This diagram illustrates the above statements:
Function diagram
0 %
5 %
2 K
SET-ON
TFrst
On
Frost alarm
SET-ON
Frost hazard limit value
Legend
TFrst Frost
temperature
Xp P-band
If the plant is off, the controller controls the air heating coil temperature to an
adjustable plant OFF frost protection (SET-OFF) value with PI control (OFF XP,
OFF TN) so that the air heating coil already has stored heat on startup.
Behavior if the plant is
off
This function acts on all heating sequences of the configured control loop (including
step switches but:
The outside air damper remains closed (refer to section 8.3 "Heat recovery
(HREC)”)
143 / 174
Siemens
Universal Controllers RLU2…
CE1P3101en
Building Technologies
Frost protection (FROST)
29.08.2008