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

[Victoss]

The idea here is gfci 1, 2 and 3 are all in parallel (you can't put gfci's in series) indicated here by being attached to the line side of the gfci. When you add a receptacle to the load side of a gfci it is now protected by that gfci (in this case #3). So when ever gfci 3 trips so will the receptacle. I don't think this is to code by you would use multiple gfci's so that when one trips all of your equipment will not turn off.

 

[Boga]

i fall into the \"electrically ungifted catagory\" .. so why would the above diagram have 3 GFCI outlets if only 1 is required?

Just an example. Ignore the first two GFCI and you can add more standard receptacles in parallel.

I prefer more GFCI because let's say one power head fails and you have everything connected to one GFCI then everything shuts down.
If you have more GFCI's, then only few consumers will go down. Pistol explained something similar on post#19.

 

[jroovers]

[quote author=jroovers link=topic=7695.msg80050#msg80050 date=1391735980]
[quote author=Victoss link=topic=7695.msg79994#msg79994 date=1391723186]
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.
[/quote]

My last statement there was to explain that because of the way a gfci works if your touching a hot and a neutral at the same time with no ground the gfci would't trip. This is because a gfci measures the difference between the neutral and hot (current coming in and and current going out), it dose not measure any current that could be on the ground. If you have a grounding probe and current goes through it instead then there will be an imbalance that will trip the gfci (if over 5ma).
[/quote]

I think I understand what you are saying.  Here's a question of a hypothetical situation, what if you plug everything into a GFCI, but not the grounding probe (you put it into another receptacle that is NOT GFCI).  I'm guessing that is no biggy because in theory the GFCI should protect you in the event of any difference over 5ma?

I see stray currents coming from:
- leakage of AC sources (heaters, pumps, T5 lighting).
- leakage of DC sources (DC pumps, LED lighting, other sensors)
- induction sources (rotating magnetic fields - pumps), which can create inductive stray currents in the conductive saltwater.
- other surrounding sources (phone, big transformer near house, natural gas line, etc)

The T5 part interests me - how does the stray current from a T5 fixture per se enter into the water column?  I can understand when something is submersed but with a fixture hanging above the water, how does that happen?  So it sounds like measuring actual stray current is very hard to do, and not necessarily something someone should be doing if they don't understand what could happen?

 

[Petercar (RIP Dec 2017)]

The idea here is gfci 1, 2 and 3 are all in parallel (you can't put gfci's in series) indicated here by being attached to the line side of the gfci. When you add a receptacle to the load side of a gfci it is now protected by that gfci (in this case #3). So when ever gfci 3 trips so will the receptacle. I don't think this is to code by you would use multiple gfci's so that when one trips all of your equipment will not turn off.

but yu cant do that if everything is plugged into the apex powerbar

 

[Boga]

[quote author=Boga link=topic=7695.msg80069#msg80069 date=1391738753]
I see stray currents coming from:
- leakage of AC sources (heaters, pumps, T5 lighting).
- leakage of DC sources (DC pumps, LED lighting, other sensors)
- induction sources (rotating magnetic fields - pumps), which can create inductive stray currents in the conductive saltwater.
- other surrounding sources (phone, big transformer near house, natural gas line, etc)

The T5 part interests me - how does the stray current from a T5 fixture per se enter into the water column?  I can understand when something is submersed but with a fixture hanging above the water, how does that happen?  So it sounds like measuring actual stray current is very hard to do, and not necessarily something someone should be doing if they don't understand what could happen?

[/quote]
If the light fixture is hanged above water from ceiling, then threre are no stray currents from it.

I thought the case when the light fixture is supported by the tank rim (two legs). In this case there is a possibility that salt creep, huminity, splashes and drips, corrosion, to create a leak path to the water.

 

[AdamS]

Here's a question of a hypothetical situation, what if you plug everything into a GFCI, but not the grounding probe (you put it into another receptacle that is NOT GFCI).  I'm guessing that is no biggy because in theory the GFCI should protect you in the event of any difference over 5ma?

Yes, to make a circuit work you need an in (called 'hot' wire, this is the black one) and an out (called neutral, white wire). Electrons travel through the black wire, through your electrical device, and back out the white wire. If you have a 'leak', electrons are coming from the black wire but not going out the white wire. What goes in must come out, so a GFCI measures what is coming in the black, what is going out the white and compares them. If they differ by more than 5mA it trips. So in conclusion it does not care where those other electrons are going (through a probe, through your hand, whatever) it simply says they are not going back into the neutral as they are supposed to be.

