PAT Testing.

Split from this thread:-

https://www.vintage-radio.net/forum/...d.php?t=179413


We had the PAT folks round today and one admitted they "have to do" an insulation test from the earth pin even if it is plastic, apparently this will soon be replaced by a mere visual check. They don't check that a double insulated power supply output is isolated at all. Can of worms or what, no brains involved.

[SiriusHardware]

PAT folks round today and one admitted they "have to do" an insulation test from the earth pin even if it is plastic

As the resident PAT tester (among other things) where I work I have to say that is just not true. There is a lot more leeway for common sense than is suggested by the above.

I am glad to hear so, ours seem to be tick box folks.

[Techman]

Originally Posted by merlinmaxwell

we had the PAT folks round today and one admitted they "have to do" an insulation test from the earth pin even if it is plastic,

I seem to remember a PAT tester doing that a few years ago where I used to work.

[ortek_service]

We've had PAT-Testers fail lots of brand-new LCD-monitors, because of 'too much' earth-leakage due to their mains-filter capacitors as they hadn't set their machine right.

And another who failed Weller soldering-iron bases, because the tip of the iron didn't measure to earth, even though there was a Earth point 4mm socket on these that did connect to tip and they were double-insulated.
So these ended-up getting scrapped, because they didn't a double-isolated symbol on them, even though it was obvious they had to be.

I do recall that there originally was a requirement to do a (4kV?) flash-test on double-insulated equipment. But this could cause damage, so you can now do this at just a few hundred volts.

[emeritus]

Around 20 years ago I acquired a vintage GEC metal- cased double insulated (and marked with the double squares symbol) 2kW fan heater from work when the PAT tester failed it for no earth. The original 2 core cable had been replaced by a 3 core one with the earth cut short at the point where it emerged from the cable's outer sheath and was not connected to the plug's earth pin (AFAIR 2 core flex rated for 2kW was uncommon at the time). It still gets occasional use - its fan is whisper-quiet, unlike most modern ones.

[pmmunro]

PAT has retired! There is a new Code of Practice on "The In-service Inspection and Testing of Electrical Equipment" 5th Edition in which the distinction between portable and other equipment is removed.

https://electrical.theiet.org/wiring...cal-equipment/

The new CoP emphasise the need for user checks and an assessment of inspection intervals based on conditions of use. It also makes clear that most Class II equipment does not need to be tested but all equioment must be inspected appropriately.

I would seriously doubt the competance of anyone who insists on attempting an earth test on equipment fitted with a plug which has an ISOD (Insulated Shutter Opening Device) instead of a metallic earth pin.

The CoP also describes how testing may be done with instruments other than a decicated Portable Appliance Tester although some testing organisations use them as data loggers, in which case there may be a case for connecting tem to Class II appliances.

PMM

[Lucien Nunes]

Having been involved in the rollout of PAT on a large scale in the early days of the Electricity at Work Regulations '89, and having had involvement in assessment of testing practice and performance over the years, I can say that there is no field of work in which the level of skill and efficacy varies more widely. As it came to be seen as a box-ticking exercise, PAT was a race to the bottom with some companies offering such low test prices that no satisfactory inspection or test could be conducted in the available time.

Thus on the one hand there are companies offering knowledgeable electrical folk inspecting with a keen eye, and using instruments to test appliances for safety, in a logical and technically valid manner. On the other there are companies sending out people with effectively zero technical knowledge to slap stickers on, more or less indifferent to whether the appliance ever got plugged into the magic box and what the box had to say about it, let alone seeing whether the plug was wired properly. They are the ones who can't work out how to program the tester correctly so that it doesn't do an earth-continuity test on a Class II device. These two services were called by the same name and often charged at the same rate.

In the quest for correct test procedure, I forbade all automation. I trained test crews to use fully manual, analgoue instruments. Real humans decided which tests and limits to apply and took responsibility for accurately recording and interpreting results. They were also keenly aware that visual inspection is the most important part of the process, with fully 75% of all defects being detected without the use of a test instrument. Unsurprisingly, they were well received on the front line, with very few unwarranted failures and many subtle hazards discovered and/or corrected with a minimum of fuss. Eventually, we caved to the pressure of the barcode and the computerised test instrument, but teams still had to be capable of programming the tester without assistance from blank to fully operational for all the different test regimes.

