Chilled ceiling with chilled water (CcgChw11)

This application function operates chilled water valve(s) for radiant ceiling device(s) such as ceiling panel(s) or passive chilled beam(s).

The valve position is calculated based on a request signal (from the room controller) received for cooling.

Multiple panel control is supported.

There is an optional binary input for condensation detection.

Required elements and how to configure them:

Element	I/O	Signal type
RcgVlvPosC "Radiant ceiling valve position for cooling"	On-board output, Radiant ceiling valve position 1	Chilled or Chilled beam passive

Function

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

Radiant ceiling cooling request (RcgCReq) is received and processed into the output signal for radiant ceiling valve position (RcgVlvPosC).

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.

	Command or request (or related)
	Notification of condition or status, or availability
	Device mode

Chilled water valve modulation: In response to cooling demand, 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.

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.

Multiple panel control: The radiant ceiling valve position cooling collection object (RcgVlvPosCCol) can reference and control multiple ceiling valve actuators.

Radiant ceiling valve position cooling objects (RcgVlvPosC) are referenced by the radiant ceiling valve position cooling collection object (RcgVlvPosCCol); this collection object is a common node for any / all RcgVlvPosC object(s). The value for RcgVlvPosC comes from RcgVlvPosCVal.

Condensation monitoring with cut-off switch: Condensation monitor (CdnMon) binary input objects are referenced by the condensation monitor collection object (CdnMonCol); this collection object is a common node for any / all CdnMon binary input object(s).

The CdnMon objects are analyzed using an OR statement. If one or more objects detect condensation, the binary result object (CdnMonRs) switches from 0 to 1 (On). When a single safety trips, all panels turn off (device mode is set to off and cooling valve(s) close).

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

Dew point temperature monitoring with cut-off logic: This AF monitors the primary chilled water temperature (RcgTChwPm) 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 RcgTChwPm is below the dew point temperature by a configurable difference (TDiffDwpChwMin), device mode is set to off at priority 4 and the cooling valve(s) are commanded closed at priority 5. When RcgTChwPm 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).

Device mode: The input signal for device mode is a multistate value.

RcgDevMod supports the following states:

Off
Control mode (modulation)
Fully open

Cooling available status: When the ceiling panel(s) are available for cooling, the binary output signal for "Radiant ceiling available for cooling" (RcgAvlC) will be "Yes" (available). RcgAvlC is used by the system to regulate cooling resources. For example, if there is a call for cooling but the ceiling panel(s) are not available because they are already at maximum capacity (because device mode is fully open), then RcgAvlC will signal "No" and the next available cooling resource in the temperature control sequence will be activated.

For cooling available status to be "Yes", device mode must equal "Control mode" (modulation).

Supply chain interface, CdnMsg: The output signal for the condensation message is Boolean and the two 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 CdnMsg 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.

Supply chain interface, RcgChwDmd: The output signal for the radiant ceiling chilled water demand is a multistate value.

RcgChwDmd supports the following states:

Off (no demand signal)
Cooling demand (demand signal is active)
Free cooling (cooling device is in free cooling mode)

Free cooling can be initiated by the central plant when surplus cooling capacity is available. Under certain conditions, the room can take advantage of surplus cooling capacity in the absence of an explicit cooling demand; the room temperature must be below the setpoint associated with the current room climate mode (Comfort, Pre-Comfort etc.). This type of free cooling is different from "economizer" free cooling, which uses an outside air damper.

The following figure(s) illustrates control modulation and related functions.

HysChwDmd	Hysteresis for chilled water demand
RcgChwDmd	Radiant ceiling chilled water demand
RcgVlvPosC	Radiant ceiling valve position for cooling
SpC	Setpoint for cooling
SwiOnPtChwDmd	Switch-on point for chilled water demand

Configuration

Parameters

Description	Parameter	Default value
Condensation prevention
Enable condensation monitor input ▶ Enable input, when a radiant ceiling condensate detector (binary input) is present. When radiant ceiling condensate detector is closed, the radiant ceiling cooling device mode will turn Off at priority (4:Protection 1). When radiant ceiling condensate detector is open, the radiant cooling ceiling device mode will be released to 15: Automatic mode 6). 0:No 1:Yes	EnCdnMonIn	0:No
Enable dewpoint temperature 0:No 1:Yes	EnTDwp	0:No
Minimum difference dewpoint temperature/chilled water temperature	TDiffDwpChwMin	1 [K] 1.8 [°F]
Hysteresis for minimum difference dewpoint temperature/chilled water temperature	HysTDiffDwpChw	1 [K] 1.8 [°F]
Chilled water demand
Switch-on point for chilled water demand ▶ When the cooling coil valve position is greater than the switch-on point, the cooling coil enables request chilled water for cooling.	SwiOnPtChwDmd	4 [%]
Hysteresis for chilled water demand ▶ When the cooling coil valve position is less than the hysteresis value, the cooling coil disables request chilled water for cooling.	HysChwDmd	2 [%]
Internal settings – do not change
Temperature difference unit ▶ Defined by selected engineering unit – do not change.	TDiffUnit	[K] [°F]

Interface

Interface		Description	Type	Ref.	Owned by
RcgVlvPosCCol		Collection of radiant ceiling valve position for cooling	ColView	●	-
	RcgVlvPosC	Radiant ceiling valve position for cooling (1...n)	AO	◉	Room segment / Field device
RcgVlvPosCVal		Radiant ceiling valve position value for cooling	APrcVal	●	-
CdnMonCol		Collection of condensation monitor	ColView	●	-
	CdnMonRs	Result of condensation monitor 0:Off 1:On (condensation detected)	BCalcVal	●	-
	CdnMon	Condensation monitor (0...n)	BI	◉	Room segment / Field device
CdnMsg		Condensation message 0:Normal 1:Alert	BCalcVal	●	-
RcgDevMod		Radiant ceiling device mode 1:Off 2:Control mode 3:Fully open	MPrcVal	●	-
RcgCReq		Radiant ceiling cooling request	ACalcVal	●	-
RcgAvlC		Radiant ceiling available for cooling 0:No 1:Yes	BCalcVal	●	-
RcgChwDmd		Radiant ceiling chilled water demand 1:Off 2:Cooling demand 3:Free cooling	MCalcVal	●	-
RcgTChwPm		Radiant ceiling primary chilled water temperature	APrcVal	●	-
RcgSplyChw		Radiant ceiling supply chain for chilled water	GrpMbr	●	Room segment

Engineering and commissioning

Verify operation for single output and multiple output.

When troubleshooting, check effect of condensate detectors. Verify shut down on condensate detection for single and multiple objects.

Consider controlling the space as separate segments, rather than multiple objects in one segment. This allows the panels to operate individually in case of shutdown on condensation detection.