 

[jroovers]

Installed a GFCI.  Easy enough.  Interestingly, one of my T5 ballasts is tripping it.  So obviously there is an issue, and maybe has been for a long time.  Not sure what could be causing it, but instead of trying to sort it out, I may just get rid of my DIY T5s that I wired myself, and get a 4 x 54w T5 fixture, maybe the ATI Sunpower, that can be screwed into my existing canopy lid.  Or some type of retrofit kit.  Anyhow, pretty crazy how this played out.  For the time being, my T5 lighting is down to half.

 

[Pistol]

Good choice on the install, now you know 3 things, you are safer, you have an issue with your light and your GFCI works. Congrats

 

[jroovers]

Good choice on the install, now you know 3 things, you are safer, you have an issue with your light and your GFCI works. Congrats

Very true!  Now just more work to sort out the lighting.  It never ceases to amaze me how there is always something to deal with, sort out etc. with my system.  All part of the experience I guess.

 

[jroovers]

Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

 

[KBennett]

Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

Correct.  If your circuit is overloaded, the breaker (or fuse) in your service box will trip, not the GFCI.

 

[Boga]

Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

[quote author=jroovers link=topic=7695.msg80513#msg80513 date=1391963692]
Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

Correct.  If your circuit is overloaded, the breaker (or fuse) in your service box will trip, not the GFCI.
[/quote]

You are very correct on this.
I am wondering if short pulses of ON/OFF/ON/OFF on a inductive load will trip the GFCI? Pulses coming from a loose contact in an outlet or maybe a defective ballast? The inductive load may generate short inductive voltages, not in sync with the main power. The GFCI will sense a difference between hot and null and trip?

 

[Pistol]

They do make special GFCI breakers for motor circuits to prevent nuisance tripping, I believe they require 25ma to trip.

 

[KBennett]

[quote author=jroovers link=topic=7695.msg80513#msg80513 date=1391963692]
Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

[quote author=jroovers link=topic=7695.msg80513#msg80513 date=1391963692]
Here is another question, if you have an outlet that is overloaded, the GFCI won't necessarily trip, as it is simply measuring the difference between what is going out and what is coming back in?

Correct.  If your circuit is overloaded, the breaker (or fuse) in your service box will trip, not the GFCI.
[/quote]

You are very correct on this.
I am wondering if short pulses of ON/OFF/ON/OFF on a inductive load will trip the GFCI? Pulses coming from a loose contact in an outlet or maybe a defective ballast? The inductive load may generate short inductive voltages, not in sync with the main power. The GFCI will sense a difference between hot and null and trip?
[/quote]

The GFCI senses current - the inductive load will cause voltage transients and cause the current to lag the voltage, but current in will always equal current out.

 

[Pistol]

Some motors and equipment will trip a GFCI (5ma sense) under normal conditions so there is a GFEP (ground fault equipment protector) circuit breaker that has a 30ma sense to alleviate this problem, they are also used to prevent nuisance trips in heat tracer circuits.

 

[curiousphil]

I don't know how T5 ballasts are designed... but if they have large capacitors in them, is it possible that loading the capacitors would temporarily hold some of the current and keep it from going back to ground?  I know that all the power would all get back to ground eventually but I'm wondering if the delay in charging large capacitors would be enough to trip a GFCI.

My understanding of electronics is very limited I know just enough to be dangerous.... know enough of how things works to follow instructions and build my own projects (audio amplifiers, LED fixtures and Arduino controllers), and do some basic troubleshooting, but I have very little understanding of the physics part of how things work.

 

[Pistol]

T5 ballasts, especially electronic, should not trip a GFCI, some motors have large enough capacitors and enough winding loss to trip them, variable speed drives are also known to trip them, almost all the stuff we deal with should not.

 

[jroovers]

T5 ballasts, especially electronic, should not trip a GFCI, some motors have large enough capacitors and enough winding loss to trip them, variable speed drives are also known to trip them, almost all the stuff we deal with should not.

So what would be tripping the GFCI from my T5 lights, the wiring, as opposed to the actual ballast?

 

[Pistol]

I would think it's a defective ballast or an end cap that is leaking to ground. If you disconnect the ballast one wire at a time you might be able to isolate it.

 

[Boga]

I would think it's a defective ballast or an end cap that is leaking to ground. If you disconnect the ballast one wire at a time you might be able to isolate it.

+1
I would go first for end caps. Maybe corrosion or salt deposits.

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