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Roof Exhaust Fans and ESFR Sprinklers

Roof Exhaust Fans and ESFR Sprinklers

Roof Exhaust Fans and ESFR Sprinklers

As far as I can tell, there is varied opinion about the performance of ESFR sprinklers under automatic roof vents. There is no opinion about ESFR performance in the presence of roof intake or exhaust fans, other than FM 2-0 which proposes a 5 ft/sec air velocity limitation in the vicinity of any head. I am looking for justification of the 5 ft/sec specification. As far as I can research, there is none. In these cases I suspect it is a carry forward from years ago: indeed, we used to equate roof venting square foot as equivalent to mechanical venting with this dimension. But nothing for forced ventilation.
This is for roof fans only, not HVLS or wall ventilators. What is the justification of the 5 ft/sec specification?
There is an older thread on this topic, but it does not address the specification. The old thread asked if such velocities exist in the presence of sprinkler heads in common buildings and I add support to the fact that they do.
thanks anyone for response,

RE: Roof Exhaust Fans and ESFR Sprinklers

All references about sprinkler heads and heat detectors (e.g handbooks, nfpa codes etc) concerning their testing, refer to the time constant (το) parameter measured to a reference velocity of 1.5 m/sec (5 ft/sec). I believe FM also adheres to this industry standard velocity limit for measuring the performance characteristics. Greater velocities can negatively impact them, at least bring them operating out of their listing criteria.

RE: Roof Exhaust Fans and ESFR Sprinklers

thanks UFT12;
I took a tour through the FM Approval Standard and noted that the plunge tunnel test uses 8.4 ft/sec. Further thoughts are that RTI is a function of the square root of the air velocity, so it lessens the effect a bit? Appreciate any further thoughts; I still can't find any testing on suppression mode heads in air streams.

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