Siemens Simatic M7-400 Reference Manual page 415

Signaling Concept Example
You can check the fault-free functioning of the fan subassembly using digital inputs.
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:
Relay K2:
The following diagram explains the circuit in the fan subassembly when all fans are
functioning.
... to the digital input module
Evaluation
(digital input module)
Evaluation
(digital input module)
... to the power supply module
Figure 9-1 Example of a Message Concept
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
No. 1...3
No. 4...6
1
L+ 2
3
4
5
6
24 V
Status: All fans operating
Cable Duct and Fan Subassemblies
... in the fan assembly
K1
K2
... to the mains
... to the monitor
... to the monitor
9-3