Whilst I might generally agree, I'm not certain that I've ever heard anyone refer to the Disk Operating System (DOS) as the DOS OS, but simply DOS. That said, OS/2 was the superior OS despite the stranglehold of Windoze, but now I digress.
Is PAT testing law?
- Thread starter markymark2406
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Whilst I might generally agree, I'm not certain that I've ever heard anyone refer to the Disk Operating System (DOS) as the DOS OS, but simply DOS. That said, OS/2 was the superior OS despite the stranglehold of Windoze, but now I digress.
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Not forgetting that "Galapagos" means tortoise, so the "Galapagos tortoise" is the "tortoise tortoise"...
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Many of the old computers running DOS did not have a disk they used tape so DOS = device operating system not disk operating system but of course we can change what a letter means I was taught L = Live but now we are told L = Line and I often wonder when I refer to Line in a post if the reader understands and should I still call it Live?
Place names are something else I live in Bryn-y-baal and bryn is Welsh but baal is not, but most Welsh place names are descriptive like "St Mary's Church in the hollow of the white Hazel near to the rapid whirlpool of Llantysilio of the red cave." but in fairness the name did not exist before the 1860's when the railway came to town.
But English also has some descriptive names "Coed Nant" in English would be a "Dingle". And place names like Coalville don't really stretch the imagination when working out why it got that name.
Sometimes it goes the other way. People talk about their car being due for a Ministry of Transport.
What does the 'B' in Benoît B. Mandelbrot stand for?
What does the 'B' in Benoît B. Mandelbrot stand for?
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I disagree, IMO testing floating DC power suplies, for isolation is a very important test
Better that you find out the insulation in the substanrd chinese transformer or the capacitor which was supposed to be "Y rated" but isn't is failing with your pat tester than someone finds out when it gives them a shock.
Yes and no, using a dedicated pat tester has a few advantages
1: many of them can do run tests with earth leakage and power consumption measurements. Earth leakage tests can be useful because many appliances isolate parts from the mains when turned off, power consumption measurement is useful to detect failures that cause excessive current draw.
2: many of them can do mains voltage IR tests which are useful if you have appliances with transitant suppressors that kick in just above mains voltage or if you are worried about damaging the appliance when testing (personally I think the latter is a copout)
3: it's already all set-up with the right conectors so no need to mess around with adaptors to connect your test gear to the device under test.
Having said that you can certainly satisfy the minimum reccomendations for pat testing of most appliances with an IR tester and a low ohms meter.
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That is the problem with most PAT machines it requires a host of adaptors to be carried around with it to allow connection. Mine has an IEC C14 plug but to test IEC C6 clover leaf required an adaptor, same with C16A, C20 and C22.
As to phone chargers there are so many connectors and even if you can connect one has no idea as to what damage may be done by testing isolation. Be it testing earth leakage with 500 volt or testing class II with 2500 volt there is always a risk that the test can cause damage.
Today the 2500 volt test is reserved for repaired equipment before returning to service to test in case any screw is too long and would only be used by the repairer so he would be aware of any items likely to be damaged.
I accept with a 500 volt insulation resistance test modern equipment should be able to withstand the test on the low voltage side however I would still use leakage current only on IT equipment.
To use extra low voltage to prove isolation is of course useless but also to test with 500 volt between the extra low voltage output of a switched mode supply and the low voltage input is really asking for trouble.
The point is not only may it cause damage it could also stress components causing them to fail at a latter date so instead of the test ensuring safety it could actually cause a hazard.
To me using even 250 volt between an USB connector and a mains plugs pins is crazy.
Basic way a switch mode power supply is AC to DC then back to AC at high frequency and transformed down. So far so good but then the next step is to sample the DC output and alter the mark/space ratio of the DC to AC bit to control the voltage this return link may have enough of a capacitive or inductive link to be damaged by testing for isolation.
I would be interested to see if anyone other than "plugwash" sticks even 250 volt between the ELV and LV connections of a switched mode supply as part of a standard PAT inspection.
