If I were to run a 14-3 to feed two bedrooms, respectively, will the arc faults operate appropriately? It is my understanding that the arc fault monitors the current on both the hot wire and the neutral for each circuit; if it doesn't read the same amount of current returning on the neutral as fed through the hot wire, it will trip--assuming an arc in the circuit. So with a 3-wire feed, won't there be a problem with the arc fault detectors functionality? This tells me, no more feeds with shared neutrals when wiring bedrooms...
AFCI compatability w/shared neutral feeds?
- Thread starter ctroyp
- Start date
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Re: AFCI compatability w/shared neutral feeds?
I have no first hand experience with AFCI's yet. My experience is dated, dusty, and rusty. I am here dusting things off while I get my legs back after a workplace injury. Here is something to chew on while you await your final word:
Google search for shared+neutral+arc+fault+circuit
The quick answer is an AFCI will fail on a shared neutral circuit. I will check back for the final word.
../Wayne
Image property of: www.zlan.com
manufacturer of self-testing AFCI circuit breakers.
[ September 05, 2003, 10:22 PM: Message edited by: awwt ]
I have no first hand experience with AFCI's yet. My experience is dated, dusty, and rusty. I am here dusting things off while I get my legs back after a workplace injury. Here is something to chew on while you await your final word:
Google search for shared+neutral+arc+fault+circuit
The quick answer is an AFCI will fail on a shared neutral circuit. I will check back for the final word.
../Wayne
Image property of: www.zlan.com
manufacturer of self-testing AFCI circuit breakers.
[ September 05, 2003, 10:22 PM: Message edited by: awwt ]
- Location
- Massachusetts
Re: AFCI compatability w/shared neutral feeds?
Waynes correct AFCI breakers can not share the grounded conductor, no more than a GFCI breaker can.
I have heard that there is NM available with two whites, black and red for use with AFCIs.
Maybe someone can provide some more info on the NM.
Waynes correct AFCI breakers can not share the grounded conductor, no more than a GFCI breaker can.
I have heard that there is NM available with two whites, black and red for use with AFCIs.
Maybe someone can provide some more info on the NM.
Re: AFCI compatability w/shared neutral feeds?
Yes, I have purchased a 2 pole AFCI made by General Electric. We used it during a service panel replacement job where the two bedrooms had previously been rewired with one 12-3 as a shared neutral circuit. That AFCI cost us $89. Wow!
Mike
Yes, I have purchased a 2 pole AFCI made by General Electric. We used it during a service panel replacement job where the two bedrooms had previously been rewired with one 12-3 as a shared neutral circuit. That AFCI cost us $89. Wow!
Mike
russellroberts
Senior Member
- Location
- Georgia
Re: AFCI compatability w/shared neutral feeds?
I've used the cable iwire describes. It does indeed have a red,black,white,white with a white stripe,and bare egc. I believe southwire calls theirs 12-4wg, and some I've seen is called 12-2-2.
It's handy for the afci ckts when 2 bedrooms are close together. Also nice for remodel jobs where it's sometimes a pain to pull multiple ckts.
I guess some ahj's could cite 200.6(A) but I've had no problems so far on inspected jobs.
Russell
I've used the cable iwire describes. It does indeed have a red,black,white,white with a white stripe,and bare egc. I believe southwire calls theirs 12-4wg, and some I've seen is called 12-2-2.
It's handy for the afci ckts when 2 bedrooms are close together. Also nice for remodel jobs where it's sometimes a pain to pull multiple ckts.
I guess some ahj's could cite 200.6(A) but I've had no problems so far on inspected jobs.
Russell
Re: AFCI compatability w/shared neutral feeds?
it doesnt work. i think afci measures potential between line and neutral? among other things. well i installed them in my own home. i had all split outlets in my bedrooms(broken bar one switched one always on). neutrals where of course from two different phases and bus bars on most of them. well i had to redo all the wiring in these boxes. what a pain. these don't seem great for boxes with two circuits on a split recept. will they come out with one that makes it easier to use on a split? the manufacturers should know that splitting outlets in bedrooms is common. not all bedrooms have a ceiling light anymore. these afci's are a royal pain. i hope they start to improve both the installation and effectiveness of them. i should have waited untill they mature since i didn't need them anyways. ahh well. job is already done.
ron g.
it doesnt work. i think afci measures potential between line and neutral? among other things. well i installed them in my own home. i had all split outlets in my bedrooms(broken bar one switched one always on). neutrals where of course from two different phases and bus bars on most of them. well i had to redo all the wiring in these boxes. what a pain. these don't seem great for boxes with two circuits on a split recept. will they come out with one that makes it easier to use on a split? the manufacturers should know that splitting outlets in bedrooms is common. not all bedrooms have a ceiling light anymore. these afci's are a royal pain. i hope they start to improve both the installation and effectiveness of them. i should have waited untill they mature since i didn't need them anyways. ahh well. job is already done.
ron g.
