Smoke Detector/Alarm in Series with a Light at the End

12055 Views 10 Replies 6 Participants Last post by fireguy, Nov 15, 2009

memetic

Discussion Starter · Nov 13, 2009

I came into a situation where someone had setup smoke detectors in series starting in the basement and ending on the other end of the house on the second floor. Then, someone (maybe the same person?) took a line off the end and ran it to a switch to power a light. I don't care if it is to code, but is this safe? I don't want to touch this situation at all, unless there is serious risk of damage, injury or death. Thanks.

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480sparky

· #2 · Nov 13, 2009

Smoke detectors in series?

I doubt it, especially if you're talking about plain-jane 120v resi smokes. In series, they will not function. I think you mean in parallel.

If so, unless there's a local Code that requires they be on a seperate circuit, there's no NEC violation.

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memetic

Discussion Starter · #3 · Nov 13, 2009

Good to know. I wouldn't feel right not letting them know there may be a danger (but, I really don't want to get involved with this electrical issue).

Re: series vs parallel. I don't know actually. I know that the 14g wire starts at the box, goes to the 1st smoke, then the 2nd, then the 3rd, and ends at the light on a switch.

Thanks

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480sparky

· #4 · Nov 13, 2009

memetic said:
Good to know. I wouldn't feel right not letting them know there may be a danger (but, I really don't want to get involved with this electrical issue).

Re: series vs parallel. I don't know actually. I know that the 14g wire starts at the box, goes to the 1st smoke, then the 2nd, then the 3rd, and ends at the light on a switch.

Thanks

I'll bet it's parallel. I can't think of any house wiring that would be in series.

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KennMacMoragh

· #5 · Nov 13, 2009

He means parallel, I've heard people say that before. If you have three lights that turn on together or something, they'll say it's in series, but they don't know what it means.

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memetic

Discussion Starter · #6 · Nov 13, 2009

Oh yes, of course, parallel. I meant that the detectors go from one to the next and nothing branches out from anything - except at the very end being the light (and switch). I should have realized what you meant - sorry for the brain fart.

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KennMacMoragh

· #7 · Nov 14, 2009

Yeah, first thing they teach in electrical is the difference between series and parallel, series circuit (left-hand side). Just think, Christmas lights are in series, probably the only series circuit you'll find in a house.

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Zinsco

· #8 · Nov 15, 2009

memetic said:
I came into a situation where someone had setup smoke detectors in series starting in the basement and ending on the other end of the house on the second floor. Then, someone (maybe the same person?) took a line off the end and ran it to a switch to power a light. I don't care if it is to code, but is this safe? I don't want to touch this situation at all, unless there is serious risk of damage, injury or death. Thanks.

To answer your question the code permits this and it is safe assuming it was done properly. I'll run 3 or 4 smoke detectors in a chain like that then feed 2 entire bedrooms with the circuit.
.
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Magnettica

· #9 · Nov 15, 2009

Zinsco, do you wire your smoke detector series circuits normally open or normally closed?

I know if you wired my house like that and the 2 bedrooms didn't work because the damn smoke detectors were activated I'd be pissed.

But then again I think you're only jerking everyones chain when you post anyway.

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Zinsco

· #10 · Nov 15, 2009

Magnettica said:
Zinsco, do you wire your smoke detector series circuits normally open or normally closed?

I know if you wired my house like that and the 2 bedrooms didn't work because the damn smoke detectors were activated I'd be pissed.

But then again I think you're only jerking everyones chain when you post anyway.

Well this is a case where I'm serious. When you say "normally open" or "normally closed" it is clear *you're* talking about a commercial fire alarm system. I suppose to use the proper terminology I'm talking about a hard wired "smoke alarm" you buy at Home Depot for $12.

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fireguy

· #11 · Nov 15, 2009

Zinsco said:
Well this is a case where I'm serious. When you say "normally open" or "normally closed" it is clear *you're* talking about a commercial fire alarm system. I suppose to use the proper terminology I'm talking about a hard wired "smoke alarm" you buy at Home Depot for $12.

I like to see the smoke alarms wired like you do. There is less chance of the breaker to the smokes being turned off when a smoke goes into alarm. http://www.oregon.gov/OSP/SFM/docs/Comm_Ed/Smoke_Alarm_Info/Smoke_Alarm_Q-A_Sheet2.pdf

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