Arc-Fault Code

An electrician buddy of mine just told me that he is required to put arc fault protectors to all runs going to bedrooms. An inspector recently pinged him because he did not put the fire detectors in the bed room on the arc fault run.
Why would the code potentially disable your smoke detectors because there was an arc fault? This doesn't make sense, unless smoke detectors are responsible for bedroom fires...
Anybody know the *reason* behind the code?

I wonder how many lives, if any, will be saved by this particular code change. That's supposed to be the reason for the code, but economic interests seem to be what really drive things.
snipped-for-privacy@yahoo.com (William Wallace) wrote in message
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| I wonder how many lives, if any, will be saved by this particular code | change. That's supposed to be the reason for the code, but economic | interests seem to be what really drive things.
If arc fault detectors were real arc fault detectors, I'd want to have them in many places (and bedrooms first). But based on the designs I have seen, they are detecting arcs that specifically draw higher levels of currents, though not as high as a short would produce that a regular breaker would pop on. That's an arc between hot and either neutral or ground, but not a physical contact between conductors. It's a genuine fire hazard that normal breakers don't catch fast enough, so they are a good thing in that respect. But they are being marketed as doing what their designs won't do, and that's catch other forms of arcing that can also be dangerous, but have relatively low current (well under the whole circuit rating). Loose plugs, for example, will arc and/or produce hot spots, and can cause a fire. These AFCI devices can't detect that. If they could, it might be worth it.
I don't have an actual AFCI right now to test with, but it looks like they won't be as susceptable to RFI as GFCIs are. Well, I hope not. RFI will put a common mode current on the wires, which won't cancel out on the sensor. They will need a common mode RF filter to prevent the problem. AFCIs have a higher trip level, so maybe they won't be affected as much. Also, AFCIs will go in the breaker panel, mostly, and there is better opportunity to put some RF filtering on the wires.

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In absolute numbers there are really not that many people who die in house fires. It is a very small fraction of the number who die in cars but the NFPA strives to bring that low number lower. Bedrooms are the most dangerous rooms in the house since people there are usually sleeping when a fire starts. Smoke detectors in each bedroom are aimed at getting the inhabitants out in a timely manner and the AFCI is designed to prevent a common cause of fires at the source. Arcing faults from pinched cords are a common cause of a bedroom fire. These faults can be far below the trip value of a breaker but still spark enough to start a fire in a rug, sheet, blanket or even the dust bunnies under a bed. In the end we may only be talking about saving a dozen lives a year but if one of them is your kid you will want to spend the $40 for the AFCI.

snipped-for-privacy@aol.com (Greg) wrote in message
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Is the number even as high as a dozen? I seem to recall seeing a number more like 1 or 2 deaths per year blamed on this problem in bedrooms.
$40 per bedroom does not sound like a lot, but I seem to recall there are something like 300 million bedrooms in the US. The eventual replacement of all those CBs would indicate a cost well over $1 billion. All that for the dubious premise of saving 1 or 2 lives a year.
If people want to spend $40 to replace an existing CB with an arc fault unit, I have no problem with it, but I think smoke detectors have far broader utility for protecting people from fire then do arc fault breakers.
OTOH, smoke detectors have gotten quite cheap, the patents are all expired, and there is little profit in them. Call me a cynic, but arc fault beakers seem to me to be just a way of squeezing a few more bucks out of the average consumer with little real benefit on the whole.

bob peterson wrote:
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You have to consider all bedroom fires due to arcs, not just those that resulted in death. And the code does not require retrofit for the existing 300 million (or whatever the number is) bedrooms. New construction and re-models would need it.

So, a pinched cord causes an arc and a spark, starts a fire, the arc fault detecter trips the circuit, and the smoke detector no longer works.
Sound like this change could result in more deaths, not fewer.
And how does a cord get pinched when somebody is sleeping?
snipped-for-privacy@bellatlantic.net wrote in message
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(remove NS to use the address) 614.937.0463 voice 208.975.1011 fax
http://worthingtonengineering.com

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Smoke detectors are required to have battery backup now too.
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When its caught under a bed frame wheel? The electric blanket or heating pad fail? I'm really reaching to think of these...
-- Mark Kent, WA

William Wallace wrote:
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You replied to me - but I did not post anything about pinched cords or fire detectors. I believe - but I do not *know* - that the idea is that the AFCI will trip long before there is enough arcing to start a fire, and that arcing in electric blankets was a main (the ? main) concern - thus the bedroom requirement.
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Oops, sorry, I was out of sequence.
Who uses electric blankets? Turn the heat up:)
snipped-for-privacy@bellatlantic.net wrote in message
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snipped-for-privacy@yahoo.com says...
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Hogwash! Throw on another blanket! ...get cozy!

snipped-for-privacy@yahoo.com says...
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Agreed. I don't think this was the idea though.
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Cats? ("Christmas Vacation", anyone?)

snipped-for-privacy@bellatlantic.net says...
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If it's a couple of bucks, go fer it. Forcing a retrofit just doesn't make sense. ...though wait until it becomes a political tool...
GFCI was at one time expensive. GFCI receptacles are now dirt cheap.

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But they are a pain when you buy a new house and the electrician ran the GFI through 3 rooms, and you can't figure out why your outlet in the hallway won't work (it's on the basement GFI). I bet more than one electrician was called to fix a non-functioning outlet only to discover the GFI in some other room had been triggered (or the wife pushed that button on the outlet not knowing what it was).

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You're right, it's a nuisance. So why do the Electrical companies do it? Let's assume 2 outside plugs on one GFCI and 3 washroom plugs on another GFCI. You've saved 3 GFCI's or about $30. Extra wire cost would be in the range of $5. Net savings $25. If you're wiring 500 new homes per year this adds up to $12,500. Why not save the money? Almost all new homes have customer requested extras. I've never seen a customer request GFCI's at all protected outlets. Appears customers don't care. Builders often have specific requirements for all of their homes (ie copper service wire, plastic boxes, etc.). If the builders considered it a selling feature they would require GFCI's at all protected outlets. None do. If your home has a GFCI outlet protecting a number of regular plugs and you don't like this, change it! You're local code may require that you change the box to a deep box. Join the line and load wires at each box with a tail for the GFCI and add the device. If you're good at it you can change the box and add the GFCI in ten minutes or so. Russell
on a

The NEC limits this somewhat by the number of circuits that can have no other outlets. Kitcahens and bathrooms have such limits. I usually see the outside receptacles on the garage GFCI if they are trying to cheap out.

(remove NS to use the address) 614.937.0463 voice 208.975.1011 fax
http://worthingtonengineering.com

@yahoo.com says...
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How is that different than a GFCI breaker (located outside the house) that controls three bathrooms and an outside outlet? Why are 3 rooms on one GFCI? Why a GFCI for regular rooms? Idiot electricians can make a mess of anything.
OTOH, GFCI outlets are so cheap there is no reason to muck things up this way. Put them wherever they're needed.

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Does this mean I am no longer going to be able to run my arc-producing appliances such as my Tesla coil with a rotary spark gap and my Jacob's ladder on my bedroom outlets?
Beachcomber