How many smoke alarms , combination smoke/ co, heat detectors on a circuit?

Knuckle Dragger

Master Electrician Electrical Contractor 01752
I know this topic must have been covered before at some time.

Back ground on this topic there is a total of 5 combo and 5 smoke alarms already installed in an existing house. I need to add 2 combination, 1 heat and 1 photo smoke to the existing system.

When I asked First Alert the above question they emailed me this, but six additional combination smoke/ co units doesn't sound right.
Do any of you access to NFPA to back up this claim?
What has your experience been with this?
Thank you!

Thank you for your inquiry. According information provided by the National Fire Protection Agency (NFPA), the maximum number of detectors allowed on one residential circuit breaker is 18. However, out of those 18 detectors only 12 can be smoke alarms. So the break down of that would be up to 12 smoke detectors and the other 6 can be a mixture of combination smoke and carbon monoxide units, just carbon monoxide, or a heat detector. Here is a link to our website with an explanation about the information you are seeking as well http://www.brkelectronics.com/faqs/oem/how-many-smoke-alarms-can-be-interconnected. A commercial panel would be required if you were trying to interconnect more than 12 detectors. You can also visit the NFPA website for an in dept break down of this information along with code regulations.
Thank you for contacting first alert.
 

gadfly56

Senior Member
I know this topic must have been covered before at some time.

Back ground on this topic there is a total of 5 combo and 5 smoke alarms already installed in an existing house. I need to add 2 combination, 1 heat and 1 photo smoke to the existing system.

When I asked First Alert the above question they emailed me this, but six additional combination smoke/ co units doesn't sound right.
Do any of you access to NFPA to back up this claim?
What has your experience been with this?
Thank you!

Thank you for your inquiry. According information provided by the National Fire Protection Agency (NFPA), the maximum number of detectors allowed on one residential circuit breaker is 18. However, out of those 18 detectors only 12 can be smoke alarms. So the break down of that would be up to 12 smoke detectors and the other 6 can be a mixture of combination smoke and carbon monoxide units, just carbon monoxide, or a heat detector. Here is a link to our website with an explanation about the information you are seeking as well http://www.brkelectronics.com/faqs/oem/how-many-smoke-alarms-can-be-interconnected. A commercial panel would be required if you were trying to interconnect more than 12 detectors. You can also visit the NFPA website for an in dept break down of this information along with code regulations.
Thank you for contacting first alert.
Ehhh, I don't think so. IMO, the smoke alarm portion of any combo unit counts as one of the baseline 12, not as "other". You're shy one slot by my reckoning; 5 combo + 5 smoke/only is 10, 2 more combos puts you at the limit, and the last photo puts you over. The heat detector at this point is just along for the ride.
 

Cow

Senior Member
The manufacturers instructions will tell you the maximum amount of devices.

I can tell you we took a call from one of our customers about a year ago to replace the smoke detectors in their mansion sized log cabin at their hunting resort. Upon investigation, we determined they had originally wired 19 devices all on the same circuit. We replaced all 19 with 10 year Kidde combo's, if I remember right. Tested all of them, expected to get a call back for a false alarm or two, but haven't heard anything since. For what it's worth.
 

Frank DuVal

Senior Member
the smoke alarm portion of any combo unit counts as one of the baseline 12, not as "other".
No, the directions clearly state 12 can be smoke and the next 6 can be combination smoke/CO detectors.

up to 12 smoke detectors and the other 6 can be a mixture of combination smoke and carbon monoxide units, just carbon monoxide, or a heat detector.
 

Knuckle Dragger

Master Electrician Electrical Contractor 01752
The manufacturers instructions will tell you the maximum amount of devices.

Yeah, That is what I am struggling with. The instructions say one thing but the so called tech on the phone told me I could add 6 more combination smoke/ cos to the 12 smokes which doesn't seem correct to me. The link she sent me doesn't seem to back up what she said.
Although it would work out great for me and the homeowner if what she wrote and said is true.
Thanks!
 
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