It's a frustrating issue. In a typcal "real"
building, the VAV central coil resets based on
the zone with the highest cooling demand. On
cold mornings, the reset can be as high as 70?
F. According to the documentation in
DOE22Vol2-Dictionary, the keywords COOL-CONTROL,
HEAT-CONTROL, HEAT-SET-T, COOL-MAX-RESET-T and
HEAT-MIN-RESET-T and some others should allow you
to simulate a VAV system that has a heating coil
that can reset the supply air temperature. I
have never been able to find that magic
combination that results in the hourly reports
the heating coil providing heating when I would expect it to.

The issue with the preheat coil is that you have
to set the exiting temperature a few degrees
lower than the cooling MIN-SUPPLY-T to account
for fan heat so you don't increase heating
significantly. This still results in too much reheat required at the zones.

sa>When using the VAV or PVAV system types the

>> Christopher Jones, P.Eng.