Siemens 125-699 owner manual Compressor Staging, Reversing Valve Operation, Application Notes

Siemens BACnet Heat Pump Controller - Multi-Stage Owner’s Manual

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.

12 Siemens Building Technologies, Inc.