Siemens BACNET 125-699 - Manual (Page 20)

Siemens BACnet Heat Pump Controller - Multi-Stage Owner’s Manual
12 Siemens Building Technologies, Inc.
Application 2583: Multiple Compressor Heat Pump
with Reversing Valve Control and Mixed Air Control
In Application 2583 (Figure 5), the controller controls a multi-stage heat pump with a
reversing valve controlled by the heat pump controller. In addition to compressors, this heat
pump may also be equipped with electric heat for auxiliary heat and mixed air control for free
cooling. The mixed air control can use either a spring return or a floating control damper
motor.
Compressor Staging
Three compressors or electric heat stages are available for use. Each compressor has a time
delay (at least 30 seconds) to lessen the demand of having more than one compressor stage
start at once.
Reversing Valve Operation
The reversing valve determines the operation of the heat pump's compressors (heating or
cooling) depending on the demand.
Application Notes
1. If the heat pump cycles excessively, temperature swings in the room are excessive, or
there is trouble maintaining the setpoint, the cooling loop, the heating loop, or both need
to be tuned. Contact your local Siemens Building Technologies representative for more
information.
2. The Heat Pump Controller—Multi-Stage, as shipped from the factory, keeps all
associated equipment OFF. The controller and its equipment are released to application
control at start-up.
3. Running the mixed air loop during night mode can increase energy savings by taking
advantage of free cooling at night to pre-cool the building for day mode, and, thereby,
reduce the need for mechanical cooling during day mode. This method for pre-cooling
the building can also improve indoor air quality because it is accomplished with fresh air.
A field panel program can be written to pre-cool the building with this application. Contact
your local Siemens Building Technologies representative for more information.