Basic Documentation

10 Frost protection (FROST)
10.1 Purpose and types of monitoring
The FROST (frost protection) function block protects air heating coils against
freezing.
Purpose of FROST
This function is available only once in all devices. It provides for the following types
of frost protection monitoring:
Types of frost
protection monitoring
• Frost protection unit (DIG)
• 2-stage frost protection on the air side (DC 0…10 V)
• 2-stage frost protection on the water side (NI)
Please note that the frost protection function cannot protect the plant against frost
damage if there is insufficient heat output (e.g. no heating water)!
Note
10.2 Activating the function block
To activate this function, configure the identifier (LABEL) of an input as frost
(FRST).
Configuration
The TYPE (identification) setting defines the type of monitor or sensor used for
frost detection. One of the following frost protection functions becomes active
depending on the setting:
Setting
Setting Frost protection function
DIG Frost protection unit
0-10 2-stage frost protection on the air side, frost protection sensor with
active signal DC 0…10 V = 0…15 °C.
NI 2-stage frost protection on the water side, frost protection sensor with
passive signal LG-Ni1000
Note the following points with regard to planning and activation of the frost
protection function:
Notes
• It must be possible to switch off the fans in case of frost hazard. For that
purpose, the fan release relay (ALM OFF) can be configured (refer to section 6.3
“Fan release”). We recommend configuring function block output Q to controller
output Q1 with:
– Changeover contact Q11-Q14 closed => fan release
– Changeover contact Q11-Q14 open => frost hazard
• For proper functioning of the 2-stage, water-side prost protection function, there
must be an air heating coil pump. If you want to switch it on via the controller,
the outside temperature signal must be available
• Additionally, the controller assigned to the frost protection function must be the
one to which the air heating coil at risk from frost is connected
• If, at the same time, other influences act on the sequence controller, the priority
order according to subsection 9.1.4 “Function priorities” applies
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Siemens Universal Controllers RLU2… CE1P3101en
Building Technologies Frost protection (FROST) 29.08.2008