Very true, also true of other class 2 appliances such as power tools, I've seen a class 2 drill break down and put voltage on the chuck before.
That said, I am not sure of the ability of the test to weed out all dodgy adapters, I once came across a batch which would indicate a voltage of between 50 and 100v between the dc out and mains earth when tested with a high impedance voltmeter, and a volt stick would light when held on the 12v cable. I expected them to fail pat on the pri-sec insulation, supprisingly they did not, so not 100% sure what was going on there, other than stab in the dark says a lack of transformer isolation, but the path between one side to other being capacative in nature as to block the dc insulation test?... Oh by the way, I had no issue with taking them out of service... they had been fitted with moulded 13A plugs with no fuse!
The "float up to half mains" issue is pretty much a fundamental characteristicwith class 2 SMPSUs.
The problem is the flyback transformer generates high frequency noise between input and output. To suppress this capacitors need to be connected between input and output.
If you know which side is neutral then you can arrange your capacitance so your output floats towards neutral but while we brits are fanatical about the live-neutral distinction most of the rest of the world isn't.
Usually you will find that while the open circuit voltage is high the current available is in the microamps so it won't actually do any harm.
The problem is the flyback transformer generates high frequency noise between input and output. To suppress this capacitors need to be connected between input and output.
If you know which side is neutral then you can arrange your capacitance so your output floats towards neutral but while we brits are fanatical about the live-neutral distinction most of the rest of the world isn't.
Usually you will find that while the open circuit voltage is high the current available is in the microamps so it won't actually do any harm.
I did think that perhaps it was something like that as I have come across the same effect on non suspect items since.
I just used the logic that if they can manufacture a 13A plugtop without a fuse and incorrect dimensions then what are the chances of the internal clearances likely to be like and are the components going to be the right grade? .... Flex had odd core colours and few little copper as well if I remember correctly as well... definatly one where CE means Chinese export I think.
Perhaps not as bad as the mains voltage LED christmas and novelty lights that come out of the place though - some of those are positively shocking.. which goes to show that the most important part of pat is to open your eyes and look at what is actually laid before you rather than just watching for the beep and green light
I just used the logic that if they can manufacture a 13A plugtop without a fuse and incorrect dimensions then what are the chances of the internal clearances likely to be like and are the components going to be the right grade? .... Flex had odd core colours and few little copper as well if I remember correctly as well... definatly one where CE means Chinese export I think.
Perhaps not as bad as the mains voltage LED christmas and novelty lights that come out of the place though - some of those are positively shocking.. which goes to show that the most important part of pat is to open your eyes and look at what is actually laid before you rather than just watching for the beep and green light
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Some of the corn cob style LED lights also have live parts which you can touch. Many years ago I bought a BUSH TV and found it had 100 volts on the aerial to earth connection at that time I used an AVO Mk8 and the voltage varied according to scale used so was clearly very low.
I returned it under complaint only to find the replacement was the same. Then phoned manufacturer who said it was permissible to have 3.5 mA (or some other low figure) at the aerial I personally felt any voltage which could make one jump on a ladder could be fatal as it could cause one to fall off the ladder.
But unless one has been warned about possible faults then likely one would not find the fault in an inspection.
In general when testing we are looking for faults which were not there when manufactured. It is beyond our remit to disassemble except for checking fuse in the plug.
From time to time we do find new equipment which fails the standard test with our PAT tester and as a result where I worked all items were tested from new not just after a year of use both to ensure labeled and to identify any faulty new equipment plus enter it on the equipment register.
There was in one place I worked an incident where some one walked into the garage and took an extension lead out of the mechanics personal locker and used it. It proved faulty and some one got a shock so HSE was involved.
I was interviewed and told inspectors how I had refused to issue a 230 volt extension lead and for some odd bits of equipment I had got step up transformers allowing 230 volt equipment normally used off site to be used on site but these items were not permitted on the factory floor. My equipment register was taken and the HSE was satisfied that it was as near complete as as could reasonable be expected.
