10.3.3 2-stage frost protection on the air side (DC 0…10 V)
This picture shows an application with 2-stage, air-side frost protection:
Application example
3101S23
T
AI
X1
x
Y
SIGNAL Y
LABEL
FRST
Reliable frost protection depends on correct sensor placement!
Note
If the temperature falls below the set starting point (= limit value + 2 K + P-band),
the following actions are triggered:
Temperature drops
below starting point
• All heating sequences are steplessly opened and all cooling sequences are
steplessly closed
• The air heating coil pump is switched on
The purpose is to prevent the temperature from falling below the "frost hazard" limit
value (SET-ON).
If the temperature still drops below the above limit value, the following actions are
triggered:
Actions if temperature
drops below limit value
• 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 the air heating coil pump on.
=> Important: Step switches are switched on as well!
• If 2 controllers are configured in the RLU2…, the second (other) control loop is
switched off as well
• The outside air dampers are closed
139 / 174
Siemens Universal Controllers RLU2… CE1P3101en
Building Technologies Frost protection (FROST) 29.08.2008
To Next Page
Loading...
