Eletrical current leak in fish tank!

[jsoong]

OK, I was doing my usual PWC & noticed a shock when I touched both my fluorescent light housing (which is grounded) and the water at the same time. I concluded that there must be a short into the aquarium. I took out my voltmeter & measured 100V between the tank water & ground .... eek!

Luckily, the current is not high, only about 10 microamps, not enough to trip the GFI curcuit that eveything is plugged in.

I eventually found a busted heater (it was hidden in the sump, so I can't see it). However, after removing the broken heater, I still register 10V between water & ground (although the current is undetectable & no more shocking encounter with the light).

This leakage current is from my almost new sumersible pump (Hydor 40II - 700gph). I don't think the small leak is dangerous, but is this normal? or is my pump going too?

Well, I have to go shop for a new heater .....

 

[Alshain]

Its possible the damaged heater damaged the pump. Incredibly likely in fact. I personally wouldn't trust it.

 

[frostby]

Believe it or not, fluorescent lights are a conductor, the air below, an insulator, and the aquarium water is another conductor. You have a natural capacitor. Just this theory will allow you to have measurable voltage between the two. You can't avoid this stuff with fluorescent lighting and AC impeller type devices.

I'm not saying you are "safe" by any means, but it would be wise to unplug your sump and remeasure.

 

[malkore]

this is also why they sell grounding probes for aquariums.

http://www.drsfostersmith.com/Produ...ll&Ntx=mode+matchallpartial&Np=1&N=2004&Nty=1

 

[sherry]

malk do those probes make tanks safer for those of us that "swim" when they are planting and pruning?

 

[hashbaz]

Personally, I would think that since the pump is (or at least should be) electrically insulated from the water - that the faulty heater would have no effect on the pump.

Like Frostby said, the 10V may be natural. Do you have any items that run on 10V? Pumps and heaters run on 110V and would give you 110V in your water and not just 10V (I would think).

I wanted to give you a more informed opinion, but my volt meter is at the new house and I am not. Thanks a lot. Now I am dying of curiosity about my tank's voltage.

PS There was a discussion here a while back about electrical safety and aquariums. Thanks for offering yourself as the guinea pig.

 

[jsoong]

I am not sure if grounding the tank water would make it safer for the fish ... With the broken heater, I had a live wire exposed to water, but there was no current flow without a ground path. It was only when I touched both water & ground that I completed the curcuit & got the little shock. If there was a grounding probe, the broken heater would send a current to the probe & probably fry any fish between the 2.

The grounding probe would have protected me ... however .... the majority of the current would flow through the probe & not me .... and since I have a GFI, would trip that & shut off the power as soon as the heater broke. I would definitely have one of those for salt water. FW being rather less conductive could not carry much current. (OTOH, if I had touch the exposed live wire on the heater instead of just the water I might have thought otherwise... )

That 10V in the tank is definitely from the pump. If I unplug it, I got zero, 10 when plugged in. I can't see how a leak from 110V wires can give you a 10V potential difference either .... unless the rotating magnet is generating some low voltage DC or something?

 

[frostby]

Jsoong, you are on the right path, sortof... The 10 volts is AC (not activated carbon ha ha ha) coupled with the water, acting sortof like a step down transformer - found on many portable electronics. With a coupling like this it is very normal to have a percentage of the original voltage. There's a coil in your impeller, which creates the magnetic field causing the impeller magnets to spin.

A ground probe will remove that voltage and any current, but 10 volts will NOT cause your fish any harm, like you said, there's nowhere for the current to go. You can sit on a 100 volt battery terminal and not feel a thing- until you touch a return.

The only way you are going to see 110v is if you have an exposed wire/ or broken component in contact with the water.

 

[jsoong]

I have come to the conclusion that the 10V is likely EM noise generated by the coil or impeller. <and yes, it is AC - reading on DC is zero.>

I diconnected the pump return from the tank (so the sump is now electrically isolated from the main tank), but I can still measure the 10V from the tank as long as the pump is running. The fact that I cannot measure any current flow points to noise as well.

So I guess I won't lose any sleep over that reading .... but maybe I should now check for 110V before I stick my hand into the tank just in case I have another broken heater or wire!