Disassembled General Electric RCD. 
<ul><li>Due to overheating, insulation of some wires inside melted and some hot wires faced with relay wires. When I've pushed "test" button, I closed the 400V circuit; due to too low resistance there comes sparks next to my finger and wire gauge was not enough to beat out C50 circuit breaker. So, my finger got some little skin burn.</li></ul>
I'm saying nothing against DIY, but don't overlimit maximum allowed current. If some installation has marking "25A", it means that maximum allowed circuit breaker is 25A or less. If you have 50A circuit breaker installed by energy company and sealed, it means,.that other installations should be designed for 50A or even more (some reserve).
<a href="//commons.wikimedia.org/wiki/User:Dmitry_G" title="User:Dmitry G">Dmitry G</a>
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<span class="int-own-work" lang="en">Own work</span>