ixo65

It is more important to provide the solenoid with a flyback diode or other protection.

 While external flyback diode won't hurt, this is not neccessary. Don't trust always ixo65. All transistor output logos use Infineon power switch (ITS4140N) specially designed for switching inductive loads. I don't know how many CE logos ixo65 installed to real systems or how much he reads datasheets. As one can see from next post, he can't resist to have last word.

ixo65

Don't trust WWEE.

The LOGO! isprotected, but not necessarily the solenoid.

A flyback diode costs next to nothing.

Hm... Please teach me (and others) how freeweel diode protects relay or contactor solenoid? So far those used for protecting switching element (transistor or relay contacts) but not actuator.

Second argument - every additional discrete component on electric switcboard adds complexity. Diode costs pennies, but adds another layer to check on case of errors. Most wiring in today's switchboards are done with ferrules, so no plain wires are exposed. Adding diode to DIN mountable relay screw connection in parallel to wiring ferrule in a way that diode terminals are covered too is not so easy as said. Imagine installing 48 or more in this way in one day, you can simply multiply required time to wire every relay by 2-4. If one wants to be correct to "bones", then diode and resistor must be installed.

By the way, many today relays contain (or can be added as optional accessory) diode as indication element too. Again no point to build additional complexity for yourself.

As i said previously - additional flyback diode with LOGO or DMnn with transistor output. won't hurt, but not neccessary either.