Testing for stray voltage

[100gallonreefer]

I’ve seen the articles that state to test for stray voltage you should set voltage meter to 200 AC Volts, place black probe in ground of receptacle, place red probe in the water and the read meter(after unplugging ground probe in tank).
My question is will this setting on meter also read voltage that may be leaking from DC pumps and power heads?
TIA

 

[NY_Caveman]

Should be the same in this case I believe, since it is a conversion, but I bet @Brew12 knows for sure.

 

[Brew12]

I’ve seen the articles that state to test for stray voltage you should set voltage meter to 200 AC Volts, place black probe in ground of receptacle, place red probe in the water and the read meter(after unplugging ground probe in tank).
My question is will this setting on meter also read voltage that may be leaking from DC pumps and power heads?
TIA

Yup, this setting should work fine. The typical meter won't read the induced voltages from a DC pump very accurately because it isn't a sine wave, but the DC pumps do use a modified AC waveform so it will read on the AC setting.

 

[Auto-pilot]

Wait I'm not sure it's going to be so accurate. You might read something but on a DC pump the power supply rectifys it from AC to DC the DC pump will leak DC voltage. On ac house electricity runs at 120V ac and usually DC pumps run 12-19v DC if you want to check for DC current I would just simply put the meter on a DC setting and see what it reads. Salt water is a semi conductor so it would probably read a little lower than pump voltage if it were leaking

 

[Auto-pilot]

Actually as a mechanic who works on planes I know that if I'm testing a AC cuircuit with a DC setting it reads nothing and if I test a DC cuircuit with an AC setting it also will read nothing

 

[Brew12]

Wait I'm not sure it's going to be so accurate. You might read something but on a DC pump the power supply rectifys it from AC to DC the DC pump will leak DC voltage. On ac house electricity runs at 120V ac and usually DC pumps run 12-19v DC if you want to check for DC current I would just simply put the meter on a DC setting and see what it reads. Salt water is a semi conductor so it would probably read a little lower than pump voltage if it were leaking

No, the DC pump will not leak DC current. The rectifier converts it to DC but the controller then converts is back to some form of AC. There is no such thing as a brushless motor that runs on DC. They all require some form of AC applied to the stator to get the rotor to turn.

 

[Auto-pilot]

No, the DC pump will not leak DC current. The rectifier converts it to DC but the controller then converts is back to some form of AC. There is no such thing as a brushless motor that runs on DC. They all require some form of AC applied to the stator to get the rotor to turn.

Ok that makes sense, did not realize the controller controller converted it back. Also makes sense with the brush less motor part

 

[100gallonreefer]

Should be the same in this case I believe, since it is a conversion, but I bet @Brew12 knows for sure.

Thank you!

 

[100gallonreefer]

Yup, this setting should work fine. The typical meter won't read the induced voltages from a DC pump very accurately because it isn't a sine wave, but the DC pumps do use a modified AC waveform so it will read on the AC setting.

Thanks!

 

[100gallonreefer]

Thanks to all for reply. Highest reading I got on the 120 ac was 5.1 volts. Does this seem like it could be an issue or would magnetic drive pumps and power heads produce a little reading anyway in the water?

 

[100gallonreefer]

The reason I tested for stray voltage is that once in a while I will have an acro that has been doing well and then start “stn” for no reason I can find with water tests.

 

[ca1ore]

Maybe somebody could explain to me why this isn’t just one big old red herring? If I get a short or exposed wire in any of my submerged equipment, wouldn’t it just pop the GFCI? As it is I only have a couple of submerged sicce pumps; otherwise everything else is fully isolated. Any voltage I do feel is induced and quite minor.

I suppose stray voltage is a convenient ‘cause’ - hard to measure, hard to source and no reliable linkage to observed problems.

 

[Brew12]

Maybe somebody could explain to me why this isn’t just one big old red herring? If I get a short or exposed wire in any of my submerged equipment, wouldn’t it just pop the GFCI? As it is I only have a couple of submerged sicce pumps; otherwise everything else is fully isolated. Any voltage I do feel is induced and quite minor.

I suppose stray voltage is a convenient ‘cause’ - hard to measure, hard to source and no reliable linkage to observed problems.

A GFCI may not trip when a fault occurs if there isn't a path to ground for current flow. If you run a ground probe or a 3 pronged titanium heater the GRCI should trip immediately.
I am not convinced that an induced voltage causes any issues at all. I doubt voltage or current from failed equipment does, either. The big risk to me from this is the introduction of contaminants like copper entering the system.

 

[Auto-pilot]

A GFCI may not trip when a fault occurs if there isn't a path to ground for current flow. If you run a ground probe or a 3 pronged titanium heater the GRCI should trip immediately.
I am not convinced that an induced voltage causes any issues at all. I doubt voltage or current from failed equipment does, either. The big risk to me from this is the introduction of contaminants like copper entering the system.

Yeah I had a power head that had cracked and every time I put my hand in my tank I felt a little pinch randomly when putting my hand in the tank. It was cracked and leaking voltage but nothing was really affected all that much. I eventually touched the power head and it really shocked me! I then realized what was happening and I removed it.

 

[100gallonreefer]

A GFCI may not trip when a fault occurs if there isn't a path to ground for current flow. If you run a ground probe or a 3 pronged titanium heater the GRCI should trip immediately.
I am not convinced that an induced voltage causes any issues at all. I doubt voltage or current from failed equipment does, either. The big risk to me from this is the introduction of contaminants like copper entering the system.

I do run a ground probe and tank is on GFCI outlets. I’ve seen many articles on stray voltage and just wanted to eliminate that possible problem. I’ve said it before and I’ll say it again. The more I think I know in this hobby, I realize the less I really know in this hobby!(and I use the term hobby loosely, it’s more an obsession).

 

[Brew12]

Yeah I had a power head that had cracked and every time I put my hand in my tank I felt a little pinch randomly when putting my hand in the tank. It was cracked and leaking voltage but nothing was really affected all that much. I eventually touched the power head and it really shocked me! I then realized what was happening and I removed it.

I'm a big advocate of using a ground probe and GFCI, but only to let you know when you may be leaking contaminants. Fish have much higher resistance than the surrounding water, so other than skin irritation, they are unlikely to be affected by current.

 

[100gallonreefer]

I'm a big advocate of using a ground probe and GFCI, but only to let you know when you may be leaking contaminants. Fish have much higher resistance than the surrounding water, so other than skin irritation, they are unlikely to be affected by current.

All my fish are fat and happy and I have not lost anything since hurricane Irma. SPS corals are another matter altogether and are the basis of my question.

 

[ca1ore]

Yes, there have been articles written on the subject; I just personally find them highly suspect. I agree that potential contaminants are more problematic.

 

[Brew12]

All my fish are fat and happy and I have not lost anything since hurricane Irma. SPS corals are another matter altogether and are the basis of my question.

I would consider doing an ICP lab test.

 

[WVNed]

I assure you that if you have an energized tank you will know. A bare wire in contact with a conductive surface around the tank it is a very stimulating experience. Glass with salt creep and moisture is enough. It doesn't just tingle.

Ever touched an electric fence. Probably not, but it is like that.

A puppy chewed a wire and I pulled it into the sump doing maintenance on my skimmer.

I had a tank crash from a heater that failed that also energized a tank. But I am 99% sure it was the products of the heater burning inside being released into the water that did the tank in. Not the electricity.