There is a great deal of debate at the moment about whether or not computers should be PAT tested. For those unfamiliar, a Portable Appliance Test (abbreviated to PAT Test but that’s another article) is a process by which an electrical appliance is checked to see if it is safe. Most appliances in use in workplaces today will have a green sticker on them to indicate that they have been tested.

In the old days of PAT testing, engineers used to carry out a test called a ‘flash test’ whereby 3000V was applied across the insulation to detect any breakdown. At the time, the only items which were PAT tested would be power tools and machinery – then people started to test computers (with disastrous consequences) and all hell broke loose.

Very quickly, the advice given was not to test computers! Of course the test equipment manufacturers quickly modified their testers to carry out ‘soft tests’ for computers, and the computer manufacturers redesigned their power supplies so they would not be damaged by the test.

Unfortunately, even many years later you still meet people who refuse to have their machines tested for fear of damage. This does, however, mean that people may be using computers unaware of a dangerous fault…..

Nowadays, the only two tests which are carried out on PC’s are the Earth Bond Test and Insulation Test. The Insulation Test might cause damage to the power supply, UNLESS it is manufactured to BS EN 67950. ALL computers (and monitors and fax machines etc) have to comply with this standard, and have done since the early 90’s. So the ‘correct’ procedure is to carry out earth and insulation tests on all modern computers, but to leave out the insulation test if the device appears to be more than about 10 years old. (not too many computers – but occasional monitors and printers are quite old.)

My company did the PAT testing for a large organisation, and it turned out that they NEVER shut down their PC’s. They just went home at night leaving them on, and after a few minutes of screen saver the computers went into ‘sleep’ mode.

In a few cases we found PCs where the CMOS batteries (which retain the system settings when the computers are switched off) were completely dead, but nobody knew about it because the computers had never been turned off. Of course, we had to turn them off (and unplug them from the mains) to test them, so a couple of machines refused to start properly after the test. They were quickly sorted out though.

However, a properly conducted PAT test will never cause damage to a PC.

I will concede that there are a few PAT testing engineers out there who don’t possess all of the requisite knowledge, and unfortunately there is a lot of subcontracting going on which means that the testing is done by the lowest bidder! It is possible for damage to occur if the wrong tests are carried out.

Anybody in any doubt about having their computers tested should speak to a professional PAT testing company.