Siemens 125-699 Applications, Basic Operation, Control Temperature Setpoints, Day/Night Mode

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Applications

Basic Operation

The Siemens BACnet Heat Pump Controller—Multi-Stage provides Direct Digital Control (DDC) technology for multiple compressor heat pump applications. Temperature control varies with the application. If present, mixed air temperature control and up to three stages of electric heat or staged heating and cooling can be provided.

Control Temperature Setpoints

The controller maintains a specified temperature setpoint based on Day/Night mode, the heating/cooling mode, and the setpoint dial (if used).

Day/Night Mode

The controller maintains the specified day setpoint temperature during daytime hours and the specified night setpoint at night.

Night Mode Override Switch

If the RTS has an override switch, it can be used to command the controller into day mode for an adjustable period of time. This only affects a controller in night mode.

Control Loops

Heating Loop – maintains room temperature setpoint by turning compressors and electric heat stages on and off.

Cooling Loop – maintains room temperature setpoint by turning compressors on and off and using free cooling (mixed air control) when available.

Mixed Air Control Loop

The heat pump is controlled by three Proportional, Integral, and Derivative (PID) control loops; a cooling loop and a heating loop. This section describes the mixed air control loop.

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