PAT testing IT and associated power packs.

[Elidor]

Would very much appreciate some feedback from experienced PAT testers on this topic. It has been raised previously but I don’t believe it’s been addressed in the level of detail needed to put this issue to sleep forever, at least for me that is lol.

I have broken it down to 2 questions.

1) Is a laptop / mobile phone charger considered to be IT equipment?

Most are officially Class I devices but have no exposed conductive parts other than the DC end of the power supply where some have continuity from the earth pin of the plug to the outer ring of the DC connector but have very high impedance and would technically fail the 100mA earth continuity test and some have no continuity from earth pin to any part of the DC connector with no safety isolation symbol on the device.


2) If I’m unable to confirm the device conforms to BSEN 60950 and don’t want to risk the insulation resistance test, would the substitute / supplementary touch current test be pointless without the DC end of the power supply being under load which would mean connecting to the IT equipment I don’t want to risk damaging?

If all IT equipment will leak hence the requirement for functional earths, why are some IT power adapters supplied as Class II with no earth?

 

[ringer]

Good question - it will be interesting to read any answers given by those in the know, particularly about what happens to the earth leakage current emanating from a laptop.
For the record, I generally test the power supply/charger (disconnected from the laptop) as a class II item (even if it has an earth in the lead, there is no exposed conductive part to clamp on to) and put a sticker on it, and then just do a visual on the laptop and put a sticker on that as well. The sticker on the laptop doesn't mean much, but it makes the customer happy.

 

[Patman]

What makes the customer happy is an explanation why only the power pack and its lead need testing and not the "computer" itself.

 

[truckster]

As I understand it you should plug the lead into the laptop and perform the I/R test. As you say many laptops are class 1 but there are no exposed metal parts so I list it as Class 1 (plastic)If you can find an earthing point only test at 20-200mA's or you can blow it.

IT equipment leaks due to functional earths but laptops run from a dc battery even when plugged into the mains so the f/e is provided by the ground(0V) circuit. I think.