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Application example
Note
Frost protection control
functions
Note
Siemens
Building Technologies
10.3
Operating principles and settings
10.3.1 Frost protection unit (DIG)
This picture shows an application with an air- or water-side frost protection unit:
DI
T
Reliable frost protection depends on correct sensor placement.
If the temperature falls below the set limit value, the frost protection unit sends a
signal to the controller. Meaning:
Contact (Q11 - Q14 / terminals 1-3) closed: No frost hazard
•
Contact (Q11 - Q14 / terminals 1-3) open: Frost hazard
•
A frost hazard signal triggers the following actions:
The fan release relay is deenergized (no release of fan)
•
The control loop configured with the air heating coil at risk from frost switches off
•
all cooling sequences, and opens all heating sequences to 100%. It also
switches on the air heating coil pump.
=> Important: Step switches are also switched on in the process!
If 2 controllers are configured in the RLU2..., the second (other) control loop is
•
switched off as well
The outside air dampers are closed
•
The frost protection function with frost protection unit is activated in all operating
modes (Comfort, Economy, Protection). Therefore, it also overrides limitations and
disabling as a function of the outside temperature!
Universal Controllers RLU2...
Frost protection (FROST)
X1
LABEL
FRST
x Y
T
137 / 174
CE1P3101en
29.08.2008
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