Looking back over 30 years of PAT, in my opinion, the step-change of the 1990s was the most beneficial outcome. The initial phase succeeded in purging a vast accumulation of highly defective equipment from commercial inventory, some of it having been hanging about with live casings and bare wires for decades. Today, with a much narrower and more predictable range of hazards to locate, the 5th Ed. of the ISITEE CoP slims down the process to focus on the known troublemakers. Those haven't changed much.

[russell_w_b]

Originally Posted by pmmunro

The CoP also describes how testing may be done with instruments other than a decicated Portable Appliance Tester...

We were doing this at the British Steel Corporation's Workington works offices back in the mid-1970s before PAT became a thing. It was a task referred to as 'portables' and we apprentices, under the guidance of the electrical instructor, a former Bessemer electrician, would go into the offices armed with a 500V Megger, an AVO 7 or 8, our eyes, and a notebook to record the figures.

It was a once-monthly exercise as I recall.

[G6Tanuki]

Lucien's post pretty much sums up my experiences too: there were good and bad PAT-people along with good and bad test-scenarios. So long as the testers worked properly with the customer the outcomes could be beneficial [as noted, there was quite a bit of horribly-unsafe gear to be found in garages, farms, workshops and labs; quite a number of horrors still appear at radio-rallies!]

"Working together" was always important: I recall a particular incident where 13A fuses in plugs were replaced with 3A ones because they were feeding PCs/monitors whose badged power-consumption was only a couple of hundred Watts. That didn't take into account the switch-on surges [SMPS inrush currents, Trinitron monitor-degauss] which took-out the 3A fuses after a few dozen switch-on cycles.

If only the testers has asked-before-acting, a lot of grief could have been averted.

[Lucien Nunes]

There have been much worse consequences of inappropriate tester action. My initial involvement was in the aftermath of a commercial testing service having tested a roomful of monitors, failed them all for low insulation resistance (that was correct and a pass) and cut their original factory-fitted plugs off the captive mains leads. New plugs were then badly fitted by the customer, resulting in a brace of electrical faults. A similar plug-chopping exercise at a school resulted in a pupil receiving a direct shock, when one of the plugs, discarded with an inch stub of flex projecting, was plugged into a socket outlet.

On the subject of schools, even our highly competent test crews managed to invoke the wrath of a head-teacher by failing the study kettle and the bell-ringing system. The contacts of the school's Synchronome programmer completed a circuit from a 1930s transformer that stood unenclosed on a filing cabinet, with a mains flex from a 13A plug connected to exposed screw terminals. Whoever had considered that an adequate solution was long gone; it had been that way as far back as anyone could remember. Unfortunately, the moment it was decommissioned, chaos ensued and we had to make and dispatch a new transformer in a box plus a new kettle with a special envoy to calm the situation.

[duncanlowe]

Originally Posted by Lucien Nunes

A similar plug-chopping exercise at a school resulted in a pupil receiving a direct shock, when one of the plugs, discarded with an inch stub of flex projecting, was plugged into a socket outlet.

I have always made plugs I cut off in this way impossible to plug in, by bending or preferably breaking off the pins. I saw someone simply chopping off and not doing anything and suggested they should similarly 'disable' it. They said I was stupid, and that anyone else stupid enough to plug one in deserved a shock (or worse). They were still very proud of how perfectly they did their entire job when I left.

Incidentally, I also recently destroyed a mains lead I had hung on my rack, when I realised it was one of those fake dangerous ones (sleeved earth). Just disposing of it 'could' have seen it reclaimed somehow.

[Dave Moll]

Originally Posted by Lucien Nunes

A similar plug-chopping exercise at a school resulted in a pupil receiving a direct shock, when one of the plugs, discarded with an inch stub of flex projecting, was plugged into a socket outlet.

That reminds me of an item I bought at a local auction once where, "for safety reasons" the plug was chopped off, but the chopped-off plug was included in the lot!

