Siemens SIMATIC S7 Functional Safety Manual page 24

Product overview
1.4 S7-1200 Fail-Safe signal modules (SM)
Outputs
You can use each of the two relay output channels for SIL 3 applications.
Note
Relay contacts of the SM 1226 F-DQ 2 x Relay are designed to Overvoltage Category III.
You can use them in AC mains circuits without further overvoltage protection.
Relay contact outputs on the following products do not meet requirements for Overvoltage
Category III, the requirement for EN 50156-1 conforming equipment:
• CPU 1214FC DC/DC/RLY CPU (6ES7 214-1HF40-0XB0)
• CPU 1215FC DC/DC/RLY CPU (6ES7 215-1HF40-0XB0)
• SM 1222 DQ 8 x Relay (6ES7 222-1HF32-0XB0)
• SM 1222 DQ 16 x Relay (6ES7 222-1HH32-0XB0)
• SM 1223 DI 8 x 120/230 VAC In / DQ 8 x Relay (6ES7 223 1QH32 0XB0)
When using the SM 1226 F-DQ 2 x Relay in safety critical circuits of burner applications, you
can use the relays on any of the products listed above, but only if used in one of the
following:
• SELV/PELV circuits
• Circuits connected to the electrical mains with permanent, recognized protection that
reduces transients to Overvoltage Category II
Otherwise, the CPU and I/O system, including the SM 1226 F-DQ 2 x Relay, will not meet
the Overvoltage Category III requirement for burner applications.
Adjacent relay contacts in the same channel of the SM 1226 F DQ 2 x Relay are not rated
to separate AC line from SELV / PELV.
Death or serious personal injury and damage to machines and equipment can result if
SELV/PELV circuits are wired adjacent to high voltage circuits on this module.
The A and B circuits of each output must either be both AC line or both SELV.
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WARNING
S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA