AFCI circuits need separate neutrals?
- Thread starter cppoly
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If you have a MWBC then you need a multi-pole AFCI circuit breaker or an AFCI device where the circuits split, one for each circuit of the MWBC. The latter choice may have other requirements regarding wiring methods.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
I added the emphasis. The NEC is silent about this.
Whether an AFCI circuit has to have its own individual neutral is determined by the way the AFCI behaves.
There are now six manufacturers of AFCI protective devices (GE, Siemens, Square D, Cutler Hammer, Leviton and Pass & Seymour). At present, GE is the only AFCI (breaker or receptacle) that works using single pole AFCI "MOD 3" combination AFCI on a shared neutral multiwire branch circuit, that I am aware of.
You don't say whether the homeruns are existing or new installation. Bottom line, to answer your question, you have to read the manufacturer's instructions for the AFCI device you must use. If you have a choice of AFCI, then pick the one that fits the situation best. If you don't know the type of AFCI device you must use, I recommend not using shared neutrals, if possible.
Excellent thank you.
brycenesbitt
Senior Member
- Location
- United States
For K&T
For K&T
For retrofitting Knob & Tube, a second white is not an option. The Siemens Q220AFC has worked for me in this situation.
This in theory protects against chafing insulation where the old wires enter metal junction boxes.
For K&T
For retrofitting Knob & Tube, a second white is not an option. The Siemens Q220AFC has worked for me in this situation.
This in theory protects against chafing insulation where the old wires enter metal junction boxes.
You could use GE gfci breakers.
http://apps.geindustrial.com/publib...TNR=Application and Technical|DET-719|generic
and identified handle tie per 210.4(B)
the catch is in manual attached to breaker it says 'for 120/240 system' and in my area I have 120/208 3 phase system so I guess I can't use it. Either way we wire all apartments with 12/2 AC. But one time after reading the above article I wanted to wire apartment with 12/3 AC like in good days (but I did not) and a couple months later I read the note that came with breaker
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Knob and Tube ........ Time for a rewire in my opinion.
I think most major insurance companies don't like the stuff.
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
I live and work in the inner city of a city of three millions. Here there is a huge base of pre-1940 buildings wired with Knob & Tube, and "I think" most major insurance companies ply their wares here.
Knob & Tube is still a Chapter 3 wiring method.
mwm1752
Senior Member
- Location
- Aspen, Colo
al hildenbrand
Senior Member
- Location
- Minnesota
- Occupation
- Electrical Contractor, Electrical Consultant, Electrical Engineer
In noting that K&T is a Chapter 3 wiring method, I said nothing about new installations of K&T. The NEC is a new construction standard. The existence of K&T that WAS installed to the Code in effect at the time of its installation is not challenged by TODAY's NEC. That is, unless there is local ordinance that is retroactive to Premises Wiring (Systems) legally installed under earlier editions of Code. The mere existence of K&T in the wiring of an old building is not an automatic indictment of all the K&T present. The condition of existing K&T requires a nuanced discussion, taking into account environmental and historical use factors of the specific installation one is looking at.
And there is the beginning of a nuanced discussion about a specific installation. -- As an aside, most historic branch circuit extensions in my inner city area were done either with individual conductors sleeved with continuous loom tubes, or with early armored cable (BX). The inner city had established an "all-metal" Code from the 1930s into the 1970s precluding NM from being used. It is interesting to note that, when used for the extension of an ungrounded wiring method, the metallic sheath of that old BX, during the early years, was permitted to be installed without a connection to an existing grounding means.
You can find many modern Article 310 conductors, per 394.104, at the supply house.
mwm1752
Senior Member
- Location
- Aspen, Colo
Now thats specific to the parts of my comments about a vague response.
- Location
- Massachusetts
We used to have a frequent poster here from the San Francisco area and he was a pro at extending K&T circuits with more K&T.
He knew the rules and as there was a huge base of K&T in his area he used his knowledge on many jobs.
He knew the rules and as there was a huge base of K&T in his area he used his knowledge on many jobs.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
There are several mfgs of shared neutral AFCIs, perhaps 3.
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