My understanding is that it can damage the pc (Hard Drive), but they will check the lead as this is the item likely to be faulty / damaged.

I am sure somebody will come back with a more technical answer ;-)


Rob35

As a rule delicate electrical equipment such as computers are not PAT certificated. I have been told that there is specialist equipment available which will PAT certificate computers and not damage the internal gubbins. Mentioned already, but there is no legal requirement to PAT.

Pretty sure the rule of thumb with portable appliances is 'does it plug into a socket?'

The most recent guidance extends testing to almost anything connected to the fixed wiring through a flexible cord - even if connected via a spur outlet.

We do test our computers, but not as often as equipment which might be prone to abuse/damage. I am not aware of any computers which have been damaged by this test for many years, but we certainly had a few fried ones in the early days...

PS if any one wants to charge for testing phone chargers etc they are at best incompetent at worst ripping you off. A visual check of the plug is all that is required (a test wont achieve anything).

Not so at all.
Most phone chargers (& similar power pupply units) would be Class II appliances, and so a Class II insulation resistance test (after the visual inspection) would certainly be applicable.

If you still think that is a rip-off, have a read of the research that the Electrical Safety Council & Trading Standards have been doing on sub-standard plug-in chargers: http://www.esc.org.uk/bu...y/research/chargers.html

Fascinating.

I suppose the obvious rejoinder is to ask why you didn't invent a test kit that the average PAT test gadgee can use effectively without causing damage to PCs?

Seriously, I assume that theer is a variety of kit for different aplications and with inadquate training and limited experience damage will be done.

What is the solution? A reputable contractor, better manuals with a high hope that someone actually reads them, failsafe equipment design [I presume its better now than at the time to which I referred], regular backups of PC data etc etc? It's all good stuff but if your PC has just been fried none of it offers solice and the business impact can be particularly severe.

mark.g wrote:PS if any one wants to charge for testing phone chargers etc they are at best incompetent at worst ripping you off. A visual check of the plug is all that is required (a test wont achieve anything).

Not so at all.
Most phone chargers (& similar power pupply units) would be Class II appliances, and so a Class II insulation resistance test (after the visual inspection) would certainly be applicable.

If you still think that is a rip-off, have a read of the research that the Electrical Safety Council & Trading Standards have been doing on sub-standard plug-in chargers: http://www.esc.org.uk/bu...y/research/chargers.html

A phone charger is typically either a voltage divider set up or combination of transformer diodes etc dependent on the power required. An insulation resisitance test between live and neutral would achieve nothing as the live and neutral are connected through the voltage divider / transformer.. There is no earth. The output is typically below 50 volt ac 110 volt dc (usually much less) which are classed as safe values. Any live parts at 230 volt ac are not accesable provided the plug top is not damaged. i.e. if there is no physical damage there is no danger.
I take your point on the black market but again a PAT test would not be effective in detecting sub standard workmanship as this is down to the materials used level of segregation quality of build. To counteract this always buy from a reputable supplier etc

mark,
You almost got there in the end!

In PAT, the insulation resistance test in NEVER between line and neutral (for very obvious reasons, if you think about it), but rather between live parts (line & neutral combined) and earth for Class I, and live parts and exposed metal for Class II.
On the majority of Class II chargers and other power supplies, the only, and most obvious, exposed metal part is the concentric barrel connector on the end of the output lead. This makes an ideal point to perform the IR test.
Obviously, performing an IR test between live parts and the plastic casing would be a nonsense, and a waste of everyones time.

'Portable Appliance Testing' is rather an outdated term nowdays, but one that persists in usage (and hence the associated confusion).
The correct term for the whole can-of-worms is 'In-service Inspection and Testing of Electrical Equipment', as outlined in the IEE Code of Practice: http://www.theiet.org/pu...ng/books/wir-reg/cop.cfm which covers all electrical appliances, from small, handheld through to large, fixed hardwired items.

mark.g
I concur with Grizzly over this.
Also a small portable power supply such as a phone charger is unlikely to be a voltage divider, the transformer rectifier solution is more likely, it may also be a switched mode power supply these days.
Also note that they are not a safety isolated device, there is the possibility under certain failure modes for the input voltage to appear at the output terminals.
That is they are NOT, SELV, or PELV devices.
They should be tested.
IF that is the procedure that you wish to implement.
Remembering that the IET CoP gives further guidance, as do various HSE and ESC guidance as has already been suggested.


