Grounding Probes, GFIs, current, voltage,etc. for the electrically ungifted

[Petercar (RIP Dec 2017)]

lets say yu have the mps pumps which have no cords in yur display.    but yu have cords in yur sump....not yu have a bad cord that is putting stray foltage in yur sump.    .that pump is still pushing water up to yur display and back down the returns...is that stary voltage travelling thru the water ?

 

[Pistol]

Pure water does not conduct electricity but salt water is a very good conductor so yes current from your sump can travel to your display even with no wires in the display.

 

[Victoss]

I'm not 100% on the physics of electricity in water but I would find it hard to believe the shortest path to ground is to avoid the grounding probe within a foot or 2 of my equipment to go up all the way to the display and then either go back down the drains (probably 6-8ft of travel in most tanks) or go through my resistive body to the ground somewhere (floor).

 

[Pistol]

I'm not 100% on the physics of electricity in water but I would find it hard to believe the shortest path to ground is to avoid the grounding probe within a foot or 2 of my equipment to go up all the way to the display and then either go back down the drains (probably 6-8ft of travel in most tanks) or go through my resistive body to the ground somewhere (floor).

The potential would be the same everywhere in the system, the ground probe would be the least resistance but say you don't have a GFCI or your GFCI is defective and not tripping and you have an amp of current flowing from a heater with a broken nuetral and you give the current a path of slightly higher resistance it is guaranteed that it will take that path as well, how much depends on the math.

 

[Victoss]

This is true as in parallel circuits, but if current in water shoots out like a web most of the ends on this web will be directed to the ground, where a few out of the hundreds? thousands? of these paths will take the long way around (more resistance) are going to have a very insignificant current. If were talking about insignificant currents we could start talking about static electricity created by the water and fish moving and go on about this forever. However oceans have electrical currents too so the static electricity could be argued as natural, but this gets back to my point, how much insignificant current can we have before it's too much.

 

[Reef Hero]

I run all circuits on multiple GFCIs, I have an EB4 and an EB8 on separate GFCIs with heaters plugged into each in case 1 trips, I keep a ground probe in at all times because lets face it if you only put it in to do work on the tank then you will forget. If something happens to trip a GFCI then you might as well know about right away, it's no different then a power outage, you need to be prepared, I will get an email from my controller.
GFCIs like everything are fallible and sometimes fail to trip in which case the ground probe would give a path of least resistance and possibly cause the circuit breaker to trip and either way it could be a life saver.

Again, I feel the need to restate that a grounding probe does not protect you from any shocks....it will not protect you at all in the case that your gfci fails.... It might be a path of less resistance for the current to flow but when you stick your hand into the water and there is current leaking then you will still get current passing through your body as well because both you and the grounding probe are in parallel connections to the tank.... Yes, it might trip the breaker if there is a bad enough current leakage but this would take close to 20 amperes.... The human body can go into heart fibrillation with as small as 15mA passing through your heart.... I would suggest both the use of a grounding probe and gfci but never anything without the gfci.....personally I do not use a ground probe but maybe I should get one to toss into the tank before I work on it just in case my gfci is faulty and there is the possibility of an extreme current leak in which case the breaker will trip....


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[Reef Hero]

lets say yu have the mps pumps which have no cords in yur display.    but yu have cords in yur sump....not yu have a bad cord that is putting stray foltage in yur sump.    .that pump is still pushing water up to yur display and back down the returns...is that stary voltage travelling thru the water ?

Yes, the current will easily travel through saltwater....so will most likely be everywhere in your system as long as it is all connected together using water or other conductive materials....
Another point I would like to bring up is the electrical code that requires any use of electric radiant heating line sets to be protected by gfci.... Whether it is in floor heating, heating lines on a pipe, etc.... Must be gfci protected!! A very good code rule that unfortunately did not come into effect until it was too late for some....


