 100-300 millivolts on the cen-tek, now i'm reading 70 AC volts on the tektronix meter! It was clearly noise though because it has an analog bar representing the reading at the bottom that looked like it was dancing to rock music.

So, i would definitly say to measure amps, not voltage if you're looking for a current leak. Voltage of an open wire just doesn't make sense and will depend on your meter.

 

[Floyd R Turbo]

Excellent explanation! You must be an engineer or an electrician. I am an EE and you just put me to shame.

 

[steveb_52]

Check for a bad or loose ground somewhere in the circuit. I had a stray current issue that turned out to be a loose ground wire on an outlet, rather than a bad pump or heater.

 

[erayk1]

I'll have to check my amps, seems like that is the consensus between everyone.

 

[alton]

Stray current and stray voltage are two different animals. Stray voltage is unusible power which comes from open lamps over your tank and internal pumps. Stray current is power leaking into your tank from a bad heater or pump. The reason why you have to have a grounding probe is one it grounds out all the stray voltage plus a GFCI will only trip with 4 to 6 MA if there is an imbalance of the grounded/neutral and ungrounded circuit. An aquarium being made out of glass is insulated so the only time it would create a path for the unbalanced current to flow is when you stick your hand in the tank. 1ma and you can feel a tingle, 3ma is a zap. I tested this theory with a bad pump that was leaking 60 volts into a bucket plus a good amount of current and it would not trip 3 different brands of GFCI receptacles or a GE GFCI breaker, installed a grounding probe and they all tripped. Before you install a Grounding probe make sure you have a good service ground, if not your service will use your tank as a ground and you will get shocked this happened to a friend.