C-H,
All that the "Test Monthly" advice,is to remind people to test their RCD's, failing this, the Mechanical part ot the RCD can freeze up, meaning that it will probably not Trip, when required to do so.
However, very few people even take any notice of their Switch-boards, unless something goes wrong.
I use a tester, that gives actual trip times and currents and you can use these on your Certificate Of Compliance, which shows you have actually tested the Installation.
An RCD is a life-saving device, why is it not treated accordingly!!.
