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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Dennis Wiggins on December 04, 2013, 10:15:09 am

Title: AFCI Breakers
Post by: Dennis Wiggins on December 04, 2013, 10:15:09 am
First off; I am not an electrician.

I found this, regarding AFCI breakers in residences.  I don't know what is code for commercial space. 

210.12(B)Dwelling Units.

All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sun rooms, recreation rooms, closets, hallways , or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type installed to provide protection of the branch circuit.

Note 1:  Not all states require this.

Note 2:  AFCIs resemble a GFCI/RCD (Ground-Fault Circuit Interrupt/Residual-Current Device) breaker in that they both have a test button although each has a different function. GFCIs and RCDs are designed to protect against electrical shock of a person, while AFCIs are primarily designed to protect against electrical fires caused by arcing. Some outlets must be protected by both a GFCI and an AFCI, such as an outlet near a wet bar in a family room.

-Dennis
Title: Re: AFCI Breakers
Post by: Stephen Swaffer on December 07, 2013, 01:21:52 am


AFCIs have not been required by the NEC in commercial spaces yet-their purpose is completely different than GFCIs-and they do the most good when used with NM cable wiring-wiring that is prone to being damaged by nails or screws usually not used in commercial applications.  I haven't yet read the 2014 code but I am hearing that virtually every receptacle in residential will be required to be either AFCI or GFCI protected depending on the location.

They do cost more of course-and I have personally dealt with situations where AFCI's would have been very helpful-but I am not going to argue for or against them!
Title: Re: AFCI Breakers
Post by: Mike Sokol on December 07, 2013, 02:13:59 am
They do cost more of course-and I have personally dealt with situations where AFCI's would have been very helpful-but I am not going to argue for or against them!
First generation AFCI's were very poor at differentiating between the normal sparking of something like a light switch turning on an incandescent bulb, and a partial short inside a wall that's sparking and creating a fire hazard. I think the later gen designs are much better, but have not personally done any testing on them. I would say that running a sound system from AFCI breakers could be fraught with circuit breakers tripping at inopportune times. For instance, how many times have a stage amp's power plug been pulled out of the receptacle accidentally without being switched off first? That spark would probably be enough to shut down your back-line power feed.

The entire argument over the actual need for AFCI's to begin with has always been a money vs. any actual reduction of electrical house fires issue. Plus the random AFCI tripping from normal light switch sparking doesn't make a homeowner happy when they have to reset the breaker every week.

For now, code is only requiring AFCI breakers in branch circuits feeding bedrooms in homes and such. But I can see code extending this to wall circuits in venue stages pretty soon. Then it's going to get interesting when the back-line power goes out during a music set.   
Title: Re: AFCI Breakers
Post by: Tim McCulloch on December 07, 2013, 03:16:45 am


For now, code is only requiring AFCI breakers in branch circuits feeding bedrooms in homes and such. But I can see code extending this to wall circuits in venue stages pretty soon. Then it's going to get interesting when the back-line power goes out during a music set.   

Compartmentalization... each duplex outlet protected by its own AFCI (like GFCI outlets can be done today).  If it's a genuine problem, the NFPA committee might carve out an AFCI exemption for specific uses in particular special occupancies as has been done for GFCIs.
Title: Re: AFCI Breakers
Post by: Cailen Waddell on December 07, 2013, 07:20:37 am
Or suddenly every PAC will own a small power distro they tie into a disconnect to provide power and all the outlets will be taped over...
Title: Re: AFCI Breakers
Post by: TJ (Tom) Cornish on December 07, 2013, 08:35:54 am
Compartmentalization... each duplex outlet protected by its own AFCI (like GFCI outlets can be done today).  If it's a genuine problem, the NFPA committee might carve out an AFCI exemption for specific uses in particular special occupancies as has been done for GFCIs.
That defeats some of the purpose of AFCIs - the intent is to protect the branch wiring in the walls from picture hanging nails, and the fire mentioned from too many pieces of Romex under a staple. If the AFCI protection was done at the receptacle, the branch wiring would have no AFCI protection.
Title: Re: AFCI Breakers
Post by: Stephen Swaffer on December 07, 2013, 11:44:57 am
In a commercial or stage setting with EMT/GRC used as a wiring method, protection of branch wiring from nails/screws would not be a major concern-but AFCI recepts might be helpful to shut down bad SO cords etc.  But in that situation, GFCI is more important in my mind-if exposed cords get hot enough to burn with people around they should get noticed.  Concealed wiring where people are sleeping is a much bigger concern and easier to justify the cost.  I think the main reason for AFCI receptacles at this point is time is that electricians will no longer be allowed  to install a non-AFCI recept in a residential location-and  AFCIs cannot use a shared neutral-so to extend a circuit with a shared neutral you will need to install an AFCI to feed downstream. 
Title: Re: AFCI Breakers
Post by: Tim McCulloch on December 07, 2013, 02:32:53 pm
That defeats some of the purpose of AFCIs - the intent is to protect the branch wiring in the walls from picture hanging nails, and the fire mentioned from too many pieces of Romex under a staple. If the AFCI protection was done at the receptacle, the branch wiring would have no AFCI protection.

We're comparing different occupancies... IF the NFPA were to adopt AFCI for our occupancy, the AFCI would be upstream, yes, but I propose that each duplex outlet be protected by its own upstream AFCI.  That way someone doing a hot un-plug wouldn't take out the rest of the stage stringer.

I can see how my 2am post could be interpreted to mean that AFCI *outlets* would be adequate when they clearly are not.  I'll clear that up later.