Help using voltmeter to find stray voltage.

[MHannon]

I definitely have something leaking voltage into my aquarium. I have a few small cuts on my hands and I can feel a strong tingling.... its not just the salt burning because when I turn everything off the pain stops. And with a half dozen pumps, 4 sets of light fixtures, 3 heaters, etc.. its hard to tell what is causing it.

I have a voltmeter that I have no idea how to use and need some help. I want to start turning the pumps off one by one to find out what it is, and how much voltage it is leaking into the tank.

What settings should I have the voltmeter on? Here are some pics.

 

[uncleof6]

You cannot feel voltage. So the stray voltage is not an issue. If you have a ground probe in your tank, then you have current flow in your tank, and that is an issue. Induced voltage from lights is not a problem, though it will exist in your tank, and can be measured as a potential difference between the water and whatever you use as ground. Other ways to get current flow in your tank:

Bare wires in the water: abraded insulation on cords to power heads, either shorting between the hot and neutral of one cord (current flow would be local to that cord-- not across the tank, unless a grounding probe is installed) or the hot on one cord, and the neutral of another cord across the tank.

Shorting pump (submersible): Current flow would be local to the pump, rather than across the tank, unless a grounding probe is installed.

Shorting heater: for the current to think about getting in the water, the case has to be broken, but the current flow would be local to the heater, not across the tank, unless a grounding probe is installed.

Not all inclusive.

Checking stray voltage in your tank will not help isolate the problem if there is one.

What you can check: visually inspect all the cords to electrical equipment IN THE WATER. (heaters, power heads, submersible pumps.) Check the casings of your heaters for cracks, however small. If you suspect a shorting motor, you can check resistance between the ground lug of the cord, and the line side of the cord, and between the ground lug and the neutral side of the cord. Resistance is the omega symbol on your dial. (two clicks clockwise)

More sophisticated testing requires a megohmeter.

HTH,

Jim

 

[MHannon]

So I can not use any of the settings on this voltmeter to measure the current or electricity in the water?

I definitely feel electricity, I have been shocked many times. I can almost exactly relate the feeling to when I go to the chiropractor for my back and he uses an electric muscle stimulator. Its very low power but still provides an intense tingling and makes the muscles twitch.

I guess if theres no device I can use to measure it, ill just keep my hand in the tank and have someone start unplugging things until the tingling stops.

 

[uncleof6]

Have you checked the things I have suggested you check?

 

[kcress]

MHannon; You can use your meter.

Here's what you do.

Get a three prong extension cord.

Plug it into a nearby outlet.

Change your meter to the RED V with a squiggle over it. . The next one up from your picture's setting.

Now place one probe into the ground hole of the extension cord.

Place the other probe into the widest remaining prong slot. You should see some very low reading. Perhaps a volt or three. This is the Neutral. This is just making sure your ground is really a ground.

Now move the probe from the wide slot to the the narrow one.

You should now see something around 120V. This is the HOT.

If these last two things happened as I stated then your outlet that the extension cord is plugged into is in all likelihood correctly wired.

Now to test your tank. Before going further you need your Ground test lead to be reliable or you can make bad errors. Like thinking something that is fatally live, is not. So you should grab some masking tape or electrical tape, (not scotch or duct), and tape the probe snugly into the ground hole on the extension cord. Once this is done you should be able to wiggle the test lead a bit and not have the ground probe connection interrupted.

When done taping, again test the ground by probing the Hot again.

If that reads correctly you're set to go.

Using the free probe touch it to your tank water - read the meter.
you will likely see something like 60V or possibly even 120V. If so you have a PROBLEM.

Leave that probe in contact with the water, you can tape it somehow, (here you could use duct tape on the probe handle).

Now while checking the meter start unplugging things one at a time.

Do this until the reading plunges to very close to zero. The last thing that you unplugged was the culprit. Once you think you have the culprit always take the probe back to the hot slot in the extension cord and prove nothing has changed to cause the meter to stop working, like the ground probe has come out of contact, or a test lead has failed. Once you've re-proven the test setup you can be confident that you really found the problem.

Remove the problem completely from your aquarium setup and if it has exposed metal like a light fixture you can re-power it and then touch the probe directly to it while it's isolated from the system. This will confirm your prior test.

If it IS a fixture. Unplug it again and then examine it. You may find a frayed wire or cracked insulation, or a large salt buildup somewhere. If it is a cracked or frayed cord inspect for other age issues. Are the lamp prongs all corroded? If so you should replace all that, or pitch the entire fixture. If it's just the cord DO NOT try to repair the cord. It's a fools errand! Replace it with a new cord.

