PAT Testing a TFT Monitor, external adapter

[enjay]

Am I right in thinking that a visual inspection is sufficient for a TFT monitor with an external power adapter?

[p858snake]

Based on http://www.edugeek.net/forums/behind-red-door/51092-providing-extended-services.html#post468942 you will need to do the removable cord part (socket to female IEC) which plugs into the transformer box.

[fafster]

Based on http://www.edugeek.net/forums/behind-red-door/51092-providing-extended-services.html#post468942 you will need to do the removable cord part (socket to female IEC) which plugs into the transformer box.

 

It depends. If the cord's plug is a sealed unit, a visual inspection would be fine.

[powdarrmonkey]

No you are not correct (and on this basis, you shouldn't be testing things. This is a really basic question...)

 

If the flying lead is not permanently attached to the transformer, it needs a separate IEC test. The transformer itself probably needs a class II test, but only if it's double insulated. If it's not, it gets a class I.

 

 

edit: and yes, you need to attach the monitor.

Edited March 2, 2010 by powdarrmonkey

[powdarrmonkey]

It depends. If the cord's plug is a sealed unit, a visual inspection would be fine.

 

NO. NO, No, no.

[mgarland]

The power supply will need testing but there is not test for the monitor itself as it is running on a low voltage.

[powdarrmonkey]

The power supply will need testing but there is not test for the monitor itself as it is running on a low voltage.

 

Wrong, you need the monitor connected to provide real-world load conditions, eliminate short behaviour, etc.

[enjay]

So, I plug it into a (known good) cable, and turn it on - right?

 

I am registered to test stuff here, but have never actually done it! I went on the course several years ago, and when it transpired how little IT equipment actually needs testing, I largely walked away from it.

[powdarrmonkey]

So, I plug it into a (known good) cable, and turn it on - right?

 

What's this "it"?

[enjay]

The adapter and monitor.

 

We've been given it second-hand, so I want to have it tested (we were advised not to bother with brand new equipment).

[fafster]

Sorry Powdarrmonkey, I believe you are incorrect. As it's a transformer, and the voltages within the appliance are below 50 volts, it's a Class 3 appliance. It doesn't need testing. Therefore, you perform a formal visual inspection. Check to see there is no damage to the transformer, cable or device, and that it has the correctly rated fuse.

[powdarrmonkey]

Hypothetically, since I don't think you should actually be doing it, you:

 

1. Plug both ends of the IEC into your tester and perform an IEC test;

2. Plug the tail end of the IEC into the adaptor, connect and switch on the monitor, and perform the appropriate test, which depends on the adaptor;

3. GET BACK ON THE COURSE BEFORE YOU KILL SOMEONE.

[powdarrmonkey]

Sorry Powdarrmonkey, I believe you are incorrect. As it's a transformer, and the voltages within the appliance are below 50 volts, it's a Class 3 appliance. It doesn't need testing. Therefore, you perform a formal visual inspection. Check to see there is no damage to the transformer, cable or device, and that it has the correctly rated fuse.

 

Nope, not unless it carries the class III mark and the transformer is certified to BS3535, in which case it also has a specialist mark. I have never seen a sealed consumer power supply that isn't class II or, more unusually, class I. If it's marked double-insulated, it's class II; if it's not marked at all it's class I.

[enjay]

Sorry Powdarrmonkey, I believe you are incorrect. As it's a transformer, and the voltages within the appliance are below 50 volts, it's a Class 3 appliance. It doesn't need testing. Therefore, you perform a formal visual inspection. Check to see there is no damage to the transformer, cable or device, and that it has the correctly rated fuse.

 

That was my understanding and is confirmed by http://www.hse.gov.uk/pubns/indg236.pdf.

[powdarrmonkey]

That was my understanding and is confirmed by http://www.hse.gov.uk/pubns/indg236.pdf.

 

That document doesn't even contain the words "Class 3".

 

I think I understand what you're getting at. The monitor itself is an SELV device, but you're not testing the monitor. You're testing the adaptor, which plugs into the mains and is class I or II, unless you've paid $$$ for it. FFS, look at the brick and tell me if you see the class II or III mark on it.

[enjay]

3. GET BACK ON THE COURSE BEFORE YOU KILL SOMEONE.

 

The course I went on said not to test PCs and other low-voltage IT equipment, as the testing can damage it; it is sufficient to test the power cables and perform visual inspections; new equipment does not need testing. This is what I've been working to ever since.

 

Are you saying - with supporting evidence please - that this is incorrect?

[fafster]

The document that enjay linked to mentions that class 2 computer equipment doesn't need to be tested.

[ICT_GUY]

From our recently trained in house guy.

 

Every 12 months for visual inspection on class 2 equipment and every 48 months for combined inspection and testing.

 

This applies to school environment.

[enjay]

That document doesn't even contain the words "Class 3".

 

No, but it does contain the words "IT equipment" and "VDU screens" (page 5), hence me thinking it relevant to this monitor.

 

I think I understand what you're getting at. The monitor itself is an SELV device, but you're not testing the monitor. You're testing the adaptor, which plugs into the mains and is class I or II, unless you've paid $$$ for it. FFS, look at the brick and tell me if you see the class II or III mark on it.

 

No Class II or Class III marks, nor the double-square thing. It does say "listed level 3" though, is that the same as Class III. I can put a picture up here if that would help...

 

I guess my question is that since I can't test just the cable and shouldn't test the monitor, how do I do this?

[fafster]

From our recently trained in house guy.

 

Every 12 months for visual inspection on class 2 equipment and every 48 months for combined inspection and testing.

 

This applies to school environment.

 

There's no law that states how often something needs inspection and/or testing. It's basically all just common sense. But that timetable he was given sounds reasonable enough.

[powdarrmonkey]

The course I went on said not to test PCs and other low-voltage IT equipment, as the testing can damage it; it is sufficient to test the power cables and perform visual inspections; new equipment does not need testing. This is what I've been working to ever since.

 

What kills soft equipment is the 26A earth bond test, so you reduce it to 100mA. Oh, and the flash test, which is unnecessary in 99% of cases.

 

Are you saying - with supporting evidence please - that this is incorrect?

 

See the 17th editions.

[fafster]

I guess my question is that since I can't test just the cable and shouldn't test the monitor, how do I do this?

 

You can't. If it works, and there's no damage on inspection, it'll be fine.

[powdarrmonkey]

No, but it does contain the words "IT equipment" and "VDU screens" (page 5), hence me thinking it relevant to this monitor.

 

It also says "if doubly-insulated", and so far you have no evidence that this is the case.

 

nor the double-square thing.

 

That would be "doubly-insulated", the class II mark. I rest my case.

 

It does say "listed level 3" though, is that the same as Class III.

 

No.

 

I can put a picture up here if that would help...

 

No.

 

I guess my question is that since I can't test just the cable and shouldn't test the monitor, how do I do this?

 

You're not testing the monitor! FFS!

[enjay]

You're not testing the monitor! FFS!

 

Firstly, calm down. Secondly, I know that - I'm asking if I need to test the adapter and how I go about that.

[ICT_GUY]

There's no law that states how often something needs inspection and/or testing. It's basically all just common sense. But that timetable he was given sounds reasonable enough.

 

Straight from the IEE code of practice. That is the recommendation, stray from it and you will have to justify yourself should something go wrong.