The mechanic said as far as he was concerned items in his personal locker were not for general use and the extension lead had been placed there so it could not be used until he had seen me to test it. So as far as he was concerned it was in quarantine.
However the HSE fined the mechanic for bringing faulty equipment on site. Not a large fine but he was fined. The firm and myself got away with it and this was due to the records kept showing how all items were regularly tested.
Personally I felt the guy who stole the extension lead out of the mechanics locker was the person who should have been fined but HSE said he was not trained to a level where he was able to appreciate the danger but the skilled mechanic was. I think likely the mechanic gave the extension lead to the guy to run the space heater and it was not stolen out of his locker and he had just said it was stolen to try to get out of being blamed. I think the HSE saw through his story.
However the question is if PAT testing is required by law. And the answer is of course no. But also clearly not to have PAT tested and kept careful records would have likely have meant I would have needed to fight a court case. So in real terms PAT testing is required. Or at least the record keeping so one can show what one is aware of on site.
I was not popular in a safety talk in an office by the safety officer. He stated all items must be PAT tested before use and have a label on them. I asked why he did not practice what he preached since he had so many items in his office without labels. His reply was show me what doesn't have labels at which I started to make a pile of all the lead sets on the table. He even went to plug them back in only when I said do I take it extension leads may be used without labels did he realise he would have to do without his computer and printer until tested.
OK company rule not law.
As to plugtop without fuse that's normal the fuse fits in the bottom of the plug!
I returned it under complaint only to find the replacement was the same. Then phoned manufacturer who said it was permissible to have 3.5 mA (or some other low figure) at the aerial I personally felt any voltage which could make one jump on a ladder could be fatal as it could cause one to fall off the ladder.
But unless one has been warned about possible faults then likely one would not find the fault in an inspection.
In general when testing we are looking for faults which were not there when manufactured. It is beyond our remit to disassemble except for checking fuse in the plug.
From time to time we do find new equipment which fails the standard test with our PAT tester and as a result where I worked all items were tested from new not just after a year of use both to ensure labeled and to identify any faulty new equipment plus enter it on the equipment register.
There was in one place I worked an incident where some one walked into the garage and took an extension lead out of the mechanics personal locker and used it. It proved faulty and some one got a shock so HSE was involved.
I was interviewed and told inspectors how I had refused to issue a 230 volt extension lead and for some odd bits of equipment I had got step up transformers allowing 230 volt equipment normally used off site to be used on site but these items were not permitted on the factory floor. My equipment register was taken and the HSE was satisfied that it was as near complete as as could reasonable be expected.
The mechanic said as far as he was concerned items in his personal locker were not for general use and the extension lead had been placed there so it could not be used until he had seen me to test it. So as far as he was concerned it was in quarantine.
However the HSE fined the mechanic for bringing faulty equipment on site. Not a large fine but he was fined. The firm and myself got away with it and this was due to the records kept showing how all items were regularly tested.
Personally I felt the guy who stole the extension lead out of the mechanics locker was the person who should have been fined but HSE said he was not trained to a level where he was able to appreciate the danger but the skilled mechanic was. I think likely the mechanic gave the extension lead to the guy to run the space heater and it was not stolen out of his locker and he had just said it was stolen to try to get out of being blamed. I think the HSE saw through his story.
However the question is if PAT testing is required by law. And the answer is of course no. But also clearly not to have PAT tested and kept careful records would have likely have meant I would have needed to fight a court case. So in real terms PAT testing is required. Or at least the record keeping so one can show what one is aware of on site.
I was not popular in a safety talk in an office by the safety officer. He stated all items must be PAT tested before use and have a label on them. I asked why he did not practice what he preached since he had so many items in his office without labels. His reply was show me what doesn't have labels at which I started to make a pile of all the lead sets on the table. He even went to plug them back in only when I said do I take it extension leads may be used without labels did he realise he would have to do without his computer and printer until tested.
OK company rule not law.
As to plugtop without fuse that's normal the fuse fits in the bottom of the plug!
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