Summer Mode - Metasys - LIT-12012070 - Field Device - VAV: Variable Air Volume Controller

Air Handling Unit Reset Application Note

Brand
Metasys
Product name
VAV: Variable Air Volume Controller
Document type
Application Note
Document number
LIT-12012070
Revision date
2018-03-01
Language
English

The purpose of the summer mode is to maintain the pressure request setpoint, which allows the AHU supply fan to run efficiently.

In the summer mode, the discharge temperature setpoint is set to a fixed temperature setpoint (default 55°F). Only the discharge air static pressure setpoint adjusts.

  1. When the supply fan starts, the discharge air static pressure setpoint is equal to the fan start pressure setpoint (default 0.7 in. W.C.).
  2. After a time interval (default 5 minutes), the logic totalizes all of the pressure requests from the VAV boxes.
  3. If the occupancy status equals Occupied, the logic continues to the next step. If the occupancy status does not equal Occupied, the logic holds the discharge air static pressure setpoint at its current value and returns to the previous step.
  4. If the total number of pressure requests is greater than the pressure requests setpoint, the logic increases the discharge air static pressure setpoint by the respond pressure setpoint (default 0.06 in. W.C.).
  5. If the total number of pressure requests is equal to the pressure requests setpoint, the logic holds the discharge air static pressure setpoint at its current value.
  6. If the total number of pressure requests is less than the pressure requests setpoint, the logic decreases the discharge air static pressure setpoint by the trim pressure setpoint (defualt 0.04 in. W.C.).
  7. The discharge air static pressure setpoint does not adjust higher than the maximum pressure setpoint (default 1.3 in. W.C.) or lower than the minimum pressure setpoint (default 0.15 in. W.C.).
  8. When the supply fan stops, the logic adjusts the discharge air static pressure setpoint to equal the fan off pressure setpoint (default 0.2 in. W.C.).