All:

My building has individual 4-pipe FCU's attached to a central plant. I am
seeking clarification as to how eQuest interprets an undefined 'fan
schedule' versus creating a fan schedule.

It is my understanding that, per the help topics, if a fan schedule is left
'undefined' the "program assumes the fans are always available when needed."
This seemed to be a viable option when designing a baseline building. Since
I know the fan schedule I created one; on during occupied hours, off during
unoccupied with night-cycling enabled (per ASHRAE section G). This had a
significant impact on steam consumption, changing from 415 MBTU in the
'undefined option' versus 228 MBTU in the 'scheduled option'. Since I am
forcing the fans to be on in the scheduled option one would think it would
result in higher energy consumption values.

Could someone clarify why adding a fan schedule would impact energy
consumption so significantly? Could it be left as 'undefined' simply
allowing the fans to operate when they're needed? Does this schedule,
listed as a 'cooling' fan schedule only operate cooling and if 'yes', is the
heating schedule defined under the 'Heating' --> 'Coil Cap/Control'
'Availability Sch' (which I have as 'undefined'?

Thank you all in advance for your assistance.

Robert Des Rosiers, LEED-AP