quogueelectric
Senior Member
- Location
- new york
2008 code will change this convenient thinking drastically. Why cant they invent an arc alarm??brian john said:
Cooper GFCI
- Thread starter gar
- Start date
- Status
ptonsparky
Tom
- Occupation
- EC - retired
quogueelectric said:
They did, when your lights go out, that is the alarm status.
ptonsparky
Tom
- Occupation
- EC - retired
quogueelectric said:
NE did not adopt the 08 so I am lagging behind on the update studies. Can you send me to a code section?
ELA
Senior Member
- Occupation
- Electrical Test Engineer
gar said:
It appears that the devices have changed design over time and that the National schematic is not an accurate representation of the devices you have recently reverse engineered.
I liked the idea that the coil was removed from the circuit when tripped as in the National schematic. It makes sense that the more recent devices could have the issue of the coil burning up in the event of a shorted diode or shorted SCR.
Do you consider the current design a better one?
Right after I finish my beer :grin:gar said:
Yes I see that nowgar said:
Gar,
Do you have a lot of free time at your job?
I appreciate your determination and your sharing of the results.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080906-1332 EST
ELA:
From a philosophical perspective I sort of like what Leviton and Cooper are doing. That is: you can not latch the contacts without performing a relatively complete circuit test at the time of RESET.
If there is a failure, then does it matter if the coil burns up? Maybe not because the part will not be repaired anyway.
I think the most important criteria, if possible, is that a failure cause unlatching.
In the Leviton if the 15 k test resistor was to fail it would not be possible to RESET the GFCI. This is a rather good fail safe mode. I believe the P&S can be RESET whether the electronics works or not.
.
ELA:
From a philosophical perspective I sort of like what Leviton and Cooper are doing. That is: you can not latch the contacts without performing a relatively complete circuit test at the time of RESET.
If there is a failure, then does it matter if the coil burns up? Maybe not because the part will not be repaired anyway.
I think the most important criteria, if possible, is that a failure cause unlatching.
In the Leviton if the 15 k test resistor was to fail it would not be possible to RESET the GFCI. This is a rather good fail safe mode. I believe the P&S can be RESET whether the electronics works or not.
.
wptski
Senior Member
- Location
- Warren, MI
What about a N-G trips? Also that can only happen on the load connected side or downstream if used?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080907-1440 EST
Bill:
Anything on the load side of the GFCI that causes a difference in the neutral current relative to hot line current in excess of the threshold limit will cause the GFCI to trip.
If a conductive path from the load side neutral to the ECG shunts enough (greater than about 5 MA) of the load current from the neutral, then the device will trip.
If I get a 1000 V AC source from somewhere and reference this to the neutral at the service entrance, connect a resistor of about 125,000 ohms (about 8 MA) between the 1000 V and either one of the load side current wires, then the GFCI will trip.
It does not matter how we produce the unbalanced current thru the current transformer of the GFCI, if it is above the threshold, then trip occurs.
Since the detection method is a current transformer any reasonable DC level does not trip it.
.
Bill:
Anything on the load side of the GFCI that causes a difference in the neutral current relative to hot line current in excess of the threshold limit will cause the GFCI to trip.
If a conductive path from the load side neutral to the ECG shunts enough (greater than about 5 MA) of the load current from the neutral, then the device will trip.
If I get a 1000 V AC source from somewhere and reference this to the neutral at the service entrance, connect a resistor of about 125,000 ohms (about 8 MA) between the 1000 V and either one of the load side current wires, then the GFCI will trip.
It does not matter how we produce the unbalanced current thru the current transformer of the GFCI, if it is above the threshold, then trip occurs.
Since the detection method is a current transformer any reasonable DC level does not trip it.
.
wptski
Senior Member
- Location
- Warren, MI
gar:gar said:
A N-G short on the line side doesn't cause a GFCI to trip, correct? Or meaning a GFCI that's the last receptacle on a branch circuit.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080907-1721 EST
Bill:
A GFCI that is at the end of a circuit, meaning no other devices connected to the load terminals, but with a load plugged into the front slots of the receptacle, and a jumper wire from the neutral load terminal to the EGC or possibly a water faucet will divert some of the load neutral current to the EGC and cause the GFCI to trip.
I could plug an extension cord into this outlet, go outside, put a small load on the extension cord, like a 10 W bulb, and run a wire from the extension cord neutral to a screwdriver pushed into the ground and maybe trip the GFCI. This depends upon the relative resistance of the earth back to the service grounding electrode. If ground resistance is 10 ohms thru the above path and the extension cord neutral resistance is 0.1 ohms then the load current needs to be above 100*5 = 500 MA to get 5 MA thru the earth. This will likely take a 50 W or more load to trip the breaker. It all depends upon relative resistances. Certainly if it is from the hot wire to earth it will trip.
