- Location
- Bremerton, Washington
- Occupation
- Master Electrician
So explain how a GFCI circuit breaker works. It clearly does not have a "ground".quogueelectric said:
GFCI's do not need an EGC (moved from another thread)
- Thread starter quogueelectric
- Start date
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
So, from what we see in pic #2592A, the receptacle slots and the load terminals are separated when the GFCI trips. The movable contacts are basically double-pole switches.gar said:
That's what keeps backwards-wired GFCI receptacles from functioning as plain receptacles. Interesting. Thanx for the link, Gar!
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Same way a GFCI receptacle works without one.tom baker said:
76nemo
Senior Member
- Location
- Ogdensburg, NY
LarryFine said:Same way a GFCI receptacle works without one.
Cha-Ching
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080816-2010 EST
Larry:
Yes that is Leviton's trick to prevent incorrect wiring relative to source (line) and load. There are two patent numbers on the device and this technique might be part of their patent coverage.
Incorrect connection will not allow setting the GFCI nor will power flow to the front slots until wiring is correct and the GFCI has been RESET, and it can not be RESET without the 8 MA test being successful which is done as part of the RESET operation. No power flows, even momentarily, to the output terminals or the front slots until the test is successful. It is a mechanical design of the latch mechanism that prevents closure of the breaker contacts until the unlatch coil is pulsed. This is truly a test of all the electronics including the unlatch solenoid and operation of its plunger.
tom baker:
I believe if you read back thru the many posts you will find the answer several times. To understand the operation you need to understand current transformers and the direction of magnetic fields about a wire.
.
Larry:
Yes that is Leviton's trick to prevent incorrect wiring relative to source (line) and load. There are two patent numbers on the device and this technique might be part of their patent coverage.
Incorrect connection will not allow setting the GFCI nor will power flow to the front slots until wiring is correct and the GFCI has been RESET, and it can not be RESET without the 8 MA test being successful which is done as part of the RESET operation. No power flows, even momentarily, to the output terminals or the front slots until the test is successful. It is a mechanical design of the latch mechanism that prevents closure of the breaker contacts until the unlatch coil is pulsed. This is truly a test of all the electronics including the unlatch solenoid and operation of its plunger.
tom baker:
I believe if you read back thru the many posts you will find the answer several times. To understand the operation you need to understand current transformers and the direction of magnetic fields about a wire.
.
brother
Senior Member
I thought this thread wouldve been LOCKED by now!!
brother said:
Why? Have you not been reading the information Gar has been providing in the latter posts?
There is no flaming or nonsense being posted here, just educational discussion that is still relative to the topic.
Roger
brother
Senior Member
roger said:
It just seems rather redundant, and going in circles. Yes there was good info given from the first few, but HOW many times can you keep saying the same thing only in a different way?? HOW many more examples can you give?? Ive just seen in the past where it got like this and moderators (with good reason) would lock the thread and close it out. I guess there is a 'favoritism' type of judgement when it comes to these type of posts. JMHO.
brother said:It just seems rather redundant, and going in circles. Yes there was good info given from the first few, but HOW many times can you keep saying the same thing only in a different way?? HOW many more examples can you give?? Ive just seen in the past where it got like this and moderators (with good reason) would lock the thread and close it out. I guess there is a 'favoritism' type of judgement when it comes to these type of posts. JMHO.
Well here's a suggestion, don't come back to this thread again and you won't be irritated by it. :wink:
BTW, when it gets up to 700 posts I promise I'll close it if another Moderator doesn't
Roger
Last edited:
brother
Senior Member
roger said:Well here's a suggestion, don't come back to this thread again and you won't be irritated by it. :wink:
BTW, when it gets up to 700 posts I promise I'll close it if another Moderator doesn't
Roger
Never said i was 'irritated' by it (i dont let internet peeps that i will never meet get to me, its silly) , just that it was redundant, and there appears to be favoritism given. JMHO
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080820-1848 EST
brother:
GFCIs are intended to be an important safety device, and more are going to be required in the future. The responses to this thread indicate a great deal of misunderstanding on how these work and how to test them. A true understanding of the function of a GFCI is important for effective troubleshooting and/or correct installation. This thread would not be this long except for many providing misinformation, or being misinformed.
This thread should continue and others should disassembling different GFCIs to determine what differences in function exist. Can anyone find a GFCI that actually won't work without an EGC connection? Additionally since the report referenced by M.D. seemed to indicate a defect level of about 10% for GFCIs, then it is important to know what brands, model, year of manufacture, country of manufacture, and what failed. This information can come from readers that have experienced these defects. 10% is an excessively high rate. I would consider an 0.1% defect rate excessive if this was the infant mortality (that means early failures --- maybe within 1 year).
The reference originally mentioned by M.D. in post #65 from EC&M is a very important reference because it provided some background discussions on GFCI specificatrions. Here is the reference again
http://ecmweb.com/mag/electric_leaving_mark/
.
brother:
GFCIs are intended to be an important safety device, and more are going to be required in the future. The responses to this thread indicate a great deal of misunderstanding on how these work and how to test them. A true understanding of the function of a GFCI is important for effective troubleshooting and/or correct installation. This thread would not be this long except for many providing misinformation, or being misinformed.
