Stray Voltage Brain Teaser

[MHG]

So here is a brain teaser for you on stray voltage.

Echotech MP10's adding 2 volts....

External 12 volt power adapter for Apex adding 9 volts. Thats with probes, skimmer, return, heaters, and ato unplugged.

Everything with contact to the water unplugged including the apex power supply and echotechs and I get 5 volts...

New battery in volt meter (for those about to ask). Add a ground probe using same ground I am testing with and it drops to zero...


I am thinking something in my house wiring is causing strange reading.


Just for reference I have 30 years experience in electronics....

 

[Gandolfe]

I had a powerhead go bad and was adding stray voltage...actually got shocked a few times feeding my fish

 

[fermentedhiker]

I'd double check the ground you are using against another circuit. It sounds like a poor connection in the ground you are using and that throwing off your reading.

 

[MisterP]

Add a ground probe using same ground I am testing with and it drops to zero...

If you have 30 years experience in electronics you should know your ground and neutral circuit in your home is screwed up. You don't have a zero reference any more which is why when everything is unplugged you still get 5 V potential.

 

[MisterP]

Let me re-phrase slightly.... the ground neutral circuit on the fish tank is screwed up not your entire house....I wouldn't think.

Have you measured other circuits in your home?

Is it bonded....ground/neutral?

 

[alton]

What do you get when you go from the grounding probe/slot to the grounded probe/slot on your duplex receptacle? And what voltage do you get going from your ungrounded probe/slot first to your grounded and then switching over to your grounding probe/slot? My next question is what type of room lighting do you have in this room, and does your voltage change when you turn it off? And or is your tank lights on when you perform your test?

 

[n2585722]

Is you lighting on when you get this voltage?

 

[MHG]

If you have 30 years experience in electronics you should know your ground and neutral circuit in your home is screwed up. You don't have a zero reference any more which is why when everything is unplugged you still get 5 V potential.

Wow. A bit harsh. For the record I said electronics not as an electrician. Outlets test fine. No hot or neutral swap and it certainly did not magically swap on its own as this was all in the millivolt range a few months ago when I tested it last. However thanks for the suggestion.

Let me re-phrase slightly.... the ground neutral circuit on the fish tank is screwed up not your entire house....I wouldn't think.

Have you measured other circuits in your home?

Is it bonded....ground/neutral?

I get the same reading when measuring off my tank outlet (on mu sub panel) as well as one of the homes original outlets off the main CB panel.

When I moved in I had a new 200 amp service put in and it was all bonded to two new ground rods as well as the water main. But I will double check those connections...

I am tending to think it is a grounding issue...

What do you get when you go from the grounding probe/slot to the grounded probe/slot on your duplex receptacle? And what voltage do you get going from your ungrounded probe/slot first to your grounded and then switching over to your grounding probe/slot? My next question is what type of room lighting do you have in this room, and does your voltage change when you turn it off? And or is your tank lights on when you perform your test?

You may need to rephrase this. You lost me... I have incandescent in that room and the lights are almost never on.

Is you lighting on when you get this voltage?

Yes and no. Voltage is there when DIY LED's are plugged in or un plugged.



Just for more reference. The DT is running off a 3K UPS. The apex power supply is not. It is there only to tell the Apex that there was a power outage. Both are running off the same sub panel.

Also I have a EB8 Module in my fish room and it runs off the same ups.


If I bypass the UPS I still get the same issue, so I dont think that has anything to do with it.

 

[MisterP]

Wow. A bit harsh. For the record I said electronics not as an electrician. Outlets test fine. No hot or neutral swap and it certainly did not magically swap on its own as this was all in the millivolt range a few months ago when I tested it last. However thanks for the suggestion.

Sorry not trying to be harsh just came out wrong....My thoughts don't always get put on paper the best way. I'm not an electrician either but an EE and I figured if your worked with electronics that long it should be easy to troubleshoot.



Is that outlet grounded to common ground or do you have a common ground and separate "local" grounds, if you will, such that you lose your common reference point and now have a potential difference between the 2 grounds?

 

[MHG]

Sorry not trying to be harsh just came out wrong....My thoughts don't always get put on paper the best way. I'm not an electrician either but an EE and I figured if your worked with electronics that long it should be easy to troubleshoot.



Is that outlet grounded to common ground or do you have a common ground and separate "local" grounds, if you will, such that you lose your common reference point and now have a potential difference between the 2 grounds?

I will open the panels and eyeball them...Thanks.

 

[stk731]

run a dedicated ground all the way to the panel

 

[MHG]

I will confirm it has one. But I believe it does...

 

[alton]

On your duplex receptacle you have three slots, U shaped is the grounding, large slot is the grounded, and small slot is the ungrounded. I always check for voltage between the large slot and U shaped slot to make sure there is no floating or loose neutral. Then I check for voltage from the large slot and the small slot which you should have 120+/- volts and then going from the small slot to the U shaped slot you should have the exact same voltage. Also this requires PPE using gloves and safety glasses minimum. Remember the only place you can bond the grounding conductors and grounded conductors is at the service. All sub panels shall have a separate grounding bar, and the grounded conductors shall have an insulated bar for terminations. If you combine the two on the same bar and use a grounding probe I have seen where the sub panel will use your tank as a grounding means.

