[HCcl23] Heating/cooling coil, temperature-controlled, humidity-controlled

The control of the supply air humidity (dehumidification) is preset to absolute humidity (HuCtr21). You can change it to relative humidity in the Function configurator.

Delay of time for the operating state in case of cooling:
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 are "False". The operating state of the cooling coil is read by CMDSEQ_B if used in an air handling unit plant (which is most likely the case). If the plant is about to be switched off and the cooling coil was active, the plant runs for some time with a cooling coil switched off to dry the coil. During the switching-off, CMDSEQ_B receives the operating state "True" for the duration of this delay and waits there before continuing with the switch-off. This helps to dry the coil.

Delay of time for the operating state in case of heating:
A delay-off time for the signal for the operating state keeps its value to "True" after the heating coil becomes inactive. Both operating states of the valve and the optional pump are "False". Keep the delay-off time low, e.g., 5 seconds, unlike the electrical heating coil or the cooling coil, to not delay the switching-off sequence of CMDSEQ_B if used in an air handling unit plant (which is most likely the case).

If the humidity controller is active, a calculated value indicates that the dehumidification process is active. This information is read by other components in the air handling unit, e.g., by the heating coil and the energy recovery, and their temperature control is blocked.

This program block has the following optional functions:

Option: Changeover valve flow (1xBO, 2xBI)

Controls a changeover valve in the flow part that switches between hot water and chilled water (Vlv21).

Option: Changeover valve return (1xBO, 2xBI)

Controls a changeover valve in the return part that switches between hot water and chilled water (Vlv21).

Option: Frost protection (1xBI, 1xAI)

Performs frost protection (FrPrt21).

Delete this option if this coil is used as a reheater.

Option: Pump (1xBO, 4xBI)

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

The pump starts when one of the valves is active (valve position over a specific value, e.g., 4 %) and stops with optional delay when the valves are 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: Disable heating at high outside temperature

Heating is disabled above a specific outside air temperature, e.g., above 18 °C.

Delete this option if this coil is used as a reheater.

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.

Delete this option if this coil is used as a reheater.

Option: Do not generate disturbance signal switching off the plant at high outside temperature

To increase the availability of the air handling unit at high outside temperature, the generation of a disturbance signal that switches off the plant is disabled, and the plant continues running in the event of an alarm from the heating/cooling coil.

Option: Flow temperature (1xAI)

Creates a flow temperature.

Option: Heating/cooling state

Provides an interface to a heating/cooling changeover and logic to switch off the heating or the cooling temperature controller, and to deactivate the frost protection in case of cooling.

This option can only be applied successfully for 2-pipe systems with a central changeover between heating and cooling.

Option: Hot water demand

Generates a signal that hot water is demanded. This is typically read by the functions for hot water supply coordination, e.g., SplyHw21, SplyHw22.

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

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: Support for purge

Provides an interface and logic to open the heating valve at 100 % during the startup purge and a ramp to close the heating valve from 100 % to 0 % in a given time, e.g., 5 minutes. Most likely, the heating valve does not return to 0 %, because the temperature control takes over.

Delete this option if this coil is used as a reheater.

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