[Hpu25] Heat pump, 1-stage, temperature setpoint

Controls a heat pump with own external control unit.

An interface to the control unit of the heat pump (HpuItf25) enables it, sends a setpoint (it changes following the signal for heating or cooling priority), and reads optional signals for fault, feedback, defrost status, and present power.

The program has settings for the nominal power of the heat pump and for the transient state times (a signal that the heat pump is in a transient state that blocks the logic for generating further step-up and step-down pulses for the power control and compensation) when switching on or off (e.g., 5 minutes when switching on and 2 minutes when switching off).

The switch-on and switch-off sequence for the valves, the pump, and the interface to the control unit are defined in the function block CMDSEQ_B.

This program block has the following optional functions:

Option: Pump (1xBO, 4xBI)

Controls a pump (Pu21). Different alternatives are possible, e.g., TwnPu21.

The pump runs when the heat pump is running, and the optional shutoff valve is open.

Option: Shutoff valve (1xBO, 2xBI)

Controls a shutoff valve that opens when the heat pump is running (Vlv21).

Option: Flow temperature (1xAI)

Creates an analog input for the flow temperature and reads its signal. It can generate an alarm (high and low limit).

Option: Frost protection

If the flow temperature (outlet) and/or the return temperature (inlet) of the heat pump fall below a certain value, e.g., 8 °C, the shutoff valve opens and the pump starts to ensure water circulation.

If the temperatures fall further, e.g., to 5 °C, the interface to the control of the heat pump enables the heat pump and the heat pump starts.

Option: Heating/cooling state

Reads the calculated heating/cooling state in another part of the program via BACnet and passes it on to the heat pump interface (HpuItf25).

Option: Operating mode switch (1xMI=2xBI)

Reads the state of an operating mode switch, normally at the front of the electrical panel, and has the states "Auto", "Off", and "On".

Option: Return temperature (1xAI)

Creates an analog input for the return temperature and reads its signal. It can generate an alarm (high and low limit).

Option: Setpoint shift with external signal for operating mode "Fixed"

The heat pump with its own external control unit has an operating mode "Fixed". The operating mode "Fixed" comes after the mode "On". It ensures that this heat pump stays at its nominal power and that another energy generator that has been switched on after it is modulating maintains the main flow temperature.

A PID controller in another program block (HGenCtl22) compares the main flow temperature to its setpoint and, in case of a deviation, increases its output (in %). The heat pump can read this signal and if its operating mode is "Fixed", it results in a local setpoint increase, e.g., 0-100 % increases the setpoint of the heat pump by 0-3 K). This keeps the heat pump at its nominal power and prevents its modulation.

See also

• Predefined I/Os
• Trend types
• Module families

The extension for alarming for the predefined I/O for the optional element "Feedback" (in the program block interface) must be deactivated.

See also

• Predefined I/Os
• Trend types
• Module families