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RTU Open
45
Unoccupied Free Cooling
Unocc Free Cool Enable
allows rooftop equipment with an economizer damper to utilize outdoor air for free
cooling during unoccupied periods.
The following conditions must be true for unoccupied free cooling to operate:
•
Unocc Free Cool Enable
set to
Enable
•
The system is unoccupied
•
The outside air temperature is below the
Economizer High OAT Lockout Temp
setpoint
•
The outside air temperature is less than the space temperature
•
Enthalpy
(if enabled) is
Low
When the RTU Open schedule is unoccupied and the space temperature rises at least 1° above the
Occupied
Cooling Setpoint
, the supply fan starts. The economizer damper opens as necessary to cool the space. The
RTU Open continues to operate in this mode until the space is satisfied or the outside air conditions are no
longer suitable for free cooling.
Optimal Start
The RTU Open may utilize
Optimal Start
.
Optimal Start
adjusts the effective setpoints to achieve the occupied
setpoints by the time scheduled occupancy begins.The Optimal Start recovery period may begin as early as 4
hours prior to occupancy. The algorithm works by moving the unoccupied setpoints toward the occupied
setpoints. The rate at which the setpoints move is based on the outside air temperature, design
temperatures, and capacities.
The following conditions must be true for unoccupied free cooling to operate:
•
On the
Properties
page >
Equipment
tab >
Configuration
>
Setpoints
>
Optimal Start
, the
Default Value
must be set greater than
0
and less than or equal to
4
(
0.00
disables
Optimal Start
).
•
The system is unoccupied
NOTE
If the Open controller does not have a valid outside air temperature, then a constant of 65° F is used.
This value is not adjustable.