CFM in supply and return for duct smoke detectors 2

[brushfire]

I have been reading all morning and can't find the answer to the question of what are the minimum CFM's for duct detectors to be required. I looked through the nfpa 72 but couldn't find my answer and I know I read it somewhere. If you know the answer and the place where it is located please give me the answer. thank you.

 

[DRWeig]

Hidey Ho, Brushfire!

Hereabouts the code being enforced is the Standard Mechanical Code with local amendments. Below 2000 CFM, nothing required. 2000 to 15,000 CFM smoke detector in supply air, heat detector in return air. Above 15,000 CFM smoke detector in supply and return, plus heat detector in return. Only exceptions are made for 100% outdoor air units, in which case the mechanical inspectors will often waive the return air requirements.

Your codes and local amendments may vary. I've seen many variances around the country. Best solution is to ask a local mechanical engineer who designs HVAC for a living, or better yet the Mechanical division of the local authority having jurisdiction. Note that if a return air detector is required, it must be installed to sample the total return air for the system, before any outdoor air is mixed with it.

Cheers and good luck with your project!

Old Dave

 

[Henn]

Try NFPA 90A-2000, specifically 6.4.2.1

Merry Christmas