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Posted by LightsAREon on August 26, 2006, 12:20 pm
Bud-- wrote:
> LightsAREon wrote:
>> mm wrote:
>>
>>> On Thu, 24 Aug 2006 21:59:15 -0400, "Methos"
>>>
>>>> the way a GFCI functions, would it trip
>>>> if a bad connection were made to it ?
>>>>
>>>> (if say, a terminal with the hot or
>>>> neutral wasn't screwed down tight &
>>>> a plugged in load drew current causing
>>>> the terminal to warm up - would the
>>>> GFCI trip ?)
>>>
>
> I agree with others that a GFCi wouldn't trip on a loose connection.
>
>>>
>>> I don't think so. Why would the resistance of a bad connection be any
>>> different from the resistance of a light bulb.
>>>
>>> I wouldn't assume there will be arcing just because a connection isn't
>>> tight enough. So I wouldn't assume that even an arc fault circuit
>>> breaker would be tripped by a loose connection. Am I right or wrong?
>>>
>
> 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--
Methos
It sounds like bud has the right answer. I hadn't heard about the
upcoming AFIC's but will certainly pass the info on to everyone at my
office (I'm a construction administrator for a large architectural
firm). Thanks bud for the education.
LightsAREon
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