Reversible coil with water

Access 5.x

The reversible water coil (a.k.a. Changeover or Combi coil) is an external water coil, used for seasonal heating or cooling of the supply air.

It operates in either heating or cooling mode depending on the season, supplied by a reversible heat pump or central plant. Only one mode is active at a time.

Performance of the reversible water coil is controlled from the main AHU's controller (Access) through hardwired components:

Valve actuator (AO signal for flow adjustment)

Pump control (DO signal for pump start/stop)

Indication of mode (DI signal from external heating/cooling system to the AHU is telling if hat water for heating or cold water for cooling is available)

Flow of the heating / cooling medium is controlled by valve actuator.

Reversible coil with water (configuration example)
	Variable	Available options & Selection	Note
	Enable and configure Heat pump sequences
	Configuration > Functions > Function activation > Heating/Cooling sequence setup > SEQ-G Heating 2
	Name	Heating 2	The "Heating 2" sequence set as Combi coil type heater. Freeze protection and other relevant settings can be enabled if necessary
	Type of sequence	\| Heating \|
	Type of heater	\| Combi coil \|
	Type of freeze protection	\| Temperature sensor \|
	Freeze protection sensor	\| Freeze protection temperature 1 \|
	...
	Configuration > Functions > Function activation > Heating/Cooling sequence setup > SEQ-H Cooling 2
	Name	Cooling 2	The "Cooling 2" sequence set as water type cooler. Additional settings for indication can be enabled if necessary
	Type of sequence	\| Cooling \|
	Type of cooler	\| Water \|
	...
	Combine Heat pump sequences under changeover function
	Configuration > Functions > Function activation > Heating/Cooling sequence setup > Changeover 2
	Name	Changeover 2	The "Heating 2" and "Cooling 2" sequences shall be combined under "Changeover 2" function. Changeover type set to "Combi coil"
	Changeover sequence for heating	\| Heating 2 \|
	Changeover sequence for cooling	\| Cooling 2 \|
	Type of changeover	\| Combi coil water (1x valve + 1x pump) \|
	Interface to the zone sensors and valves
	Configuration > I/O allocation settings >
	Analog inputs > Freeze protection temperature 1	Any available input / output	Immersion or contact temperature sensor for the freeze protection
	Digital inputs > Cooling/(Heating) changeover 2		Indication for the Access if HOT or COLD water is available
	Analog outputs > Changeover 2		Valve control
	Digital outputs > Changeover 2		Indication that function is active (might be used for starting/stopping pump)