Re: AFCI compatability w/shared neutral feeds?
i just realized one more thing i never saw before!
per awwt's diagram. these things have diodes and an ic present in a nonsealed ac line voltage enviorment? the ac is pulled high into a dc converter to feed the detection circuit and used as the clamp? there is also an eeprom present apparently to hold some type of serial or firmware? even a thermal diode instead of the trusty bimetal! well it was discussed elsewhere here that these could fail. even fail in the closed position. now from the diagram i am sure that they can and will fail. it is basic science. heck there is not even a decent heatsink on the ac/dc mov!
ron g.
i just realized one more thing i never saw before!
per awwt's diagram. these things have diodes and an ic present in a nonsealed ac line voltage enviorment? the ac is pulled high into a dc converter to feed the detection circuit and used as the clamp? there is also an eeprom present apparently to hold some type of serial or firmware? even a thermal diode instead of the trusty bimetal! well it was discussed elsewhere here that these could fail. even fail in the closed position. now from the diagram i am sure that they can and will fail. it is basic science. heck there is not even a decent heatsink on the ac/dc mov!
ron g.
iceman2610
Member
Re: AFCI compatability w/shared neutral feeds?
Read on to 200.6(D)
russellroberts
Senior Member
- Location
- Georgia
Re: AFCI compatability w/shared neutral feeds?
Hi Iceman. Different systems?
Russell
[ September 05, 2003, 10:46 PM: Message edited by: russellroberts ]
Hi Iceman. Different systems?
Russell
[ September 05, 2003, 10:46 PM: Message edited by: russellroberts ]
Re: AFCI compatability w/shared neutral feeds?
ctroyp,
An AFCI breaker has a GFCI like capability as well so you are correct, two single-poles can't be used on a multi-wire circuit. The threshold for line-neutral imbalance is not low enough to qualify as GFCI protection for personell so you don't see it touted as such. I don't know if this capability is incidental to the design of the AFCI or if it was added for some other reason (I'm not bright enough to follow the schematic posted earlier).
When AFCI's were first required, I was curious about how they worked and I though I would test this GFCI-like operation on the first ones I installed. I used my Wiggy to check from hot to ground and sure enough, the AFCI tripped. Curiousity got the better of me so I reset the breaker and tried my little pocket-sized cheap-o GFCI tester and it tripped the breaker as well. I didn't expect that to happen, so I moved to a different bedroom and tried the GFI tester there as well. As it turns out, out of the three AFCI breakers serving the bedroom receptacles, one of them would "trip" when using the GFI tester while the other two would hold. When I bought the breakers, the supplier was almost out of them, so I had to go to one of the box stores to get one more to finish the job. You guessed it, the one from the box store was the one that would trip. I honestly don't know if it meant anything or not, but I returned that one and waited for my supplier to get another batch in
Russell,
I've been curious about the 12/4 NM-B but haven't really seen it around here yet. What did you think about it? You bring up a good point about 200.6(E) and I think this may be expounded upon in the next code cycle. Also, I suppose it depends upon your interpretation of the wire colors . . . . Maybe that's not white with red stripes . . . maybe it's a red wire with REALLY wide white stripes
Jim
ctroyp,
An AFCI breaker has a GFCI like capability as well so you are correct, two single-poles can't be used on a multi-wire circuit. The threshold for line-neutral imbalance is not low enough to qualify as GFCI protection for personell so you don't see it touted as such. I don't know if this capability is incidental to the design of the AFCI or if it was added for some other reason (I'm not bright enough to follow the schematic posted earlier).
