Stray current and stray voltage (wiki)

[mike31154]

Originally Posted by syncro

Stray current refers to unintentional electricity flowing through the aquarium water. Malfunctioning and deteriorating equipment are the usual sources and can represent a danger to the aquarist and livestock. Stray current is closely related to stray voltage - a voltage potential between the aquarium water and ground.

== Stray current vs stray voltage ==
In typical household circuits, current is far more dangerous than voltage.

Stray voltage is an electrical potential difference between the water and earth ground. A voltage difference does not indicate any electricity is actually flowing through the water. It indicates the possibility of current to flow if a suitably low resistance path between the water and ground is introduced. So stray voltage on its own is not directly harmful. It is common to have some stray voltage as pumps can induce a voltage potential with their rotating magnets.

Stray current refers to flowing electricity. It is typically harmful to humans at and above 6mA [1]. A properly functioning tank should not exhibit any measurable stray current (< 1mA). Stray current may or may not trip a GFCI receptacle depending on the path it takes.

== Recommendations ==
An aquarium should have no detectable stray current. Eliminate all sources of stray current. Consider installing a ground probe (in conjunction with a GFCI outlet) to identify stray current sooner. Stray voltage can be safely ignored provided there is no stray current.

Good info, but not sure I'm comfortable with the "Recommendations" wording, particularly the last sentence "voltage can be safely ignored provided there is no stray current." This could be misinterpreted & hazardous. To "Eliminate all sources of stray current." you would have to pull every piece of electrical gear out of & away from your tank/sump.

As explained earlier in the article, any voltage present has the potential to cause current flow "if a suitably low resistance path between the water and ground is introduced". By the simple act of using a multimeter connected from the water to ground, if there is any voltage potential present in the water, you are causing current to flow through the test leads & multimeter to ground where formerly no current was flowing. This current could flow through you if the voltage potential in the tank is high enough & you are unfortunate to become the low resistance path to ground or neutral for that matter. In rare cases, under the right circumstances (Murphy's Law), when there are multiple electrical cords/components in the water (which is the case with most of our systems), there is the possibility of current flowing from Line to Neutral or Ground from one cord to another. This current will flow from one component to the other, through the water & may not necessarily be measurable with a meter to ground. It will most probably affect your livestock though. Current measurement is tricky & can lead you down the garden path.

It's therefore a good idea to keep electrical cords out of the water so far as this is possible and of course as the article says, ensure the electrical cords & components physically in the water are in good shape by doing periodic inspections. GFCI devices offer protection from most scenarios involving shock hazard to you & should be used. Don't rely on a heater manufacturer's claim that their product is fully submersible, cord & all. I always keep the control dial & cord on heaters above the water line. You can further minimize the risk by using low voltage DC pumps & lighting. EcoTech, Tunze & even Koralia (I think) offer low voltage pumps. If you haven't already, consider switching to LED lighting since it uses lower DC voltages than the traditional MH & flourescent AC technology. Try to keep the high voltage AC stuff as far way from the water as practical, have drip loops & consider using moisture resistant electrical receptacles such as those used outdoors.

[NorthernCoral]

I used to get a small shock sometimes when touching the water in my old tank. Especially with cuts, just thought it had something to do with the salinity. Thanks for the info!

[syncro]

Thanks Mike. Great advice. I'll incorporate it. Also feel free to edit the page. I'd be nice if I could update the original post.

[mike31154]

Originally Posted by syncro

Thanks Mike. Great advice. I'll incorporate it. Also feel free to edit the page. I'd be nice if I could update the original post.

Edit the page? You mean the wiki? To be honest I tried editing a wiki page a few years back & couldn't get it to work. Besides, I'm only a humble retired technician, not an engineer so don't feel all that qualified to be a 'pedia contributer. Electricity is a funny animal sometimes & there are many failure scenarios depending on what you have in & around the water, AC, DC, how it's all hooked up, interconnected & the condition the equipment is in. Suffice it to say that with GFCI protection around water (which is pretty much electrical code everywhere these days), you will minimize the risk to your personal safety & that of your family, guests, etc.

I will add a bit more info to the thread here, with regard to grounding probes. I personally don't use one since I'm not convinced it will significantly add to the safety factor in my situation. I could be wrong, again, Murphy's Law. Here are several links that I like to refer to from time to time on the subject. While somewhat dated, it's excellent info on the subject provided by a research engineer. Draw your own conclusions with regard to grounding probe, but in any case, use GFCI protection.

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

http://angel-strike.com/aquarium/GFI...alDetails.html

[Magma]

few things that worry me so lets start at the top and work down

Stray current refers to flowing electricity. It is typically harmful to humans at and above 6mA [1]. A properly functioning tank should not exhibit any measurable stray current (< 1mA). Stray current may or may not trip a GFCI receptacle depending on the path it takes.

