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wallywombat:
Ah yes, 643.8, where a "30mA" RCD which happily lets 140mA run through you until you're dead, is deemed from testing to be satisfactory.
Guidance note 3 used to suggest that an earth fault loop test be carried out before testing R.C.D.s. to prove effective earthing. It is easy to protect people and livestock during this test AND the testing of R.C.D.s as well, by warning people before hand, and keeping them away from exposed conductive parts and extraneous conductive parts.
R.C.D.s do not limit the magnitude of current flow during a fault they just disconnect it quickly. The note under Table 41.1 interests me. "Where compliance with this regulation is provided by an R.C.D., the disconnection times in accordance with table 41.1 relate to prospective residual fault currents significantly higher than the rated residual operating current of the R.C.D."
And we must not forget Reg. 415.1.2. "The use of R.C.D.s is not recognised as a sole means of protection and does not obviate the need to apply one of the protective measures specified in Sections 411 to 414."
Bearing in mind that R.C.D.s are not 100 per cent reliable,
Can become faulty,
And can sit untested for ten years or more.
We should be wary.
Z.
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