Neary 30 years ago work (a past work place, now long gone) the PAT tester insisted that IEC cables where paired with the equipment and tied (using a very strong ty-rap) a brass serial number disk/label to the cable. It didn't take much wiggling to make the disk cut into the cable, 67% chance you got a live one (neutral being a live conductor).

Not long ago I made a lead with two 13A sockets in series terminating in a 13A plug, this is a high power "lamp limiter" using a 3kW fan heater as the lamp for fault finding a particularly large power supply we get back for repair occasionally. It does save tripping out the whole lab. Took a while to convince PAT that it was OK.

[ortek_service]

Originally Posted by pmmunro

PAT has retired! There is a new Code of Practice on "The In-service Inspection and Testing of Electrical Equipment" 5th Edition in which the distinction between portable and other equipment is removed.

https://electrical.theiet.org/wiring...cal-equipment/

The new CoP emphasise the need for user checks and an assessment of inspection intervals based on conditions of use. It also makes clear that most Class II equipment does not need to be tested but all equioment must be inspected appropriately.

I would seriously doubt the competance of anyone who insists on attempting an earth test on equipment fitted with a plug which has an ISOD (Insulated Shutter Opening Device) instead of a metallic earth pin.

The CoP also describes how testing may be done with instruments other than a decicated Portable Appliance Tester although some testing organisations use them as data loggers, in which case there may be a case for connecting tem to Class II appliances.

PMM

That's useful to know, as I hadn't heard about these changes so far. And I wonder if this means people doing PAT-Testing will need to re-qualify to the latest procedure.

I do recall that we had some in-house people once doing it, who had passed a brief course. But later on, it was decided they should re-do this (after amendments to it?) and they hadn't passed the new test (I think they said the new tutor wasn't very good). So most of the PAT-testing equipment they all had was disposed of, and contractors brought in (who often seemed to not be that clued-up on appropriate testing).

I did once buy a PAT-Testing training DVD you watched then had 3 'free' attempts to pass the online test, to see if I could get myself 'qualified'. But I never got round to doing this, so I wonder if that test would no longer be valid anyway / what date any changes come into force (like with new IET wiring regs, where there's a period before they become mandatory).

Although, if testing is now done with much relaxed current and voltages, then it seems like equipment to do the testing might be a lot cheaper - although no doubt you may have to pay to have its calibration periodically-checked.

[dglcomp]

As I understand it the low voltage side of a PSU hasn't ever technically needed to counted as exposed metal as part of an insulation test and as such does not need to be tested, just visually inspected.
As for doing an insulation test on a plastic item, the only thing it could possibly test is that the plug hasn't become conductive and isn't shorting between earth and live but if it has a plastic ISOD then that won't do anything.
I certinaly don't put plastic devices on the tester at work as it would be stupid to do so and I do open all rewireable plugs (and check teh fuses on non-rewireable plugs) and if someone doing testing did not do that then they should not be doing testing, how an you tell otherwise that the plug is wired correctly, all terminals are tight and the fuse is correct (there is actually a real fuse which appears to be genuine)

Testing hard wired items is an interesting conundrum, partially because you don't need to be trained as an electrician to do appliance testing but would potentially need to be to test hard wired appliances as you would have to touch the fixed wiring (in my world that would be hairdryers and some microwaves). Plus add appliances that can't easily be moved and you have a conundrum. Again I just do a thorough of a visual test that is possible and it gets a visual only test sticker and it is noted on the paperwork that only a visual inspection has been carried out.

Also like other people I do make plugs unusable if they are unsafe.

As for interpreting test/inspections I hate that our machine at work only gives you a pass/fail indication so you can not tell how much something has failed by and try and see if the fault can be remedied, and on the wrong fuse question, we had a load of Cello 22" TV's that had 13A fuses fitted which I failed them on as I would doubt inrush current would be an issue on a 12V 3A PSU!

Another thing that does annoy me is testers putting passed stickers on low voltage appliances, what have they tested?, the cynic in me thinks they are doing it to make extra cash is they are being paid per item, and random sticker placement. They had someone in this year to do all the items in our office/stores and all our vacuums had stickers in random places which look a mess, plus it make me question if they did the inspection properly. They also put a sticker on the water tank of our small coffee pod machine, so that you could not remove the water tank without removing it.

