Changeover is a separate unit providing both heating and cooling on demand. The changeover is a standalone unit with separate controller present. The demand for heating or cooling is switched and regulated from the hardwired Access controller.


The table below shows a configuration example of the changeover unit.



Variable

Available options & Selection

Note


Sequence selection

Configuration > Functions > Function activation > Heating/Cooling sequence setup

Sequence for heating

|...| SEQ-G Heating 2 | SEQ-H |...|


Sequence for cooling

|...| SEQ-G | SEQ-H Cooling 2 |...|



Sequence settings

Configuration > Functions > Function activation > Heating/Cooling sequence setup > Heating 2

Type of sequence

|...| Heating |...|


Type of heater

| Water | Electric| DX | Combi coil |


Type of feedback

| None | Alarm | Run indication |


Digital start output

| No | Yes |


Sequence output when recirculation/support

| 0% | 100% | Auto |


Sequence output min limit

0%


Sequence output max limit

100%


Sequence output when the unit is stopped

0%


Configuration > Functions > Function activation > Heating/Cooling sequence setup > Cooling 2

Type of sequence

|Cooling |...|


Type of cooler

| Water | DX | DX with exchanger control |


Type of feedback

| None | Alarm | Run indication |


Digital start output

| No | Yes |


Sequence output when recirculation/support

| 0% | 100% | Auto |


Sequence output min limit

0%


Sequence output max limit

100%


Sequence output when the unit is stopped

0%



Changeover settings

Configuration > Functions > Function activation > Heating/Cooling sequence setup > Changeover settings

Changeover 1



Changeover sequence for heating

… | Disabled | …


Changeover sequence for cooling

… | Disabled | …


Changeover 2



Changeover sequence for heating

… | Heating 2 | …


Changeover sequence for cooling

… | Cooling 2 | …



PID Settings

Configuration > PID controllers > Heating 2

P-band

10 oC


I-time

100 s


D-time

0 s


Configuration > PID controllers > Cooling 2

P-band

10 oC


I-time

100 s


D-time

0 s



Hardwired interface to the pump & valve

Configuration > I/O allocation settings >

Digital inputs > Feedback Heating 2 (SEQ-G)

Any available I/O


Digital inputs > Feedback cooling 2 (SEQ-H)


Digital inputs > Cooling/(Heating) changeover 2


Digital inputs > Lock PID controller supply


Digital outputs > Cooling 2 start (SEQ-H)


Digital outputs > Changeover 2


Analog outputs > Changeover 2



Heater starting and stopping

Data & Settings > Temperature control > Heating 2

Digital start output start point

10%

Output of the supply controller to start and stop the heater

Digital start output stop point

1%


Cooling control settings

Data & Settings > Temperature control > Cooling 2

Digital start output start point

10%

Output of the supply controller to start and stop the DX cooler

Digital start output stop point

1%

Block DX-cooling if outdoor temperature <

0 oC


Block DX-cooling if supply air fan output signal <

0%


Hysteresis if outdoor temperature block

1 oC


Reduction of min limit supply air if active DX-cooling

5 oC



Graphical representation

Flowchart


58 % - indicates the output of either Heating 2 sequence or Cooling 2 sequence (depending if there is a demand for heating or cooling)


Chapter info                              

Last reviewed: 06/21/2022

Access version: 4.6-1-02 (3354)