[Erc23] Energy recovery, run-around coil, temperature-controlled

The temperature controller dynamically changes its control action for heating or cooling based on conditions from another program block.

The minimum and maximum pump speed can be parameterized in the program. The maximum pump speed can be defined by an optional logic for its limitation following the extract air volume flow.

This program block has the following optional functions:

Option: Valve (1xAO, 1xAI)

Controls the position of a bypass valve that increases or reduces the power of the energy recovery (Vlv24).

Option: After purge, start with 100 % for a configured time

Provides an interface to the state of the "Start-up purge" function and logic to keep the energy recovery at 100 % for a configurable time, e.g., 4 minutes, after the "Start-up purge" function has finished.

Option: Differential pressure monitor (1xBI)

Reads the signal from a differential pressure monitor over the energy recovery. If the differential pressure increases due to ice forming on the surface of the energy recovery aggregate, it reduces the output of the temperature controller for the valve to perform anti-icing protection.

Option: Disable temperature control in case of dehumidification

Provides an interface (most likely to the cooling coil) and logic to disable the temperature control in case of dehumidification to not preheat the air when the cooling coil performs dehumidification.

If the energy recovery is set for cooling, it runs at 100 %.

Option: Efficiency

Calculates the efficiency of the energy recovery. The function block MON_ERC is used in the program.

This efficiency calculation needs the option "Supply air temperature after energy recovery".

Option: Flow temperature (1xAI)

Reads the signal from a flow temperature sensor.

Option: Generate disturbance signal switching off the plant at very low outside temperature

If there is a problem with the energy recovery at very low outside temperature, the heating power may be insufficient, and the resulting supply air temperature may drop to a level that is above the frost protection, but still very uncomfortable. This is why a disturbance signal that shuts down the air handling unit plant is generated.

Option: Glycol temperature (1xAI)

Reads the signal from the glycol temperature sensor and performs anti-icing protection with a PID controller that limits the output of the temperature controller to the valve and continuously opens the bypass.

Option Minimum pressure (1xAI)

Reads the signal from a pressure sensor in the glycol circuit and generates an alarm if the pressure is too low.

Option: Pump speed limitation by extract air volume flow

Calculates an optimal maximum pump speed depending on the air volume flow.

To achieve an optimal energy recovery efficiency, the criteria defined by the following equation must be met:

Heat capacity of the air = Heat capacity of the heat transfer media

= Mass flow air

= Specific heat capacity of air

= Mass flow heat transfer medium

= Specific heat capacity of heat transfer medium

During the commissioning, the relationship between Ṁ_w and the pump speed can be measured. Based on this, the relationship between the mass flow air and the pump speed is calculated and set up in the program (CHAR_LIN). This helps to keep the mass flow of the heat transfer medium at the optimum level and prevents it from being unnecessarily high.

If the pump speed is not limited, there is likely a range, e.g., 70-100 %, where the output of the temperature controller increases while the power of the energy recovery does not increase. The temperature controller keeps the token until the maximum output is reached. The maximum output is not limited by the comparison of the heat capacities. It takes longer for the next aggregate in the temperature control sequence to be released for control and the total power output increases again.

Option: Return temperature (1xAI)

Reads the signal from a flow temperature sensor.

Option: Supply air temperature after energy recovery (1xAI)

Reads the signal from a supply air temperature sensor after energy recovery.

This is an important sensor for calculating the utilization rate of the energy recovery with ErcUtzRate21.

Option: Two-position control for cooling

2-position control mode for the temperature controller in case of cooling.

See also

• Predefined I/Os
• Trend types
• Module families

See also

• Predefined I/Os
• Trend types
• Module families