Another Stray Voltage thread

[Reefer1978]

Hey folks. I am with stray voltage in one of my tanks.

How I tested: Multimeter on AC, one probe in outlet - large slow, second probe in the tank. Result - 40v.

How I troubleshooted:

• Unplugged devices one by one - voltage reading goes down a little bit, to 36v, but not fully down to 0.
• Unplugged all devices that are in the water, the only thing that's still plugged into the power strip is the light - no change
• Turn off the strip - voltage reading is 0

Any thoughts how else to troubleshoot this? Is is the devices / power bricks being right next to the sump?

 

[Gumbies R Us]

@Troylee

 

[KrisReef]

I’m wondering how voltage is getting into the tank if the light and power strip are not in the water? I would guess that you are measuring the voltage potential difference between the light and ground and not current traveling through the tank?

 

[Reefer1978]

I’m wondering how voltage is getting into the tank if the light and power strip are not in the water? I would guess that you are measuring the voltage potential difference between the light and ground and not current traveling through the tank?

I could see that, but at 40v ???

 

[BeanAnimal]

Why are you measuring at all? Is there a problem?

Or has the conventional wisdom of the hobby given you the wrong idea that you should dunk a meter in the water and measure, because that is what you should do?

"Stray voltage" is not what you think it is and unless you are reading somewhere 90 VAC or above, then you are likely reading induced voltage, not fault voltage. Two very different things and with no current reference a "stray voltage" number tells you very little.

Is your tank protected by a GFCI? It should be. If there is actual fault current, then GFCI will trip.

 

[Reefer1978]

Why are you measuring at all? Is there a problem?

"Stray voltage" is not what you think it is and unless you are reading somewhere 90 VAC or above, then you reading induced voltage, not fault voltage. Two very different things and with no current reference a "stray voltage" the number is meaningless.

Is your tank protected by a GFCI? It should be.

Tank is protected by GFCI!!!

I felt a little shock, thus I started checking. I changed some equipment that I suspect is at fault for the stray, but continue to see readings.

 

[Euphylliaphyle]

Any thoughts how else to troubleshoot this?

Run an extension cord from another circuit in another room/area and plug the power strip into that, and see if you get the same results with/without other devices plugged into the strip.
Could salt creep in the area be involved?

 

[Reefer1978]

Run an extension cord from another circuit in another room/area and plug the power strip into that, and see if you get the same results with/without other devices plugged into the strip.
Could salt creep in the area be involved?

That's exactly what I did. And no, it's a newer tank, no salt creep.

 

[BeanAnimal]

Tank is protected by GFCI!!!

I felt a little shock, thus I started checking. I changed some equipment that I suspect is at fault for the stray, but continue to see readings.

If all of the equipment is on a GFCI and there was a fault, the GFCI would likely have tripped when you felt the tingle. There are exceptions, but they would be rare. Say a bare HOT exposed on the water and an ungrounded fixture with a metal enclosure, allowing you to bridge between HOT and NEUTRAL and you not being grounded...

The point is that the GFCI is your safety assurance and your "voltage" detector. If it trips, you have issues to look into.

The induced voltage can still cause a tingle, but it has no meaningful current behind it and will not trip the GFCI because it is not a fault.

Anything that causes a magnetic field (pumps impellers, wires, heating elements) induces voltage. This all adds up to what you measure as "stray" voltage.

 

[redfishbluefish]

Agree with Bean, induced voltage. That "tingle" you felt in your hand was a paper cut or hang nail or little boo-boo. Try sticking your other hand in the tank and see if you feel that tingle.

 

[Reefer1978]

I should add the shock was hard enough for me to yank my hand out a little more than a tinkle

 

[BeanAnimal]

Add a ground probe, even of only temporarily to determine if there is a fualt.

It will trip the GFCI if there is a fault.

It will drain induced voltage read on a meter between the water and ground. No more tingle.

 

[Reefer1978]

Add a ground probe, even of only temporarily to determine if there is a fualt.

It will trip the GFCI if there is a fault.

It will drain induced voltage read on a meter between the water and ground. No more tingle.

I will try thank you!!

 

[Freenow54]

Add a ground probe, even of only temporarily to determine if there is a fualt.

It will trip the GFCI if there is a fault.

It will drain induced voltage read on a meter between the water and ground. No more tingle.

I am sorry but I understand that if a cut cord is on wet grass then there is a path to ground , lowering the returning amperage to cause a trip. However the water in the tank is not grounded so what causes the GFI to trip as the amperage is not effected ?

 

[BeanAnimal]

I am sorry but I understand that if a cut cord is on wet grass then there is a path to ground , lowering the returning amperage to cause a trip. However the water in the tank is not grounded so what causes the GFI to trip as the amperage is not effected ?

It may not trip until there is a fault path. That is why I told him to add a ground probe, even temporarily for testing.

Otherwise, without, the the tingling finger either tingles due to induced voltage or fault current, but in the case of fault current, the GFCI trips.

Want to test with a finger or a ground probe?

 

[Freenow54]

It may not trip until there is a fault path. That is why I told him to add a ground probe, even temporarily for testing.

Otherwise, without, the the tingling finger either tingles due to induced voltage or fault current, but in the case of fault current, the GFCI trips.

Want to test with a finger or a ground probe?

I get it a fault path to ground from anything will be measurable . I was not questioning the probe . I have one in all my tanks, and GFI protection as well as advised by you . just like to understand every scenario.

 

[Reefer1978]

It may not trip until there is a fault path. That is why I told him to add a ground probe, even temporarily for testing.

Otherwise, without, the the tingling finger either tingles due to induced voltage or fault current, but in the case of fault current, the GFCI trips.

Want to test with a finger or a ground probe?

There’s no more tingling as I replaced the faulty equipment. Just wanted to clear that up.

 

[Euphylliaphyle]

There’s no more tingling as I replaced the faulty equipment. Just wanted to clear that up.

What equipment was faulty? This info may help others. Sorry if I missed it above.

 

[Reefer1978]

There’s no more tingling as I replaced the faulty equipment. Just wanted to clear that up.

What equipment was faulty? This info may help others. Sorry if I missed it above.

I don’t know for sure but I swapped the heater and the power head. As Bean said, I am not testing equipment with a finger ;)