[Ccl21] Chilled water cooling coil, temperature-controlled

There is a delay off time, e.g., 5 minutes, for the signal for the operating state that keeps its value to "True" after the cooling coil becomes inactive. Both operating states of the valve and the optional pump equal to "False". If used in an air handling unit plant (which is most likely the case), the operating state of the cooling coil is read by CMDSEQ_B. If the plant is about to be switched off and the cooling coil was active, then the plant runs for some time with a cooling coil switched off to dry the coil. During the switch-off, CMDSEQ_B receives the operating state "True" for the length of time of this delay and waits there before continuing with the switch-off. This helps to dry the coil.

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 starts when the valve is active (valve position over a specific value, e.g., 4 %) and stops with an optional delay when a valve is inactive (valve position below a specific value, e.g., 2 %).

Option: Chilled water demand

Generates a signal that chilled water is demanded. This is typically read by the functions for chilled water supply coordination, e.g., SplyChw21 or SplyChw22.

There is a delay off time for the chilled water demand.

Option: Disable cooling at low outside temperature

Cooling and dehumidification are disabled below a certain outside air temperature, e.g., below 12 °C.

Option: Flow temperature (1xAI)

Creates a flow temperature.

Option: Pump activation at low outside temperature

Starts the pump at low outside temperature, e.g., below 4 °C, even if the coil is not running.

This improves the frost protection.

Option: Return temperature (1xAI)

Creates a return temperature.

Option: Switch-off delay for pump

Switch-off delay for the pump when the valve was active.

The pump stops without delay if there is a signal for exception from a superior logic (plant level).

See also

• Predefined I/Os
• Trend types
• Module families

See also

• Predefined I/Os
• Trend types
• Module families