Burnt conacts cause of overcurrent. 
When I dissasembled it, I was too surprised cause previous electrician from big company hadn't considered AC motor's start current and put weak relay.
<a href="//commons.wikimedia.org/wiki/User:Dmitry_G" title="User:Dmitry G">Dmitry G</a>
<span class="int-own-work" lang="en">Own work</span>