N
Newboy
The way that the wire is connected to the immersion terminal looks (to my eyes) poor - there is uneven pressure on the stranded core. Where the connection is poor, there's the potential for a high resistance connection, that leads to heat being generated at the connection point and, as the core(s) are copper, the heat is conducted along the core leading to what you found on your first installation.
Personally I'd prefer the see the stranded conductor form a circle around the centre of the terminal so that when the clamp is tightened there is more even pressure over a greater contact area.
Personally I'd prefer the see the stranded conductor form a circle around the centre of the terminal so that when the clamp is tightened there is more even pressure over a greater contact area.