When AFCI's were first required, I was curious about how they worked and I though I would test this GFCI-like operation on the first ones I installed. I used my Wiggy to check from hot to ground and sure enough, the AFCI tripped. Curiousity got the better of me so I reset the breaker and tried my little pocket-sized cheap-o GFCI tester and it tripped the breaker as well. I didn't expect that to happen, so I moved to a different bedroom and tried the GFI tester there as well. As it turns out, out of the three AFCI breakers serving the bedroom receptacles, one of them would "trip" when using the GFI tester while the other two would hold. When I bought the breakers, the supplier was almost out of them, so I had to go to one of the box stores to get one more to finish the job. You guessed it, the one from the box store was the one that would trip. I honestly don't know if it meant anything or not, but I returned that one and waited for my supplier to get another batch in
Russell,
I've been curious about the 12/4 NM-B but haven't really seen it around here yet. What did you think about it? You bring up a good point about 200.6(E) and I think this may be expounded upon in the next code cycle. Also, I suppose it depends upon your interpretation of the wire colors . . . . Maybe that's not white with red stripes . . . maybe it's a red wire with REALLY wide white stripes
Jim
Re: AFCI compatability w/shared neutral feeds?
After some research, I have found further information, courtesy of Square-D.
AFCI Tripping
Shared Neutrals
[ September 11, 2003, 01:47 PM: Message edited by: ctroyp ]
After some research, I have found further information, courtesy of Square-D.
AFCI Tripping
Shared Neutrals
[ September 11, 2003, 01:47 PM: Message edited by: ctroyp ]
G
Guest
Guest
Re: AFCI compatability w/shared neutral feeds?
Please keep in mind that this schematic is for a patented and proprietary self-testing AFCI breaker. Your mileage may vary. Please click on the link in my OP to see the details regarding the type of AFCI breaker that uses this non-standard schematic.
../Wayne C.
Ron (and all):
Please keep in mind that this schematic is for a patented and proprietary self-testing AFCI breaker. Your mileage may vary. Please click on the link in my OP to see the details regarding the type of AFCI breaker that uses this non-standard schematic.
../Wayne C.
curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
Re: AFCI compatability w/shared neutral feeds?
Jim
Standard AFCI breakers do NOT have GFCI protection. Cutler-Hammer does make a model that is a combination AFCI/GFCI. AFCI breakers do have ground fault protection but it is set at a higher level than GFCI protection. A GFCI must trip at 4-6ma and a AFCI is set to trip at aprox. 30-50ma. I know that Siemens (Murray) AFCI's initially had the Ground Fault Protection set at a lower level (6-10ma) but changed it to the higher level. My guess is that you got a hold of some of the older breakers which is why they were tripping with the GFCI tester. Even at the initial lower level they are not approved as Class A (GFCI) protection.
Jim
Standard AFCI breakers do NOT have GFCI protection. Cutler-Hammer does make a model that is a combination AFCI/GFCI. AFCI breakers do have ground fault protection but it is set at a higher level than GFCI protection. A GFCI must trip at 4-6ma and a AFCI is set to trip at aprox. 30-50ma. I know that Siemens (Murray) AFCI's initially had the Ground Fault Protection set at a lower level (6-10ma) but changed it to the higher level. My guess is that you got a hold of some of the older breakers which is why they were tripping with the GFCI tester. Even at the initial lower level they are not approved as Class A (GFCI) protection.
russellroberts
Senior Member
- Location
- Georgia
Re: AFCI compatability w/shared neutral feeds?
Jimb,I've used the 12-4 several times in some remodel jobs. It was a time saver for mebecause most old houses here have a crawlspace thats really tight,and the less time and # of pulls you can make are big pluses when keeping one eye peeled for rattlers and copperheads found in abundance around here
Russell
Jimb,I've used the 12-4 several times in some remodel jobs. It was a time saver for mebecause most old houses here have a crawlspace thats really tight,and the less time and # of pulls you can make are big pluses when keeping one eye peeled for rattlers and copperheads found in abundance around here
Russell
Re: AFCI compatability w/shared neutral feeds?
Here is a link to Southwire's NM-B product list.
You will see the 14-2/2 and 12-2/2 near the bottom.
Southwire NM-B Product List
Would anyone know off the top of their head what a 250' roll runs approximately?
Here is a link to Southwire's NM-B product list.
You will see the 14-2/2 and 12-2/2 near the bottom.
Southwire NM-B Product List
Would anyone know off the top of their head what a 250' roll runs approximately?
pierre
Senior Member
- Location
- Westchester County, New York
Re: AFCI compatability w/shared neutral feeds?
At the IAEI convention, AFCI's were a hot topic as we can all guess why. Some important information was brought forth. I will to the best of my ability in as short a format as possible explain what I heard.
