Relay stuck after turned on for too long

Using Arduino Project Guidance
1

Hello,
im using a ESP2866 to adress a 4 way Relay Module (SRD-05VDC-SL-C). This Relay then is used to turn some electrical sockets on and off (230V AC).
My Problem is, that after a socket has been turned on for a couple of hours, it is stuck in that on position, driving current through NO and NC at the same time.
The code is not the Problem, i have already tested various different approaches of fixing this problem through the code.
Im gonna upload a basic drawing of the wiring.

Im hoping one of you has the necessary knowledge of electronics in order for me to fix this.

71LyrM2tGcL.AC_UF894,1000_QL80
71LyrM2tGcL.AC_UF894,1000_QL801920×1669 164 KB

2

You may have overloaded the relay contacts, so that they are effectively welded together.

driving current through NO and NC at the same time.

That should not be possible. Please post the details of the 220VAC devices that are being switched, and a link to the relay module product page.

3

Just tested them and yeah you´re right, not both are on at the same time just 1 which dosent switch back. I dont think they are overloaded since they are rated for 250v 10A and i only draw around 150watt max from one, so all in spec.

https://www.makershop.de/module/relais/4-kanal-relais/

After some further research, people seem recommend SSR Relais instead for they are more reliable for AC Applications.

4

If the load is a motor, heater or incandescent light bulb, there is a startup surge current as high as 10x the steady state value. That could easily weld the relay contacts.

5

It is a couple of LED lights on the 150watt device, but then again it also happened while using a pump which only has 12v 2A...

6

Startup surge of > 10A. I am not joking about this.

7

But why does it not happen right after startup, but after leaving them running for about 2hours.

8

You will notice the contact welding only when you try to turn the relay off. The welding tends to happen intermittently.

Also, the relay current rating may be for resistive loads, and not inductive.

You need to do some reading on this topic. It is a serious problem.

The bottom line is that if those relays fail, that is the clearest possible indication that they are totally inadequate for your application.

9

Fair enough, current surges might have done them in.

But you do you think if i was to continue using these relays, adding a MOV in parallel to the Load would sorta "dampen" the surge?

10

Look up "relay arc suppression" and "relay snubber circuits" for tutorials.
Example: Snubber Circuits for Protecting Relay Contacts from Arcing

Also consider SSRs (Solid State Relays) for AC circuits. If bought from a reputable manufacturer (avoid cheap Chinese fakes), they are more reliable than electromechanical relays.