Separation from Air Return Vents
“The AHJ would like clarification on minimum spacing for sprinklers near air return vents (non-heat source)” We have reviewed NFPA 13D, 2016 edition as the applicable standard. Our informal interpretation is that no separation is required. All installation standards for sprinkler systems have minimum separation requirements for different HVAC equipment. More accurately stated, one must have either a minimum separation OR a higher temperature rating. The reason is to avoid unintended activation of the sprinkler due to exposure to high temperatures. For example, NFPA 13D requires sprinklers with an ordinary temperature rating to be at least 24 inches away from the edge of a ceiling-mounted hot-air diffuser per Table 7.5.6.3. This is reduced to 12 inches for an intermediate temperature rating. This is all about hot air being discharged onto the sprinkler. There is no separation requirement associated with an air return vent (or grill as it's often called) because the air is the ambient temperature of the room. Occasionally, the question arises on whether the air flow negatively impacts the activation time of the sprinkler. The momentum of the ceiling jet generated by a fire far exceeds that produced by the HVAC system. If that weren't the case, there would be a minimum separation requirement from the diffusers, regardless of temperature rating of the sprinkler. It should be noted that NFPA 13 recognizes that some systems, such as heat pumps, operate at a lower air temperature and there is no separation required from the diffuser. It should also be noted that a diffuser will have a higher air velocity than the air return vent. As such, a sprinkler can be installed immediately adjacent to the air return vent. ========= Technical Update is prepared by the Technical Services Dept. of the AFSA: Roland Huggins, a PE registered in fire protection engineering, Vice President of Engineering and Technical Services; and Tom Wellen, a PE registered in fire protection engineering and Tom Noble E.T., a Technical Programs Specialist. This is provided with the understanding that the AFSA assumes no liability for this opinion or actions taken on it and they are not to be considered the official position of the NFPA or its technical committees. Copyright 2017, American Fire Sprinkler Association. All Rights Reserved. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.firesprinkler.org/private.cgi/sprinklernotes-firesprinkler.org/attachments/20170605/2db45e75/attachment.htm>