1. AFCI do not moniter hot to neutral, they have micro chips that detect the 'signature' sign wave of particular 'Arc faults'. This is the significant difference between the AFCI and the GFCI.
2. Most AFCI are set to trip (depending on the manufacturer) at 50 to 75 amps from an 'arc fault'. Lower values were causing nuisance tripping.
3. Most if not all manufacturers are producing their AFCI's with GFCI protection set at around 40 milliamps. These are not listed as combo units as some have suggested.
4. Square D has now (as of Sept 2, 03)come out with a 'combination' AFCI Breaker. Combination in the sense that it will protect the circuit from an arc fault, and a utilization equipment plugged into the receptacle. They say this is a first in the industry. They will not be readily available for a few monthes. Because of the new technology they are able to have the AFCI detect faults as low as 5 AMPS. Much lower than even their previous Arc fault breaker.
5. A large percentage of the arc fault breakers tripping have been found to be wiring mistakes. The manufacturers want to be able to further develop the product, and will send a technician out to your site if you are experiencing problems. In this process they have learned that 90% of the problems in the field are neutral to ground connections in the circuit that are tripping the device.
Because AFCI's are not going to disappear, I suggest two things. Get the manufacturers to come to a local meeting to educate the members as to the functions and trouble shooting process for the devices. And contact them for any problem or info, as any and all will help in the future development of the product.
Because the GFCI protection of an AFCI breaker is set at 40 milliamps, some breakers are not tripping until a load is introduced on the circuit. A 4-6 amp class 'A' GFCI trips almost instantaneously, because it does not take too much leakage current in the circuit to trip it. On the otherhand a 40 milliamp device will not detect the low level leakage and therefore a load will need to be introduced. That is why some will say the breaker does not trip until they turn the fan, light or whatever on. In this case 'most' times it is a neutral-ground connection somewhere in the circuit.
There is a race on with the different manufacturers to put the best product out. Because of this they are working with us on this. I made a suggestion for them, produce an AFCI that will indicate when it has tripped, if it tripped on GFCI or AFCI. Wouldn't that solve some issues?
Contact the manufacturers with your suggestions!
Pierre
At the IAEI convention, AFCI's were a hot topic as we can all guess why. Some important information was brought forth. I will to the best of my ability in as short a format as possible explain what I heard.
1. AFCI do not moniter hot to neutral, they have micro chips that detect the 'signature' sign wave of particular 'Arc faults'. This is the significant difference between the AFCI and the GFCI.
2. Most AFCI are set to trip (depending on the manufacturer) at 50 to 75 amps from an 'arc fault'. Lower values were causing nuisance tripping.
3. Most if not all manufacturers are producing their AFCI's with GFCI protection set at around 40 milliamps. These are not listed as combo units as some have suggested.
4. Square D has now (as of Sept 2, 03)come out with a 'combination' AFCI Breaker. Combination in the sense that it will protect the circuit from an arc fault, and a utilization equipment plugged into the receptacle. They say this is a first in the industry. They will not be readily available for a few monthes. Because of the new technology they are able to have the AFCI detect faults as low as 5 AMPS. Much lower than even their previous Arc fault breaker.
5. A large percentage of the arc fault breakers tripping have been found to be wiring mistakes. The manufacturers want to be able to further develop the product, and will send a technician out to your site if you are experiencing problems. In this process they have learned that 90% of the problems in the field are neutral to ground connections in the circuit that are tripping the device.
Because AFCI's are not going to disappear, I suggest two things. Get the manufacturers to come to a local meeting to educate the members as to the functions and trouble shooting process for the devices. And contact them for any problem or info, as any and all will help in the future development of the product.
Because the GFCI protection of an AFCI breaker is set at 40 milliamps, some breakers are not tripping until a load is introduced on the circuit. A 4-6 amp class 'A' GFCI trips almost instantaneously, because it does not take too much leakage current in the circuit to trip it. On the otherhand a 40 milliamp device will not detect the low level leakage and therefore a load will need to be introduced. That is why some will say the breaker does not trip until they turn the fan, light or whatever on. In this case 'most' times it is a neutral-ground connection somewhere in the circuit.
There is a race on with the different manufacturers to put the best product out. Because of this they are working with us on this. I made a suggestion for them, produce an AFCI that will indicate when it has tripped, if it tripped on GFCI or AFCI. Wouldn't that solve some issues?
