# Contacts on Safety Relay

I'm trying to replace this Banner part (an E-Stop Safety Relay) with a Siemens part that will do the same thing. Originally, I had picked this replacement, but became concerned when looking at the datasheets, because the replacement candidate doesn't have contact ports S11, S12, S21, and S22. Will it still work? What do these port numbers mean; is there a spec somewhere that describes them?

Edit: The input is 4.2 A of 24V DC from this power supply (which is coming from 20 A, three-phase 230V AC power).

• Please describe your application in more detail. Jun 21 at 15:29
• What details do you have in mind?
– DJG
Jun 21 at 16:03
• Like a circuit diagram or block diagram with what is connected to the relay, with currents and voltages Jun 21 at 16:04
• My boss would probably be very upset if I shared drawings.
– DJG
Jun 21 at 16:09
• Usually, 10 is the first contact common pin, 11 the first contact normal open pin and 12 the first contact normal closed pin. And so on with 20,21,22. But that pin numbering is different, so you have to check the datasheet schematic. Jun 21 at 16:17

Contact numbering follows the format

XY
Y = 1/2 (normally closed) or 3/4 (normally open).
X = contact number 1, 2, 3, etc.


simulate this circuit – Schematic created using CircuitLab

Figure 1. Six contacts of a fictitious relay with their numbering.

Figure 2. The Banner safety relay terminal numbering.

Neither the Banner or the Siemens parts have contacts 11 - 12 or 21 - 22. I don't see a problem here.

Section 14 of the Siemens SIRIUS 3SK1 user manual shows how to wire the module. There are too many configurations for me to guess the correct one for your application.

• Ah, thanks for the explanation. I didn't realize there was a difference between 11 and S11 (I was talking about S11, S12, etc.) -- question updated to reflect
– DJG
Jun 21 at 17:17
• I've added a link to the user manual which will explain the Siemens module. Jun 21 at 17:26