Class 2 insulation tests

[deedar]

Hi, I did C&G 2377 a couple of years ago and have only recently been asked by company to do some portable appliance testing for them.
Now, I'm trying to remember how to test class 2 equipment. I've looked around the internet the best I can and haven't really found an answer.

How I understand it class 1 items testing consists of 1, visual inspection, 2, earth continuity, 3, insulation test 4, polarity (on IEC leads)

However, when testing class 2 appliances and 2 core leads testing consists of 1, visual inspection, 2, insulation test

Am I right in saying that on class 2 appliances, 2 core leads and SELV equipment that you can only do an insulation test if there is exposed metal work? And if there isn't any exposed metal work then the only test that can be done is a visual inspection? So, for example I'd only be able to do a visual check on mobile phone chargers and on laptop transformers?
Are they any other tests that can be carried out on class 2 equipment?

I've heard mixed advised given on this subject, but I would really like to find out the correct procedure if anyone can help.

Thanks

 

[telectrix]

on the "PSU in a plug" equipment, all you can do is a visual.

 

[Graeme Moo]

You do insulation test between L-N for Class2. Exposed metalwork is for earth continuity on Class 1

 

[telectrix]

and most of the time you can;t do IR test L-N. 1. you will read the resistance of the appliance. 2. you might destroy trhe appliance.

 

[deedar]

You do insulation test between L-N for Class2. Exposed metalwork is for earth continuity on Class 1

I read somewhere that when you do an insulation test on a class 2 appliance you need to connect your probe to any exposed metalwork so that if a fault occurred then a reading would be sent back to the PAT Test machine, is this not correct?

Please see this video on youtube from seawards explaining the insulation tests on a class 2 appliance: An Introduction to PAT Testing - YouTube hopefully you'll see where my confusion comes in.

Thanks for replying

 

[telectrix]

you are correct . but a lot of class II appliances do not have any exposed metalwork, so you can't test it.

 

[deedar]

you are correct . but a lot of class II appliances do not have any exposed metalwork, so you can't test it.

Does that mean that only a visual check can be done?

 

[RISElectrical]

Plug in machine, machine asks if its class 1 or 2, you tell machine, machine does test, computer says YES or NO and you give GREEN sticker or RED...

Sorry, i just came back from doing 50 PATS and that was enough for this year!

 

[telectrix]

yep. visual + check correct fuse is fitted.

 

[deedar]

yep. visual + check correct fuse is fitted.

Just doing and insulation test on a class 2 appliance without a probe would basically do nothing then?

Thanks for your answers you've helped a lot

 

[Graeme Moo]

Class 2 equipment has double or reinforced insulation around the live parts. exposed metalwork should never be able to become live unless there was a major fault that would be visually obvious. That is what i was taught anyway. Dont know where they are coming from with that utube clip.

 

[deedar]

Class 2 equipment has double or reinforced insulation around the live parts. exposed metalwork should never be able to become live unless there was a major fault that would be visually obvious. That is what i was taught anyway. Dont know where they are coming from with that utube clip.

So, you can do in insulation test on a class 2 appliance/lead without using a probe? just run the 500v insulation test on my tester?

 

[deedar]

A sample from Leeds University PAT Testing requirements:

1- IT equipment – summary
Class 1 IT appliance:
Earth bond test:
· If the equipment has a metal case, carry out normal earth bond test.
· If the equipment has a plastic case and the only exposed metal parts are connectors, carry out a low current earth bond test
· If the equipment has no exposed metal parts, there is no need to carry out the earth bond test.
Insulation test:
· This test should only be carried out if the appliance conforms to BS EN 60 950.

Class 2 IT appliance:
Earth bond test:
· This test should not be used on class 2 appliances.
Insulation test:
· All insulated appliance (no exposed metal parts) - no test necessary
· Double insulated appliance (some exposed metal parts) – carry out the insulation test only if the appliance conforms to BS EN 60 950


Hmmm I don't what to think . . . anybody able to give me a definite answer please?

 

[Adam W]

The way I was taught is with a class 2 appliance you do the IR test (which joins line and neutral) and touch the wander lead over any metallic parts and parts the user will touch, which should pick up any electric which is leaking out.

 

[deedar]

So would u say that a class 2 appliance with no exposed metal parts can't have an insulation test conducted on it?

 

[Adam W]

Chances are there will be metal screws exposed. Otherwise you can touch the wander lead on any parts the user will touch, eg buttons, casing etc where the insulation may have become thin or worn. That is the point of an insulation resistance test - to measure the resistance of the insulation.

 

[deedar]

Chances are there will be metal screws exposed. Otherwise you can touch the wander lead on any parts the user will touch, eg buttons, casing etc where the insulation may have become thin or worn. That is the point of an insulation resistance test - to measure the resistance of the insulation.

so doing it without a probe would be pointless?

 

[rich.250]

Yes, you need to do a ins test to prove the outer casing isn't breaking down or been contaminated with a conducting substance. Eg oil and the like.
Get a copy of the pat testing guidelines from the iet.
Can't think of The name

 

[rich.250]

http://electrical.----------/books/inspection-test/in-service-inspection.cfm

 

[deedar]

Code of Practice - IET Electrical

Thanks. I did have this book when I did the 2377 course. But l can't find it atm. All I'm really trying to find out is how to carry out insulation test on class 2 items both with exposed metal parts eg. Drills, hairdryers etc without exposed metal parts eg. Phone chargers, class 2 detachable leads, radios etc.