Difference of zone heating load reported in HVAC Sizing Summary and Coil Sizing Summary

asked 2023-10-06 18:38:45 -0500

xchen's avatar

updated 2023-10-07 09:52:53 -0500

I have a VAV with reheat system and notice that the zone heating loads reported in HVAC Sizing Summary report for Zone Sensible Heating table (e.g. 84,199Btuh) is different from the Design Size Rated Capacity in Coil:Heating:Water table , or Design Coil Load in Heating Coils table or Coil Sizing Summary Table. (these three tables all have similar loads around 66,508Btuh)

How is the Zone Sensible Heating load calculated in the HVAC Sizing Summary report? And why is it different from the loads that is used to size the terminals and reheat coils? Looks like the peak times are the same.

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For example, in the Coil Sizing Details Report, "Coil Sensible Capacity at Ideal Loads Peak [Btu/h]" for the example zone (and same for the other zones) is listed as 66,508Btuh, and "Zone Sensible Heat Gain at Ideal Loads Peak [Btu/h]" is listed as 84,199Btuh. There is only VAV reheat box in the zone and no other zone units (no fan heat, etc). What causes the difference between those two numbers? And why is the heating coil not sized based on "Zone Sensible Heat Gain at Ideal Loads Peak [Btu/h]"?

xchen's avatar xchen  ( 2023-10-09 12:15:16 -0500 )edit