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[Pistol]

Again, if you had a faulty heater and the current from the heater was travelling through the ground probe as a path of low resistance and you put your hand in the water and give it another path to flow at a higher resistance then some current would take the new path and provide a shock of lesser power to you then it would if there was no ground probe, 15 ma across the heart can kill but a few hundred ma in your hand and out your foot is not as likely to kill you as 1 or 2 amps would, I'm not saying it would or could kill you, people have survived strong electrocutions, I'm saying that if the current has a path of low resistance then less of it will try to flow through you and that could save your life, but it might not. 

 

[AdamS]

For people reading this that maybe cant follow the technical part, can we all agree that GFCI protection is absolutely necessary for safety?

 

[Pistol]

Absolutely but a GFCI is only good if it is tested monthly, how many of us do that?, I test mine periodically but have to admit not monthly, but that being said, I inadvertently tested one last week when I was doing a water change, I had put an extra heater in the end compartment of my sump because of the cold weather, when I drained the 10 gallons it empties a lot of that compartment and the heater was out of the water and when I added the water the glass shattered and the GFCI tripped, without a ground probe I would have had a tank at @ 120V potential and might not have noticed untill I put my hand in the tank, a real live test I guess.

 

[Victoss]

Again, if you had a faulty heater and the current from the heater was travelling through the ground probe as a path of low resistance and you put your hand in the water and give it another path to flow at a higher resistance then some current would take the new path and provide a shock of lesser power to you then it would if there was no ground probe, 15 ma across the heart can kill but a few hundred ma in your hand and out your foot is not as likely to kill you as 1 or 2 amps would, I'm not saying it would or could kill you, people have survived strong electrocutions, I'm saying that if the current has a path of low resistance then less of it will try to flow through you and that could save your life, but it might not. 

I totally agree with you and would like to suggest the same scenario without the grounding probe, now you have the full current going through you. In either case a gfci would trip if you had one, but with a grounding probe there is less chance that if your gfci were to fail you would get the full blunt of the current.

To summarize, GFCI is a MUST

 

[KBennett]

I am an electrical engineer.  Yes, there is a gradient, and the probe would act as a voltage divider, but it all depends on where you stick your hand, and there is no garauntee that the voltage gradient is constant.  It's not something you should bet you health on.
GFCIs are a requirement.

By the way, no one has ever lived through being electrocuted.  That word means death due to electric shock.  It's like saying I drowned and survived.  Sorry, that's a pet peeve of mine...

 

[Pistol]

I am an electrical engineer.  Yes, there is a gradient, and the probe would act as a voltage divider, but it all depends on where you stick your hand, and there is no garauntee that the voltage gradient is constant.  It's not something you should bet you health on.
GFCIs are a requirement.

By the way, no one has ever lived through being electrocuted.  That word means death due to electric shock.  It's like saying I drowned and survived.  Sorry, that's a pet peeve of mine...

OK yes that is technically correct, I should have said people have survived powerful electric shocks, I witnessed a guy get shocked once and it knocked him on his ass, and I didn't guarantee anything but the fact that the current will take every path available. I will keep my ground probe in because there is a chance it could save my life in the event that one of my GFCIs should fail.

 

[AdamS]

Absolutely but a GFCI is only good if it is tested monthly

This is very false, yes you should test your device monthly to make sure it works, but testing just proves that it worked, not testing does not stop it from working. The point am trying to make is a GFCI adds such a large level of safety for such a small cost, its crazy not to do it.

 

[Pistol]

[quote author=Pistol link=topic=7695.msg80018#msg80018 date=1391728737]
Absolutely but a GFCI is only good if it is tested monthly

This is very false, yes you should test your device monthly to make sure it works, but testing just proves that it worked, not testing does not stop it from working. The point am trying to make is a GFCI adds such a large level of safety for such a small cost, its crazy not to do it.

[/quote]Now we're getting stupid, Not testing it is living in a world with a false sense of security and actually it should be tested prior to anytime you put your hand or foot or tongue or ear or or ass or whatever part of your body you put in your tank.

