Electric heating coil two stage, two binary outputs (HclEl14)

This application function operates 2-stage electric heating coil.

The stages are calculated based on a request signal (from the room controllers) received for heating.

There is an optional binary input for overtemperature detection.

This application function is NOT available for:

DXR2x09T.

Required elements and how to configure them:

Element	I/O	Signal type
HclEl1StPos "Heating coil electric position first stage " HclEl2StPos "Heating coil electric position second stage"	On-board output, Heating coil valve position	Electric 2-stage Normally open

WARNING

Electric heat coils require safety limit thermostat

Improper installation of electric heating coils can result in fire and cause destruction of life and property.

Install a high temperature cut-out switch on all electric heating elements.
Ensure that all wiring and installation conform to applicable safety codes and regulations.

Function

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

Heating coil heating request (HclHReq) is received and processed into binary output signals for the dual electric heating coil stage positions (HclEl1StPos, HclEl2StPos).

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
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.	No related parameters in electric coils. AirFlSta is hard-coded.
AirFlHReq	Boolean	Out	Air flow heating request ▶ Initiates air flow (fan turns on or VAV supply 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".
AirFlHldH	Boolean	Out	Air flow hold for heating ▶ Interlock signal to fan or supply damper requesting equipment protection air flow support for a period of time, such as when the electric heating coil has just turned off.	See Configuration section for parameters named "...AirFlHldH".
AirManOff	Boolean	In	Air manual off ▶ Interlock signal to turn off electric heating element if air source (fan or damper) is manually turned off. If AirManOff is True, HclDevMod =1:Off at priority 4 (protection mode 1).

Binary control of two electric heating coils for 2-stage operation: In response to heating demand, the heating coil electric position objects (HclEl1StPos / HclEl2StPos) are staged on/off to control the room temperature at setpoint. They also can be commanded in response to external trigger(s) for special modes such as warm-up or cool down, or safety conditions.

The electric heating coil receives a percentage of the heating demand signal (HclHReq) and translates it into the number of stages that should be turned on.

Note
There are no delay on / off timers for turning the coil on and off.

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.

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

HclDevMod supports the following states:

Off
Control mode (modulation)
Fully open

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

High temperature cut-out switch: This AF has a heating coil over-temperature detection input (HclOvrTDet) from a high temperature cut-out switch. When the switch activates, the coil is commanded off at equipment protection priority and a signal is sent to the source of air flow to hold / maintain air flow. A timer prevents the source of air flow from stopping until after the timer expires.

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

Electric power usage: The nominal electric power usage of the electric heating coil(s) is provided for energy monitoring and coordination with other devices. Power usage is calculated as follows (zero power is used when coil is off):
When one electric heat coil stage is on: HclElPwr = NomElPwr / 2
When both stages are on: HclElPwr = NomElPwr

Configuration

Parameters

Description	Parameter	Default value
Nominal electric power ▶ The nominal electric power (kW) for the electric heating coil. The total power for the electric heating coil can be found on manufacturer’s data sheet.	NomElPwr	0.4 [kW]
Enable overtemperature detector input ▶ Enable input, must be set to 1:Yes when an electric heating coil over temperature detector (binary input) is present. When electric heating coil overt temperature detector is closed, the heating coil device mode will turn Off at priority (4:Protection 1). When heating coil over temperature detector is open, the heating coil device mode will be released to 15: Automatic mode 6). 0:No 1:Yes	EnOvrTDetIn	0:No
High outside air temperature lockout
Enable lockout heating coil at high outside air temperature ▶ IF EnLockHclTOaHi is Yes AND the outside air temperature is greater than LockHclTOaHi and is valid, the device mode is set to Off. IF EnLockHclTOaHi is False OR the outside air temperature is less than LockHclTOaHi minus HysTOaLockHcl OR is invalid, this function has no effect on the device mode. 0:No 1:Yes	EnLockHclTOaHi	0:No
Lockout heating coil at high outside air temperature ▶ See EnLockHclTOaHi for functionality.	LockHclTOaHi	13.0 [°C] 55.4 [°F]
Outside air temperature hysteresis for lockout heating coil ▶ See EnLockHclTOaHi for functionality.	HysTOaLockHcl	1.0 [K] 1.8 [°F]
Interlocks
Switch-on point for air volume flow hold heating ▶ When the heating coil position (in percent) is greater than the switch-on point for air volume flow hold heating, the airflow volume hold heating interlock to the fan goes to True.	SwiOnAirFlHldH	33 [%]
Hysteresis for air volume flow hold heating ▶ When the heating coil position (in percent) is less than the hysteresis value, the air volume flow hold heating interlock goes False.	HysAirFlHldH	16 [%]
Switch-off delay for hold signal for air volume flow heating ▶ The time after the switch-off point for air volume flow hold heating is True, then the air volume flow hold heating goes from True to False.	DlyOffAflHldH	30 [s]
Switch-on point for air volume flow heating request ▶ When the heating coil heating request (in percent) is above this value, the air volume flow heating request goes to True.	SwiOnAirFlHReq	33 [%]
Hysteresis for air volume flow heating request ▶ When the heating coil heat request (in percent) is below this value, the air volume flow heating request goes to False.	HysAirFlHReq	16 [%]
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 heating request goes from False to True.	DlyOnAirFlHReq	0 [s]
Internal settings – do not change
Temperature unit ▶ Defined by selected engineering unit - do not change.	TUnit	[°C] [°F]
Temperature difference unit ▶ Defined by selected engineering unit - do not change.	TDiffUnit	[K] [°F]

Interface

Interface	Description	Type	Ref.	Owned by
HclEl1StPos	Heating coil electric position first stage 0:Off 1:On	BO	◉	Room segment / Device
HclEl2StPos	Heating coil electric position second stage 0:Off 1:On	BO	◉	Room segment / Device
HclOvrTDet	Heating coil overtemperature detector 0:Off 1:On	BI	◉	Room segment / Device
HclDevMod	Heating coil device mode 1:Off 2:Control mode 3:Fully open	MPrcVal	●	-
HclHReq	Heating coil heating request	ACalcVal	●	-
HclAvlH	Heating coil available for heating 0:No 1:Yes	BCalcVal	●	-
HclElPwr	Heating coil electric power	ACalcVal	●	-

Engineering and commissioning

Troubleshooting tip: Why is the coil off at high priority? Probably because there is no airflow. Check fan or damper. Maybe because of high temperature safety input. (Confirm function of safety switch.)

Design engineer may choose the type of output to the electric coil(s). The logic to create each output type is embedded in the controller. There are two types of output:

PID loop control creates 0 to 100% analog heating demand signal to drive a staged electric heating coil
Staged loop control creates 0 / 50 / 100% staged signal to drive a staged electric heating coil