Do you really want to shove 500 volts into a computer or a TV? I think not and the machine you are looking at does just that on the insulation test. You REALLY do need one that specifically states it's suitable for IT/sensitive equipment. Most of this type of equipment can be tested at 5yr intervals so maybe it's worth considering hiring something more suitable. From memory I don't think the PAC500 does IEC leads unless you have the box of tricks that goes with it and they're £120 each.
If tested between earth and the two supply pins of the appliance connected together (as recommended in every test procedure I'm aware of) then there should be no problem with using 500V. The exception is where there is a MOV connected to earth, (but such equipment is a disaster waiting to happen ) and some standards then allow testing at a lower voltage to prevent the MOV conducting.
Equipment in service is exposed to transients that will stress the insulation well beyond the peak voltage of the supply.
I can't comment on PAT testers because I find their "go/no go" indication of limited value. I prefer to know what the actual resistance is so that even if it is legally OK but lower than expected, the cause can be investigated.
-- Regards Malcolm. Remove sharp objects to get a valid e-mail address
Don't want to get into a long drawn out argument but transients shouldn't get anywhere near enough to damage equipment. , if they do then the supplier has a problem.that needs attention.As for MOVs well, how would you know? Which is why some PAT tester are rated for IT equipment
I read in sci.engr.electrical.compliance that Malcolm Moore wrote (in ) about 'P.A.T', on Thu, 26 Feb 2004:
You are quite right, and this is an unadressed matter in safety standards. They specify only a minimum acceptable insulation resistance, which is in the region of 2 Mohm. But a piece of equipment may well measure 100 Mohm or more (I've measured 1 Gohm in very dry conditions) when new, so a degradation to 2.1 Mohm ought not to be a 'pass' but evidence of a significant problem. Even 10 Mohm ought to be suspicious.
In my line of work I can't just check fuse/check lead/meter/sign the form
Some testers can do that cos thats all that's needed.
I have to consider a baby crawling on the floor that could conceivably pull out an IEC connector and suck on it so I don't follow the 'earth all exposed metal' rule
I also remove EMI filters with neutral fuses
I also use a loop tester for earth integrity as the PAT tester only confirms earth to the appliances plug
Horses for courses - do what you have to in order to protect people - I've done death at work and take H&S at Work seriously.
We all carry voltsticks & contact handheld voltmeters to check for lost earth on an EMI filter which gives you a nasty 110V zap
Just PAT'ed a video game which would have normally passed but was concerned by the electrostatic zap from the screen (happens sometimes) found no earth to the aquadag backing cos of a bent pin in a plug ....the zap was enough to rip a muscle & sue somebody
I read in sci.engr.electrical.compliance that Chris Oates wrote (in ) about 'P.A.T', on Fri, 27 Feb 2004:
You don't have any authority to waive requirements of BS 7671.
By doing any such modification you invalidate the safety approval of the product concerned. You also probably make it violate the EMC Directive! Do your customers know that you do things like this?
Please explain where this '100 V zap' could be delivered. Have you actually every found an open earth on an EMI filter? In my experience, this is an exceedingly improbable fault.
PAT testing does not extend to opening up equipment and repairing perceived faults.
You are not doing 'PAT testing' but, at least in some cases, re- designing installations or products to conform to your own views on electrical safety, and should seriously consider the huge responsibilities you are taking on by performing the actions you describe.
This is covered on the C&G PAT training course. It is one of the reasons you should keep PAT test records. The other reason is so you can see if you are testing either more often than is necessary, or not often enough.
I might add that I've seen many PAT test inspections carried by and for various different companies. It's extremely rare to find the operative has the slightest clue what they are doing. If you are looking for someone to do PAT testing for you in the UK, make sure the person doing the testing brings their C&G certificate (C&G 2377 IIRC) with them to show you. Otherwise, you might as well bring your grandmother in to do the testing. Anyone reasonably compitent at wiring plugs, doing ohms law calculations, and who knows the difference between milliohms and megohms can take the 2 day course and pass the exam -- it is specifically designed to be achieveable without you having to be a practicing electrician. Actually, it's quite hard to find electricians who are qualified to perform PAT testing -- most electrical companies we tried had no one (not that this stopped them from doing it).
If someone starts off a PAT test by connecting the appliance to a PAT tester, then you just saw someone who doesn't know what they are doing.
The point is that the most important part is the visual inspection, and the piece of test equipment can't do that! Over 90% of test failures come from the visual inspection part of the test -- checking condition of the equipment (cracked/damaged casing, etc), checking it is appropriate for its usage and environment, checking the cable isn't nicked, checking the right fuse in the plug, checking the plug and socket for signs of over heating, checking cord grips and screw terminals, checking for IP2X compliance, and more I don't remember off the top of my head. You can actually do the most import parts of the PAT test with no test equipment whatsoever.
You don't put the appliance anywhere near the test equipment until all these have been checked out, indeed it can be dangerous to the test person to do so. If you don't do the visual inspection part, you will miss most test failures. You can easily spot someone who doesn't know how to PAT test an appliance because they will nearly always just connect it to the test equipment and probably won't do the formal visual inspection at all.