Dear All,
I searched the archives to answer this question and didn't see anything,
but may have missed something. I am trying to model (for LEED 2009) a
warehouse that trucks occasionally drive into. The space has the usual
ventilation air prescribed for a warehouse by 62.1 supplied by RTU's.
Additionally, there are fans that turn on (3.73 kW for 16,000 cfm of
outside air) when trucks are present. I created a schedule for "trucks
present" using fraction type at 1.2 hours per day each weekday. I'm not
sure how to add the outside air or get the extra fans to only run during
those hours.

Possible solutions:

1. fans as separate "equipment load" in the zone, on the schedule and
add outside air to the standard ventilation air as a fraction of
16,000 cfm. So new vent = std vent + [(1.2/40)*16,000]. This
wouldn't give the same peak load as having a full 16,000 cfm though.
2. create dummy zone with no loads, walls, area, etc. and give that
zone and system the 16,000 cfm and 3.73 kW on the truck schedule.
Tried this and only got a runtime error with no explination.
3. change the max OA to std vent + 16,000cfm and change the Min OA
schedule to reflect truck presence (run OA at 7.25% for all hours
1.2 truck hours per day). Also, changed supply flow to system
supply=9,000 + 16,000. Tried this, but the supply flow shown in
hourly output reports was always 25,000!

Any suggestions?

Jacob Goodman , LEED AP