Arc Fault Breakers?

[cm]

Can some one please educate me on arc fault breakers. Wha t is there purpose? What are some of the reasons one might trip in a new house?

Thanks,

Craig

[Robert Barr]

[Chris Hill]

Designed to shut down if an arc is detected, aka a short between hot and neutral caused by wire damage. They will trip if you do something as simple as plugging a small fluorescent light when it is already turned on. Their main purpose is to drive up the cost of new construction; additional safety is just a side benefit.

[Greg]

Most bedroom fires are caused by arcing faults and most people who die in residential fires are sleeping when the fire broke out, that is not a minimal "side" benefit.

[Joe Fabeitz]

Chris Hill is misinformed!

The "arc fault" function of these breakers do NOT respond to the high current that results when "...a short between hot

respond to excessive current.

An arc fault interrupter (breaker) is designed to sense the condition that occurs when a intermittent connection produces an arc and therefore, possibly heat. For example, a wire loosely connected to a wall switch or lamp fixture might arc and therefore produce undesirable heat, but would not cause the current to increase.

Likewise, this fault would not result in a current imbalance between the supply wire (black) and the return wire (white) and, therefore, would not be detected by a traditional GFCI.

The National Electrical Code (NEC) recently added a requirement that all bedroom outlets be protected with an arc fault interrupter device. Note - generally this only refers to new or rehab. work, not to existing homes. Also remember that the NEC is a set of recommended rules but your community code is what applies to your property.

[Greg]

... or a lamp cord pinched under the night stand leg, sitting on a polyester carpet and buried in lint.

[Chris Hill]

Depends. What is your chance of being involved in such a fire? I like the idea, but just because it improves safety does not mean it should be mandated. Why not just ban outlets in bedrooms? That'd improve safety too.

[default]

according to FEMA,

A bit under 14 fire-related deaths per year per million people, (not counting military and terrorist activity)

80% of which occur in residences, a bit under 14% of which occur in bedrooms...

so: .14 x .80 x 14 / 1000000

Thus, your chances of getting killed by a bedroom fire in any given year are about 0.0001568%,

Of course, it doesn't say how many of those are electrical fires, but it DOES say the the three biggest sources of residential fire deaths are smoking, arson, and problems with your heating system problems. If we assume that elecrical arc-fires are number four, then they can't be more than 25% of that total, which means that AFCI protection is designed to save you from a hazard that has a less than

1 in 2.5 million chance of killing you in any given year. Of course, if you otherwise plan to live for an even hundred years, your chances of eventually getting killed by a fire that AFCI could have prevented go up to around 1 in 25 thousand....

--Goedjn

[Greg]

The danger is statistically worse than the chance of a kid being killed in a handgun accident and we know how bad everyone's panties are in a wad over that. I don't necessarily agree with enhancing the nanny state I am only expressing the "justification" that is presented. BTW I haven't felt the compelling need to run out and buy some to retrofit my house.

[gerry]

It also doesn't subtract the added deaths due to sleepy persons stumbling down stairs to reset a false trip.

"There are three kinds of lies: lies, damned lies and statistics."

- Autobiography of Mark Twain

gerry

[Joe Fabeitz]

[Chris Lewis]

According to Joe Fabeitz :

[Not to contradict Joe, just to clarify]

An AFI doesn't detect arcs per-se.

An AFI detects extremely rapid fluctuation in current flow (especially down near to zero), too rapid to be normal demand variations, almost always indicative of a poor connection and arcing.

As a FYI, AFIs _do_ contain GFI functionality, but at 15ma imbalance trigger point rather than the usual 3-5ma of dedicated GFIs.