Chilled water cooling coil, active chilled beam (CclChw13)

Required elements and how to configure them:

Function

The figure below shows BACnet objects associated with this application function. Primary signal flow is summarized as follows:

Cooling coil cooling request (CclCReq) is received and processed into the output signal for cooling coil valve position (CclVlvPos).

Basic function: Accept request signal from associated room controller and pass it through a device mode logic switch; Output the result as a command to the BACnet object that controls the device.

Note
To reduce the risk of condensation, the modulating water valve can be closed at equipment protection priority by cut-off logic in the condensation monitoring feature and/or dew point temperature monitoring feature (optional; must be configured). The dew point temperature monitoring feature compares the dew point temperature in the room to the chilled water temperature.

Sequence

Chilled water valve modulation: In response to a cooling request the cooling valve is modulated to control the room temperature at setpoint. In response to external triggers for special modes such as warm-up, cool down, or safety conditions, the cooling valve may be set to off or fully open.

Request signal from a room temperature PID controller is received from the associated "room" AF.

Note
This AF does not perform loop control; its main purpose is to run commands. Loop control processes (for this AF) are managed in the "room" AF(s) that collaborate with this AF to command the end device.

Condensation monitoring with cut-off logic: This AF has a condensation monitor detection input (CclCdnMon). When condensation is detected, device mode is set to off at priority 4 and the cooling valve is commanded closed at priority 5.

Parameter EnCdnMonIn must be set to 1:Yes for the cut-off logic to function (see Configuration).

Dew point temperature monitoring with cut-off logic: This AF monitors the primary chilled water temperature (CclTChwPm) and compares it to the current dew point temperature of the space. (Dew point temperature (TDwp) is calculated elsewhere and received via internal signal.)

When CclTChwPm is below the dew point temperature by a configurable difference (TDiffDwpChwMin), device mode is set to off at priority 4 and the cooling valve is commanded closed at priority 5. When CclTChwPm rises above TDiffDwpChwMin plus a configurable deadband (HysTDiffDwpChw), device mode is released.

Parameter EnTDwp must be set to 1:Yes for the cut-off logic to function (see Configuration).

CclDevMod supports the following states:

Interlocks

Interlocks are (typically) binary signals that ensure equipment protection. Additional signals help coordinate the interaction sequences between HVAC devices.

Signals in table are internal signals, not BACnet objects. For this reason they are not visible in the tool, but the parameters associated with them are. See comment column for hints on parameters that affect interlock functionality.

Supply chain interface, CclChwDmd: The output signal for cooling coil chilled water demand is a multistate value.

CclChwDmd supports the following states:

Supply chain interface, CclCdnMsg: The output signal for the condensation message is Boolean. The two supported states are:

• Normal (both the condensation monitor input and the dew point monitoring logic output are False)
• Alert (either the condensation monitor input or the dew point monitoring logic output is True)

If CclCdnMsg switches to Alert in a specified number of chilled beams, the primary plant can take appropriate action. For example, the primary chilled water temperature setpoint can be set to a higher value.

Configuration

Parameters