This is my second Sonoff POW R1 that blew up. I was running Tasmota. I’m very lucky that by house didn’t burn down and that the flame was contained
This particular device was running well for >1year with daily automations turning on and off several times a day. It was connected to a water heater and placed behind the wall plate
FYI: Saw that @piotrposted back in 2018 witnessing two POWs going up in flame
I’ve replaced with a Sonoff POW R2, I really hope these designed better but I will be looking to replace with a safer alternative (Shelly 1PM?) - suggestions highly appreciated.
I cant recommend anything branded as i don’t have too much experience with such branded products at least with this much load. From what you have said, the water heater must have drawn more than 11A for some time and this led to the melting of the PCB. In that case you should loo for a relay module that can withstand more load. If you are ok with DIY solution, you can look into this relay module.
This can withstand upto 30A 250VA. It is available in 5v. If you couple it with a nodemcu or wemos d1 mini, both can run with a single power supply. More over with the optocoupler in this your esp8266 will be fine even if the module fails.
There’s nothing wrong with the relay. It’s the unaffected black box halfway up the PCB.
Seems to me that most of the damage is around the fuse.
If the fuse was loose in the holder that could create heat from arcing or just energy being dissipated in a high resistance. I’ve seen screw terminals glow red hot from poor contact / high resistance.
Another option is that the fuse went open circuit (“blew”) but was unable to interrupt the current because of metal splattered around inside the cartridge. Which would again cause a lot of heat from arcing.
HRC (high rupture capacity) fuses are filled with silica sand to prevent this happening. It fuses around the molten metal.
