Stray voltage Please help!

[pszemol]

ExFOWLR is right: faulty electrical insulation in connection with saltwater certainly can be a deadly combination and you should make sure all your devices are in good order. As a precaution you could switch EVERYTHING off before you put your hands in the tank water if you worry about it. I do not know anybody who is that careful...

Now - do your measurements indicate you have a device with a faulty insulation? I think not, and I would ask ExFOWLR to measure his tank in a similar way to compare the results... You can judge for yourself how unreliable the reading is if it increases when you touch the sump glass with your hand... In my opinion you are measuring imperfections of the insulation but they do not sound life threatening to me. It is very hard to tell what is the right reading- for sure it will be "smaller = better" in this case.

 

[ExFOWLR]

. I use a high quality Fluke brand meter for my day to day use. You are right about the quality of meters giving different readings plus saltwater is highly conductive and magnetic fields from motors and other electical devices cause electricity to do all sorts of strange things. Having any "feeling" of electricity with your hand in the tank should set off alarm bells. To get a shock you have to be grounded unless the voltage is very high. Are you touching the chassis of the light when you had your hand in the water?

ExFOWLR is right: faulty electrical insulation in connection with saltwater certainly can be a deadly combination and you should make sure all your devices are in good order. As a precaution you could switch EVERYTHING off before you put your hands in the tank water if you worry about it. I do not know anybody who is that careful...

Now - do your measurements indicate you have a device with a faulty insulation? I think not, and I would ask ExFOWLR to measure his tank in a similar way to compare the results... You can judge for yourself how unreliable the reading is if it increases when you touch the sump glass with your hand... In my opinion you are measuring imperfections of the insulation but they do not sound life threatening to me. It is very hard to tell what is the right reading- for sure it will be "smaller = better" in this case.

 

[taylor t]

What is the flooring around the tank like? Do you wear shoes while sticking your hand in the tank?

 

[pszemol]

EXFOWLR - Fluke brand are usually very good quality meters but I was not talking about the quality of the meter. Rather reliability of the choosen method of measurements, which in this case depends strongly on the very high internal volt meter resistance (actually: impedance) and this parameter varies from meter to meter with no particular relationship to the overal "quality" or the reputation of the manufacturer.

So, ExFOWLR... when you measure voltage between the tank water and the ground connector on the wall - what does your meter show on AC setting?

I have measured voltage in my tank and got 3.4V AC between water and ground socket.
I do not have the platinium grounding probe submerged in my sump - if you have one, you need to remove before measurements, otherwise the measurements will not compare.

What would be more interesting, in my opinion, is to measure maximum AC current which can flow from your tank/sump water to the grounding socket in the wall when circuit is almost shorted with the low resistance of the AC Ampere meter. This will not be easy because not all universal meters have the Amp setting for AC measurements, but if you have one with such please do measure it. This reading would give you the maximum current which could potentialy flow through your body to ground if you touch the water. Your body/skin resistance is higher than the amp meter resistance in most cases, so the current actually flowing through your body would be even less than the meter shows.

 

[goat585]

how close are the lights to the water? If you raise them does the voltage go down?

 

[javiersito91]

sorry for getting out topic but how can you find out if there is strsy voltage in your tank?

 

[jlnielsen13]

Update:

Multimeter reads 2.1 today and no shock at all- I don't have a heater on the tank as that seems to be compromised so I ordered a new one that should be here today. Still, when I plug anything in it goes up a little bit each time. Also, if I touch the glass on the sump it still sky rockets to about 7.2??? Placing my hand in the tank takes it down to about 1. I am pretty sure "I" am acting like a grounding probe here. I bought a grounding probe when I ordered the heater but after a ton of research am really nervous about adding it and think I will probably return it.

Couple of answers from questions:

The lights are only adding 1.1 volts now when on so I am leaving them on all the time. I don't think it is the lights anymore and think just the fact that I am plugging "4" separate plugs in as no matter what I plug in new or old the multimeter goes up by a few volts. Here is a picture of my lights:

The conduit bracket in the middle is what was "hot" before and gave me a shock- that no longer happens.

My tank is on carpeting in my family room which was wet when it overflowed which could have been an issue- I have had fans on the last three days to help get this issue solved.

Everything in the tank looks happy but I am wondering if I should still be worried about the 2.1 v. Also, I need to plug in about 6 more things to get the system back and running properly, which WILL make that go up. Should I still be concerned or do you guys think it is just how my system is going to be. I obviously don't want to get shocked again but also can't stand worrying about this everyday! All livestock seems to be happy?!?

