# FPB vs VAVs



## Introyble (Jul 10, 2010)

Um is this a HVAC thread?


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## I_get_shocked (Apr 6, 2009)

Fan powered boxes have a fan- either series or parallel and a source of heat. Parallel boxes place the fan perpendicular drawing from plenum air and only run the fan during heating mode. Series fan powered boxes place the fan in line and run it during all occupied modes, heating or cooling. Every fan powered box I have seen has a reheat (either hw coil or electric heating coil).

VAV cool only boxes are strictly a damper on RTU air, while VAVs with reheat have HW or electric heating coils after the damper to provide heating. A VAV with reheat requires the RTU to run in order to provide heating since they contain no fan.


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## keepdry (Jul 24, 2012)

Thanks for the info. 
That clears things up.


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## bobelectric (Feb 24, 2007)

VAV short for variable air volume.


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