Re: CQD answer published Thursday, May 14, 2015 - AFCI Protection
Hi Charlie, Thanks for your work
In regards to the AFCI question from the anonymous CMP-6 member, I think a couple of more interesting questions are; "What percentage of house fires with electrical causation happen in homes with AFCI installed?" I bet that number is low. Maybe not because of efficacy of AFCI but rather- "When are electrically kindled fires most likely to happen, in a new home or an older home?" Also- "Why would we assume that fires would only be kindled by the wiring serving the bedroom?" and "Why would we assume an AFCI's ground fault protection to NOT be protective against a "glowing connection" in a grounded cable?". And finally "Is the rate of fire different in states that actually adopted the AFCI requirements compared to those states that didn't?". Because it is in the Code does not mean it is adopted . The gross number of house fires wouldn't tell you much about AFCI efficacy, in my opinion.
Given that the fire cause and origin stats show that 85% of the dwelling unit fires that are said to be of electrical origin occur in dwelling units that are at least 20 years old, it will be a long time before there are any numbers that show a reduction of dwelling unit electrical fires because the AFCI prevented them.
If you apply that information to the rate of dwelling unit fires that are said to be of electrical origin, you would find that for the first full year of compliance with the 2014 AFCI rule, and assuming that the AFCI is 100% effective in preventing electrical fires, you would prevent ~55 fires. Of course that number compounds as time goes by, but it will be some time before there any real numbers.