PAT Testing failures

[DJ Jules]

I've just had my kit PAT tested by a new guy with a sparkling new machine.... and it's failed a whole load of my kit on Earth Leakage.

I'm interested to know if anyone else has had similar problems with similar kit, and what they've done about it. The failures don't appear to be caused by equipment fault as the numbers are consistent between both of the RCF's, so it seems to be something to do with the equipment design. The kit which failed was:

2 x RCF ART 422A speakers - 49 microamp leakage (consistent for both speakers)
1 x BENQ DLP Projector - 34 microamp leakage
1 x Mackie 16 channel desk - 1milliamp+ leakage

All of the above are class II insulated equipment. The above figures didn't change on re-test either. Failure is apparently anything above 30microamps of leakage between live/neutral and earth.

Thanks in advance,

Julian

[musicologydisco]

That sounds suspicious to me. I know it's further expense but I would get a second opinion. It's either earthed or it's not as far as I understand. Never heard of "leakage".

[DJ Jules]

There seems to be three tests which are done now:

1. For class one equipment (e.g. with a metal shell) then they test Earth continuity which is the resistance between the earth pin on the plug and any exposed metal parts on the kit.

2. For both class one and two they now test earth leakage (the amount of current that "leaks" between live/neutral pins and the earth pin on the plug). If this number is too high, then it'll trip out the RCD at the fuse box (though admittedly more like 30ma not 35microamps) .

3. For both class one and two they also now seem to test insulation resistance which apparently should be the resistance between the live/neutral and the case.

Interestingly... this is the guys tester (http://www.pattesters.co.uk/seaward/seaward-primetest-100-pat-tester)

Julian

[deltic]

the seaward prime test 100 is only a very basic tester, and not the best for sensitive IT/audio equipment , don't even think it has a setting for sensitive equipment.

i would get your kit re tested by somebody with a proper tester.

[coley]

how the hell can somebody with £100 tester say a state of the art electronic device is unsafe to use. as soon as the cabling enters the enclosure it wired to a transformer. I am I right in thinking this

[DJ Jules]

How the hell can somebody with £100 tester say a state of the art electronic device is unsafe to use. as soon as the cabling enters the enclosure it wired to a transformer. I am I right in thinking this

Nope, you're wrong. All the kit which failed uses Switch mode power supplies which are a lot more complicated than transformers (think high efficiency computer style power supplies, not big lumps of ferrite wound with copper) They have a lot higher earth leakage currents than traditional transformer based kit as the earth is probably connected to one of the power rails on the low voltage side of the supply (as opposed to just being connected to the case). The tolerances on the testing kit are incredibly low though and the currents we're talking about are tiny. As an example, the IEC lead had a 10 microamp leakage (through it's insulation) and the failure current is only 3 times this value (30 microamps).

And the tester is £269 :P

It's interesting that they're even doing these kinds of tests on Class II insulated kit as the tests used to just be a visual inspection of cables/housing and nothing else.

I think I'll get a second opinion, but if the second guy turns up with the same tester, then I'm likely to have the same problem :zip:

Julian

[Corabar Entertainment]

I may be talking complete, total and utter rubbish here, as I do not profess to know anything whatsoever about the subject matter, but I do know that Steve often has problems getting a decent connection for the earth tests - often because the screws are painted - meaning that it gives a false 'fail' report.

[MikeW]

I may be talking complete, total and utter rubbish here, as I do not profess to know anything whatsoever about the subject matter, but I do know that Steve often has problems getting a decent connection for the earth tests - often because the screws are painted - meaning that it gives a false 'fail' report.

Just had my pat testing done and that was one of the main problems.

[DAVESOUNDS SERVICES]

Sounds like your tester should read this
Table 3: Maximum permissible protective conductor current
Appliance Class Maximum Current note (1)
Portable or hand-held Class I Equipment 0.75 mA
Class I heating appliances 0.75 mA or 0.75 mA per kW, whichever is the greater, with a maximum of 5 mA
Other Class I equipment 3.5 mA
Class II equipment 0.25 mA
Class III equipment 0.5 mA
Table 4: Additional requirements for equipment having higher leakage current
Permanently wired or supplied by an industrial
plug and socket-outlet
Protective conductors
Label The equipment should have a label bearing
the following warning or similar wording
fixed adjacent to the equipment primary
power connection (based on clause 5.1.7 of
BS EN 60950)
Has he got the current COP Code of Practise or is he a "60 quid sid" Tester?
some quality gear has filters and caps that dump noise to eath so test up pretty poor to the untrained eye.

Hope that helps any problems pm me Cheers

JUST LOOKED TOO RCF speakers aint class2 they are 3 wire metal bonded to earth,,,CLASS 1 THINK the projector is too
Better ask for a refund and find a better tester . Sorry i dont cover your area,

[Corabar Steve]

What tester do you use Dave?

[DJ Jules]

JUST LOOKED TOO RCF speakers aint class2 they are 3 wire metal bonded to earth - CLASS 1

That'd explain it, the limits are a lot higher for Class I kit (as you've said). Where's the earth on the RCF's though?? The cabs are plastic and there's very little metal exposed - is this where scratching the paint off screw heads comes in?


Better ask for a refund and find a better tester . Sorry i dont cover your area,

I'm sorry you don't cover my area too.

On the plus side, the guy forgot to ask for any money so it's not like I've paid him for anything yet :D

Julian

[Excalibur]

What tester do you use Dave?

From memory,in case Dave isn't here soon, something looking a couple of grades up from the one in question, and one the size of a small weekend case.

I think that the main point here is that it's not what you've got, it's the way you use it. Ooer missus!

[Corabar Steve]

I think that the main point here is that it's not what you've got, it's the way you use it. Ooer missus!