.
Bill:
A GFCI that is at the end of a circuit, meaning no other devices connected to the load terminals, but with a load plugged into the front slots of the receptacle, and a jumper wire from the neutral load terminal to the EGC or possibly a water faucet will divert some of the load neutral current to the EGC and cause the GFCI to trip.
I could plug an extension cord into this outlet, go outside, put a small load on the extension cord, like a 10 W bulb, and run a wire from the extension cord neutral to a screwdriver pushed into the ground and maybe trip the GFCI. This depends upon the relative resistance of the earth back to the service grounding electrode. If ground resistance is 10 ohms thru the above path and the extension cord neutral resistance is 0.1 ohms then the load current needs to be above 100*5 = 500 MA to get 5 MA thru the earth. This will likely take a 50 W or more load to trip the breaker. It all depends upon relative resistances. Certainly if it is from the hot wire to earth it will trip.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080907-1756 EST
Bill:
I reread your question. Any short from neutral or hot that are on the input (line side) of the GFCI to an EGC point will not trip the GFCI because this does not cause a unbalanced current thru the GFCI.
There could be transient voltages generated by such a short that might trip a GFCI due to noise generation, but it would not be caused by an unbalanced current.
.
Bill:
I reread your question. Any short from neutral or hot that are on the input (line side) of the GFCI to an EGC point will not trip the GFCI because this does not cause a unbalanced current thru the GFCI.
There could be transient voltages generated by such a short that might trip a GFCI due to noise generation, but it would not be caused by an unbalanced current.
.
wptski
Senior Member
- Location
- Warren, MI
gar:
Have seen many responses here about tripping GFCI's and one thing that's always suggested is a N-G short in the wiring.
I constructed a end of the line GFCI, put a 100W light on it, shorted N-G and nothing happened. Connect the same load to the "load" terminals of same GFCI, short N-G and it trips.
Have seen many responses here about tripping GFCI's and one thing that's always suggested is a N-G short in the wiring.
I constructed a end of the line GFCI, put a 100W light on it, shorted N-G and nothing happened. Connect the same load to the "load" terminals of same GFCI, short N-G and it trips.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080907-1923 EST
Bill:
Your experiment confirms the description I provided above. Your load could be on the slots on the front face of the GFCI and connect the short from the load neutral terminal to the EGC, or short from the remaining neutral slot to the EGC and tripping will occur.
When using a direct short like this about 1/2 of the neutral current flows back thru the current transformer and the other half thru the EGC connection. Thus, for a 100 W bulb something under 0.5 A.
Just visualize two incoming wires going thru a current transformer. In the Leviton there is an MOV directly across the line terminals before the current transformer. All other circuitry is connected after the current transformers except one wire from the line side neutral to a test switch contact. The other side of the test switch connects thru a 15 k resistor to the hot line on the output side (load side) of the current transformer. When this switch is closed the 15 k resistor provides an 8 MA unbalanced current thru the current transformer.
All electronics are powered from the hot and neutral lines following the current transformer but before the breaker contacts. When in the tripped state there is no connection of hot and neutral to either the front slots or to the load terminals and there is no continuity between the load terminals and the front slots.
.
Bill:
Your experiment confirms the description I provided above. Your load could be on the slots on the front face of the GFCI and connect the short from the load neutral terminal to the EGC, or short from the remaining neutral slot to the EGC and tripping will occur.
When using a direct short like this about 1/2 of the neutral current flows back thru the current transformer and the other half thru the EGC connection. Thus, for a 100 W bulb something under 0.5 A.
Just visualize two incoming wires going thru a current transformer. In the Leviton there is an MOV directly across the line terminals before the current transformer. All other circuitry is connected after the current transformers except one wire from the line side neutral to a test switch contact. The other side of the test switch connects thru a 15 k resistor to the hot line on the output side (load side) of the current transformer. When this switch is closed the 15 k resistor provides an 8 MA unbalanced current thru the current transformer.
All electronics are powered from the hot and neutral lines following the current transformer but before the breaker contacts. When in the tripped state there is no connection of hot and neutral to either the front slots or to the load terminals and there is no continuity between the load terminals and the front slots.
.
wptski
Senior Member
- Location
- Warren, MI
gar:
Not sure if your not getting me or I'm not getting you?
If I create a end of line GFCI and plug in a 100W light into it. Short G-N termainals, nothing happens, short N-G prongs on the plug and it trips. If you short G to the N on the load termainal, it trips.
So if a end of line GFCI is tripping, it can't be caused by N-G short in the wiring to the GFCI. It's either what's plugged into it or itself is defective.
Here's a good one for you. A Home Depot purchased "Shock Buster" plug in GFCI, when tripped, 50VDC from a insulation tester RESET's it!
Not sure if your not getting me or I'm not getting you?
