I live in the UK for about 8 months of the year & 4 months at my place in Spain.
In Spain I live in the middle of no where & mains electricity is not possible, about 5 years ago i had a Spanish election fit 6 solar panels, 6 batteries & a inverter etc.
All worked well until last year when i built a small extension on to our property & I fitted a British consumer unit with a rcd breaker since then 3 inverters have blown/fused/burntout
I now need to by another new inverter
I do not want this one to fuse/burnout like the last 3 have done.
Any help you can give me would be greatly appreciated, do you think my problem is caused by the rcd breaker. or is it possible the Spanish electrition got some of the negative & possertive wires the wrong way round

 

I doubt anyone can help you without more detail of the installation, maybe some photos and a diagram, and model numbers for the relevant equipment.

Is it possible that you added more load with your "small extension"? (Meaning that the RCD and box have no effect on the problem).