stray voltage levels in saltwater aquarium

[scottayy]

I'll have a look at the breaker box and see if i see copper wires going anywhere.

Also just tested my meter on my laptop charger (says output 18.5V) and my meter reads about 48.. so yeah think it's the meter.

 

[scottayy]

Well that meter was good. I bought another meter, this one a little bit more expensive and auto ranging.

Reads 16.02 volts.

 

[meegosh]

What are you landing your return on? You need to land it on a good ground that is tied to earth ground. From the picture it looks like a screw sitting on the floor.

 

[scottayy]

It is. But it reads the same if I stick it on my thumb or in the grounding prong of an outlet.

 

[scottayy]

Actually if I put it in the grounding hole it reads all kinds of different numbers depending on how i angle the lead.

 

[Gregcoyote]

Try the screw that holds the cover plate on, it is grounded to the outlet and might be easier to get a good contact. Sounds like there might be a bit of voltage, but almost no current.

 

[Gregcoyote]

I finally brought my Extech meter home. Put it on AC volts, autoranging. Showed 0.07 volts unhooked to anything. Grounded the black probe to the wall outlet ground and touched the red lead to the water at several different places, sump, skimmer, frag tanks, etc. Got a constant reading of 34 volts AC. That surprises me a bit. No tingling from touching the water on a concrete floor with wet bare feet, so there must be almost zero current. I am wondering now if a ground probe wouldn't be a good idea to bleed off this small charge I am seeing.

 

[Gregcoyote]

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:


http://angel-strike.com/aquarium/GroundingProbes.html

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.

 

[scottayy]

Oh, wow. So you read 34VAC.

What you're saying is this is voltage with low current potential? I definitely do not feel any tingling anymore after taking out the one heater that was reading almost 10V by itself.

What are you going to do about your 34v?

 

[scottayy]

I think I read the same post as you just now. This guy sounds like he knows what he's talking about.

This guy says that stray voltage is expected from magnetic pumps, but a failing piece of equipment would leak stray current, measured in amps.

I'm about to check for amps and if I have no reading I'm going to get a ground probe for my 20V induced stray voltage.

 

[Gregcoyote]

If there is any significant current at all, the GFCI will pop. I think the voltages I am reading are almost like low voltage static electricity. No current can be measured on my meter at all and this meter reads down really low. It's not unusual to have different things in the house showing a difference in potential it looks like. If no current, or a minuscule amount is there, it seems to me that a probe might not be needed. But I want to study it more. Real interesting topic.

 

[scottayy]

Indeed, it is. And you and others input in this thread is a bunch of golden nuggest of electrical knowledge.. which after much studying myself seems like a widely misunderstood topic in reef keeping in general.

I set my meter on AC mA and I read 0.02. That's milliamps right? So 0.02 is nothing to worry about?

 

[Gregcoyote]

That is very little current and I think it is safe. As was mentioned by the electrician, it only takes milliamperes to kill you if it conducts across your chest. But that is much more than what you were reading.

 

[Gregcoyote]

A good test it it run a temporary circuit (use your meter lead unplugged) from the water to the ground. If that trips the GFCI, I would be really worried. If not, you are probably okay from a safety aspect.

 

[scottayy]

Just did that, no problems!

Going to get a ground probe and call it a wrap. Periodically check for ac current as part of my maitenance routine so I can detect failed equipment.

I think a thorough write-up on this topic somewhere would be much appreciated by many.

 

[scottayy]

My 4g tests 0.00 AC mA.

I think I'm going to do the unplug test on my equipment in the 55 to see what's giving out the 0.02 and keep an eye on it.

 

[scottayy]

Okay just tested the 55 again to unplug stuff. I got a 0.03 reading this time. Unplugging the skimmer pump drops me to 0.01 and unplugging the reactor pump in addition gives me 0.00. So these two are the culprits!

At what levels would they need replacing?

 

[Gregcoyote]

I don't know. Certainly not now, these are very low numbers.

 

[scottayy]

Installed my grounding probe that I received in the mail today. I now read .217 VAC stray voltage, and 0.00 AC mA.

Hope this helps things.

 

[Gregcoyote]

You'll probably start hearing short wave broadcasts from the tank now...