Testing a microwave

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Remember, before carrying out any electrical tests on an appliance, the Test Operative must have read the test equipment instructions and be competent in its use.

Identify the construction of the microwave.  In this example, the microwave is Class I (non-sensitive)

microwave
  1. Carry out a full Formal Visual Inspection. Only test if the item passes the Formal Visual Inspection.
  2. Plug the microwave into the tester
  3. Attach the earth wander lead (test lead) to exposed bare metal on the microwave – not painted or coated. For example, you could use the casing screws on the back of the item or maybe the door hinges.
  4. Switch on the microwave by turning the timer knob to 1 minute, to ensure we have a ‘closed circuit’ within the appliance (it will not power up whilst performing an Earth Continuity Test or an Insulation Resistance Test).  If the microwave is electronic, you may have complete a Current Leakage test using mains electricity, in order to power up the appliance and overcome any electronic switching issues.
  5. Set the test device to ‘Class I’ using a 20 Amp test current where possible. If using a battery powered test device, you will be pressing the ‘Class I’ button.
  6. Before you start any tests, remember:
    1. Plug the appliance into the test device
    2. Switch the appliance ‘on’
    3. Attach the test lead to exposed bare metal on the appliance under test
    4. DO NOT TOUCH THE APPLIANCE UNDER TEST
  7. Start the test.
  8. Test results will be displayed for Earth Continuity and Insulation Resistance. Depending upon the make/model of test device being used, you may get additional test results e.g. Current Leakage.
  9. Check the results against known values.
  10. Re-test the appliance if required (for example, if there are multiple metal parts), or if the test results are questionable.
  11. Continue to the next part of the process.