Turn off outside air for air loop during unoccupied period
In case of an office building, my system should be running 6am to 10pm, and should cycle with the load at night, except I want to make sure I don't have any outside air during the night cycle (unless economizer is activated for cooling).
Let's call my schedule HVAC Operation Schedule
, and it has a value of 1 between 6 am and 10pm, and 0 otherwise
I've set an AvailabilityManager:NightCycle for the airloop an assigned HVAC Operation Schedule
as fan schedule.
I figured that to turn off the outside air I should assign the HVAC Operation Schedule
to the Controller:OutdoorAir
.
Instinctively, I have set this schedule to the Maximum Fraction of Outdoor Air Schedule Name
field. This made sense to me: if I say the maximum is zero, it should be turned off!
This doesn't seem to be doing what I want, since when cycling at nighttime, it's apparently still pulling Outside Air.
After investigation in the documentation and confirming it by looking at the DOE Commercial reference buildings, it seems that the field I should use is Minimum Outdoor Air Schedule Name
. From the docs:
Minimum Outdoor Air Schedule Name
The name of a schedule which uses decimal values (0.0 1.0). These values are multiplied by the minimum outdoor air flow rate. This schedule is useful for reducing the outdoor air flow rate to zero during unoccupied or start up hours. If this field is not entered, the minimum outdoor air flow rate either remains constant during the simulation period (Minimum Outdoor Air Control Type = FixedMinimum) or varies in proportion to the supply air flow rate (Minimum Outdoor Air Control Type = ProportionalMinimum).
I'm having trouble following the logic here... Can someone enlighten me?
Not sure but I think
Maximum Fraction of Outdoor Air Schedule Name
can be used forEconomizer
Free Cooling condition. it applies for VAV system when ambient conditions is appropriated forEconomizer
operation. -> air flow of supply fan in VAV system is mostly bigger than Ventilation Requirements (Minimum outdoor air flow ). ThisMaximum Fraction of Outdoor Air Schedule Name
can be bigger than 1.0 (fraction of minimum outdoor flow). Please look at in Engineer Documentation for more investigate here outdoor air damper