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Arc Fault on Smoke Detector Circuit??

Hiker's picture

Just finished electrical inspection and our one deficiency was that we did not have an arc fault breaker on the smoke detector circuit.  Is this really NEC required on a residence?  If so could you explain what we are protecting against?  I am honestly curious about the logic on this. 


Not really a big deal, fast and easy fix, but it seems like electric code is headed toward all GFCI receptacles, all arc fault breakers, and a bubble covers every where in case in rains in the living room.


Thanks for any insight


Bruce

(post #77017, reply #1 of 3)

There was a thread on this lately, try the search function. IRRC, some jurisdictions have begun to require this, others not. Opinions are many and various.

Scott.

Always remember those first immortal words that Adam said to Eve, “You’d better stand back, I don’t know how big this thing’s going to get.”

(post #77017, reply #2 of 3)

The 2002 and subsequent NEC requires all bedroom "outlets" to be AFCI-protected.  An outlet is either a receptacle outlet or a lighting outlet, or any other place power is taken from a circuit.  A smoke detector fits this description.


Some local jurisdictions modify this requirement to apply only to receptacle outlets.  That's their right, the NEC is a set of standards, not a regulation with the force of law.  The Code requirements can be changed when it's adopted. 


The NEC requirement that any bedroom outlet be AFCI-protected is based on the assumption that an arc fault is as likely to occur at any place where power is taken from the circuit.  There are going to be splices or terminals at these points of use, so the logic sort of makes sense.


OTOH, the rationale behind requiring AFCIs for receptacle outlets and not lighting or other outlets (like smokes) is twofold: first, a lighting outlet is probably going to draw much less power from the circuit (a typical fixture is likely to be 300 watts or less, usually less--figure 2 to 3 amps, compared to a possibly 12-15 amp load from a space heater plugged into a receptacle).  Second, a receptacle outlet generally sees movement every time a plug is inserted or withdrawn.  This can loosen up the connections over time.  That's more likely to cause a loose wire and possibly then an arcing fault.


In fact, the first NEC requirement for AFCIs was limited to receptacle outlets.  The '99 Code required AFCIs for receptacles in bedrooms starting in, IIRC, 1/1/2001.  The 2002 & 2005 NEC requires all bedroom outlets to be AFCI-protected.  It looks like the 2008 Code will require AFCIs for all 120V, 15 or 20A branch circuits.


The issue with smoke detectors on AFCIed circuits is covered by the fire code requirement that smoke detectors have battery backup.  If the AFCI trips because of an arcing fault that starts a fire, the 9v battery will power the smoke.  That is, if there a good battery in the unit.


IS that clear as mud?


Cliff

(post #77017, reply #3 of 3)

CAP,


Thanks,


So all circuits are going to AFCI breakers in the near future.  So we can plan on doubling the amount of the panels so a well wired house will have a wall of panels.  Has anyone come up with the 1/2" AFCI?


Bruce