GFI on a GFI
- Thread starter danickstr
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Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
There is a sensor as part of the GFCI device. Each device will have the sensor work independently of the other and will not affect the way one or the other operates.
If the GFCI trips, it is not because they are daisy chained.
If the GFCI trips, it is not because they are daisy chained.
- Location
- Logan, Utah
I agree with Ken and Pierre, Plugging in a GFCI protected cord into a GFCI protected receptacle will not cause either one to trip any differently then before.
About the only problem that I can see is if there is a ground fault you won't know which one will trip.
Chris
About the only problem that I can see is if there is a ground fault you won't know which one will trip.
Chris
Dave6
Member
- Location
- Deployed...FL when I'm not
"Plugging in a GFCI protected cord into a GFCI protected receptacle will not cause either one to trip any differently then before."
Will the same hold true of wiring two GFCI receptacles in series? Little background...Myself and two other electricians agreed that when two GFCI receptacles are wired this way, the first would trip (all based on experiance/learning the hard way). Our EE (term used very loosely) asked why, because he wants every outlet in the bathrooms to be GFCI. Based on 08 Handbook (why we don't have the code book is another story) but that is what he is going by....Anyway I wired up a test board with 2 GFCIs in series and it works fine. I kinda answered my first question there. But, what has changed? Why does this work now? All 3 of us are curious and would of bet against this working.
Mods; I'm new here. If I'm out of line please point me in the right direction.
Will the same hold true of wiring two GFCI receptacles in series? Little background...Myself and two other electricians agreed that when two GFCI receptacles are wired this way, the first would trip (all based on experiance/learning the hard way). Our EE (term used very loosely) asked why, because he wants every outlet in the bathrooms to be GFCI. Based on 08 Handbook (why we don't have the code book is another story) but that is what he is going by....Anyway I wired up a test board with 2 GFCIs in series and it works fine. I kinda answered my first question there. But, what has changed? Why does this work now? All 3 of us are curious and would of bet against this working.
Mods; I'm new here. If I'm out of line please point me in the right direction.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Why would you wire GFCI's in series. We are not talking about series connections but parallel. A GFCI feeding another GFCI recep. or plug should not cause any tripping unless there is a problem with one of the units.
I am not a mod but I don't think you are out of line but I do think you are incorrect.
BTW-- welcome to the forum
- Location
- Logan, Utah
macmikeman
Senior Member
- Location
- Planet macmikeman
That's when you ask the inspector for a code reference.
Chris
I had an inspector come up with the same deal except it was garage/ outdoor gfi's . When he said I would have to change the outer one to a non gfi receptacle protected off the first, I asked for a code reference. I got some gobbledygook that went like this" (picture index finger pointing skyward and reflective, I am more knowing look than you are on his face as he speaks).. I am relying on my judgement that it will be a problem for the customer, because it will cause him to not know how or where to restore power if the upstream one trips. Now I am a guy who has had to go out and restore tripped gfi devices for people at least 200 times in my life where they either forgot where the gfi breaker was located at or they were just ignorant about gfi devices. Some people will not learn how to reset a gfi no matter what type or configuration it is wired with. It is just one of the little inconvenient things I get to contend with, make rules up as you go inspectors.... I swapped it, got paid the final billing and just put the story into my growing log book that I am keeping about such things.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
macmikeman,
I like that pointing up to the heavens and the holier than thou look.
If I go back into inspecting, I am going to remember that one.
I like that pointing up to the heavens and the holier than thou look.
If I go back into inspecting, I am going to remember that one.
Dave6
Member
- Location
- Deployed...FL when I'm not
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Quote:
Originally Posted by Dave6
Anyway I wired up a test board with 2 GFCIs in series and it works fine. I kinda answered my first question there. But, what has changed? Why does this work now? All 3 of us are curious and would of bet against this working.
Why would you wire GFCI's in series. We are not talking about series connections but parallel. A GFCI feeding another GFCI recep. or plug should not cause any tripping unless there is a problem with one of the units.
Let me explain a little more...First, completely agreed that this is stupid, no reason to etc. I believe we are on the same page there. The reason is our EE wants us to. Because he is interperting the code incorrectly and is convinced that every outlet in these bathrooms needs to be a GFCI. He is not grasping the GFCI protected concept. So...my plan to show him it wouldn't work was to make a test board with two in series. This is based on something I learned the hardway 15+ years ago when I put two in series and the first one in line automatically tripped. I called my boss at the time to ask why, he cussed me out and told me to take the second one out. Two other electricians I work with had similar experiances back in the day and all were taught that two GFCIs can't share the same neutral in series. What has changed with GFCIs to allow them to be put in series? We have a couple theories...but all 3 of us our curious and confused.
I think that about covers it...This is probably going to be a case of agreeing with the EE, then doing the right thing in the field.
