Quote:
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.
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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.