Stray Voltage Brain Teaser

[MHG]

Attached is a drawing of what I have. What I have found is the guy who ran the sub panel used BX with a bonding strip rather than MC with an independent ground. However the two panels are bonded together and ohm out with no problem. However if I lose a neutral on my sub panel this bonding is not going to handle and significant current so I need to fix this. I dont know if NEC allows for me to bond my sub independent to ground. The water main is 10' away and I can also sink independent grounds into the earth just outside the wall. I believe NEC will allow for that but I don't know. Either way they are currently bonded and is not the source of the 5 volts I have with nothing plugged in as I have discovered that...

I have three outlets running to my DT. Two are on a 3KVUPS and one is not. I needed the one not on a UPS because my apex needs to monitor the power so it knows when it is out and adjust the loads so the UPS lasts as long as possible. All three outlets test fine with a outlet tester. All three ohm out to ground with each other and with one outlet I have near by that runs off the main.

However when trouble shooting I noticed that if I disconnect one of the outlets from my UPS (located in the basement near my sub panel) and plug it into a GFI next to my frag system near the sub panel it pops the GFI. It will not let me reset it. However if I plug them both into the GFi, I do not pop it. It does not matter which one I plug into the UPS and which one I plug into the GFI. In either case the GFI trips. So while testing voltage in the DT If I plug outlet #1 into either the UPS or the GFI I get 0.0XXX volts in the DT. When I plug in outlet #2 in I get 3-5 volts (goes up and down). Even with nothing plugged into outlet # 2. Keep in ming both outlet 1+2 plug into a UPS in the basement and run upstairs to two outlets behind my DT. So if I have my apex plugged into outlet#1 and nothing plugged into outlet#2 I get 3-5v in my DT water. This was not the case when this was installed 4 years ago and has not been the case up until a month or so ago.

So That feed running from my UPS to my DT is causing the voltage with nothing in the water. Don't know how but don't care. It is an issue so I have abandoned that outlet as it can not be fixed with out draining and removing the DT.

So continuing on with my stray voltage trouble shooting starting at 0.0xx or lower voltage...

here is what each item adds to my voltage and the original point of my original questions.

• MP10's .6-3 volts (varies as pumps surge)

• Apex 12v power supply 5 volts

• DIY LED Drivers 0 volts when on but ar zero percent. 1-2 volts whan ramped up to 100%

Still with nothing contacting the water turned on. Heaters, skimmer, return pumps all off...and un-plugged. Now I know most aquarium stray voltage are inductive so I get the MP10's But DC drivers where the transformers are mounted 20" away is throwing me for a loop and the 5 volts from a 12 power supply that is over a foot away is confusing as hell...

I do have a bad skimmer pump. That is putting 16 volts into the water. I have ordered a new one...And all the other strange ancillary voltages (heaters, and return pump) are no longer an issue with just the one feed removed from the equation.

 

[dkeller_nc]

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.
...

Keep in mind that most multimeters will indeed measure AC current without the use of an inductive probe, though I'll take your word for it if yours does not. However, if your meter isn't measuring any current, and you can actual feel current if you put your hand in the water (and not just a transient shock from a static discharge), it may be time to replace the multimeter.

 

[MHG]

My current DT tank has no feeling of shock. But my old frag system shocked me. as well as a friends... Because of my profession I have a wide variety of multi meters at my disposal. including a Fluke 190 scope meter (I have 8 of them and whenever I sign one out I get the same readings).

Again, I appreciate the assistance. And I by no means know everything and I am for certain learning things every day on this issue. My main focus on this thread is to see if anyone can assist me with explaining the voltages from items not touching the water...

 

[Christian J]

Couldn't alternating magnetic fields outside the tank induce a voltage?

 

[Utwo229]

Hi, just saw your post. I'll try to answer what I can. I am an electrician.

Attached is a drawing of what I have. What I have found is the guy who ran the sub panel used BX with a bonding strip rather than MC with an independent
However the two panels are bonded together and ohm out with no problem.

Can't tell from your drawing, but in the sub-panel the neutral should not be bonded to the case and the ground bar should. Bonding strap on BX is code compliant...

However if I lose a neutral on my sub panel this bonding is not going to handle and significant current so I need to fix this.

