what i was told about the effectiveness of afci's

[rong111]

hi, all.

the following was told to me by an engineer that desigens these devices. he asked for me not to use his name. if any of this seems to be misinformation i would appreciate comments.

i do industrial work so i am not involved with these. i questioned their use in my existing home. bottom line: i was told "since your(my) entire home is wired in emt and you have a qo load center with redundant ground, you have little use for afci's".

the reasons given were:
1) these devices are most effective at opening on a line to ground arc. with other types of arcs they become much less efective.

2) they provide very little protection beyond the recptacle. (which was what they were originally marketed for.) they do not provide much protection beyond ordinary breakers from a intermittent connection between line and netural or an intermittent arc in line only beyond the outlet (bad lamp cord). as far as a constricted cord causing too much resistence, ordinary breakers handle this just as well as afci's (they trip mainly on heat not overcurrent). although, quite a bit of heat has to be generated to trip either type of breaker. still, ignition of surrounding materials from heat is fairly rare.

3) the most likely scenario of a zip cord to cause ignition, "dead short", will instantly trip a ordinary breaker.

4) as far as a intermittant arc in a zip cord or a glowing connection at a nut is concerned, sparks are more likely to be a source of ignition than heat. these devices will trip on the later condition before heat becomes an issue, but not before sparks have been produced, if indeed they would be produced.

comments appreciated,
ron g.

 

[charlie b]

Re: what i was told about the effectiveness of afci's

Originally posted by rong111:The following was told to me by an engineer that designs these devices. I would appreciate comments.

I don?t design these devices, but I am an engineer. My first comment is that the information you were provided is full of equivocating terminology, such as ?very little protection,? and ?do not provide much protection,? and ?fairly rare,? and ?most likely scenario,? and ?more likely.? From your description, I conclude that the engineer who gave you this information did not say either ?the devices are of no value,? or ?the devices make the house less safe.?

My second comment is that the NEC requires the use of these devices in specific applications ? see 210.12(B). My final comment is that the purpose of the NEC is ?the practical safeguarding of persons and property from hazards arising from the use of electricity? ? see 90.1(A). Neither of these two facts is diminished by the low probability that any given house (or homeowner) would be saved by one of these devices.

 

[tom baker]

Re: what i was told about the effectiveness of afci's

Mike Holts web site has a whole section on AFCI's, under newsletters. There is more there then we can possibly list here. Start there and if you have other questions please revisit us.

 

[rong111]

Re: what i was told about the effectiveness of afci's

thank you for the replies.
indeed, the person i talked with about these did NOT say they are useless or unsafe. i think what he was trying to tell ME specifficaly is that i did not have a huge need for them and that the nec does not require them in existing construction. if i was in a situation that actually required their usage i would not even question that. i just asked him simply, "should i run out and spend my money on these even though i am not required to install them in existing residential constructuion" i guess he just pointed out that in my specific case they would not be of high value. he certainly however did not say that they are of little value. more or less he told me to draw my own conclusion. which is why i came here. which i should have said in the first place. instead of typing out my whole conversation with this person. honestly, i probably badgered those answers out of him. he did not outright state that they are bad in any way.

i think what he was trying to tell me is that my particular house is not going to enjoy considerably greater fire safety with the installation of these devices in the bedroom branches. all i really wanted to know was if anyone here agreed or dissagreed. i apoligize for being so long winded about it.
now in retrospect i also realize that the members of this board are probably not at liberty to make a statement as to either effect.
furthermore this is the answer i have gotten from everyone "draw your own conclusion". and i now understand why. no one wants to be liable, nor should they be.

i am not green as grass as i may have made my self to appear in my first post here. i am just not a wireman or in residential construction.

anyways, i have settled all of this very simply!
like (charlie b) stated, and one fact i am sure everyone can at least agree on is "these devices can do no harm".
so i went to home depot this afternoon and purchased these devices. i will install them tonite. i guess that was a real easy way to settle my concerns. i pretty much was looking for someone to talk me out of spending $200 on these things, no one would do that. once again, i did not require these, however i am always intrested in any new safety devices. wether they be electrical or otherwise.

thank you,
ron g.