Accessible metal parts connected to secondary ground

Talsh

Registered
#1
Hi everyone.

My system include a BF applied part connected to a Panel PC

The system is driven by a medical power supplier with output of 18 VDC .
The panel PC has a metallic accessible part (VESA mount and connectors) which are connected to the panel PC functional ground.
The accessible metallic part is not protective earthed - no electrical connection between the accessible part and mains ground.

The medical power supplier provides 2 MOPP, and the BF applied part is isolated with 2 MOPP form the panel PC.
Dia.jpg

My questions are:
  1. Is this design acceptable?
  2. Can the metal accessible parts be left not connected to protective earth ?
  3. If so, does this system can be considered as class II ME ?

Thanks in advance,
 
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Peter Selvey

Staff member
Super Moderator
#2
Yes, the design is acceptable, and the parts can be left earth free or functionally earthed (e.g. connected to earthed 0V for EMC/noise purpose, but not earthed for electric shock protection).

The classification (Class I, Class II) is related to the mains connection, so it is really only applicable to the power supply, which in the diagram seems to be Class I. The main unit does not in principle have a class (or would be Class III in other standards). IEC 60601-1 is a bit vague about this, which is historically based, bit of a long story. Many people (and test labs) still call the main unit Class II, and put the double box symbol on. However, if the standard is read carefully, all the clauses that are relevant for Class II, including marking of the double box symbol, are not applicable as the Clause title or text limits the application to mains parts.
 
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