Not sure why you'd loose a neutral, but if you do then you should have a short circuit and the breaker will trip.

I dont know if NEC allows for me to bond my sub independent to ground.

No. Not allowed. The equipment grounding conductor (ground) needs to connect all metal parts to the service main. Only the service main is bonded to the grounded conductor (neutral). The neutral shall never ever be bonded to ground except at the service main. No time to explain electrical theory here, but that's the way it's done.

The water main is 10' away and I can also sink independent grounds into the earth just outside the wall. I believe NEC will allow for that but I don't know. Either way they are currently bonded and is not the source of the 5 volts I have with nothing plugged in as I have discovered that...

Attaching independent grounding electrodes (ground rods) is a bad idea. The entire system ground within your house must have the same voltage reference to the earth so it should only be connected in one place. Hopefully your water pipes are all connected to the system ground, but there is no telling if they may have an interruption at a valve or meter between where you are and where they are bonded.

 

[Utwo229]

GFCi' s attached to your UPS are tripping because the ups isolates the neutral and the gfci sees an imbalance. Probably can not mix match the ups and the gfci's. I suggest a cord attacted gfci that goes between the device and the outlet.. It should work in either a regular outlet, a gfci outlet, or the ups outlet. Can get them at any big box store.

 

[Utwo229]

I went back and read some of the old posts.. Stray voltage will have more to do with leakage than grounding. Leakage is more apt to occur if you have a loose neutral rather than a loose ground.. The neutral returns electrons (well not really, but not going to explain electrical theory here) to the transformer, not the ground.. The equipment ground is there to safeguard against short circuits? It is not uncommon to see a few volts between neutral and ground but a significant voltage means you have a loose neutral probably in your main panel or even at the service point.. If that's the case, your power company will have to fix it.

 

[MHG]

Hi, just saw your post. I'll try to answer what I can. I am an electrician.

Attached is a drawing of what I have. What I have found is the guy who ran the sub panel used BX with a bonding strip rather than MC with an independent
However the two panels are bonded together and ohm out with no problem.

Can't tell from your drawing, but in the sub-panel the neutral should not be bonded to the case and the ground bar should. Bonding strap on BX is code compliant...

However if I lose a neutral on my sub panel this bonding is not going to handle and significant current so I need to fix this.

Not sure why you'd loose a neutral, but if you do then you should have a short circuit and the breaker will trip.

I dont know if NEC allows for me to bond my sub independent to ground.

No. Not allowed. The equipment grounding conductor (ground) needs to connect all metal parts to the service main. Only the service main is bonded to the grounded conductor (neutral). The neutral shall never ever be bonded to ground except at the service main. No time to explain electrical theory here, but that's the way it's done.

The water main is 10' away and I can also sink independent grounds into the earth just outside the wall. I believe NEC will allow for that but I don't know. Either way they are currently bonded and is not the source of the 5 volts I have with nothing plugged in as I have discovered that...

Attaching independent grounding electrodes (ground rods) is a bad idea. The entire system ground within your house must have the same voltage reference to the earth so it should only be connected in one place. Hopefully your water pipes are all connected to the system ground, but there is no telling if they may have an interruption at a valve or meter between where you are and where they are bonded.

Thanks. The Neutral is only bonded in the main. Thanks on the info on not adding grounds to sub panel. Sub panel ground is bonded to case. Is there a particular connector used to bond the BX and bonding wire to the case? It is currently only one of those two piece clamps. But there has got to be a better way...

 

[MHG]

GFCi' s attached to your UPS are tripping because the ups isolates the neutral and the gfci sees an imbalance. Probably can not mix match the ups and the gfci's. I suggest a cord attacted gfci that goes between the device and the outlet.. It should work in either a regular outlet, a gfci outlet, or the ups outlet. Can get them at any big box store.

Thanks again. One of my feed from my UPS to the back of the DT causes all sorts of problems. Yes probably a loose neutral. But no way to get to it behind the tank so I abandoned it.

Leaky voltage skimmer pump replaced. Now I only have voltages from two sources. 2-3 volts from my MP10's and 5 volts from the apex backup power supply. I swapped it out but it makes no difference... also my PC Fuge light adds a couple of volts when its on. so only things not touching the water causing problems...