Wires in Attic for Bedroom Smoke Detectors

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Old 08-15-09, 11:09 AM
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Wires in Attic for Bedroom Smoke Detectors

I'm adding 4 smoke detectors in the bedrooms and tying them into the existing 3 (1 per floor). All the new wiring will be in the attic where I have blown in insulation.

Can these cables run along the top of the joists (actually, code says they'd have to go through, not on top, of the joists right?) where they'll be covered by the insulation or do they need to come up out of the insulation and run along the ceiling?

It seems that having them buried in the insulation wouldn't be a good idea, but maybe it's not a big deal.
 
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Old 08-15-09, 11:15 AM
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The cables need to be protected within 6 foot of the attic scuttle. Due to the hassle of drilling through the joist I just settle the cables down to the top of the joists and staple to the top of the joist. If you have trusses you should not drill through them.
 
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Old 08-15-09, 06:47 PM
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Originally Posted by pcboss View Post
The cables need to be protected within 6 foot of the attic scuttle.
Sorry, but does that mean the opening used to access the attic? And protected how?
 
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Old 08-15-09, 06:51 PM
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Yes, scuttle is another word for hatchway. Anywhere the cable is likely to be stepped upon it needs to be protected against damage. Normally this means a "running board" used either under the cable or along side the cable to prevent someone from placing their foot on the cable without it also being on a structurally sound piece of material.
 
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Old 08-15-09, 06:58 PM
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Got it. So, what about it running 'buried' in the insulation? OK or no?
 
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Old 08-15-09, 07:33 PM
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In my opinion it is the same thing. If the cable is running perpendicular to the joists then it is subject to damage unless it is far enough away from any place where a person may stand.

My attic has blown-in insulation over the tops of the truss chords but it is pretty obvious where those chords are and where I need to step when wading around. If the cables were simply run across the top of the chords I could inadvertently step on one of the while trying to make the chord with my foot. That would put quite a strain on the cable and could cause a problem.

Now IF the cable is run close to the outer edge of the truss/chord span, where the clearance to the underside of the roof precludes anyone from standing, I see no reason for the running board and simply strapping/stapling the cable to the top of the chord (or joist) is code compliant and also relatively safe.
 
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Old 08-15-09, 08:24 PM
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Originally Posted by salguod View Post
Got it. So, what about it running 'buried' in the insulation? OK or no?
No issue with running wire through, in, or under insulation. Another reason that you probably don't want to drill the joists, you'll have to displace all that insulation and put it back... just a pain.

Wherever possible, keep it in places that you wouldn't walk (like at the really low-head-clearance areas, and if you have to run where you or someone might walk, use running boards.
 
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Old 08-15-09, 08:36 PM
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I'll have to displace enough putting the ceiling boxes in.

I was hoping not to have to do this, but any remodeling means bringing smoke detectors up to current code and that's 1 per bedroom. I was initially told that batter operated would do, but the inspector says if I can easily run the wires, they need to be hard wired.
 
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