This isn't right at all, current kills, end of story even in the mA range you can get a poke which will set your heart off rhythm and die later. I pulled this from a few of the electrical modules I still have:

Currents of less than 0.02 amp may produce sensations ranging from tingling to sharp pain. A more serious effect occurs if the current causes muscles to contract. A person touching a live wire with their outstretched hand may literally not be able to let go of the wire due to the current's effect on the muscles. Experienced electricians who must sometimes deal with wires which may be live always use the backs of their hands to move the wires; if a current were present, the contacting muscles would cause the hand to pull away from the wire. Currents from 0.03 to 0.07 amp will begin to impair the ability of the person to breathe.

The most dangerous range of currents is from 0.1 to about 0.2 amp. Currents in this range can cause death by initiating fibrillation (uncontrollable twitching) of the heart, which stops the regular flow of blood to the rest of the body. Currents much larger than 0.1 amp do NOT result in fibrillation and instead stop the heart completely. If the duration of the current is short, the heart will usually start to beat by itself after the current is removed.

So in other words if your not sure don't touch, it doesn't take much to end up in a serious situation which could lead to more problems or death.

So next up....another problem

Ensure all equipment is connected to a GFCI outlet. While this is not required for to measure current it will significantly reduce the risk of harm and/or death if a mistake is made.

If your not an Electrician this is a problem because as every sparkie knows you need to use a clamp on amp meter to measure the current this involves taking the plug out of the box and clamping onto the hot conductor then turing everything back on to measure the current, or a really expensive meter which you can hook up in series with your setup. Just dont do it because unless you know what your doing you will get hurt.

Finally

== Recommendations ==
An aquarium should have no detectable stray current. Eliminate all sources of stray current. Consider installing a ground probe (in conjunction with a GFCI outlet) to identify stray current sooner. Stray voltage can be safely ignored provided there is no stray current.

Stray voltage can be just as bad. As a human your body as a ridiculous high ohmic value which allows us to touch wire which has potential voltage on it but again unless you understand how you are able to touch the wire don't do it. Also have to be aware that if you skin is wet your resistance drops significantly and if you have a cut your ohmic value is now no more than a light bulb.

Dont get me wrong I have been poke a few times from different things anything from 120v up to 347v its not fun. But you have to be able to say I know what im doing and I bet my life on it. Also really shouldn't be using a ground probe to solve the problem IMO, if you know you have a voltage leak then get on it and find it and fix it because if you have a leak how do you know in a day, week or month that something isn't going to go wrong and you end up with a blown pump or busted heater? Find the problem by turning on things one at a time once that's done remove the faulty equipment and go from there.

Edit: forgot to mention you should add in there "What ever the guy at home depot tells you, dont listen to him hes not an electrician, hes customer service."

[syncro]

Thanks for all the feedback Mike and Magma. I've tried to incorporate most of it to the best of my ability.

Originally Posted by mike31154

Edit the page? You mean the wiki? ... I'm only a humble retired technician, not an engineer so don't feel all that qualified to be a 'pedia contributer.

I think anyone with good intentions is qualified to contribute in the same way we are contributing to this forum. The real difference is a wiki page can be reviewed and improved. At the very least, I hope spending 5 min reading that article is time better spent than 5 min searching forums. Long term, I hope others will make small (and large) improvements.

Originally Posted by Magma

Just dont do it because unless you know what your doing you will get hurt.

Can you suggest the proper way to do this? I understand your point and certainly don't want anyone to get hurt or worse. I also know people will still do it for the same reason people change their own brake pads despite the danger of driving several tons of metal down the road with failing brakes. I'd rather have the information so if someone decides to take the risk they can at least minimize the risk.

[syncro]

Link to the updated article:
http://www.theaquariumwiki.com/Stray_current

[Magma]

Originally Posted by syncro

Can you suggest the proper way to do this? I understand your point and certainly don't want anyone to get hurt or worse. I also know people will still do it for the same reason people change their own brake pads despite the danger of driving several tons of metal down the road with failing brakes. I'd rather have the information so if someone decides to take the risk they can at least minimize the risk.

IMO don't count a ground probe as a solution to the problem of stray voltage. It works yes but all its doing is allow the original problem to get worse.

I see you mentioned drip looks in your article which is great to help with water seeping into the plugs, also should add to inspect your equipment on a regular basis, check the cords, check the ends just make sure it still looks ok. How many of us have thrown a nasty crab into the sump at some point? whats to say he didnt get angry and try to crush your cords for your skimmer or return pump? Visual checks on regular basis.

If you do find some stray voltage unplug everything and test the water with each component one at a time to see what is causing it. If you cant find it after that then go to the other options/steps no point in trying the hard fix when you might be able to do something faster and more simple.

[syncro]

Originally Posted by Magma

IMO don't count a ground probe as a solution to the problem of stray voltage. It works yes but all its doing is allow the original problem to get worse.

I agree. Don't use it to solve the problem. What about using it to test for the problem? It won't catch all situations but it is probably safer than using a multimeter.