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PostPosted: Sun Feb 26, 2012 11:31 pm 
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I thought I would bring this to the table and start an interesting debate about testing of 3 Phase assets/appliances.

I had an interesting chat that went on for nearly an hour with an engineer who has been testing 3 phase for over 15 years( thank god for free minutes!) about the way that 3 phase appliances are tested using the made up (I and must add ‘professionally’) 4 or 5 pin red sockets attached to a 13 amp plug.
The way that these are wired up is that all the lives (L1 L2 L3), Live pins are linked mechanically together inside the plug/socket (that’s the red socket and not the 13amp plug/IEC) and the PAT then electronically connects both the Lives and neutral together and carries out say the insulation test as would when performing a standard 13amp conventional appliance test. Now this is where it gets interesting when the PAT carries out a test, it performs a polarity test to ensure that all is well prior to electronic interconnection of both live and neutral and the desired test is performed.

The issue is that when all the live conductors are physically interconnected via the 3 phase socket/plug the tester is unable to perform separate tests on the phases to ensure both that the phase sequence is correct (wired correctly to the correct pins) and more important that there is no breakdown of the live conductors e.g. that is that one of the conductors (live) is not damaged /compromised in anyway, in which by interconnecting physically would not show this under test conditions (insulation test / continuity).

Imagine that both the cpc (earth cable) and the neutral cable insulation properties are in great shape, along with say 2 of the live conductors, but the other live insulation has been damaged/compromised internally by one means or other, and yes you might say that you might pick this up via the visual, but then again it might not be in the flex or cable, but internal. Also due to most PAT’s are unable to perform a run test due to the higher current usage (beyond the scope of most PAT's) then only a Visual, Bond, Insulation, and Sub leakage test (tester type permitting) could be performed (non-run test).

So back to the table!

Is the method of mechanically interconnection of the lives correct and adequate enough to ensure that this appliance is safe?

Should we perform tests to the individual phases (L1 N CPC, L2 N CPC etc) to prove both correct phase sequence of the lives and insulation / continuity properties of each?

Look forward to your views and comments :?:

_________________
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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PostPosted: Tue Feb 28, 2012 11:12 am 
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Steve. wrote:
...4 or 5 pin red sockets attached to a 13 amp plug.
The way that these are wired up is that all the lives (L1 L2 L3), Live pins are linked mechanically together inside the plug/socket (that’s the red socket and not the 13amp plug/IEC)


That's pretty much the standard way. For an even safer adaptor lead (one that would further prevent any nastiness if a random person were to plug it into a 13A outlet), one would only connect the N inside the 13A plug, and then connect this to N, L1, L2 & L3 in the 60309 trailing socket. It makes no difference to the IR test.

Quote:
The issue is that when all the live conductors are physically interconnected via the 3 phase socket/plug the tester is unable to perform separate tests on the phases

*snip*

Also due to most PAT’s are unable to perform a run test due to the higher current usage (beyond the scope of most PAT's) then only a Visual, Bond, Insulation, and Sub leakage test (tester type permitting) could be performed (non-run test).


Unfortunately, that's the drawback of using a test instrument designed for single phase to test 3-phase items.
The other option is to use a continuity & IR test instrument, and perform the tests individually.

Quote:
Is the method of mechanically interconnection of the lives correct and adequate enough to ensure that this appliance is safe?


The method is correct, if using a portable appliance tester, but I'd say that it would be down to the testing technician's own assessment as to if it is adequate :S

Quote:
Should we perform tests to the individual phases (L1 N CPC, L2 N CPC etc) to prove both correct phase sequence of the lives and insulation / continuity properties of each?


That's probably the most complete way, but to do it you'd either need a separate test instrument (as mentioned above), or 3 different adaptor leads, or an adaptor lead with some switching built-in, so you could change the phase under test.

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C&G 2377-01 & -02


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PostPosted: Tue Feb 28, 2012 11:09 pm 
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Hi Grizzly

Many thanks for your very constructive comments.

One thing that this does seem to bring out is that testing of 3 phase in a bit of a disarray, and I personally believe that this is outside the scope of conventional what we know as general PAT.

