Basic Documentation

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Siemens Universal controllers RMU710B, RMU720B, RMU730B CE1P3150en
Building Technologies Frost protection (basic types A and P) 03.10.2011
17.2.2 2-phased frost protection air side (Active DC 0...10 V =
0...15 °C)
N.X1
x
3140S31
Frost
T
AI
Reliable frost protection depends on correct sensor placement.
When the temperature drops below the adjusted level (= Risk of frost limit + 2 K +
P-band), all heating sequences are continuously opened and all cooling sequences
continuously closed. It also switches on the heating coil pump. The temperature is
thus prevented from falling below the "risk of frost limit".
If, in spite of this, the temperature does drop below the limit value, the following
actions are triggered:
 The fans are switched off
 The configured control loop with the relevant heating coil keeps all heating
sequences open and all cooling sequences closed, the heating coil pump
remains on
 The step switches remain on if not locked via input "Release external"!
 All the other control loops are switched off
 The outside air dampers are closed (see section 10.5 "Mixed air damper (basic
types
A, P)")
100 %
0 %
Xp
5 %
Xp/2
2 K
3150D05en
FT
On
Off
Heat valve
RFL
PumpsFault
Key:
RFL Risk of frost limit
FT Temperature measured on the
frost sensor
The frost protection function remains active when the plant is off.
Application example
Note
Caution
Function diagram