Electrical Q

christyf5 · #1 03-20-2010, 04:31 AM

Earlier today I set up a mag 7 on a reactor. Everything was fine. The mag 7 is plugged into my aquatronica power bar. During a water change I turned off everything in the sump (I do my waterchanges via the sump) did my waterchange and restarted everything. Upon restart of the mag 7, the GFCI tripped. I thought it odd but turned off power to the halides (they suck the most power 2x250W) and tried again, tripped the GFCI again.

I unplugged the mag 7 and tried plugging it directly into the GFCI, tripped again. I then plugged the mag 7 into a non GFCI circuit and it works fine.

However, now I'm wondering wtf is up with the mag 7. Is it leaking power? I have no grounding probe.

Its my understanding that it doesn't take much to trip a GFCI but it takes more to trip a breaker? The plug is completely dry. Why did it work fine earlier and now its causing problems?

So my question is, if something trips a GFCI and not a breaker, should I be removing it from my tank or is it just "one of those things" and its probably fine. The fish look fine however I don't want to wake up in the morning to a bunch of dead or wonky looking fish.

H22_TURBO · #2 03-20-2010, 04:40 AM

maybe try plugging it into another gfci and test it? could be the gfci is no good anymore???

christyf5 · #3 03-20-2010, 04:52 AM

but everything else on the GFCI is fine when I run it without the mag 7 so the GFCI appears to be fine (?)

Delphinus · #4 03-20-2010, 05:02 AM

I'm a little bit fuzzy on how a GFCI works in that it either implies power on the ground wire and thus a "leak", or whether there is an imbalance between hot and neutral and thus a "leak". Either way though, I'd say it's not good. I would look at that mag 7 and see if there's anything wonky with the wire where it attaches to the pump itself.

In an electrical leakage situation, the fish themselves aren't ground so they're fine (although it's still not good for them - think it can cause HLLE ?), but as a person with feet on the ground it's bad.

At least that's how I sort of understand it.

Starry · #5 03-20-2010, 05:32 AM

could always put the mag in a tub of sw and meter it for stray current. (not with your fingers standing barefoot on concreat)

ottoman · #6 03-20-2010, 05:33 AM

Is it possible that you have a bit of splash or moisture on the plug or GFCI during the water change? Just my thought.

DiverDude · #7 03-20-2010, 05:42 AM

GFCI's work like this: Normally, current flows between HOT (black/larger blade of the plug) and NEUTRAL (white/smaller blade). Under normal circumstances, there is no current flow in the ground wire (green wire).

When someone somehow makes contact with either HOT or NEUTRAL, they can potential conduct (via their body) to ground. This poses a safety risk -particularly if one hand is in contact with the live wire and the other is at ground potential since the path is across the chest and there is a chance of fibrilation (this is BAD, very bad).

Enter the GFCI. It senses if there is current flow in ground. If there is, it surmises that something is not koscher and cuts power to protect the human it supposes is doing this. It's worth pointing out that GFCI's are to protect people, not the equipment. Equipment is protected by the breaker.

So.....this would imply that your pump is leaking to ground somehow -or the GFCI is faulty. I'd try plugging the pump into another GFCI and see if it pops.

Does the Mag7 have a 2-prong plug or a 3-pin (grounded) plug ? If it has a grounded plug and pops another GFCI, I'd replace the pump.

outacontrol · #8 03-20-2010, 05:44 AM

Okay, here is how a GFCI works, it measures the current flow on the white and black wire and compares the 2 values, if the value is different by more than 6mA (0.06 amps) it will shut off the Circuit, because that current must be faulting to ground. Old GFCI receptacles had no self check circuitry in them and if they failed internally there was no indication until an accident or external test occured. New GFCI receptacles (sometimes labeled "smart lock") have an internal self check circuit and if they have an internal fault they will shut off.
So how old is the receptacle if it is newer than 2 or 3 years it might be a smart lock, and just need to be changed.
I would plug the pump into another GFCI (after checking all the wires for any damage or salt creep or moisture) and try that to see if it works.
Feel free to ask me any other questions.
I am a Master Electrician.

Delphinus · #9 03-20-2010, 05:54 AM

Everytime the question of how a GFCI works I see exactly this (which is why I said I wasn't sure). One post that says "current on the ground = trip" and one post that says "hot/neutral amp imbalance = trip". I know a few years ago I caused a GFCI to trip on an otherwise empty circuit (ie., nothing was on that was plugged in) because I touched my light reflectors and got a static shock. That suggests "current on the ground", but the "hot/neutral imbalance" makes more sense to me or at least would be a safer option because if electricity can escape out of the wires into the tank, it's not necessarily going to work it's way back to the same ground wire that the GFCI is on.

Is is possible it is a combination of both options? Sorry, I'm not trying deliberately to be dense, but I am legitimately confused since I always see the same two different explanations when this topic comes up.

Either way though - if the GFCI itself isn't faulty then it's bad that the mag pump trips the GFCI. It may be the end of the road for the pump.

outacontrol · #10 03-20-2010, 06:00 AM

the current on the ground wire would not in it self be dangerous, the danger occurs when the current leaves the wire or device and travels through you to ground.

the GFCI absolutely without doubt measures and compares the current in the hot/neutral (if you want to call it that) and respondes to an imbalance between the 2 wires of 6 mAmps.

here is a link: http://www.google.ca/imgres?imgurl=h...ed=0CCYQ9QEwCA