Basic Documentation

213/332
Siemens Universal controllers RMU710B, RMU720B, RMU730B CE1P3150en
Building Technologies Frost protection (basic types A and P) 03.10.2011
17.2 Operating principle
17.2.1 Frost protection unit operating principle
T
T
N.X1
x
DI
3140S30
Frost
Reliable frost protection depends on correct sensor placement.
When the temperature drops below the limit value adjusted on the frost protection
unit, a signal is delivered to the controller.
Meaning:
 Contact closed: No frost hazard
 Contact open: Frost hazard
Frost alarm triggers the following:
 The fans are switched off
 The control loop configured with the heating coil at risk from frost switches off all
cooling sequences, and opens all heating sequences to 100%. It also switches
on the heating coil pump
 Step switches are switched on at the same time 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)")
The frost protection function with frost protection unit is active in all operating
modes (
Comfort, Precomfort, Economy and Protection).
Application example
Note
Caution