If I create a end of line GFCI and plug in a 100W light into it. Short G-N termainals, nothing happens, short N-G prongs on the plug and it trips. If you short G to the N on the load termainal, it trips.
So if a end of line GFCI is tripping, it can't be caused by N-G short in the wiring to the GFCI. It's either what's plugged into it or itself is defective.
Here's a good one for you.
A Home Depot purchased "Shock Buster" plug in GFCI, when tripped, 50VDC from a insulation tester RESET's it!
quogueelectric
Senior Member
- Location
- new york
2008 requires almost everything residential to be tr and either gfci or arcfault at the same time. Pony up and prepare customers for sticker shock. Take a code change class. Or get it in dribs and drabs .ptonsparky said:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080908-0600 EST
Bill:
I believe we are saying the same thing.
Whether a load is on the load terminals or the front slots there is no difference when the Leviton GFCI is in the RESET state. All the respective load side points are connected together.
The front ground pin sockets and the EGC (ground) terminal are always connected RESET ot TRIPPED.
"short N-G prongs on the plug and it trips." Yes, I agree because some of the load current is shunted around the current transformer and an unbalance exists thru the current transformer.
"If you short G to the N on the load termainal, it trips." Yes, I agree for the same reason. Until tripped the neutral prongs are connected to the load neutral terminal. So shorting from either a neutral prong or load side neutral terminal to an EGC anywhere you are running a parallel path to the neutral wire thru the current transformer but outside of the current transformer.
Note also if you short the line side neutral to the load side neutral this will cause a trip with a load present.
When you short to the EGC you are really connecting to the line side neutral back at the service entrance.
.
Bill:
I believe we are saying the same thing.
Whether a load is on the load terminals or the front slots there is no difference when the Leviton GFCI is in the RESET state. All the respective load side points are connected together.
The front ground pin sockets and the EGC (ground) terminal are always connected RESET ot TRIPPED.
By "Short G-N terminals, nothing happens" I assume you mean the line side neutral to the EGC, and this can be any EGC anywhere. Yes, I agree this should not cause a trip.
"short N-G prongs on the plug and it trips." Yes, I agree because some of the load current is shunted around the current transformer and an unbalance exists thru the current transformer.
"If you short G to the N on the load termainal, it trips." Yes, I agree for the same reason. Until tripped the neutral prongs are connected to the load neutral terminal. So shorting from either a neutral prong or load side neutral terminal to an EGC anywhere you are running a parallel path to the neutral wire thru the current transformer but outside of the current transformer.
Note also if you short the line side neutral to the load side neutral this will cause a trip with a load present.
When you short to the EGC you are really connecting to the line side neutral back at the service entrance.
Absolutely correct.
I have not seen one of these.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080908-1904 EST
TOOL_5150:
Do you still have the failed Leviton.
Do you know how to find the bridge diodes and test them?
Same question for the SCR?
.
TOOL_5150:
Do you still have the failed Leviton.
Do you know how to find the bridge diodes and test them?
Same question for the SCR?
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080908-2027 EST
ELA:
The wire on the Leviton coil appears to be 0.010" or smaller. That is #30 or smaller. The caliper tips are slightly rounded and I can not get around the wire. The fusing current for #30 copper is listed as 10 A. #36 (0.005") is 3.6 A.
A failed diode will place about 120/50 = 2.4 A thru the coil, and a densely packed coil will burn out at a lower current than a straight wire.
I do not want burn up my coil.
The P&S coil is a much higher resistance, thus a more sensitive latch.
.
ELA:
The wire on the Leviton coil appears to be 0.010" or smaller. That is #30 or smaller. The caliper tips are slightly rounded and I can not get around the wire. The fusing current for #30 copper is listed as 10 A. #36 (0.005") is 3.6 A.
A failed diode will place about 120/50 = 2.4 A thru the coil, and a densely packed coil will burn out at a lower current than a straight wire.
I do not want burn up my coil.
The P&S coil is a much higher resistance, thus a more sensitive latch.
.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
Leviton GFCI backdoor
Leviton GFCI backdoor
Hey Gar,
I was looking over a Leviton 7599 and lookie what I found!
You can reset these devices without power to the unit.
(As you previously mentioned, power is normally required to feed the test switch and to energize the latch solenoid during a reset).
This "backdoor" allows you to manually press on the solenoid plunger at the same time you push the reset button and the latch reset can thus be accomplished.
Leviton GFCI backdoor
Hey Gar,
I was looking over a Leviton 7599 and lookie what I found!
You can reset these devices without power to the unit.
(As you previously mentioned, power is normally required to feed the test switch and to energize the latch solenoid during a reset).
This "backdoor" allows you to manually press on the solenoid plunger at the same time you push the reset button and the latch reset can thus be accomplished.
- Status