many appliance from outside UK they are use 2 pins such as EU and Apple's adapter from UK. Some of them they are no double insulation symbo on it. What class should define them for testing?

All Class II appliances should bear the Class II construction mark.
If the appliance doesn't, then it should be treated as Class I, even if there are no exposed conductive parts.
If there's any doubt, you could always try to contact the manufacturers for advice.

Also consider there are many fake psu sold. So if it isn't correctly maked it should be disposed of. Just look at the number of recalls

http://www.esc.org.uk/public/h...trics/product-recalls/

In the situation as an Apple's transformer (adapter) it is a US standare 2 pins and no double insulation symbol if I treat it a class I it must be fail so what should I do? Other 2 pins from EU as well.

I think all the more recent, genuine, Apple MacBook chargers do carry the class 2 'double square' symbol but it's very small so you have to search for it. Some years back they just said 'Class II' on them.

As an institutional PAT tester I would not usually pass an appliance with a non-UK plug on as safe as it would be illegal to sell for domestic use in the UK under The Plug and Socket etc. (Safety) Regulations and I think that's a fair indication that it is substandard and my employer shouldn't risk being deemed to supply or approve it. The MacBook PSUs have interchangeable mains 'plugs' so it shouldn't be an issue, if they don't have a UK one then a standard C7 2-core mains lead will fit - we regularly have to supply these to foreign visitors where I work and I now have some proper Apple UK MacBook charger 'plugs' to loan out that I salvaged off dead chargers.

If someone asks me to pass a US or Japanese phone charger with the pins moulded into the body as safe I refuse and this does cause a bit of friction but the fact is that the pins are not sleeved and could accidently be touched when plugging into any mains adaptor. The user may not be fully aware he will be risking a 240V belt instead of his domestic 110V tingle.

Watch out for the various substandard non-Apple replacements chargers that are about.

There are many, many laptop chargers about that are not marked as class 2, so should be tested as class 1, but don't carry the earth through to the DC output so can't be earth tested. I don't fail these, there is nothing wrong with them, I just skip the earth test and mark as 'no accessible earth' on the PAT records. I think it's a great failing of the Code of Practice that it didn't clarify what to do with these when it was recently revised.

I have had some that had every known international standard marked on them apart from any BS or Class 2 markings, I had to use a powerful magnifying glass to read them all, they had been sourced via a firms European IT dept. They looked OK, had been in use for a number of years and I passed them with a comment that they were not marked as class 2 but could not be tested as class 1 as per the COP. The clients responsible person then has to make a decision about there continued use.

I would say if the product has an earth cable, but it isn't carried through to the output is a fail. How do you tell the difference between this and a device where the earth has broken?

Then you would have to 'fail' the majority of earthed laptop chargers and give plenty of ammo to the anti H&S brigade. I don't think there is any requirement for manufacturers to provide a facility for testing earth continuity - however difficult this makes things for us PAT people

I haven't done many but all the chargers I have come across do have the earth connected or are class II . Most I do DELL laptops chargers.

The older Dell's carried the earth through, I'm not so sure the more recent ones do but maybe I misremember. Lenovo (was IBM) are the favourites where I work and they can't be earth tested, nor can most of the earthed Delta and APD switch-modes supplied with the external USB drives. Then there's Sony, Toshiba etc etc - each manufacturer seems to have a different approach. I've seen apparently identical Dell laptop supplies one with a 2 wire supply inlet the other with a 3 wire. The earth is probably functional rather than safety in most cases but how are we to know for sure!

Thing is we don't know what the manufacturer intends a lot of the time and just because you can't perform a test on an appliance doesn't mean it's failed.

As far as I can remember, Dell laptop chargers are the only PSUs I've tested that have the earth connection brought all the way through to the output connector. No other brands do.

To fail these others would not make sense.
All they would really need is a visual inspection anyway.

Edited to add: My HP laptop PSU brings the earth through to the 3-pole dc barrel connector as well.
But lots don't!

Edited: 04 August 2012 at 06:42 PM by Grizzly01

All good advice above.

Also useful to look for the CE mark. This will (at least in theory) help you identify appliances that have been designed and approved for the European market. If an appliance is not CE marked then it is probably an illegal import OR an appliance designed for use in the US and has not been adapted for the UK or European markets.

Hope this helps.

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Seggy T Segaran

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