Siemens S5-135U/155U System Manual page 127

Setting the Fan
You can set jumper F-R on the power supply units to choose whether or not
Monitor
the air flow monitor should switch off the internal supply voltage V
when a fan fails.
If one or both fans are at standstill, the signaling relay drops out (monitor
output). The "Fan Fault" LED lights up simultaneously.
Relay contacts 2-3 closed; this is also the normally closed contact during
power OFF (failsafe).
Caution
!
If an immediate shutdown is not possible, jumper F-R must be opened. In
this case you must ensure that the power supply is switched off after 60 s at
the latest. This can be achieved with a time relay, for example. It avoids
overheating and destruction of modules.
System Manual
C79000-G8576-C199-06
Central Controllers and Expansion Units Power Supply Units
Jumper F-R closed: V shutdown (signaled by contact)
o/p
Jumper F-R open: no V shutdown (signaled by contact)
o/p
Relay contacts 2-1 closed: fan running
Relay contacts 2-3 closed: fan failure
(5 V)
o/p
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