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 Post subject: PRCD Extention lead.
PostPosted: Tue Jan 01, 2013 1:10 pm 
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Ok.. I give in. Ive googled, bing'd and even asked that nice butler Jeeves... and im STILL at a loss.

Whilst testing, at a new client, I came across three 4 way extention leads all with "powerbreaker's"

When testing, as an extention lead, it fails on insulation.

Test as a Class 1, as advised in the training manual, it fails, again on insulation.

On each test a light, on the PRCD, illuminates to signify that there is a "supply fault"

I have read, on a google search, that they are to be tested as Class 1, but only the earth bond and then to test the PRCD to ensure that it trips as it should.

Im testing with a Metrel BetaPat+

Regards in advance,

Allan.


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 Post subject: Re: PRCD Extention lead.
PostPosted: Tue Jan 01, 2013 4:49 pm 
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Hi Allan

Do the leads have surge protection as well? Not sure if the following thread my provide a clue as to why the leads are failing the insulation test:

viewtopic.php?f=14&t=533

What voltage is your BetaPat plus testing the leads at?

Regards Richard.


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 Post subject: Re: PRCD Extention lead.
PostPosted: Tue Jan 01, 2013 10:07 pm 
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richard wrote:
Hi Allan

Do the leads have surge protection as well? Not sure if the following thread my provide a clue as to why the leads are failing the insulation test:

viewtopic.php?f=14&t=533

What voltage is your BetaPat plus testing the leads at?

Regards Richard.



No... The 3pin end is marked as a "powerbreaker". I've run a custom test, as provided by metrel, specific for surge protection leads. it failled that too. That runs the test at 250v.


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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 10:51 am 
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Interesting. I've never seen or heard of a portable RCD (I'm assuming that's what you mean by 'PRCD') that has a 'supply fault' indicator light.
Are you sure they're RCDs, and not surge protector plugs (PowerBreaker manufacture both, but not combined in one unit, as far as I know).
Can you post a link or photo?

Obviously, an earth bond test should be performed and passed, like any other extension lead.

Normally, when you perform an IR test on a BS7071 RCD (adaptor plug/lead/in-line etc.), and any surge protection notwithstanding, it should always show a pass.
This is because unless the RCD is presented with a 230V mains supply, it will not reset. The 500V (or 250V) DC used for an IR test will not enable a reset.
So, the line and neutral contacts remain open, and so you only measure the IR from the tester's socket to these contacts, and no further.
This is why an IR test is not appropriate for a portable RCD. You could have an IR fault further down the cable, but the open RCD is masking it from the tester.

So, in place of the inappropriate IR test, you should perform a leakage test (or protective conductor current test, or whatever the manufacturer of ones particular tester calls it).
When this test is run, it energises the equipment under test to 230V mains voltage, so you would be able to reset a portable RCD at the beginning of the test, and get a meaningful result.
This is in accordance with the IEE Code of Practice (see section 15.6 in the 3rd Edition)

I'm a bit puzzled as to why your leads show a FAIL on the IR test, unless there's something particular about these specific RCDs that's causing it. As I've outlined above, I'd expect them always to show a pass.
If they were indeed surge protection plugs and not RCDs, that could explain the issue, although I'd fully expect them to pass an IR test at 250V (unless they are faulty somehow).

A bit of a headscratcher...

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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 1:46 pm 
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Grizzly wrote:
Interesting. I've never seen or heard of a portable RCD (I'm assuming that's what you mean by 'PRCD') that has a 'supply fault' indicator light.
Are you sure they're RCDs, and not surge protector plugs (PowerBreaker manufacture both, but not combined in one unit, as far as I know).
Can you post a link or photo?

Obviously, an earth bond test should be performed and passed, like any other extension lead.

Normally, when you perform an IR test on a BS7071 RCD (adaptor plug/lead/in-line etc.), and any surge protection notwithstanding, it should always show a pass.
This is because unless the RCD is presented with a 230V mains supply, it will not reset. The 500V (or 250V) DC used for an IR test will not enable a reset.
So, the line and neutral contacts remain open, and so you only measure the IR from the tester's socket to these contacts, and no further.
This is why an IR test is not appropriate for a portable RCD. You could have an IR fault further down the cable, but the open RCD is masking it from the tester.

So, in place of the inappropriate IR test, you should perform a leakage test (or protective conductor current test, or whatever the manufacturer of ones particular tester calls it).
When this test is run, it energises the equipment under test to 230V mains voltage, so you would be able to reset a portable RCD at the beginning of the test, and get a meaningful result.
This is in accordance with the IEE Code of Practice (see section 15.6 in the 3rd Edition)

I'm a bit puzzled as to why your leads show a FAIL on the IR test, unless there's something particular about these specific RCDs that's causing it. As I've outlined above, I'd expect them always to show a pass.
If they were indeed surge protection plugs and not RCDs, that could explain the issue, although I'd fully expect them to pass an IR test at 250V (unless they are faulty somehow).

A bit of a headscratcher...



Indeed Grizzly...

I took the offending item to Metrel yesterday, as i was in for a re calibration.. not me personally, although i think the missus might want my "settings" checked out!!. The chap there said that the only "true " way to get a full test was to remove the RCD and rewire with a standard 3 pin plug, test as an ext lead, then refit the RCD and run a RCD test. Seems a long process, but it worked.

I guess its not really a portable RCD, in as much as its fix wired to the extension lead.


Last edited by AMP@ on Thu Jan 03, 2013 2:36 pm, edited 1 time in total.

