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#101377 - 03/13/07 06:38 AM Smoke detectors in HVAC ducts
sudsy4 Offline
Member

Registered: 04/24/02
Posts: 32
Loc: Elizabeth,PA USA
On the job I'm on, the smoke detectors in the HVAC ducts are powered from the convienience outlets in the RTU's. I don't have a copy of NFPA 72, but this doesn't seem like a good idea to me. Should any one trip or turn off a breaker for these outlets there is an alarm initiated. Any info will be appreciated.
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#101378 - 03/13/07 10:10 AM Re: Smoke detectors in HVAC ducts
rad74ss Offline
Member

Registered: 04/19/04
Posts: 154
Loc: Pryor, OK USA
I can't site a specific code but the equipment my company manufactures requires the entire smoke circuit to be operated off of a dedicated fire circuit. That includes the fire/smoke detectors, CO detectors, smoke purge and blower interlocks. If there is an outlet somebody is going to plug a drill into it eventually and depending on the fuse or circuit breaker size pop the circuit.

Edited out CO2 I must have been craving a soda.

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#101379 - 03/13/07 11:37 AM Re: Smoke detectors in HVAC ducts
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
NFPA 72 requires:

"Fire alarm systems shall be provided with at least two independent and reliable power supplies, one primary and one secondary." and:

"Connections to the light and power service shall be on a dedicated branch circuit." and:

"The OC device shall have a red marking, shall be accessible only to authorized personnel, and shall be identified as 'FIRE ALARM CIRCUIT CONTROL'."
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#101380 - 03/13/07 11:39 AM Re: Smoke detectors in HVAC ducts
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Also, that would be CO detectors, not CO2.
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#101381 - 03/14/07 09:45 PM Re: Smoke detectors in HVAC ducts
Elviscat Offline
Member

Registered: 08/13/05
Posts: 214
Loc: Seattle Washington USA
would a CO2 detector be what they use to track gases that cause global warming? j/k

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#101382 - 03/15/07 04:52 AM Re: Smoke detectors in HVAC ducts
ghost307 Online   content
Member

Registered: 05/09/05
Posts: 897
Loc: Chicago Illinois USA
CO is what they're concerned with; carbon monoxide is much more deadly than carbon dioxide (although they're both bad news in the appropriate concentrations).
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#101383 - 03/17/07 06:41 PM Re: Smoke detectors in HVAC ducts
Mark20 Offline
Member

Registered: 03/17/07
Posts: 25
Loc: Maryland
be sure the power source isn't gfi protected (760.21)

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