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Class 1 appliance with no exposed metal work to connect test lead too

Former Community Member
Former Community Member
Coffee machineOK 3rd problem class one appliance with no exposed metal work to connect test lead too how can I carry out the earth bond test given it is a class 1 appliance and not a class 2 appliance like this Coffee machine
  • 0
    Arran Cameron:

    Plastic class 1 devices where the earth conductor of the mains cable is connected to a metal chassis inside, or is used for screening EMI, has to be tested as class 1 rather than class 2 because of the potential for earth leakage current that could trip a RCD.


    There was a (at least one) case of a plastic class 1 device in a hospital that would trip a RCD because of a fault resulting in excessive earth leakage current, but it successfully passed the class 2 EST that was being used at the time.


    Is that a safety issue? I can, however, see that in hospitals, more attention is absolutely necessary with equipment that may be used in a Group 1 or Group 2 medical location - but I'd expect a greater degree of competence to test and maintain that equipment anyway?


    In any case, even testing Class I appliances in that way won't always detect issues that cause RCDs to trip - or even detect all faults.


    For example, if you test a washing machine, a faulty component or circuit may not be switched "on" until the door is closed and the interlock connects, and the component is in circuit set by the control board.


     


  • 0
    gkenyon:

    Is that a safety issue?



    Good question. Superficially it isn't a safety issue, but is it really safe to have an appliance with >30mA of current trickling down its earth wire?

     
    I can, however, see that in hospitals, more attention is absolutely necessary with equipment that may be used in a Group 1 or Group 2 medical location - but I'd expect a greater degree of competence to test and maintain that equipment anyway?

    The clinical engineering department left a lot to be desired when it came to the testing of medical devices. There was a complete lack of consistency and quality assurance between different staff and different workshops combined with a führer like management that wouldn't listen to its technically minded generals.

     
    In any case, even testing Class I appliances in that way won't always detect issues that cause RCDs to trip - or even detect all faults.


    For example, if you test a washing machine, a faulty component or circuit may not be switched "on" until the door is closed and the interlock connects, and the component is in circuit set by the control board.

     

    You make a valid point. EST should always be performed with the appliance switched on so that current flows and the tester is put under load. However, there may be situations where an appliance will pass an EST shortly after it is switched on but fail an EST at an advanced stage of operation - like when the drain pump of a washing machine is activated.

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