On 2-pipe applications, the thermostat controls a valve in heating / cooling mode with changeover (automatically or manually), heating only, or cooling only. Cooling only is factory-set (P01 = 1).
ON/OFF control
Control sequence
ON/OFF output
The diagrams below show the control sequence for 2-position control.
| Heating mode | Cooling mode |
 |
 |
| T[°C] Room temperature | SDH Switching differential "Heating" (P30) |
| w Room temperature setpoint | SDC Switching differential "Cooling" (P31) |
| Y1 Control command "Valve" or "Compressor" |
Modulating control: 3-position
Control sequence modulating output
The diagrams below show the control sequence for modulating PI control.
| Heating mode | Cooling mode |
 |
 |
| T[°C] Room temperature | XpH Proportional band "Heating" (P30) |
| w Room temperature setpoint | XpC Proportional band "Cooling" (P31) |
| Y1 Control command "Valve" |
Notes:
The diagrams only show the PI thermostat’s proportional part.
For the fan sequence see section 3.8.
Setting the sequence and the control outputs
Refer to section 3.4 Applications overview, section 3.6.1 Sequences overview (setting via parameter P01) and section 3.7 Control outputs.