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Topic Title: 411.3.3
Topic Summary: No RCD risk assessment
Created On: 07 February 2015 08:38 AM
Status: Read Only
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 11 February 2015 09:10 AM
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davezawadi

Posts: 3955
Joined: 26 June 2002

Yes John, you are right, my example was flawed, I had forgotten that for a moment as one does when posting!
Apply what I said to a similar but non medical area, such as a patient at home on a ventilator.

In fact I am a bit unhappy with 710, as such installations go to great effort to preserve the supply under almost any condition, yet I don't consider a normal RCD to have the necessary degree of reliability. It is true that they rarely trip without any discernible cause, but some types (possibly electronic ones but I have no statistical proof) do trip in strange ways. I had one a few weeks ago where it may have been caused by a powerful portable radio transceiver, or possibly one of the myriad of other EM sources which surround us, particularly in entertainment! The risk of direct contact seems to me to be negligible in such situations, so what is the RCD for? IT is not practicable in open ward environments , and again has dangers from loss of supply due to unimportant failures, which present little risk to life. It is fine in the operating theatre or similar where there are always lots of people, but for basically unattended areas, even with alarms everywhere, I think the risk is at least as great as the safety gain. It is common for alarms in high stress areas to be ignored because the current problem seems more serious, and there are never enough people to cover all the "very urgent" problems at once.

Reading 710 I am struck by the continuous warnings to beware of all the tripping hazards, but these do not seem to have had much effect on the actual regulations and there is little room left for maneuvre! Interesting, I would love to see the NHS reports on incidents in this area.

Regards

-------------------------
David
BSc CEng MIET
david@ZawadiSoundAndLighting.co.uk
IET » Wiring and the regulations » 411.3.3

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