redken,
Please see my comments below,

All,
Be very careful however, to take Grizzly's basically correct statement including large hard wired items for granted. Items such as wall heaters, built in appliances, large stationary appliances such as fridges, can be considered under a PAT regime quite easily. However, to undertake a full test on a wall mounted electric heater will necessitate dismantling and disconnection of aspects of the fixed wiring installation those undertaking such disconnections and reconnections should be competent to do so. A PAT course would not give you this level of competence. Safe isolation would be required as live working in this scenario would not be excusable.

All the PAT in the world will not protect you if there are defects in the fixed wiring installation. If the portable appliance relies on the “earth” conductor in the fixed installation for its protective measures, if this is not present or inadequate then there is still a serious hazard even if the appliance has just passed its PAT and has developed an internal fault just after, or if the fixed heater disconnected and reconnected by the PAT person did not have its circuit protective conductor (earth) correctly reinstated after test.

One must be careful of machinery built to BS EN 60204-1 standards, basically the machine equivalent of BS7671 (IEE Wiring regs).
Applying the IET CoP to such equipment by unqualified personnel leaves a lot to desired, believe me I have seen it many times! Inspection and testing on large fixed machinery such as machine tools etc. is best left to professionals, PAT companies should be extensively interrogated in their competence to undertake any such work.

rnighting,
Whilst I see and understand your points, I fail to see the place for flash testing at 1k5V or 3kV during in service inspection and testing.
This is specifically excluded as a requirement in the current IET CoP for in service I&T.
Many PAT machines for several years now have had a low current earth bond test (around 100mA) which can be utilised to confirm the continuity of the earth bond, whilst minimising the current flow through the “appliance” which also could cause damage to equipment, remembering that a “normal” earth bond test provides up to around 25A for up to around 20s.
As I understand the engineering behind this, as I have studied it, it is to highlight any possible high resistance or otherwise weak junctions in the earthing of the appliance.
This is similar to the high current test that can be applied to metallic wiring containment systems such as conduit and trunking to confirm their earthing integrity is it not?

Paul.

You're quite right to test the mains lead, which is a seperate appliance to the PC anyway.
As for the PC itself, yes, most bits of it are running on extra low voltage, but the whole PC assembly still contains the power supply unit, which is supplied at mains voltage. Therefore, the PC is a 230V appliance, and can be tested accordingly (20mA - 200mA earth bond test, 500V insulation test (if PC is built to BS EN 60950)), and at the appropriate intervals for its environment.

jericho/Chris - No backlash from me, I have on numerous occassions on this forum in the past tried to get people to take a reality check on this preoccupation with PA testing everything. I for one remain to be convinced that PA testing is in many cases a particularly good use of resources. My advice would be to apply simple risk based principles and have a look at both the HSE and IEE guidance, it is realively straightforward stuff.

I will echo Phil Rose & Grizzly's comments, however, I recently undertook PAT at a customers premises myself.
I found, a cracked multiway adaptor feeding a PC workstation, multway adaptors all over the site, and a printer lead with a very high earth bond test, printer alone, OK, lead alone OK, both just, together fail.
Customer has a blanket policy of PAT everything 12 monthly due to other areas in their organisation which do have appliances etc. that do need serious I&T.

Being a competent electrician, electrial engineer (true engineer, IEng, MIET), and qualified & comeptent PA tester, and competent to test fixed installs as well as my H&S "hat" I try to be reasonable and applly common sense.
When I got dragged out to test a few appliances the other day, (no one else available) around 30 I was told, came away with 91 test results.
I advised the customer with regard to HSE & IET guidance on their equipment and how they could save resources on annual testing by adopting a risk based approach and following published guidance.
Thier local H&S officer (multiple sites, large international blue chip co.) advised me that the management overhead to control multiple test periods outweighed the annual test everything approach!

Paul
Paul

Just a quick observation Paul; you didn't need a PAT machine to identify the cracked multiway or to identify a plethora of such adaptors did you?

Thank you for all your advice, I certainly have a better understanding now of the issues surrounding PAT testing PCs and other equipment.