PAT

[Max Demian]

Well yes extruded pairs but they can probably be used for either.

[Bill Wright]

Yes I've seen many such things. Very easy to detect. Like I said, not rocket science.

Bill

[Bill Wright]

You're moving the goalposts. See my words above: "I do know everything necessary to check the safety of a mains extension lead." I didn't mention other devices.

Let's get some examples I've encountered that would catch many pat testers out:

Bill

[Bill Wright]

What danger would befall me or others were I to do that? Bear in mind that I used to buy and install extension cables 25 at a time, and I used to buy 13A plugs fitted with 3A fuses by the hundred and use them all, and in fifty years I didn't electrocute or otherwise harm a single person.

Bill

[whisky-dave]

About 20 years ago one of our German research student wired a plug up, like that. Perhaps that one reason why we don't allow DIY lead making and if we really need to they get PAT tested.

[John Rumm]

Yup, but that is because you are generally obnoxious and have your head too far up your own arse.

[tabbypurr]

You can just address the modern extension lead if you like.

NT

[tabbypurr]

I used to do various silly things with mains when a kid, no-one got harmed, doesn't mean it was safe.

[John Rumm]

Its likely that its not wrong, however since you don't have adequate information to assess Bill's competence to verify if an extension lead is safe, the statement is pointless.

You seem to be discussing more than just extension leads here...

Can't see those being common in the average office, and your average PAT testing course is unlikely to dwell on specific instructions for vintage kit.

Wall warts in particular show one of the weaknesses of PAT tests - many are fundamentally compromised by poor design and yet you can't see that from outside of the box, and testing to prove the point would be destructive so unlikely to be popular with clients.

99%+ of what you will meet PAT testing for businesses requires some experience, a small amount of test gear, and a basic level of understanding of electrical principles. Its a skilled endeavour, but trainable. It does not require a graduate level engineer.

Rocket science on the other hand is difficult - not least because it involves a vastly wider range of disciplines and far more difficult sums!

[dennis]

One of the engineers at GEC made up some plugs that would pass a PAT tester but they were so dangerous we banned him from touching anything electrical. He stripped about 1 1/2 inches of insulation off each core and screwed the end into the terminals, we found it after fuses started to blow if you moved the flex a bit on some he hadn't tightened the strain relief enough.

[whisky-dave]

When we first started PAT testing I had to unscrew the tops off any none moulded plug for such things checks and change the fuse from 13amp to 5 amp or 3 amp. Any plug without shrouded pins was removed and replaced. I had a box of 100s of 13amp fuses at the end, probbly still have them somewhere. Then the lead was PAT tested using the PAT testing machine.

[tabbypurr]

he is oversimplifying the requirements of PAT testing. Testers that do so make bad choices here & there, exposing others to risk & themselves to the courtroom.

as I said he can confine himself to extension leads if he wishes. I'm curious to see if he picks up on all the real world gotchas.

and there lies a problem. I do test vintage kit. There are all sorts of gotchas one does not see in modern kit. And yes, some of it does pass.

OTOH the test voltage used should suffice to demonstrate them adequate (or not), even if not BS compliant. A PAT pass does not require BS compliance.

But the other 1% is less simple. I've seen so many PAT test screwups.

NT

[tabbypurr]

that's a PAT test fail on 2 points.

NT

[tabbypurr]

Modern appliances are all safe on a 13A fuse. Old ones not always.

NT

[charles]

Err - I'd fail them when I opened the plug top.

[Dave Plowman (News)]

Sadly it may as well be rocket science to many. Hence the need to test things.

Long before the days of PAT, every single bit of electrical equipment brought into a TV studio (unless from an approved supplier) had to be tested by a qualified person. Especially true of things like electric guitars and so on. Through bitter experience. And even after, was usually fed via an individual isolating transformer. And a TV studio in this respect is not so different to a church hall.

[charles]

In our amateur theatre, I failed an extension lead brought in by a guest speaker - simply on a visual inspection.

[whisky-dave]

But the fuse is to protect the cable not the appliance. I have 100s of IEC cables in the lab, which almost all have a 3 amp fuse.

[tabbypurr]

on recent stuff yes. Old stuff often really does need that 3A fuse if it's to be safe.

NT

[John Rumm]

Firstly, he was not talking about PAT testing in the broad sense, just that "necessary to check the safety of a mains extension lead". Secondly he does not explain the procedure he would use, so again its not possible to decide if it would be an over simplification.

Of course they do - in fact we all do.

Testing vintage kit is well beyond the scope of PAT testing, and there is a moderate amount of kit out there that would never have been be able to pass a PAT test - even when new.

While a PAT will include an IR test, it won't do a test with transients on the mains supply. Hence no way to verify if the internal separation between mains and ELV is adequate, or if the internal insulation of the transformer is up to it, or for that matter if it even has a thermal fuse.