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Supplementary bonding conductor in a medical location

Julien Leblanc
Hello,


After reading from many sources about the medical locations' supplementary equipotential bonding, everything is mixed in my head...


Suppose we have a current using device inside a group 1 medical location (TN-S supplied).

Then the protective conductor of that device must be connected to the EBB installed in this location by means of a supplementary equipotential bonding conductor.

Could someone clarify this:  that bonding conductor, should it comply with art. 544.2.1 or with art. 544.2.2 from BS7671, that is, the EBB should be considered an extraneous-conductive-part or an exposed-conductive-part ?


Thank you.
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  • 0
    Also "The conductors that connect the conductive parts to the equipotential node are protection conductors (PE) and their cross-section must be established using the criteria specified by the general standard; in other words, it must be at least equal to that of the phase conductors."

    That sounds like it's come from an "international" (or at least other national) source - the UK is fairly unusual in allowing reduced c.p.c.s (at least on smaller circuits). Most other countries take the, perhaps not unjustified view, that since TN disconnection times (e.g. 0.4s) are based on a touch voltage of half the line voltage then you shouldn't be picking c.p.c.s with higher impedances that might result in a higher touch voltage.


       - Andy.
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  • 0
    Also "The conductors that connect the conductive parts to the equipotential node are protection conductors (PE) and their cross-section must be established using the criteria specified by the general standard; in other words, it must be at least equal to that of the phase conductors."

    That sounds like it's come from an "international" (or at least other national) source - the UK is fairly unusual in allowing reduced c.p.c.s (at least on smaller circuits). Most other countries take the, perhaps not unjustified view, that since TN disconnection times (e.g. 0.4s) are based on a touch voltage of half the line voltage then you shouldn't be picking c.p.c.s with higher impedances that might result in a higher touch voltage.


       - Andy.
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