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Posted by Bud-- on September 26, 2006, 3:07 am
David Combs wrote:
>
>>A loose connection can produce enough heat to start a fire without
>>arcing (a "glowing" connection). Late stages in failure are likely to arc.
>>
>>AFCIs sense "parallel" arcs - from hot-to-neutral (a "fault", the F in
>>AFCI). Starting in 2008 the NEC requires them to also detect "series"
>>arcs, as in a loose connection. As far as I know, no current AFCIs
>>detect series arcs, so none would detect a loose connection.
>>
>>
>>>
>>>Methos
>>>
>>>A GFIC is made to trip on sudden line voltage changes. A slow warm up
>>>would not trip the built in breaker. This very problem cause a house
>>>fire that burned a third of my parents house to the ground. Two wires
>>>in some old Romex touched and caused a slow short but it was not enough
>>>to trip the breakers. Therefore, it warmed up long enough to catch fire.
>>>
>>>GFIC's are a nice safety feature but it certainly doesn't catch all
>>>problems
>>
>>GFCIs trip on a difference in current between the hot and neutral, not
>>line voltage changes. They are primarily for electrocution protection.
>>
>>The "slow short" you describe, an arc that trips a breaker slowly, if at
>>all, is exacty what AFCIs are designed to protect against. A more likely
>>cause is probably an abused extension cord.
>>
>>AFCIs also include 30mA ground fault protection (GFCIs have 5mA
>>protection). The idea is, I think, that if a ground wire is adjacent, a
>>hot-to-neutral arc is likely to also become hot-to-ground.
>>
>>bud--
>
>
> What is an AFIC?
>
> Thanks!
>
> David
>
>
Arc Fault Circuit Interrupter. The AFCI breakers look like, and wire
like GFCIs. AFCIs trip on arcs. The NEC requires them on new circuits to
bedrooms. The proposed 2008 NEC requires them for all residential 15 and
20A circuits IIRC (could still be changed though).
A good paper from the Consumer Product Safety Commission on AFCIs is at
http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf
It explains the rationalle for using AFCIs describes how they work.
bud--
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