Siemens BACnet Heat Pump Controller -
The mixed air loop controls only the mixed air portion of the application.
The mixed air damper motor can be either a spring return or floating control damper motor.
•For a spring return damper, the mixed air loop will control the damper through its 0 to 10 volt analog output and the digital outputs will be spare.
•For a floating control damper the mixed air loop will control the damper through DO 1 and DO 2, and the analog output will be a spare.
CAUTION:
This application does not have built in low temperature detection for the mixed air dampers. The low temperature detection is handled differently depending on what type of damper is used (spring return or floating control).
Day Mode – When heating is required and the fan is on, the damper is set to minimum position. If the fan is off, the damper is closed.
When cooling is required the damper will be modulated by the mixed air temperature control loop. Damper position will not be set below minimum position to make sure that the ventilation requirements are being met.
Night Mode – The damper is closed (0%) during night mode when cooling is not required and/or mixed air control is not used at night.
Mixed Air Control - When cooling is required the damper will be modulated by the mixed air temperature control loop.
If the cooling loop is between the limits for free cooling and all other conditions have been met for enabling the mixed air loop, control depends on the following:
•If the cooling loop was previously higher than free cooling, the mixed air loop will remain enabled.
•If the cooling loop was previously lower than free cooling, the mixed air loop will remain disabled.
NOTE: This can happen in day or night mode.
Calibration
Floating Control Damper – The damper is briefly commanded closed to get an accurate damper position during calibration.
8 | Siemens Building Technologies, Inc. |
