Heating / Cooling coil 2-pipe system (HCcl2Pipe11)

This application function operates the control valve for a heating / cooling coil that is supplied with hot or chilled water from a 2-pipe changeover system.

The valve position is calculated based on request signals (from the room controllers) received for heating and cooling.

Required elements and how to configure them:

Element	I/O	Signal type
HCclVlvPos "Heating/cooling coil valve position"	On-board output, Heating/cooling coil valve position	2-pipe any signal type

Function

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

H/C coil heating or cooling request (HCclHReq / HCclCReq) is received and processed into the output signal for H/C coil valve position (HCclVlvPos).

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.

	Command or request (or related)
	Notification of condition or status, or availability
	Device mode
	Interlock (internal signal, not a BACnet object; see Interlocks section for additional information)

Interlocks

Room automation interlocks are internal signals that coordinate interaction between HVAC devices. They are not visible in ABT Site or web interface, but parameters associated with them are. See comment column for hints on parameters that affect interlock functionality.

Signal	Type	Direction	Description	Comment
AirFlCReq	Boolean	Out	Air flow cooling request ▶ Initiates air flow (fan turns on or VAV damper provides air flow) to satisfy air flow support request for cooling. Signal is sent to fan or VAV supply damper depending on application.	See Configuration section for parameters named "...AirFlCReq".
AirFlHReq	Boolean	Out	Air flow heating request ▶ Initiates air flow (fan turns on or VAV damper provides air flow) to satisfy air flow support request for heating. Signal is sent to fan or VAV supply damper depending on application.	See Configuration section for parameters named "...AirFlHReq".
AirFlSta	Boolean	In	Air flow status ▶ Interlock signal, from a fan or a supply damper, that keeps the coil locked at equipment protection priority (PrPrio = 5) unless that same fan or supply damper provides air flow. (not active unless EnMonAirFlSta = Yes)	Parameter EnMonAirFlSta must = Yes. See Configuration section for additional information.

Sequence

Hot/Chilled water valve modulation: In response to heating or cooling demand, this application function modulates the control valve(s) 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 control valve(s) 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.

Changeover: The Heating/cooling coil changeover condition multistate object (HCclChovrCnd) provides information received from central plant regarding the status of heating / cooling changeover. Three states are supported:

Neither (the plant is switching to / from heating or cooling, and neither is available)
Heating
Cooling

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

HCclDevMod supports the following states:

Off
Control mode (modulation)
Fully open, heating
Fully open, cooling

Heating available status: When the H/C coil is available for heating, the binary output signal for "Heating/cooling coil available for heating " (HCclAvlH) will be "Yes" (available). HCclAvlH is used by the system to regulate heating resources. For example, if there is a call for heating but the H/C coil is not available because it is already at maximum capacity (because device mode is fully open), then HCclAvlH will signal "No" and the next available heating resource in the temperature control sequence will be activated.

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

Also, HCclChovrCnd must indicate that the central plant is changed over to heating.

Cooling available status: When the H/C coil is available for cooling, the binary output signal for "Heating/cooling coil available for cooling" (HCclAvlC) will be "Yes" (available). HCclAvlC is used by the system to regulate cooling resources. For example, if there is a call for cooling but the H/C coil is not available because it is already at maximum capacity (because device mode is fully open), then HCclAvlC 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).

Also, HCclChovrCnd must indicate that the central plant is changed over to cooling.

Supply chain interface outputs

HCclHwDmd supports the following states:

Off (no demand signal)
Heating demand (demand signal is active)
Warm-up (Hot water demand is initiated when plant operating mode is set to warm-up)

HCclChwDmd 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.

Supply chain interface inputs

The input signals for hot water availability / chilled water availability are binary values [No|Yes] determined by central command. They are commanded via supply chain group communication for the purpose of TOa-dependent device lockout. The relinquish default value for each is Yes.

HCclHwAvl: If the outside air temperature is above the high limit value, HCclHwAvl is set to No and the heating valve is closed. (see Central AF SplyHwxx for additional information)

HCclChwAvl: If the outside air temperature is below the low limit value, HCclChwAvl is set to No and the cooling valve is closed. (see Central AF SplyChwxx for additional information)

If for some reason HCclHwAvl and HCclChwAvl are both "No", then device mode (HCclDevMod) is set to Off at priority 9.

