Overvoltage Category Iii; A.1.16 Overvoltage Category Iii - Siemens SIMATIC S7 Functional Safety Manual

A.1.16

Overvoltage Category III

Relay contacts of the SM 1226 F-DQ 2 x Relay (6ES7 226 6RA32 0XB0) are designed to
Overvoltage Category III and may be used 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, the
relays on any of the products listed above can be used, 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.
S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA
WARNING
Technical specifications
A.1 General technical specifications
143