ronrca
12-09-2003, 11:20 AM
In the past, there has been much discussion about ‘stray voltage’. I would like to clarify this ‘stray voltage’ term and perhaps give some insight about it.
First, I use the word 'stray voltage' with caution. If we take the word ‘stray’ and look it up in the dictionary, we will find words lost, missing, wandering, drifting, etc. Thus can we describe this voltage as lost voltage or wandering voltage or drifting voltage like you would talk about a stray cat in your neighborhood? No! You can not. From an electrical view, voltage does not go 'stray'. Voltage does not go lost or missing, it does not wander or drift! Electricity follows the laws (not theories) of physics like Ohm’s Law (Current (A)=Voltage(V)/Resistance(Ω)), Kirchoff’s Law (Voltage(V)=Current(A)*Resistance(Ω)), etc. Therefore, given these laws that must be followed, voltage can not stray!
Next, lets discuss the term voltage. A dictionary defines the word volt as a unit of measurement indicating the force required to move electrons in a circuit. The moving or flow of electrons is termed as current, measured in amps. An electrical circuit is a complete path of electric current (most often to ground/neutral/negative). To measure Volts or voltage in a circuit we use a Voltmeter which measures the voltage between two points of an electrical circuit. To perhaps simplify in further, it is the difference of voltage between two points of a circuit! Ground or neutral is usually the point of reference when measuring voltage. Voltage itself does not flow or go anywhere. Current does! Current will flow between the points of voltage (between differences of high and low, between the high side to ground/neutral/negative).
So, what is 'stray' voltage then you ask?
Well, in the electrical world we call it step potentialactually! Step potential is a major concern in the Utility industry and is very dangerous. What is step potential?Well, its almost exactly like it sounds (another word for potential is voltage btw)! Basically, it’s the voltage difference between your legs as you walk towards/away from a source of electricity. The human body is a much better conductor than ground so the electricity will flow thru your body rather than ground (current takes the path of least resistance).
Here’s an example:
Lets say that there was a big storm and the power lines are down on the ground. The place of contact where the cable is touching the ground will have the highest voltage. Ground is not a very good conductor (resistance) so as you get further away from the cable the voltage drops. If you were to walk in this area, your legs would be contacting the ground in two places thus there will be a voltage difference between your legs which will create an electrical circuit thru your body. The resistance is lower thru your body than the earth (remember, current flows from high to low).
Back to our fish! Given the above, can you see how ‘stray voltage’ really does not occur in our tank? So what then is it called when I get a shock when I touch the water?
In a couple of posts in the past, I have mentioned that this 'stray' voltage should be referred to as 'equipment failure' or 'equipment malfunction' as this is actually what it is, not voltage wandering (straying) around. In many cases when people have experience this 'stray voltage', they replaced the heater, pump, etc and the problem was solved. In these cases, like a heater, the casing or whatever the electrical parts are incased in, has broken down or cracked therefore allowing electrical current into the water. This can cause a ‘shocking’ experience because by reaching your hand into the tank, you are completing another electrical circuit to ground instead of thru the electrical wires in the heater. To prevent this from happening, use a GFI receptacle. A GFI receptacle is basically a mini-breaker. It will trip by measuring the difference in current entering/leaving the receptacle/plug.
Test if your equipment is faulty
If you do not have a GFI receptacle, your discus are skittish and you are worried about equipment failure, here is a simple test. Starting by unplugging all the electrical equipment. Wait an hour and observe the discus reaction. If the discus are not skittish, then you may have an equipment failure. Next, start by plugging in the equipment one by one and observing the reaction of the discus. Give them some time like an hour between each piece of equipment. Keep plugging in the equipment one by one until you are done. Hopefully you will find the equipment that is causing the problem and replace it.
There is also another side of 'stray voltage'! (this gets much more technical btw)
Electromagnetic Fields are being generated from electrical wires everywhere, right now, looking into your monitor, fluorescent ballasts and pretty much every electrical carrying device. Right outside my office building there is a 69kV transmission line. If I were to take a fluorescent tube at night, the tube would glow! Whenever electrical current flows, an electromagnetic field (EMF) is produced. There is no physical link between the conductor and the magnetic field, and the magnetism is due to the motion of electrons in the atoms. Therefore, we are talking about magnetic fields and induction.
What does this mean in our fish tanks? Well, now we have a conductor (the water) moving through the magnetic field (created by the wire) perpendicular to the lines of flux or a collapsing field and what do we get? A charge! Remember the cloth/rod 'trick'. Rub the cloth with the rod and the rod becomes static! That is what is happening in your tank! Not a voltage induced or anything! What is happening is the water molecules are getting positively charged. You can also get static from rubbing your feet on carpet or a balloon in your hair! The tingling or perhaps tiny shock you may get is due to the fact that the earth being negative and the water being positive. This will create a small static discharge.
If you tried to measure it, what are you actually measuring? Well, it would be similar to static charge! Will it harm your fish? Doubt it, like the bird sitting on the power line. Fish cannot ground themselves unlike humans standing on the ground.
Just because you do get a shock from your tank doesn’t mean that it is something unexplainable. Voltage cannot stray. It actually may indicate a problem with your equipment instead. By using a GFI receptacle together with a ground probe, you will protect yourself from harm.
I hope that helps! ;)
Some good reference links:
http://www.stray-volt.com/articles.htm
http://www.bassengineering.com/SV_Cause.htm
http://www.bae.umn.edu/extens/aeu/aeu2.html
First, I use the word 'stray voltage' with caution. If we take the word ‘stray’ and look it up in the dictionary, we will find words lost, missing, wandering, drifting, etc. Thus can we describe this voltage as lost voltage or wandering voltage or drifting voltage like you would talk about a stray cat in your neighborhood? No! You can not. From an electrical view, voltage does not go 'stray'. Voltage does not go lost or missing, it does not wander or drift! Electricity follows the laws (not theories) of physics like Ohm’s Law (Current (A)=Voltage(V)/Resistance(Ω)), Kirchoff’s Law (Voltage(V)=Current(A)*Resistance(Ω)), etc. Therefore, given these laws that must be followed, voltage can not stray!
Next, lets discuss the term voltage. A dictionary defines the word volt as a unit of measurement indicating the force required to move electrons in a circuit. The moving or flow of electrons is termed as current, measured in amps. An electrical circuit is a complete path of electric current (most often to ground/neutral/negative). To measure Volts or voltage in a circuit we use a Voltmeter which measures the voltage between two points of an electrical circuit. To perhaps simplify in further, it is the difference of voltage between two points of a circuit! Ground or neutral is usually the point of reference when measuring voltage. Voltage itself does not flow or go anywhere. Current does! Current will flow between the points of voltage (between differences of high and low, between the high side to ground/neutral/negative).
So, what is 'stray' voltage then you ask?
Well, in the electrical world we call it step potentialactually! Step potential is a major concern in the Utility industry and is very dangerous. What is step potential?Well, its almost exactly like it sounds (another word for potential is voltage btw)! Basically, it’s the voltage difference between your legs as you walk towards/away from a source of electricity. The human body is a much better conductor than ground so the electricity will flow thru your body rather than ground (current takes the path of least resistance).
Here’s an example:
Lets say that there was a big storm and the power lines are down on the ground. The place of contact where the cable is touching the ground will have the highest voltage. Ground is not a very good conductor (resistance) so as you get further away from the cable the voltage drops. If you were to walk in this area, your legs would be contacting the ground in two places thus there will be a voltage difference between your legs which will create an electrical circuit thru your body. The resistance is lower thru your body than the earth (remember, current flows from high to low).
Back to our fish! Given the above, can you see how ‘stray voltage’ really does not occur in our tank? So what then is it called when I get a shock when I touch the water?
In a couple of posts in the past, I have mentioned that this 'stray' voltage should be referred to as 'equipment failure' or 'equipment malfunction' as this is actually what it is, not voltage wandering (straying) around. In many cases when people have experience this 'stray voltage', they replaced the heater, pump, etc and the problem was solved. In these cases, like a heater, the casing or whatever the electrical parts are incased in, has broken down or cracked therefore allowing electrical current into the water. This can cause a ‘shocking’ experience because by reaching your hand into the tank, you are completing another electrical circuit to ground instead of thru the electrical wires in the heater. To prevent this from happening, use a GFI receptacle. A GFI receptacle is basically a mini-breaker. It will trip by measuring the difference in current entering/leaving the receptacle/plug.
Test if your equipment is faulty
If you do not have a GFI receptacle, your discus are skittish and you are worried about equipment failure, here is a simple test. Starting by unplugging all the electrical equipment. Wait an hour and observe the discus reaction. If the discus are not skittish, then you may have an equipment failure. Next, start by plugging in the equipment one by one and observing the reaction of the discus. Give them some time like an hour between each piece of equipment. Keep plugging in the equipment one by one until you are done. Hopefully you will find the equipment that is causing the problem and replace it.
There is also another side of 'stray voltage'! (this gets much more technical btw)
Electromagnetic Fields are being generated from electrical wires everywhere, right now, looking into your monitor, fluorescent ballasts and pretty much every electrical carrying device. Right outside my office building there is a 69kV transmission line. If I were to take a fluorescent tube at night, the tube would glow! Whenever electrical current flows, an electromagnetic field (EMF) is produced. There is no physical link between the conductor and the magnetic field, and the magnetism is due to the motion of electrons in the atoms. Therefore, we are talking about magnetic fields and induction.
What does this mean in our fish tanks? Well, now we have a conductor (the water) moving through the magnetic field (created by the wire) perpendicular to the lines of flux or a collapsing field and what do we get? A charge! Remember the cloth/rod 'trick'. Rub the cloth with the rod and the rod becomes static! That is what is happening in your tank! Not a voltage induced or anything! What is happening is the water molecules are getting positively charged. You can also get static from rubbing your feet on carpet or a balloon in your hair! The tingling or perhaps tiny shock you may get is due to the fact that the earth being negative and the water being positive. This will create a small static discharge.
If you tried to measure it, what are you actually measuring? Well, it would be similar to static charge! Will it harm your fish? Doubt it, like the bird sitting on the power line. Fish cannot ground themselves unlike humans standing on the ground.
Just because you do get a shock from your tank doesn’t mean that it is something unexplainable. Voltage cannot stray. It actually may indicate a problem with your equipment instead. By using a GFI receptacle together with a ground probe, you will protect yourself from harm.
I hope that helps! ;)
Some good reference links:
http://www.stray-volt.com/articles.htm
http://www.bassengineering.com/SV_Cause.htm
http://www.bae.umn.edu/extens/aeu/aeu2.html