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Smoke detectors in HVAC ducts #101377 03/13/07 08:38 AM
Joined: Apr 2002
Posts: 32
sudsy4 Offline OP
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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Re: Smoke detectors in HVAC ducts #101378 03/13/07 12:10 PM
Joined: Apr 2004
Posts: 156
rad74ss Offline
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.

Re: Smoke detectors in HVAC ducts #101379 03/13/07 01:37 PM
Joined: Dec 2003
Posts: 751
earlydean Offline
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'."

Re: Smoke detectors in HVAC ducts #101380 03/13/07 01:39 PM
Joined: Dec 2003
Posts: 751
earlydean Offline
Also, that would be CO detectors, not CO2.

Re: Smoke detectors in HVAC ducts #101381 03/14/07 11:45 PM
Joined: Aug 2005
Posts: 214
Elviscat Offline
would a CO2 detector be what they use to track gases that cause global warming? j/k

Re: Smoke detectors in HVAC ducts #101382 03/15/07 06:52 AM
Joined: May 2005
Posts: 984
ghost307 Offline
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).

Re: Smoke detectors in HVAC ducts #101383 03/17/07 08:41 PM
Joined: Mar 2007
Posts: 25
Mark20 Offline
be sure the power source isn't gfi protected (760.21)


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