Thanks for all the help and any more advice on if these reading are something to be concerned about is greatly appreciated-
JIM

 

[pszemol]

I think you should not be concerned with your tank reading around 3VAC to ground.

The explanation which follows will require very basic electrical knowledge, actually just the Ohm's law.

In the setup you have (tank with no titanium grounding probe) you have all electrical devices' insulation connected in paralel between AC socket and conducting water.
The water is contained in an insulated glass tank and this insulation together with stand and floor resistance connects your water to ground. This resistance is usually so high you can neglect it in calculations.
When you measure voltage with your digital meter you connect your meter's resistance between water and ground, so it will be in series with your electric devices insulation.
Now, knowing your meter's internal resistance and knowing two voltage points (120V and 3.3V) you could estimate your devices' insulation quality.

Here is how...

Rmeter - internal voltmeter resistance
Rpump - combined insulation resistance of your pumps, heaters, lights etc

Since you are dealing with two resistors connected in series the current flowing through them is the same, so you get two eqations:
I = 3.3 V / Rmeter
I = 120 V / (Rmeter + Rpump)

From that you can write:

3.3 V / Rmeter = 120 V / (Rmeter + Rpump)

To simplify calculations without introducing too much error you could notice that the value of your electrical devices' insulation resistance will be much, much bigger than the meter's internal resistance, so Rpump + Rmeter is roughly equal to Rpump alone.

So you get:

3.3 V / Rmeter = 120 V / Rpump

Then

Rpump = Rmeter x 120/3.3

My meter's internal resistance is about 5 megaohm.
From that I conclude my devices' combined electrical insulation resistance is in a range of 180 megaohm.

Is this good or bad? I think it is good enough to not worry about...
This kind of insulation would limit the AC current flowing through your body to about:

I = 120V / 180 megaohm = 0.7 uA (uA = micro Ampere = 1/1000 of mili Ampere)

This kind of current is undetectable by our body.
We start to feel currents as barely perceptible, tingling sensation at a level of 1 mA (1000 uA).

You have no real reason to worry about it!

 

[Molehs]

One of the reasons I don't use a grounding probe is so that I know right right away if something is broken/dying. Bzzzt!

 

[pszemol]

With or without titanium grounding probe situation is the same if everything is in good working order. This minute current of 1uA or less is just flowing through the probe to ground.
In case your heater's or powerhead's insulation cracks, the probe would help to trip your GFCI or trip your regular 16A fuse and cut off the 120VAC supply.

With no probe there, your hand in the water will act as a probe...
Not sure if I would like to experience this on myself...

 

[Molehs]

With no probe there, your hand in the water will act as a probe...
Not sure if I would like to experience this on myself...

Bah, it's just 110v, it doesn't really hurt that much. :lolspin:

 

[pszemol]

I see Sean, you are looking for the thrills feeding seahorses alone cannot provide

 

[dohc97]

voltage wont get you, its the current you need to worry about, have you ever touched your ignition wire in a car and got shocked? you just experienced between 10k-30k volts and survived.

 

[jayjigga]

voltage wont get you, its the current you need to worry about, have you ever touched your ignition wire in a car and got shocked? you just experienced between 10k-30k volts and survived.

Is that what you do when you're bored!? Get back to work!! Haha...

I'd love to see what everyone else reads their setups to be. Do we all have some underlying stray current?

 

[dohc97]

for the most part everyone will have some kind of reading. current is more important than voltage so i would measure current myself. Im having a hell of a time with a problematic ford truck right now. i would rather be typing here than working

 

[mnestroy]

Google 'inductive voltage aquarium' lights/pumps can generate stray current in water from very far distances.... I think somebody measured a spike due to their kitchen light 10+ feet away.

Most people freak out about stray voltage, but the odds are if you measure any tank you will detect voltage... Many people say me not to worry, as long as you don't complete the flow electricity its like harmless and is similar to birds sitting on an electrical line....

I've can dig up 50 threads saying ground probes are good because they protect humans, and 50 saying they are bad because they give current a path to flow which is not goo for the fish...

 

[mnestroy]

Dup

 

[coolfishy101]

So your tank overflowed right? This could have left a damp trail if salt creep near the lights/on your canopy. Connecting them to the tank. Maybe once the salt creep dried up your voltage dropped. Any voltage left is from the rest of the salt creep and whatever humidity the tank is putting off. Same thing happened to me with my halides except I was running 30v through the tank, wood canopy. If u can, u can try hanging the lights off the tank see if you get stray voltage.