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

Configuration

Parameters

Description	Parameter	Default value
Manual control mode ▶ Configured during commissioning of system to define the control mode provided by the heating/cooling coil: 1:Auto 2:Heating 3:Cooling	CtlModMan	1:Auto
Interlocks
Switch-on point for air volume flow cooling request ▶ When the heating/cooling coil cooling request (in percent) is above this value, the air volume flow cooling request goes to True.	SwiOnAirFlCReq	4 [%]
Hysteresis for air volume flow cooling request ▶ When the heating/cooling coil cooling request (in percent) is below this value, the air volume flow cooling request goes to False.	HysAirFlCReq	2 [%]
Switch-on delay for air volume flow cooling request ▶ The time after the switch-on point for air volume flow cooling request is True that air volume flow cooling request goes from False to True.	DlyOnAirFlCReq	30 [s]
Switch-on point for air volume flow heating request ▶ When the heating/cooling coil heating request (in percent) is above this value, the air volume flow heating request goes to True.	SwiOnAirFlHReq	4 [%]
Hysteresis for air volume flow heating request ▶ When the heating/cooling coil heating request (in percent) is below this value, the air volume flow heating request goes to False.	HysAirFlHReq	2 [%]
Switch-on delay for air volume flow heating request ▶ The time after the switch-on point for air volume flow heating request is True that air volume flow heat request goes from False to True.	DlyOnAirFlHReq	30 [s]
Enable monitoring for air volume flow state ▶ Enable monitoring of the fan interlock signal (from fan) that keeps the heating/cooling coil closed unless the fan is running. 0:No 1:Yes	EnMonAirFlSta	0:No
Hot/chilled water demand
Switch-on point for hot/chilled water demand ▶ When the heating/cooling coil valve position for cooling is greater than the switch-on point, the heating/cooling coil enables request chilled water for cooling.	SwiOnHwChwDmd	4 [%]
Hysteresis for hot/chilled water demand ▶ When the heating/cooling coil valve position for cooling is less than the hysteresis value, the heating/cooling coil disables request chilled water for cooling.	HysHwChwDmd	2 [%]

Interface

Interface	Description	Type	Ref.	Owned by
HCclVlvPos	Heating/cooling coil valve position	AO	◉	Room segment / Device
HCclVlvPosC	Heating/cooling coil valve position for cooling	ACalcVal	●	-
HCclVlvPosH	Heating/cooling coil valve position for heating	ACalcVal	●	-
HCclDevMod	Heating/cooling coil device mode 1:Off 2:Control mode 3:Fully open, heating 4:Fully open, cooling	MPrcVal	●	-
HCclCReq	Heating/cooling coil cooling request	ACalcVal	●	-
HCclHReq	Heating/cooling coil heating request	ACalcVal	●	-
HCclAvlC	Heating/cooling coil available for cooling 0:No 1:Yes	BCalcVal	●	-
HCclAvlH	Heating/cooling coil available for heating 0:No 1:Yes	BCalcVal	●	-
HCclChovrCnd	Heating/cooling coil changeover condition 1:Neither 2:Heating 3:Cooling	MPrcVal	●	-
HCclChwDmd	Heating/cooling coil chilled water demand 1:Off 2:Cooling demand 3:Free cooling	MCalcVal	●	-
HCclHwDmd	Heating/cooling coil hot water demand 1:Off 2:Heating demand 3:Warm-up	MCalcVal	●	-
HCclChwAvl	Heating/cooling coil chilled water available 0:No 1:Yes	BPrcVal	●	-
HCclHwAvl	Heating/cooling coil hot water available 0:No 1:Yes	BPrcVal	●	-
HCclSplyChw	Heating/cooling coil supply chain for chilled water	GrpMbr	●	Room segment
HCclSplyHw	Heating/cooling coil supply chain for hot water	GrpMbr	●	Room segment

Engineering and commissioning

Device capacity configuration

The H/C coil must be configured to provide one of the following conditions: Auto (provides both heating/cooling), Heating, or Cooling. To configure the H/C coil set CtlModMan to the appropriate control mode (e.g., heat) for the room segment.

When concerned with operation of a coil in a changeover system, remember to check:

Changeover state of the central system
Local indication of the changeover state