This thread should continue and others should disassembling different GFCIs to determine what differences in function exist. Can anyone find a GFCI that actually won't work without an EGC connection? Additionally since the report referenced by M.D. seemed to indicate a defect level of about 10% for GFCIs, then it is important to know what brands, model, year of manufacture, country of manufacture, and what failed. This information can come from readers that have experienced these defects. 10% is an excessively high rate. I would consider an 0.1% defect rate excessive if this was the infant mortality (that means early failures --- maybe within 1 year).
The reference originally mentioned by M.D. in post #65 from EC&M is a very important reference because it provided some background discussions on GFCI specificatrions. Here is the reference again
http://ecmweb.com/mag/electric_leaving_mark/
.
bhsrnd
Senior Member
- Location
- Fort Worth, TX
If a GFCI trips in the woods and there is no ground present, does it make a sound?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
gar said:
The referenced article appeared back in 2002, and it looks like the failure rate data might have first been presented back in 1994, so it must be older than that. Maybe this is why UL recently (relatively) changed their standard.
I agree that there are too many "urban myths" concerning GFCIs.
gfi
gfi
I read the above posts on gfi's without egc because I've wanted to know if a gfi without a ground is better than no protection at all such as an existing outlet (110 V) and no ground attached as in no ground 2 wire romex in older house and prohibitive cost to run a ground due to location. So it does seem like a gfi would give that protection. Correct? I've asked a couple electricians I've worked with but never got a satisfactory yes or no answer.
As a fairly new helper to the trade this forum has answered many of my questions about safety and technical issues. Thanks everyone.
gfi
I read the above posts on gfi's without egc because I've wanted to know if a gfi without a ground is better than no protection at all such as an existing outlet (110 V) and no ground attached as in no ground 2 wire romex in older house and prohibitive cost to run a ground due to location. So it does seem like a gfi would give that protection. Correct? I've asked a couple electricians I've worked with but never got a satisfactory yes or no answer.
As a fairly new helper to the trade this forum has answered many of my questions about safety and technical issues. Thanks everyone.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080821-2221 EST
nevsquare:
A GFCI without the ground pins being connected to an EGC should perform its intended function. I will qualify this statement by saying I have only analyzed one model and therefore I can not say that there is not some model that might exist that requires an EGC. However, a well designed unit would not require the EGC. I doubt that any GFCI would get a UL listing if it required an EGC to work, but I have not seen the UL specifications.
Will you get a shock under some fault conditions? Yes. Maybe any conditions will produce a shock. Will the device prevent death? In most cases death should be prevented. A person with a very weak heart or other heart conditions might not survive. You should be better off with the GFCI than without it.
Is there any difference if the ground pins are connected to the EGC? Yes. Especially if the device with the fault problem has its case, enclosure, exterior surface connected to the cord ground pin. In this case if you are on the outside of the device you are not too likely to get a shock. If the leakage current to the enclosure is moderately small, then the EGC will not differ in potential much from earth. If it is a dead short to the case then about 1/2 of line voltage will develop on the case. But with a dead short the GFCI should trip within 1/2 to 1 cycle. I have not test one to see what is the shortest time to trip.
If you can get an EGC to the outlets, then do it.
.
nevsquare:
A GFCI without the ground pins being connected to an EGC should perform its intended function. I will qualify this statement by saying I have only analyzed one model and therefore I can not say that there is not some model that might exist that requires an EGC. However, a well designed unit would not require the EGC. I doubt that any GFCI would get a UL listing if it required an EGC to work, but I have not seen the UL specifications.
Will you get a shock under some fault conditions? Yes. Maybe any conditions will produce a shock. Will the device prevent death? In most cases death should be prevented. A person with a very weak heart or other heart conditions might not survive. You should be better off with the GFCI than without it.
Is there any difference if the ground pins are connected to the EGC? Yes. Especially if the device with the fault problem has its case, enclosure, exterior surface connected to the cord ground pin. In this case if you are on the outside of the device you are not too likely to get a shock. If the leakage current to the enclosure is moderately small, then the EGC will not differ in potential much from earth. If it is a dead short to the case then about 1/2 of line voltage will develop on the case. But with a dead short the GFCI should trip within 1/2 to 1 cycle. I have not test one to see what is the shortest time to trip.
If you can get an EGC to the outlets, then do it.
.
- Location
- Illinois
- Occupation
- retired electrician
Actually if you are part of the path you will get a shock. A GFCI cannot prevent shocks, it can only act to limit the duration of the shock.gar said:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
080822-1927 EST
From the following reference it appears that 5 MA and above should be classified as a shock. So some place between 1 and 5 MA the effect changes from a tingle to a shock.
See "Probable effect on human body"
http://www.osha.gov/SLTC/etools/construction/electrical_incidents/eleccurrent.html
This is probably one of the more useful references I found. It appears that 5 MA is a shock rather than a tingle.
.
From the following reference it appears that 5 MA and above should be classified as a shock. So some place between 1 and 5 MA the effect changes from a tingle to a shock.
See "Probable effect on human body"
http://www.osha.gov/SLTC/etools/construction/electrical_incidents/eleccurrent.html
This is probably one of the more useful references I found. It appears that 5 MA is a shock rather than a tingle.
.
frizbeedog
Senior Member
- Location
- Oregon
roger said:Well, once again, I promise I'll close it when it hits 700, and you and I have just contributed two more post towards the ending.
Roger
Can I add one?
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