If it is a non metallic device like a heater cut the cord off of it as close to the heater body as possible so some fool doesn't try to resurrect it. Heave it in the trash and acquire a new one.

If it's something else let us know and we can help you make a determination.

I must stress that hunting for a problem like this is not without hazard. People have died while trying to find issues like this.

Be very conscious of what you are trying to do from moment to moment. Do not touch anything that might be conductive while hunting this problem. Even a salty cord could result in injury. Commonly a high resistance fault that smarts badly can be upgraded to a fatal low resistance fault because you wiggled the wrong thing or somehow increased the contact area. Don't get all entangled under the tank or bent over a sump, or rest your hand on a piece of metal or a pump while doing this troubleshooting. Approach the problem like everything is live, and out to get you, and you will be safe.

Happy hunting.

 

[PRDubois]

Good answer!

 

[Big Boy69]

kcress, that was awesome!!!!!!!!

 

[MHannon]

Thanks a lot Kcress. Does it matter which probe is in the ground hole? (the black or red one?)

 

[MHannon]

OK, I figured out it does not matter which one it is. Ground to neutral is 0.5V and ground to hot is 125.3V. I found a powerhead that was leaking 32V and took it out. Now with everything on, I read only about 5V.

With everything off, the tank is at 0.2V then when I start turning things on one by one each appliance adds about 0.4V then when everything is on it totals about 5V which I assume I cant feel anymore and is better than the almost 50V that was there before.

 

[uncleof6]

<a href=showthread.php?s=&postid=15118033#post15118033 target=_blank>Originally posted</a> by kcress


I must stress that hunting for a problem like this is not without hazard. People have died while trying to find issues like this.

Be very conscious of what you are trying to do from moment to moment. Do not touch anything that might be conductive while hunting this problem. Even a salty cord could result in injury. Commonly a high resistance fault that smarts badly can be upgraded to a fatal low resistance fault because you wiggled the wrong thing or somehow increased the contact area. Don't get all entangled under the tank or bent over a sump, or rest your hand on a piece of metal or a pump while doing this troubleshooting. Approach the problem like everything is live, and out to get you, and you will be safe.

Happy hunting.

This is why I do not teach people to troubleshoot live electrical problems. Ultimately, the specific problem will be identified by visual inspection of the various pieces of equipment in and around the tank.

Also voltage in a tank is not that simple. The skin depth of salt water is 32.5 meters for 60HZ. So current induced from outside the tank will be uniform throughout the tank. The wavelength of 60Hz is roughly 2500 miles in air , and ~222 yards in Salt water. The far field is defined as 1 - 5 wavelengths, so the aquarium can be considered in the near field of the lights above the tank, or submersible pumps. Or even the fluorescent light in the kitchen. (improbable source, but possible) In the extreme near field, transmission does not follow the normal conditions for transmission between media. (Air/water) so an impressed (induced) voltage from a fluorescent lamp, 5" above the tank, of 80V would not be unheard of, and would not indicate there is a problem with the fixture, and the same would go for a pump, a magnetic field in the water. This is the norm for a saltwater tank.

The short treatise is there will be voltage potential in the tank, regardless of whether there is a faulty piece of equipment or not.

I do not mean to be offensive, but it would be safer doing visual inspections of unplugged electrical equipment, (something that should be done regularly anyway) than chasing phantoms in live circuits, especially for someone that does not even know how to use a multimeter. And troubleshooting insulation problems with line cords, with no visual damage,(high resistance short) would require a meghommeter.

Aside from that kcress is correct. Also the cuts on the OP's hand reduce the "skin resistance" making it possible to "feel" something, that would be below the threshold of perception.

Jim

 

[kcress]

Yep uncleof6; induced fields around a house will always give you a reading. Just hold onto the ungrounded probe tip and you will get an induced voltage reading. You're body acting as an antenna and the extremely high sensitivity of modern electronic meters will show it. A last generation mechanical movement meter would show nothing.

MHannon's issue was not induced voltage but directly conducted - bad insulation. I have to say that perhaps 1 in 4 bad insulation problems are visible. So a meter is almost always the way I find these issues.

MHannon; The few volts you are now seeing are harmless. They are the induced voltages we speak of. They represent the potential for a small current to flow. Without the folly of a ground probe, however, no current is actually flowing. Hence no work is being done. No chemistry is being screwed with. The fish feel nothing. If you add a ground probe current will start flowing. Chemistry will be negatively affected and the fish will feel something. As work will be getting done. (Work as in energy consumption). Yes you would likely read a much lower, or zero voltage from the induced voltages but that would be because current is now (unfortunately) flowing.