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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 2:06 pm 
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Thanks for the info Grizzly

On doing some more research I found a document produced by Seaward for their range of testers suggesting that the Insulation test will fail with these leads (although it didn't explain why)

http://ebookbrowse.com/seaward-testing- ... d237035086


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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 2:26 pm 
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here's a link to pics of said plug end.

https://www.dropbox.com/sh/jgn6ipe642em2cr/tzywm7Cxds


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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 7:04 pm 
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Hi Amp

Quote:
The chap there said that the only "true " way to get a full test was to remove the RCD and rewire with a standard 3 pin plug, test as an ext lead, then refit the RCD and run a RCD test. Seems a long process, but it worked


I did this the other day on a similar extension lead. The only way was to remove it from the circuit, test the extension lead separately, and rewire back the PRCD, then test the second part (the PRCD) under your RCD test code.

Very long winded but it seemed only the satisfactory way of preforming a PAT on this type of asset.

To speed things up a little, you can purchase one of those adapters that you clip in the plug end of the flex of the lead under test (minus the plug of course) and clip it into this adapter, this saves having to rewire a plug temporary, test the lead and then re-wire the PRCD back on.

Steve.


Attachments:
Safe Block Adapter.jpg
Safe Block Adapter.jpg [ 7.3 KiB | Viewed 3564 times ]

_________________
City and Guilds 2377 Qualified PAT Testing Engineer
Domestic Electrician(NICEIC)
Always looking for new customers based in Cornwall
All in accordance with The IEE CofP
www.handselectrical.co.uk
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 Post subject: Re: PRCD Extention lead.
PostPosted: Thu Jan 03, 2013 8:53 pm 
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AMP@ & Steve: Glad you found a way round it, although I don't know as I'd be particularly comfortable with taking the appliance apart, testing, then remaking.
I think I'll stick with my method of doing the earth bond then leakage test, and dropping the IR test.

AMP@: those RCD plugs look pretty old to me, and yes, that's the first time I've ever seen one with a supply fault indicator light on.
It could well be this indicator light circuitry that is causing them to actually FAIL the IR test, maybe.
I notice that there's no mention on the units of conforming to BS7071, indicating that they might be from a time before this was a requirement. Personally, on the strength of that, I'd suggest that they were replaced with new units that did unambiguously meet the standard.

richard: good find with that Seaward document, and it does rather reinforce my suggestion to do a leakage test rather than an IR test (and hence to avoid dis-assembly of the appliance).
I'm a bit puzzled by their comment that "These extension leads will of course fail the Insulation Test", as in my experience it should state that they will always meaninglessly pass the insulation test. It would have been nice if they'd 'showed their working'.

_________________
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 Post subject: Re: PRCD Extention lead.
PostPosted: Fri Jan 04, 2013 8:18 am 
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Thanks for the replies guys.

For speed, I've set up a custom test using leakage opposed to IR. Saves messing around swapping plugs etc.

Would this substitution be ok for any other appliance, eg a washing machine, that has been fitted with a RCD safety plug?


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 Post subject: Re: PRCD Extention lead.
PostPosted: Fri Jan 04, 2013 5:16 pm 
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Cheers for the posts Grizzly and Steve

Grizzly

Quote:
It would have been nice if they'd 'showed their working'.
- Yes, although I don't do any testing in the field, it would be good to understand why these devices fail.

Glad you have a working solution @Amp

Richard


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 Post subject: Re: PRCD Extention lead.
PostPosted: Fri Jan 04, 2013 7:59 pm 
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Hi Grizzly, AMP and Richard

An intresting Issue

Quote:
although I don't know as I'd be particularly comfortable with taking the appliance apart

I would hardly call this taking an appliance apart; it was no different really to removing / replacing a 13amp plug having all the same characteristics, live, neutral, earth, and a cable securing strap. (well that was the one that I came across)
The reason for me to remove the plug was for 2 reasons, I used both a Megger PAT4 and Megger PAT 420, If I perform an extension cable test for this asset, the PAT first looks for polarity, but because the PRCD is not energised (open circuit) then it will not perform any further test because it is unable to astatine this first initial test being a polarity test.

Secondly if I perform a Class 1 Test again the PAT registers an open circuit and again aborts the test thinking that it’s a fail, because of the open circuit.

So the only way I believe around this was to remove the PRCD from the extension lead replace it with a 13amp plug or adapter as mention in my last reply, perform an extension lead test, replace the PRCD and then perform a Full RCD test, therefore both items have been tested, using the reattached extension cable within the test sequence.

I have read in the last C of P 3rd Edition and i am sure its in the new version (I do have a copy) a few years ago about supplementing a IR test in-lue for a leakage tests which was an option for assets that were IR vulnerable such as IT equipment. With many new PAT's on the market today having the ability to drop down to 250v for IR testing, giving us avenues and options to test appliances.

Steve.

_________________
City and Guilds 2377 Qualified PAT Testing Engineer
Domestic Electrician(NICEIC)
Always looking for new customers based in Cornwall
All in accordance with The IEE CofP
www.handselectrical.co.uk


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 Post subject: Re: PRCD Extention lead.
PostPosted: Fri Jan 04, 2013 9:01 pm 
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Posts: 54
You know what.... Im so glad I asked now... I was a little bit hesitant, initially, fearing a multitude of "ya numpty, its easy... You do it this way....." responses.

I wonder if the weekend will bring up any further ways to test them..?

Steve. The plug on the lead I have, is very tight on space. In as much as there's only about 8mm of outer insulation removed from the flex. So to rewire it to another plug, or adaptor, would requre further outer sleeve being removed. It begs the question, which would give up first... the appliance with a "mechanical" fail or the subsequent retests rendering the flex too short to actually class it as an extension lead?

:D


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