Fly back diode for DIN mounted relay

What is the best and safe way to install a diode to a DIN mounted relay? I need to add a fly back diode to a solid state relay and it’s not in a cabinet.

Welcome to the TechForum user917.
If you have screw terminals, you will have to connected the diode leads in the appropriate terminal.
If you do not have screw terminals, you will have to solder it. You may have to solder insulated hook-up wire if the leads are not long enough on the diode.

Is the relay on a din rail outside of the cabinet? If you have room on the din rail, We do have terminal blocks that are din rail mountable here that have built in diodes. Will one of these maybe work?

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Ok thanks. I thought I could use the din blocks. What is the best way to size it? It will be used with a solid state 10 amp relay, but will operate a 3 amp impulse sealer.

That would be perfect. Can you help size it? It will run a 3amp heat impulse sealer.

A little more info… input on the solid state relay is 24vdc and the output side is 120vac

Hi user917,

Where do you intend to place this diode within the circuit?

If the output is AC, a diode will essentially short it out over half of the sine wave, so that would not be viable. If it is for the input side, it is generally not necessary, as there is no relay coil with a solid state relay, so no inductive kickback when the input is de-energized, unlike a mechanical relay coil…

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I was planning it on the input dc side, not the 120vac output side. I wasn’t sure with a SS if there would be any fly back. If it’s 0 then I guess I don’t need one.

Thank you for the help.

Right. SSR’s are almost (if not) always triggered with an infrared LED rather than a coil, so no inductive kickback, other than the tiny bit associated with the wire inductance, which shouldn’t be significant unless the wire is very long.

I’m looking for a 5-10amp din mount, solid state, normally open, 24vdc input, 120vac output zero crossing relay. Can you help with a model number?

Here’s a link to relays which meet or exceed your requirements:

I found these by going to the Product Index, scrolling down to Relays, and then clicking on Solid State Relays.


From there, check the boxes you care about in the following options:


Then, start filtering down parameters by selecting your primary requirements first, such as DIN Rail mounting, Output Type, and Circuit type, hitting the Apply button between selections. This will get you to more relevant results.

Then just drill down further from there selecting applicable Input Voltage, Load Voltage, and Load Current.