What appliance class has a plastic enclosure and an earth connection?

[Dave#2]

Hello,

I want to make a device with a plastic enclosure and an earth connection.

The device needs an earth connection because it will switch mains power to loads that have an earth, for example a metal-cased fan and a pneumatic valve.

My question is, what device class is it?

According to the wiki for double-insulated (https://en.wikipedia.org/wiki/Double_insulated) this would be a class 0 device, but these 'will eventually disappear... in favour of Class II devices'.

I could make it a class I device, with a metal chassis and earth connection, but I want to avoid this because it is heavier to ship and the enclosure is more expensive.

I can't make a class II device, because these aren't allowed to have an earth connection. (Why is it that a class II device *must not* have an earth connection? What is the danger?)

I see many devices around (such as common powerboards and light timers) that have
a) plastic enclosure
b) earth connection
but they are not labelled as class II/double insulated, and they can't be be class 0 because the world would end if powerboards were phased out. What class are these?


Thanks,
David

 

[Nigel Goodwin]

As someone who does PAT (Portable Appliance Test) testing, there are two classes:

Class I - with an earth lead.

Class II - with no earth lead.

Any portable appliance can be tested as either of these, note that the tests are completely different to each other!.

As for a Class II device that "must not have an earth lead", it's basically quite simple, if it DID, it's then Class I and not Class II.

Doesn't matter if your device has a plastic case, many Class I items do, but any exposed metal MUST be earthed, and able to withstand a 25A test current between the earth pin of the plug and the exposed metal.

 

[Dave#2]

Thanks Nigel it seems I am making a class I appliance. I have heard that unearthed, exposed metal parts are ok if they have two layers of insulation protecting them from the live bits.

 

[Nigel Goodwin]

Thanks Nigel it seems I am making a class I appliance. I have heard that unearthed, exposed metal parts are ok if they have two layers of insulation protecting them from the live bits.

For a class II (2 core lead) device you would test the insulation from the mains lead (with live and neutral joined together) to any exposed metal, with 3000V.

If it's a class I (3 core lead) device, then ALL exposed metal must be earthed, and able to withstand the 25A test current.

 

[andy88]

agree with Nigel that it mush be earthed or it will be dangerous to use it
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**broken link removed**

 

[mneary]

So, class I devices aren't required to have exposed metal. But if any exposed metal is present, it must pass the tests?

 

[Pommie]

I have a (UK) 4 way adapter with exposed screws and they are not earthed. So there must be some clarification as to what "exposed metal" is.

Mike.

 

[Nigel Goodwin]

So, class I devices aren't required to have exposed metal. But if any exposed metal is present, it must pass the tests?

Pretty well - with in reason - metal chassis, metal sockets etc. Anything that there's a chance 'could' become live.

 

[sangam]

Hi,
I'm doing a project where i require 48v to 5v DC converter ckt (min components or a single IC) could any one help me out.fast