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danielrg 08-27-2011 12:00 PM

Questions on installing Smoke Detectors
I am finishing my basement and am planning out how I am going to install the smoke alarms / detectors. I live in West Jordan, Utah.

My house is about 10 years old and has interconnected smoke alarms using 3-wire cable. I am assuming I just need to continue the "chain" in my basement. I have a few questions:

1) I have a finished room in the basement the builder put in - even though you have to walk through unfinished space to get to it. The 3-wire for smoke alarms comes from upstairs to a single smoke alarm in the unfinished basement, then another wire goes from that alarm to the one in the downstairs finished room, and the series terminates there.

My first question is: The alarm in the finished room is hard to get a new wire to. Can I branch into the basement from the alarm BEFORE it, the alarm in the unfinished space? This would mean there are three cables coming out from the alarm in the unfinished space - one to the existing downstairs bedroom, and then another to the new rooms I'll be putting in. From my understanding of electrical principles this should work fine, but I don't know if it is against code.

2) Is there a limit to how many smoke alarms can be on a circuit? Can I add all the alarms in my basement to the existing circuit and be okay? I would be adding 3 more to an existing series of 7, for a total of 10.

Thanks in advance!

Code05 08-27-2011 12:58 PM

You tap any smoke detector to another.

10 smokes is a minor load.

mbryan 08-28-2011 11:18 AM

I know that my city requires the smoke detectors to be on arc fault breakers. If your worried about staying within code you may want to look into that.

Jim Port 08-28-2011 02:10 PM

You just need to check to see how many alarms the manufacturer says can be grouped together. Even at 10 I think you will be fine. IIRC a typical limit is 18 smokes. Check the paperwork for the alarm.

danielrg 08-28-2011 04:27 PM

Thanks for your help
It looks like I'll be putting in another 4 for 11 smoke detectors total. Either way it looks like I'll be fine.

mbryan - I am hoping that since I am tapping off an existing series they won't make me upgrade the breaker for it. With what I am planning for the basement, my panel will be completely full, and a bunch of the breakers are double pole T&B breakers which I don't think can be upgraded to AFCI. [That's probably another post altogether.]

I'll tap off the easy to reach one in the basement. The series will then look like this:

upstairs --> bsmnt --> bsmnt BR
\--> NEW Remodel (4 more in series)

I love the forum, I just wish there wasn't always state and local code differences to consider - although I guess it adds to the fun :party:

Jim Port 08-28-2011 04:34 PM

You are not adding any load to the circuit to worry about upgrading the circuit. You also could not upgrade the breaker to a larger size without increasing the wire size also, unless you like creating fire hazards.

vsheetz 08-28-2011 05:22 PM

I have smoke detectors that communciate wirelessly. If allowed where you are, may be a option to consider.

danielrg 08-28-2011 05:50 PM

breaker upgrade...
Jim - I was talking about "upgrading" the breaker from a standard to AFCI breaker, not actually increasing the amperage rating. I didn't write that very well. I have these weird "duplex" breakers, and there aren't any replacements that I know of that support AFCI... and I wouldn't want to move the 2nd circuit to another breaker slot as I won't have any slots left as it is after the basement remodel.

Jim Port 08-28-2011 06:24 PM

They are commonly called tandem, duplex, twins etc. You will not find a AFCI or GFI duplex breaker. Both of those styles take a full size single pole slot.

I wanted to clarify about the breaker upgrade so both yourself and others did not create a fire hazard.

You could add a subpanel that would allow you to add more breakers as well as the AFCI protection.

TJ_in_IL 08-28-2011 07:02 PM

Make sure all of the smokes are the same make/model. Some do not work with others, and instructions specifically state this. Has to do with the interconnect tripping the sounders in the other units. If the older ones are close to 10 years old, you will want to change them as well. Average life is 10 years per manufacturers.

danielrg 08-30-2011 12:08 PM

Thanks for the comment on changing out the smoke detectors. I think I'll see if I can buy all new smokes for the house in bulk or something. Some of them are acting up anyway - draining batteries really fast, beeping a couple times then not beeping again, etc.

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