The IET code of Practice says (section 15.5) that the 500 V Insulation Resistance test is a "hard test" and that it can "damage IT equipment or other equipment containing electronic components". We look at what this means and whether it makes sense.
In my opinion this statement is not practical to implement and sows confusion for the following reasons.
1. How is a person PAT testing to determine what is 'an equipment containing electronic components'? These days many appliances have electronics in them without it being obvious. The above statement will lead everyone to be cautious and always use the 250 V setting for the Insulation Resistance. If the statement in the COP were true, it would make the 500 V setting redundant on the tester.
2. Class 1 appliances have basic insulation between the Live / Neutral wires and user touchable metal - which is usually connected to Earth. At the end of the manufacturing stage, each appliance is tested by applying 1500 V between the Live / Neutral wires shorted together and any user touchable metal.
If the equipment can withstand 1500 V during the production stage then it should certainly be able to withstand 500 V during PAT testing.
3. Class 2 appliances have reinforced insulation between the Live / Neutral wires and any user touchable metal. At the end of the manufacturing stage, each appliance is tested by applying 3000 V between the Live / Neutral wires shorted together and any user touchable metal.
If the equipment can withstand 3000 V during the production stage then it should certainly be able to withstand 500 V during PAT testing.
For Class 2 appliances without any exposed metal there would be no return path for the current and any damage is virtually impossible.
Finally I have looked widely for evidence to back up this statement in the COP but have not found any.
In my opinion this statement is not practical to implement and sows confusion for the following reasons.
1. How is a person PAT testing to determine what is 'an equipment containing electronic components'? These days many appliances have electronics in them without it being obvious. The above statement will lead everyone to be cautious and always use the 250 V setting for the Insulation Resistance. If the statement in the COP were true, it would make the 500 V setting redundant on the tester.
2. Class 1 appliances have basic insulation between the Live / Neutral wires and user touchable metal - which is usually connected to Earth. At the end of the manufacturing stage, each appliance is tested by applying 1500 V between the Live / Neutral wires shorted together and any user touchable metal.
If the equipment can withstand 1500 V during the production stage then it should certainly be able to withstand 500 V during PAT testing.
3. Class 2 appliances have reinforced insulation between the Live / Neutral wires and any user touchable metal. At the end of the manufacturing stage, each appliance is tested by applying 3000 V between the Live / Neutral wires shorted together and any user touchable metal.
If the equipment can withstand 3000 V during the production stage then it should certainly be able to withstand 500 V during PAT testing.
For Class 2 appliances without any exposed metal there would be no return path for the current and any damage is virtually impossible.
Finally I have looked widely for evidence to back up this statement in the COP but have not found any.
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