Siemens SIMATIC S7-400 Reference Manual page 379

You can cause the power supply to be cut off after the failure of at least two fans by using the
relay K2. For example, you can use an intermediate contactor to interrupt the mains.
The relay contacts are labeled as follows:
Relay K1: No. 1 to 3
Relay K2: No. 4 to 6
The following diagram explains the circuit in the fan subassembly when all fans are functioning.
... to the digital input module
to the power supply module
Figure 9-1
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
Evaluation
(digital input module)
Evaluation
(digital input module)
Status: All fans operating
Example of a message concept
9.2 Fan monitoring in the fan subassemblies
in the fan assembly
1
L+
2
3
4
5
24 V
6
to the mains
Cable duct and fan subassemblies
... to the monitor
K1
... to the monitor
K2
379