The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!


2017 NEC and Related
2017 NEC
Now Available!

Recent Posts
Parking lot pole light swap....
by gfretwell
Yesterday at 08:46 PM
International Wire Colour Codes
by Tjia1981
10/23/16 12:08 PM
Son of Sparky
by HotLine1
10/20/16 07:43 PM
Speaking of Plugmold ...
by gfretwell
10/17/16 02:37 PM
Broken battery charger? Check for cobwebs!
by gfretwell
10/17/16 02:30 PM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 14
ghost307 7
HotLine1 7
renosteinke 6
Potseal 4
Who's Online
0 registered (), 301 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#101377 - 03/13/07 06:38 AM Smoke detectors in HVAC ducts
sudsy4 Offline

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.

2014 / 2011 NEC & Related Books and Study Guides
#101378 - 03/13/07 10:10 AM Re: Smoke detectors in HVAC ducts
rad74ss Offline

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.

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

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'."

#101380 - 03/13/07 11:39 AM Re: Smoke detectors in HVAC ducts
earlydean Offline

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
Also, that would be CO detectors, not CO2.

#101381 - 03/14/07 09:45 PM Re: Smoke detectors in HVAC ducts
Elviscat Offline

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

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

Registered: 05/09/05
Posts: 883
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).

#101383 - 03/17/07 06:41 PM Re: Smoke detectors in HVAC ducts
Mark20 Offline

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


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals