In message 
<201048ea81ba0745aca78e4cc883900104781...@desmdswms201.des.grplnk.net>, 
dated Fri, 27 Mar 2009, "Haynes, Tim (SELEX GALILEO, UK)" 
<tim.hay...@selexgalileo.com> writes:

>Does this change the circuit for SELV to PELV and I thought that PELV 
>and SELV circuits could not be  "mixed and matched" as the SELV circuit 
>safety is partially dependant on there NOT being an earth?

That is indeed the 'phlogiston theory of electrical safety'.(;-) How can 
adding a THIRD safeguard to an SELV source make it unsafe?

I suspect that somewhere in the history of SELV, 'no earth is required' 
was modulated into 'no earth shall be present', for no reason.
-- 
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
Things can always get better. But that's not the only option.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

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