Stupid GFI questions

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dwellselectric

dwellselectric

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Okay stupid question because I dont understand. Say you have an old 2 wire no ground romex and the HO wants new three prong recepticals installed now the code says that you have to replace the old two prong recepticals with GFI's now why is that if when you use your GFI tester it wont trip? Okay that was one question another one my boss and I are working at this house that has a hot tub outside. The breaker is a 60 amp breaker but there is no GFI protection for the hot tub just a 60 amp breaker. Now my boss had installed a 60 amp GFI breaker but what has going me wondering if it would really make a difference is that the hot tub is a old 60 amp 220 volt system and there is no nutral in the hot tub. So would installing that breaker really make a difference? He just caped off the nutral coming from the breaker off :-? Confused I am
 
dSilanskas said:
Okay stupid question because I dont understand. Say you have an old 2 wire no ground romex and the HO wants new three prong recepticals installed now the code says that you have to replace the old two prong recepticals with GFI's now why is that if when you use your GFI tester it wont trip?
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It should trip using the integral test button on the GFI. The plug-in testers cheat by using the EGC as the path for the simulated ground fault. Without that path, the plug-in tester won't trip even though the GFI is working properly.

I don't know why he wouldn't land the line side neutral on the 240V GFCI breaker, but I believe it would still work and protect all the same. If the load was 120/240 and the neutral was not used on the load side of the GFCI breaker, the GFCI would trip when the 120V loads tried to run. With a straight 240V load, I don't think it would matter.
 
Most gfci tester only test ground to neutral so they will not trip the receptacle.

The 220 volts breaker for the hot tub will still work without a neutral but you still ned to connect the pigtail from the breaker to the neutral bar.
 
Stupid GFI questions

I don't believe there is a such thing as a STUPID QUESTION. All of use have had them. When I first started wiring thirty five years ago I couldn't understand how to wire a single pole switch. Running just a switch leg and putting a black and white wire on the switch blew my mind. Then one day it hit me that the black and white wire was really one and you were just touching them together to make the light work. I felt stupid but once the light in my head went off I got it.
I agree with the answers you got in previous replies. Hope there answers helped. Semper Fi
 
120v GFCI plug will protect properly without an equipment ground. . It just won't test trip unless a ground is connected. . It's monitoring the hot and neutral legs for a current difference of 4-6ma even if the grounding isn't there. . It needs the equip ground to provide an extra path to shunt some of the current to simulate leakage and test trip. . But it doesn't need the extra path to protect against an actual leakage.

Same for the 240v 2pole GFCI breaker. . It will protect properly without a neutral. . It just won't test trip unless a neutral is connected. . It's monitoring the 2 hot legs for a current difference of 4-6ma even if the noodle isn't there. . It needs the neutral to provide an extra path to shunt some of the current to simulate leakage and test trip. . But it doesn't need the extra path to protect against an actual leakage.

David
 
dnem said:
120v GFCI plug will protect properly without an equipment ground. . It just won't test trip unless a ground is connected. . It's monitoring the hot and neutral legs for a current difference of 4-6ma even if the grounding isn't there. . It needs the equip ground to provide an extra path to shunt some of the current to simulate leakage and test trip. .
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Not so... it will test trip just fine with the test button on its face. It is only the three prong tester that requires the EGC to operate.
 
tallguy said:
Not so... it will test trip just fine with the test button on its face. It is only the three prong tester that requires the EGC to operate.
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Correct. That is because the gfci face plate test button doesn't use the EGC to shunt current. It can shunt some of the current internaly from load side to line side, bypassing the sensing coil.
 
Thank you guys for your help that really did clear it up a lot for me. So when I was putting the panel cover back on and I saw that my boss just nuted the neutral wire lol that was not a good idea I take it? For the 220v gfi brearker
 
dSilanskas said:
So when I was putting the panel cover back on and I saw that my boss just nuted the neutral wire lol that was not a good idea I take it? For the 220v gfi brearker
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Yep-- not a good idea. :grin: Go teach your boss a lesson-- nicely of course.
 
dSilanskas said:
Thank you guys for your help that really did clear it up a lot for me. So when I was putting the panel cover back on and I saw that my boss just nuted the neutral wire lol that was not a good idea I take it? For the 220v gfi brearker
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Time for my own stupid question then... how does a 220v GFI breaker detect a fault condition given that there is no current on the grounded conductor? We're talking about a true neutral here, assuming it is not on an MWBC.

Wouldn't a fault generally cause current to drain equally from both legs, and the neutral would continue to carry no current?
 
In a 240V only circuit, the current going out one leg must return through the second one (e.g. 10 amps on one leg must be -10A on the other). If they don't match, the GFCI trips. Whether the leakage currents are the same from each leg during a ground fault (probably difficult to arrange), it still doesn't matter as less and less current is going back through the breaker where it is supposed to be going.

If the 240V GFCI breaker has a neutral pigtail, that path is also summed along with the two ungrounded legs. All three of these paths must have the current sum to nearly 0 or else it trips.
 
Thanks for the correction about the straight 240V GFCI breaker, I was thinking about it in the car after posting and was thinking the same thing as Tallguy - "Now, what a minute, how would that work...?" :)
 
Dr. Evil's time machine

Dr. Evil's time machine

If we had access to a time machine and were able to go back and come up with a name for what became the GFCI, what would it be? I think part of the confusion is that this device has a name which does not describe accurately what it does. The device itself merely detects a current imbalance between the hot and neutral. Upon detection of a certain level of imbalance, it blows some contacts open to interrupt the circuit. It has nothing whatsoever to do with ground. It is merely an assumption (a very good one) that if there is an imbalance in the hot and neutral current, there must be an alternate path for current to be flowing back to the source. This alternate path must have something to do with 'ground.' Hence, the assumption that what has been detected is a ground fault. As far as 2 pole devices are concerned, two types are made. Those that only detect imbalance on the Ungrounded and those that detect imbalance on the Grounded as well. The first type can only be used on 240 V loads. The second type can be used for multi-wire brance circuits.

So, getting back to the original question, what would we call the device?

CID - Current Imbalance Device
CICI - Current Imbalance Circuit Interrupter
IDD - Imbalance Detection Device
ICTD - Imbalance Circuit Trip Device
IUD - Imbalance Usage Device

Ok, i'm reaching here. Better stop.
 
tallguy said:
Time for my own stupid question then... how does a 220v GFI breaker detect a fault condition given that there is no current on the grounded conductor? We're talking about a true neutral here, assuming it is not on an MWBC.

Wouldn't a fault generally cause current to drain equally from both legs, and the neutral would continue to carry no current?
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If you happened to make bodily contact with the part of the line-to-line-only 240v load that happened to be at zero volts to earth, simply by being the middle of the load's impedance, there would be no imbalance current, because no current would flow through your body, and no shock.

By touching any other part of the circuit, the GFCI would trip when there is enough voltage across your body that it, along with your resistance, formed enough current (I = E / R) to reach the trip-point of the GFCI device. But, any line-to-line fault (or shock) is seen as normal by the device.
 
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