After 18months of operation, I noticed a burning smell from the solar diverter. I turned off the power and a loose connection. Neutral feed to contact had overheated due to arcing. Also, note I had forgotten to loop the end of the cables to provide a better connection. This is a 16amp 240v load.
Above Old setup with damage contactor removed from DIN rail to show damage
Inspecting the wires I noticed that I'd not folded the wire over to make better contact. Also, the cable was not tight, I did not insert and tighten the connection well.
In my defence, the unit is very small and users 2 types of screws one for small control cables and another for the 2 pole power feed.
Another issue was that I had the contactor wired with the output and input the wrong way around so the arcs were likely damaging the contacts.
Above Old setup with damage contactor in place, not lack of cooling space and Sonoff Basic at base of the enclosure
I was not happy with the plastic housing so I replaced the enclosure with a metal one and added a 3 pole isolator. The unit is on a dedicated 16amp MCB from the consumer unit.
Above New setup with the metal case & external isolation
Finally moved the Contactor to one side so there is more space for cooling. The contactor is warm when active. Much warmer than the isolator and MCB.
Wifi Signal to the Sonoff Basic was not an issue even in the metal case!
Above New setup with Contactor spaced for cooling