 

[Reef Hero]

[quote author=KBennett link=topic=7695.msg80021#msg80021 date=1391729081]
I am an electrical engineer.  Yes, there is a gradient, and the probe would act as a voltage divider, but it all depends on where you stick your hand, and there is no garauntee that the voltage gradient is constant.  It's not something you should bet you health on.
GFCIs are a requirement.

By the way, no one has ever lived through being electrocuted.  That word means death due to electric shock.  It's like saying I drowned and survived.  Sorry, that's a pet peeve of mine...

OK yes that is technically correct, I should have said people have survived powerful electric shocks, I witnessed a guy get shocked once and it knocked him on his ass, and I didn't guarantee anything but the fact that the current will take every path available. I will keep my ground probe in because there is a chance it could save my life in the event that one of my GFCIs should fail.
[/quote]

The grounding probe definitely provides added security and good on you for doing it.... Sorry for being a little bellicose but I don't think you are trying to say by any means not to run a gfci or that a ground probe is better than a gfci but just simply that it would provide added protection on top of a gfci.... Right?
I just did not want to confuse anyone that using a ground probe is a substitute for a gfci...which I think we both agree on but between the bickering we may have confused some ppl... Lol

 

[Pistol]

[quote author=Pistol link=topic=7695.msg80024#msg80024 date=1391729974]
[quote author=KBennett link=topic=7695.msg80021#msg80021 date=1391729081]
I am an electrical engineer.  Yes, there is a gradient, and the probe would act as a voltage divider, but it all depends on where you stick your hand, and there is no garauntee that the voltage gradient is constant.  It's not something you should bet you health on.
GFCIs are a requirement.

By the way, no one has ever lived through being electrocuted.  That word means death due to electric shock.  It's like saying I drowned and survived.  Sorry, that's a pet peeve of mine...

OK yes that is technically correct, I should have said people have survived powerful electric shocks, I witnessed a guy get shocked once and it knocked him on his ass, and I didn't guarantee anything but the fact that the current will take every path available. I will keep my ground probe in because there is a chance it could save my life in the event that one of my GFCIs should fail.
[/quote]

The grounding probe definitely provides added security and good on you for doing it.... Sorry for being a little bellicose but I don't think you are trying to say by any means not to run a gfci or that a ground probe is better than a gfci but just simply that it would provide added protection on top of a gfci.... Right?
I just did not want to confuse anyone that using a ground probe is a substitute for a gfci...which I think we both agree on but between the bickering we may have confused some ppl... Lol
[/quote]I am PRO GFCI, they are a must, everybody should have all their tanks circuits protected with them, and I do believe ground probes with GFCIs add a small amount of insurance, just to clarify.

 

[Darryl_V]

The only situation I don't endorse is a grounding probe with no GFCI.  Everyone should have a GFCI, a grounding probe in conjunction with that is a bonus.

 

[jroovers]

NEVER run a tank with a grounding probe if you DO NOT have a GFCI. What will happen is you touch something that is hot for example a light fixture that has a cut/short with your arm and you stick your hand in the tank. Now you have a nice toasty arm or your dead if your using both hands. Breakers don't trip fast enough to protect you, breakers are only meant to protect your home. GFCIs on the other hand will trip the instant they dectect an imbalance and you may get a very little shock at worst.

This being said I would still recommend the use of a grounding probe with a GFCI because now lets say your water is in contact with a neutral conductor (ie cut in your powerhead) and you touch your hot shorted fixture again, the GFCI won't trip without a grounding probe because there is no imbalance, all the current is coming from the neutral to the hot equally but going through you.

Can you explain this a bit further, I'm not quite following you. That said I have unplugged my grounding probe lol.

 

[Pistol]

If you are not using a GFCI then you should not use a ground probe because if you touch something electrofied such as a defective light and put your hand in the water at the same time then you could get a shock or be electrocuted because the water is grounded via the ground probe.