Water - the most common medium for heating. Sequence regulator for such heater is enhanced with freeze protection and pump control functionalities.

For freeze protection - temperature of the return water in the heating coil is monitored. If the temperature decreases to a low level, the freeze protection regulator takes control of the sequence output. Normally the output is forced up to avoid freezing. Once the risk is eliminated - the control is handed back to the supply temperature controller.

As an alternative or in addition to the freeze protection, the freeze guard (e.g. thermostat) can be used for emergency stop at freeze-risk temperatures.

The pump control includes periodic pump exercises and forced water circulation during low outdoor temperature to prevent freezing. Access also monitors if the pump is functional (run indication) then it is expected to run or if the pump has active alarms.

The table below shows a configuration example of the water heater including freeze protection, freeze guard and pump control with alarm monitoring.


Available options & Selection


Sequence selection

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

Sequence for heating

| SEQ-A Heating |...|

Sequence settings

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

Type of sequence

|Cooling | Exchanger | Heating | Damper | Fan setpoint compensation |

Type of heater

| Water | Electric | DX | Combi coil |

Type of freeze protection

| None | Temperature sensor | Freeze guard | Sensor + Guard |

Freeze protection function

Freeze protection sensor

| Freeze protection temperature 1 | ..2 | ..3 |

Pump control

| No | Yes |

Pump running mode

| Always running | Auto |

Type of feedback

| None | Alarm | Run indication |

Digital start output

| No | Yes |

Sequence output when recirculation / support

| 0% | 100% | Auto |

Sequence output min limit


Sequence output max limit


Sequence output when the unit is stopped


PID Settings

Configuration > PID controllers > Heating


10 oC

PID settings for the sequence


100 s


0 s

Hardwired interface to the heater, pump and valve

Configuration > I/O allocation settings >

Analog inputs > Freeze protection temperature 1

Any available I/O

Heating medium temperature

Digital inputs > Freeze protection guard


Digital inputs > Feedback heating (SEQ-A)

Pump control and feedback signals

Digital outputs > Heating pump (SEQ-A)

Analog outputs > Heating (SEQ-A)

Heating sequence output (input for valve)

Pump control settings

Data & Settings > Temperature control > Heating

Pump stop delay

5 min

Delay for switching off DO: Heating pump (SEQ-A)

Pump-kick hour

15 h

Daily exercise run of the pump starts at 15h

Pump running when outdoor temperature <

10 oC

Water circulation for freezing prevention

Hysteresis to allow pump stop

1 oC

Freeze protection settings

Data & Settings > Temperature control > Heating > Freeze protection 1

Freeze protection


Actual temperature of freeze protection sensor

Alarm limit running mode

7.0 oC

AL-96 Freeze protection alarm 1 if temperature < 7 oC

P-band running mode

5.0 oC

AL-64 Warning freeze protection if temperature < 12 oC (7 oC + 5 oC : "Alarm limit" + "P-band")

Setpoint standby mode

25.0 oC

If frost protection is activated - freeze protection controller will control the heating output to maintain a constant temperature at the frost protection sensor

Graphical representation


32.0 oC - indication of freeze protection temperature

87% - indication of sequence output

On - indication of pump status