 

[alton]

The reason why I asked about your lights was I have had issues with Fluorescent and MH fixtures and stray voltage in the past.

 

[MHG]

On your duplex receptacle you have three slots, U shaped is the grounding, large slot is the grounded, and small slot is the ungrounded. I always check for voltage between the large slot and U shaped slot to make sure there is no floating or loose neutral. Then I check for voltage from the large slot and the small slot which you should have 120+/- volts and then going from the small slot to the U shaped slot you should have the exact same voltage. Also this requires PPE using gloves and safety glasses minimum. Remember the only place you can bond the grounding conductors and grounded conductors is at the service. All sub panels shall have a separate grounding bar, and the grounded conductors shall have an insulated bar for terminations. If you combine the two on the same bar and use a grounding probe I have seen where the sub panel will use your tank as a grounding means.

We'll you started to say what I have read in some of my electrical reference manuals that only the main service is grounded and the sub panels are not. Or is it that only place neutral is bonded to ground is the main panel. But then you say that have a separate ground. Sub panels sold here in my do not come with a ground bus. Only a neutral...

My sub is connected to the main via a 3 wire mc cable. No copper ground. So the enclosures are bonded by the shielding. Should I run a ground from the sub to the water main?

 

[tonyscoots84]

your best bet is process of elimination. Kill the breaker which your tank is on and then see if you still have stray voltage. Then go from there. If you still do keep shutting breakers till you find the culprit and go from there. I hope you find the issue, it can be very frustrating especially after having a new panel installed and can imagine how much they charged you for it ....

 

[dkeller_nc]

Keep in mind that you cannot accurately measure "water voltage" with a voltmeter in this way (placing one probe in the tank water, and the other into a ground on a wall socket) because you're attempting to measure a floating ground.

What you need to do instead is set the meter for AC current, then place one probe in the tank water and the other in the ground conductor in the receptacle. If you measure less than 5-10 milliamps or so, you don't have a "stray voltage" problem, and your tank equipment is correctly functioning.

If you do get an amperage reading of >10 milliamps, you may well have a pump motor whose insulation has broken down, or a heater that's shorted to the water.

By the way - keep in mind that a lot of us with an electrical background think that a "grounding probe" is a bad idea because it converts a voltage potential to a current actual.

 

[MHG]

your best bet is process of elimination. Kill the breaker which your tank is on and then see if you still have stray voltage. Then go from there. If you still do keep shutting breakers till you find the culprit and go from there. I hope you find the issue, it can be very frustrating especially after having a new panel installed and can imagine how much they charged you for it ....

Thanks. I think folks are missing the original intent of the post. I am quite familiar with the trouble shooting process. The brain teaser is how can something not even connected to the water produce voltage in the water. The MP10's for example are producing between .8 and 2.8 volts. The Apex power supply is producing almost 10 volts. My LED Drivers are producing from .5 to 3 volts depending on how bright they are set...

Keep in mind that you cannot accurately measure "water voltage" with a voltmeter in this way (placing one probe in the tank water, and the other into a ground on a wall socket) because you're attempting to measure a floating ground.

What you need to do instead is set the meter for AC current, then place one probe in the tank water and the other in the ground conductor in the receptacle. If you measure less than 5-10 milliamps or so, you don't have a "stray voltage" problem, and your tank equipment is correctly functioning.

If you do get an amperage reading of >10 milliamps, you may well have a pump motor whose insulation has broken down, or a heater that's shorted to the water.

By the way - keep in mind that a lot of us with an electrical background think that a "grounding probe" is a bad idea because it converts a voltage potential to a current actual.

Well the current on the volt meter only reads in series with DC current or with an inductive probe around the AC cords. With several shocking voltages present in tanks I have tried the method you described and never measured any current.

Voltage does not get converted to current rather current is drawn. The probe provides a path to ground and can of course result in a bad thing and a high current transfer if no path previously existed and the source of the voltage was an actual conductive path and not the typical inductive lower voltage leaks. Also the a probe masks a problem and one should check regularly for stray voltage. But having been shocked in the past, I prefer to run them and check monthly for voltages without the probe in the water. Also providing that path to ground for any current will trip the GFI...

Again, I think the original brain teaser is being missed...


I am putting together a drawing that will show what I have found so far...

 

[Reef Automation]

Ground loop Voltage

Ground loop Voltage

Hello, I had an issue like this once at work. In my situation voltage was seen on the ground leg of several outlets in the building even after all the breakers in the main breaker panel were off. We found that someone in the past decided it was a good idea to use the neutral bus in the main breaker panel to bond ground lines, and also found ground lines bonded on the neutral bus.

Interestingly enough, we also found a very very slight stray voltage in our building ground from a "grounding bond" made from the local phone service utility hookup on the outside of our building.

If you can put the grounds on the ground bus and the neutrals on the neutral bus your original issue may be eliminated. hope this helps brother.

 

[alton]

Here is a picture of a service panel with the neutral bar grounded, and then sub panel with the neutral bar ungrounded. If the grounding conductors are on the neutral bar in the sub panel you have a chance to have voltage and more important current at your receptacles. What Reef Automation said is correct