[SiriusHardware]

I mentioned that I am the resident PAT tester at work: To be precise, I get handed any newly acquired items to be PAT tested before they are allowed to be used on the premises. At one time we used to do all of the PAT testing every year and we used to do it diligently because, as dgl said above, it would be unusual to go through a whole premises and not find the earth screw (or live or neutral) rattling loose in at least one plug. We also used to replace inappropriate plug top fuses with ones suitably rated for the appliance.

However, doing all of that and doing our day job (test and repair) took too long in the company's opinion so they outsourced the job, and now all of the routine yearly retesting is done by label-stickers. I've watched them go through our department and I have never seen them do any sort of electrical testing. Plugs and the appliances their flexes are hardwired to are frequently given one 'Pass' sticker each, with two different appliance numbers on them: In this way, one appliance can count as two items tested = more money.

In the canteen, we have two full height fridge freezers and a tall white floor standing cupboard unit. The first year they went through that area I noticed that both of the fridge units had PAT test stickers attached, but so did the cupboard, which had clearly been mistaken for a third fridge. Don't ask me how they PAT tested it. (I am honestly not making this up). I drew it to the attention of the person responsible for getting this job done but the same people were back again the same year, doing exactly the same thing.

[dsergeant]

Thanks for the mention of the change to PAT laws, I will have to investigate later.
I do PAT testing for our church, and yes I do try and do it properly. I also 'trained' myself with that DVD and passed their 'test'. In the Methodist Church as in most places it is a requirement to be done and declared on property returns every year, even though those who set the rules have no clue what it is about. I doubt they are aware of the changes either so nothing will change in their documentation.

Dave

[Radio Wrangler]

The formulaic rules for such testing and the laid down procedures for doing it were written by people who could not envisage all the circumstances involved. Nor could procedures be written to cover all the circumstances. Normally this sort of problem is handled by having some general guidance and relying on the intelligence of the person at the point of application.

This falls on its face when you consider the limited training and salaries involved.

As a consequence the primary imperative flips from the need to keep people safe into the imperative to do the testing as specified and on the specified date. It takes on a jobsworth aspect.

That said, people generally considered to be intelligent, qualified and knowledgeable in the doings of electrons seem no better.

HP was a respected company, and in it's R&D labs, most people had higher degrees usually with names like 'Electrical and electronic engineering' or 'physics'. So this ought to be towards the upper reaches of qualification and experience.

It was normal there to build a prototype, or to pull one apart for modifications and stick it back together, then just plug it straight into the mains without a single check. There was no suspicion that there was any risk. After someone got a shock.... Y-capacitor current due to an open ground connection in a removable mains cable... we all started thinking. I bought in a PAT tester so that something new or after invasive surgery could give things a check before plugging in.

It paid for itself almost immediately. A subcontractor had made a few cable assemblies to go in the first prototypes of a new instrument. It included the wiring to the IEC receptacle, fuse, mains switch, and the grounding tag to be riveted to the case tray. They'd only wired the case tray to the L tag of the receptacle... with green/yellow barberpole wire.

The RCDs on the feed to the lab benches might or might not have tripped, depending on whether the metal shield of the receptacle was in good contact with the rear panel.

Products on the production line destined for paying customers got proper high pot tests starting with earth continuity. But R&D prototypes would sometimes go out on demo to trade shows, customers, etc.

It was remarkably difficult to get people, qualified, bright people to be diligent about checking. They seemed to always think that they had something more important to do.

So at one end of the spectrum, electrical testing goes silly as a jobsworth exercise with blind following of rules. At the other end, people who should know better get bored or distracted and that is just as silly.

One of the primary methods of getting good safety is to have dual safety measures. What is often overlooked, is that people have to be made aware if one of those measures has failed and they're only waiting for the second one to fail before things get dangerous. Class-I equipment has its mains wiring insulated from the chassis stuff by an isolating transformer etc. The Earth wire only comes into play if the insulation fails. But what if the earth wire parts first? How do you know that one of your two lives has been used up? No fuse blows, nothing trips out. This is where the testing comes in.

David

We also used to replace inappropriate plug top fuses with ones suitably rated for the appliance.

Rated for the cable surely.