HVAC_AntiFreezeControlSensor (FB)

FUNCTION_BLOCK HVAC_AntiFreezeControlSensor

HVAC_AntiFreezeControlSensor implements a control strategy for actuators / aggregates exposed to outdoor air flow to counteract potential frost damage.

Application example

Certain actuators / aggregates - for example (water filled) HVAC heater coils, HVAC plate type heat exchangers etc. - might be exposed to outdoor air flow at intake which involves the potentially risk of frost damage.

Functionality

HVAC_AntiFreezeControlSensor does check if outdoor air falls below a limit thus causing risk of frost damage (xFrost). In case there is a risk of frost damage, the actuator output (rOut) is opened to a configured value (rSetptFrost) and a frost alarm indication (xFrostAlarm) is signaled. Otherwise the actuator output (rOut) is set for normal operation (rSetpt).

InOut:

Scope

Name

Type

Initial

Comment

Input

rOutdoorAirTemp

REAL

Outdoor air temperatur

rFrost

REAL

4.0

Frost threshold

rSetpt

REAL

0.0

Actuator setpoint for normal operation, 0..100(%) - 0% => closed, 100% => open

rSetptFrost

REAL

100.0

Actuator setpoint for frost indication , 0..100(%) - 0% => closed, 100% => open

Output

rOut

REAL

Actuator signal (0..100%).

xFrostAlarm

BOOL

Frost alarm indication