Not at al. Some testers perform the test concerned first & will pop an instant fail up & there's nothing you can do about it.

[Paul James Promotions]

I must say it does seem strange that four items have failed during your testing. I have been PAT testing occasionally for a few years and not once have I had a failure on that particular test.


I may be talking complete, total and utter rubbish here, as I do not profess to know anything whatsoever about the subject matter, but I do know that Steve often has problems getting a decent connection for the earth tests - often because the screws are painted - meaning that it gives a false 'fail' report.

Hi Angela, this is a different test, the "Earth Bond" test where you will encounter this problem. In particular I find flat screen monitors a real pain to get a good earthing connection.

Jamie

[DJ Jules]

I must say it does seem strange that four items have failed during your testing. I have been PAT testing occasionally for a few years and not once have I had a failure on that particular test.

Dave has hit the nail on the head - the equipment which failed should have been tested as Class 1 earthed equipment, not Class II insulated. The limits for leakage are much higher for Class I equipment so all the items will pass.


Hi Angela, this is a different test, the "Earth Bond" test where you will encounter this problem. In particular I find flat screen monitors a real pain to get a good earthing connection.

Bearing in mind the above (the items should have gone through a Class I test) what Angela said is now relevant.

I've got the guy coming back tomorrow to re-test the failed items as Class I - so now all I've got to do is try and find a good earth on a fully insulated plastic cab!!!

Thanks everyone for their input.

Julian

[DAVESOUNDS SERVICES]

Seaward 2000 I
Ethos 9300 ( actually is a Clone of Seaward Europa Plus!)
and a Made in york Tele Products PAT IT.
also have a seaward PAC 500 Plus in a drawer not calibrated at Lock up
got a crappy Martindale "Easypat 1600" there to that expired 30 seconds after
its 2 year warranty ran out.
Do you need a machine???i could get the PAC 500 calibrated for you?
think ive a spare PAT it too there lifetime warranty!
16126

Cheers

If he is struggling with any item simply plug in either an XLR and get the earth off the metal body,Or a metal jack plug and do the same.
Sometines the XLR release tabs are easy to use .Failing that as with most "Imported" lights take out a screw and use a small screwdriver
connected to the earth test lead
If your PAT Tester is competant i dont think i should need to be telling him that .
any probs ring me
Cheers

DAVESOUNDS

[DJ Jules]

Do you need a machine???i could get the PAC 500 calibrated for you?

Tempting as that is, it's finding the time to do the C&G course again (and get testing liability insurance) which is the problem.


If he is struggling with any item simply plug in either an XLR and get the earth off the metal body,Or a metal jack plug and do the same.

Good idea :D


If your PAT Tester is competant i dont think i should need to be telling him that

I don't think he's used to doing Disco kit, I think he's done more industrial/office kit in the past and he hasn't had the PAT tester for very long.


any probs ring me

I might be doing that yet - thanks for your help Dave.

Julian

[Corabar Steve]

Seaward 2000 I
Ethos 9300 ( actually is a Clone of Seaward Europa Plus!)
and a Made in york Tele Products PAT IT.
also have a seaward PAC 500 Plus in a drawer not calibrated at Lock up
got a crappy Martindale "Easypat 1600" there to that expired 30 seconds after
its 2 year warranty ran out.
Do you need a machine???i could get the PAC 500 calibrated for you?
think ive a spare PAT it too there lifetime warranty!
16126
No, I've got a perfectly good Europa Plus thanks.

I was wondering though if the type of tester might affect the person doing the testing's ability to interpret the results. Although it would seem that the person concerned's biggest problem is the inability to differentiate between Class 1 & Class 2 appliances.

[DJ Jules]

Quick update on this. All three items re-tested as Class I and the projector and Mackie mixer passed without issue. The RCF's passed on the leakage, but failed on earth continuity. The best reading we could get by connecting to a sleeve on an XLR connector or Jack body was 3.47ohms. He's passed them anyway as there's an earth there and it's not like they have a lot of exposed metalwork.

He's also booked me for his wedding on a Monday night (!) in November. :D

Julian

[addoaddo]

Have you seen the new document from HSE about Maintaining portable electrical equipment. You can download it free from here

http://www.hse.gov.uk/pubns/books/hsg107.htm?eban=govdel-electricity&cr=27-Sep-2013

This does stop a lot of the false claims being made by people doing PAT testing. For example leads for class 2 equipment only need visual inspection which everyone should be trained to do every time the equipment is used.

It is up to you or the duty holder to determine the frequency of tests not the person doing the actaul PAT testing, so this automatic 12 month rule is rubish. For some equipment a 2 year test plan is sensible for for something like the extension leads that are prone to a lot of damage then 6 monthly tests would be more suited.


The second misconcpetion on class one equipment is that you have to do a bond test and find a piece of metal to check connectivity. That is why the leakage test was introduced. No tester should be damaging equipment by scapping off paint to get the test done. Often it is jsut the case that the person does not know how to use the equipment.

For those of you who dryhire equipment recommends a visual and combined test before every hire.

[ckpr2]

I have designed a few SMPS.
On mine there is a resistor and capacitor to earth from the output ground line.
The resistor is 4M7 so should pass very little current.
The capacitor should only pass leakage current which again should be very small.

Some SMPS have capacitors from live and neutral to earth which will have some leakage but shouldn't be much.
These capacitors are usually small in value so they don't false trigger the ELCB.

[ckpr2]

Most of the SMPS I have seen have a lot of mains filtering.
SMPS (depending on type) can be noisy when switching. LLC SMPS is best as it alters the frequency rather than hard switch the rectified mains.
SMPS also have capacitors between neutral and live to earth.
If these capacitors go leaky then you will get a high leakage reading.