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Class II with Chassis earth bond?

Former Community Member
Former Community Member
The floating output of a Class II product, if measured to Earth may present a voltage of 80-100V AC, The reason is that there is a small capacitance connected between the output side (low voltage output) and the input side (mains) of a switch mode power supply from the safety approved Y-capacitors.

The limits for this leakage current is internationally set to safe values for humans (<250uA). The Voltage is therefore regarded safe to use, and expected.


My preference in such situations therefore to isolate the electrical parts from any user accessible metal parts, to prevent  users noticing a tingle when touching them.


My questions relates to using a bond from the accessible metal parts to a safety earth instead.


1) The earth is not required for safety, only comfort but could it affect leakage current?


2) The application is a pre-existing installation, an LED strip powered from a class 2 supply with the led tape mounted to a metal extrusion which itself is mounted to a metal container. If the extrusion were to be earthed to the metal enclosure, would the assembly then be treated as class I or remain class II ? 


3) Which standard(s) should I be referring to find these answers.



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    lyledunn:

    Andrew, apologies for butting in with a supplementary question. Is the so called leakage current a different concept to the protective conductor or touch current? In the COP for In-service Inspection and Testing of Electrical Equipment a maximum of 0.25mA is permitted or double that if the equipment has no control device or is fitted with a control device which provides 3mm clearance in the off position.  That is in-service, I know, but it would seem to tally with what Graham said. However, I was under the impression that the protective conductor current was measured with a simulated body resistance of 1000ohms.


    Isn't that "touch current" Lyle?


    Protective conductor current in terms of BS 7671 is protective conductor current from whatever source (i.e. it's undefined) and therefore includes current collected from EMI absorbed by shielding, and "leakage currents" from interconnected equipment, as well as standing protective conductor currents from noise filters on the mains, and "leakage" across insulation and transformers.


    Product standards may define protective conductor current measurements and/or touch current measurements - the touch current measurements being in the way you have defined (it's a combination resistive and capacitive network to simulate a dry body impedance).


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    lyledunn:

    Andrew, apologies for butting in with a supplementary question. Is the so called leakage current a different concept to the protective conductor or touch current? In the COP for In-service Inspection and Testing of Electrical Equipment a maximum of 0.25mA is permitted or double that if the equipment has no control device or is fitted with a control device which provides 3mm clearance in the off position.  That is in-service, I know, but it would seem to tally with what Graham said. However, I was under the impression that the protective conductor current was measured with a simulated body resistance of 1000ohms.


    Isn't that "touch current" Lyle?


    Protective conductor current in terms of BS 7671 is protective conductor current from whatever source (i.e. it's undefined) and therefore includes current collected from EMI absorbed by shielding, and "leakage currents" from interconnected equipment, as well as standing protective conductor currents from noise filters on the mains, and "leakage" across insulation and transformers.


    Product standards may define protective conductor current measurements and/or touch current measurements - the touch current measurements being in the way you have defined (it's a combination resistive and capacitive network to simulate a dry body impedance).


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