Quote:
Originally Posted by Dave6
Anyway I wired up a test board with 2 GFCIs in series and it works fine. I kinda answered my first question there. But, what has changed? Why does this work now? All 3 of us are curious and would of bet against this working.
Why would you wire GFCI's in series. We are not talking about series connections but parallel. A GFCI feeding another GFCI recep. or plug should not cause any tripping unless there is a problem with one of the units.
Let me explain a little more...First, completely agreed that this is stupid, no reason to etc. I believe we are on the same page there. The reason is our EE wants us to. Because he is interperting the code incorrectly and is convinced that every outlet in these bathrooms needs to be a GFCI. He is not grasping the GFCI protected concept. So...my plan to show him it wouldn't work was to make a test board with two in series. This is based on something I learned the hardway 15+ years ago when I put two in series and the first one in line automatically tripped. I called my boss at the time to ask why, he cussed me out and told me to take the second one out. Two other electricians I work with had similar experiances back in the day and all were taught that two GFCIs can't share the same neutral in series. What has changed with GFCIs to allow them to be put in series? We have a couple theories...but all 3 of us our curious and confused.
I think that about covers it...This is probably going to be a case of agreeing with the EE, then doing the right thing in the field.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
Dave6,
I wonder if the situation that you are remembering from 15 years ago was a set of GFCIs sharing the neutral but not the same hot conductors.
Since the GFCI functions by detecting any imbalance between the 'hot' and the 'neutral' conductor, any circuit using the load side neutral must also use the load side hot. Say you have a chain of receptacles all sharing the same neutral but using different 'hot' conductors in a common multi-wire branch circuit. You cannot GFCI protect these receptacles via the _load_ side of a few GFCI devices at the beginning of the chain. As far as the GFCI is concerned, any curent flowing on the hot that is not balanced by current on the neutral is a fault, even though it is _properly_ flowing on the other branch of the circuit.
Another possibility is that _some_ GFCIs implemented an additional type of protection with a second transformer coil. This coil was supposed to induce a small common mode voltage to detect neutral to ground faults. I wonder if this second protection system could cause problems when GFCIs are connected electrically in series.
-Jon
I wonder if the situation that you are remembering from 15 years ago was a set of GFCIs sharing the neutral but not the same hot conductors.
Since the GFCI functions by detecting any imbalance between the 'hot' and the 'neutral' conductor, any circuit using the load side neutral must also use the load side hot. Say you have a chain of receptacles all sharing the same neutral but using different 'hot' conductors in a common multi-wire branch circuit. You cannot GFCI protect these receptacles via the _load_ side of a few GFCI devices at the beginning of the chain. As far as the GFCI is concerned, any curent flowing on the hot that is not balanced by current on the neutral is a fault, even though it is _properly_ flowing on the other branch of the circuit.
Another possibility is that _some_ GFCIs implemented an additional type of protection with a second transformer coil. This coil was supposed to induce a small common mode voltage to detect neutral to ground faults. I wonder if this second protection system could cause problems when GFCIs are connected electrically in series.
-Jon
RICK NAPIER
Senior Member
- Location
- New Jersey
I too like the holier than thou look and I am ardently practicing the look to use in the future.
Dave6
Member
- Location
- Deployed...FL when I'm not
Jon,
I'm pretty sure everything was in series, neutral and hot. It was a customers trailer and the outlets on each side of the sink. As cheap as they are made I don't think they would share a neutral...but I've been suprised before. :roll:
You might be on to something with your theory. Because all 3 of us electricians here had these experiances 15-20+ years ago. So maybe something evolved in GFCI technology in that time.
Thanks
Dave
I'm pretty sure everything was in series, neutral and hot. It was a customers trailer and the outlets on each side of the sink. As cheap as they are made I don't think they would share a neutral...but I've been suprised before. :roll:
You might be on to something with your theory. Because all 3 of us electricians here had these experiances 15-20+ years ago. So maybe something evolved in GFCI technology in that time.
Thanks
Dave
DavidA
Member
- Location
- Fresno, CA
Just recently, in a commercial setting, we had some trouble with a GFI fed from the load of another GFI. One was installed at a break area counter top and then fed another outlet in a nearby bathroom. We use a fairly common brand of 15A GFI receptacle. Upon initial power up of the building we couldn't get either GFI to reset. We removed the second GFI and replaced it with a standard receptacle and all was right again.
You also could have just pigtailed the line and loads at the first GFI. This would have left each GFI with the ability to be reset at each location.
boboelectric
Senior Member
- Location
- Eighty Four,Pa.15330
macmikeman
Senior Member
- Location
- Planet macmikeman
With my situation I had a reason to do it. The reason was I forgot that there was already another gfi device upstream of it.... Now the job was an hour drive from the shop, so to go out just to replace device and multimac cover insert to duplex (or line/load connections), was the hard to swallow part. I usually do not like to drive 2 hours to correct non violations. Thats why I remember the exchange so well.
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