Glad you hunted it down successfully!

 

[stugray]

kcress,

"Without the folly of a ground probe, however, no current is actually flowing."

Well..... actually Current IS flowing even without the probe.
That is the nature of AC signals.

If current was not flowing due to the AC voltages, then the "skin-depth" of the saltwater would be infinity because there would be no charge carriers ;-)

(Sorry couldn't help myself)

Stu

 

[MHannon]

I took the 6 year old coraline encrusted maxi jet out of the sump and soaked it in some diluted muratic acid to dissolve the coraline buildup and the case appears to be solid with no cracks and the power cord once wiped clean looks brand new, its definitely the culprit though.

 

[uncleof6]

<a href=showthread.php?s=&postid=15121316#post15121316 target=_blank>Originally posted</a> by kcress
Yep uncleof6; induced fields around a house will always give you a reading. Just hold onto the ungrounded probe tip and you will get an induced voltage reading. You're body acting as an antenna and the extremely high sensitivity of modern electronic meters will show it. A last generation mechanical movement meter would show nothing.

MHannon's issue was not induced voltage but directly conducted - bad insulation. I have to say that perhaps 1 in 4 bad insulation problems are visible. So a meter is almost always the way I find these issues.

MHannon; The few volts you are now seeing are harmless. They are the induced voltages we speak of. They represent the potential for a small current to flow. Without the folly of a ground probe, however, no current is actually flowing. Hence no work is being done. No chemistry is being screwed with. The fish feel nothing. If you add a ground probe current will start flowing. Chemistry will be negatively affected and the fish will feel something. As work will be getting done. (Work as in energy consumption). Yes you would likely read a much lower, or zero voltage from the induced voltages but that would be because current is now (unfortunately) flowing.

Glad you hunted it down successfully!

Well he was typing that while I was typing my post, with many interruptions-- Unfair advantage......engineers, can't live with um.......... I still say the safe way to check for insulation problems is with a megohmmeter, (and doesn't everyone have one of those? I do........ ) glad the OP was very careful, and yes 5v is better than 50v.

Stu,

'Well..... actually Current IS flowing even without the probe.
That is the nature of AC signals.

If current was not flowing due to the AC voltages, then the "skin-depth" of the saltwater would be infinity because there would be no charge carriers ;-)'

Yes, because of the nature of salt water, movement of the water and life in the tank, there is current flow between areas with different potentials, But the magnitude of such current is small, and well below the threshold of perception. Fish on the other hand, have less "skin resistance" if you will, and will react to current flow at lower levels, (similar to the cuts on the OP's hand) and if the magnitude is sufficient, the fish will align themselves with the current flow, to minimize the affect.

Jim

 

[ckoral]

should current be monitored or voltage when troubleshooting this?

Also, how much power can be lost from leaking equipment? Enough to be noticeable on the power bill?

 

[kcress]

<a href=showthread.php?s=&postid=15126390#post15126390 target=_blank>Originally posted</a> by ckoral
should current be monitored or voltage when troubleshooting this?

Voltage.

<a href=showthread.php?s=&postid=15126390#post15126390 target=_blank>Originally posted</a> by ckoral
Also, how much power can be lost from leaking equipment? Enough to be noticeable on the power bill?

Essentially no power.


Less power than the meter itself probably uses - so no.
And if nothing like a ground probe is present NO net current flows. Remember I said, "no work is done"? Hence - no power consumed.

 

[caliking]

I just tried this test with the multimeter and am getting reading of 51. volts
When i disconnect the heater It drops to 16.3 volts,
then I disconnected the skimmer it drops down to 12. volts

Do i have a problem?

 

[kcress]

Probably Yes. At least one. Likely just the heater.

Is it a metal heater? Or glass? How is it installed?
What prompted you to test it?

 

[jrpark22000]

Like in the above you may want to unplug all devices in your tank and perform another voltage test. Then plug each device in one at a time to determine if a single device is causing a siginificant amount of voltage leak into your tank.

 

[caliking]

1. The Metal titanium heaters causes the most voltage leak.

2. They are connected to a JBJ controller and the two heater probes are in the sump area.

3. I was searching RC and ran across this thread, and i said to my self, "I have a multimeter, i should check mine to make sure".

Probably Yes. At least one. Likely just the heater.

Is it a metal heater? Or glass? How is it installed?
What prompted you to test it?