Contact the manufacturers with your suggestions!
Pierre
G
Guest
Guest
Re: AFCI compatability w/shared neutral feeds?
Have you had a chance to look at the Zlan AFCI breaker?
http://www.zlan.com
Have you had a chance to look at the Zlan AFCI breaker?
http://www.zlan.com
Re: AFCI compatability w/shared neutral feeds?
Curt,
Perhaps I wasn't clear in my earlier post, but I agree that standard AFCI's do not meet the qualifications for Class A GFCI protection. I only meant to allude to the fact that they will trip when there is a current imbalance such as could be expected in a multi-wire branch circuit, or as Pierre mentioned in an improperly wired circuit where the grounded conductor and equipment grounding conductor are connected or in contact with each other.
Part of the confusion may have come from my sidenote about the AFCI that was tripped by my GFCI tester. I included that because at the time it happened it truly perplexed me. I didn't expect that result and when it happened I didn't know whether to doubt the AFCI breaker or the GFCI tester. As it all turns out I'm glad I posted it though because you answered my question. The breakers in question were Siemens 120V 20A breakers and apparently I had one of the older ones mixed in with some of the newer ones. Thanks for that tidbit of information.
Jim
Curt,
Perhaps I wasn't clear in my earlier post, but I agree that standard AFCI's do not meet the qualifications for Class A GFCI protection. I only meant to allude to the fact that they will trip when there is a current imbalance such as could be expected in a multi-wire branch circuit, or as Pierre mentioned in an improperly wired circuit where the grounded conductor and equipment grounding conductor are connected or in contact with each other.
Part of the confusion may have come from my sidenote about the AFCI that was tripped by my GFCI tester. I included that because at the time it happened it truly perplexed me. I didn't expect that result and when it happened I didn't know whether to doubt the AFCI breaker or the GFCI tester. As it all turns out I'm glad I posted it though because you answered my question. The breakers in question were Siemens 120V 20A breakers and apparently I had one of the older ones mixed in with some of the newer ones. Thanks for that tidbit of information.
Jim
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: AFCI compatability w/shared neutral feeds?
Thanks Pierre. One thing I learned recently about an AFCI is the only way to know if it works OK is to use a AFCI tester. The test button on a AFCI only tests the trip circurity. the AFCI tester I have actually loads the AFCI circuit, and indicates the voltage drop at each recptacle. By checking the voltage drop at each receptacle you can see if there is bad connection. Also the AFCI needs a load to trip on the GFP circuit, it was suggested to me by a CH engineer that a 100W lamp be used to load the circuit.
CH has a good ten minute video on AFCI's they were handing out CD-roms at the IAEI convention last week.
And I also agree that most of the AFCI tripping problems are due to neutral to ground inadvertant connections.
Thanks Pierre. One thing I learned recently about an AFCI is the only way to know if it works OK is to use a AFCI tester. The test button on a AFCI only tests the trip circurity. the AFCI tester I have actually loads the AFCI circuit, and indicates the voltage drop at each recptacle. By checking the voltage drop at each receptacle you can see if there is bad connection. Also the AFCI needs a load to trip on the GFP circuit, it was suggested to me by a CH engineer that a 100W lamp be used to load the circuit.
CH has a good ten minute video on AFCI's they were handing out CD-roms at the IAEI convention last week.
And I also agree that most of the AFCI tripping problems are due to neutral to ground inadvertant connections.
tonyi
Senior Member
Re: AFCI compatability w/shared neutral feeds?
(at least) GE and Cutler Hammer make 2-pole AFCI's suitable for multiwire. I've only put two of the GE 2-pole units in so far and they were common trip configuration, but I know the CH units are availbale in common and independent trip configurations. Southwire is making that 12-2-2 Romex now that looks viable for two completely independent circuits. The specs indicated you had to derate it as if it were 4 current carrying conductors in pipe though. Similar configurations in MC have existed for quite a while now too.
(at least) GE and Cutler Hammer make 2-pole AFCI's suitable for multiwire. I've only put two of the GE 2-pole units in so far and they were common trip configuration, but I know the CH units are availbale in common and independent trip configurations. Southwire is making that 12-2-2 Romex now that looks viable for two completely independent circuits. The specs indicated you had to derate it as if it were 4 current carrying conductors in pipe though. Similar configurations in MC have existed for quite a while now too.
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