Like you mention that using even the latest PAT’s hardware is beyond the normal testing ability or what it PAT’s where designed for. I believe that Megger’s new 1700 series accommodates for phase rotation etc, but is not purpose designed Portabel Appliance Test, but a fully all singing all dancing multi-function elctrical installation tester. Is there a dedicated 3 phase PAT on the market :?:

But this really means that conventional testing / recording of the results what be more detailed due to the amount of data collected for each asset/appliance and therefore become a specialist field in its own right.

Speaking to the chap the other day that has a vast amount of experience in 3 phase testing, like you mentioned expressed that you would require either separate test leads each independantly connecting each Live conductor in turn, or a switching device to test each phase, along with multi tester like you suggested.

I believe that this is a very grey area, and should be more transparent and not left for the testing engineer to decide, along with written guidance at hand. I am waiting a document /guidance from my contact and when it comes available I will post it on this thread.

What I will say is that when we issue the paper work, certificate, and sticky label etc. is that item left electrically safe, have we tested correctly , have we used the correct testing hardware, should we use a general PAT for this type of testing regime, or is it a specialist testing field.
:!:

_________________
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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PostPosted: Wed Jul 25, 2012 10:58 am 
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I joined the forum today as a result of an internet search on this topic as I have been told this is now part of the C&G 2377. I am hoping to drift into retirement when my assistant qualifies and I am doing all possible to ensure that he does. Can anyone comment on this now being part of 2377 in the past 3 to 6 months? I can't seem to find any further info now college has broken up for summer.

Myself, I would favour testing each phase individually even though it would take longer, rather than all at once. Then there is the question of relays and Alan West starters which I don't think has been fully addressed. Then there may be the odd old piece of kit that just uses the three live phases and earth connections as in the case of old printing machines that did not have inspection lamps. If I was a member, it would be interesting to hear what NICEIC had to say on three phase testing!

I will be grateful for any help you can give me on this.


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PostPosted: Fri Aug 03, 2012 5:36 pm 
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Hi Alan

Quote:
Myself, I would favour testing each phase individually even though it would take longer, rather than all at once

I have heard this before from another engineer that tests 3 phase items regularly and also makes up test leads and we got into a lengthy debate on this very issue and I can see his point of view, but it seems the norm to like you say combine all phase together and test, perhaps this is something that Grizzly might like to comment on. There does not seem to be much guidance on this!

Quote:
Then there is the question of relays and Alan West starters which I don't think has been fully addressed
Not too sure about this has I haven’t done to much 3 phase work, again I think Grizzly might be the person with the experience to answer your issues

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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PostPosted: Fri Aug 03, 2012 7:37 pm 
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Steve. wrote:
Quote:
Myself, I would favour testing each phase individually even though it would take longer, rather than all at once

I have heard this before from another engineer that tests 3 phase items regularly and also makes up test leads and we got into a lengthy debate on this very issue and I can see his point of view, but it seems the norm to like you say combine all phase together and test, perhaps this is something that Grizzly might like to comment on. There does not seem to be much guidance on this!


Well, this would probably take things more out of the realms of in-service I&T, I suspect.
If you consider that for 1ph appliances & leads, one wouldn't test the IR between line and neutral, then I think it's comparable.

Quote:
Quote:
Then there is the question of relays and Alan West starters which I don't think has been fully addressed
Not too sure about this has I haven’t done to much 3 phase work, again I think Grizzly might be the person with the experience to answer your issues.


Well, again, I can only really comment on using a portable appliance tester for 3ph testing: the only tests you'd be able to do (unless you were using a PrimeTest 250 and the Seaward TPA) would be earth bond and IR, so neither of those things would become an issue.
If you were using the PT250 & TPA, then the appliance would be powered from a 3ph supply, so would just operate as normal.

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C&G 2377-01 & -02


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PostPosted: Mon Jul 01, 2013 5:40 pm 
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Re testing 3 phase items.
What size of machine would consider to be outside the remit of the isi&tee. The reason I ask this is that I have been asked to test all the equipment in a workshop. This varies from drills , routers and small 3 phase bench grinders up to large circular saws (24" blade and big motor)
The 4th edition book does not really give any examples of fixed equipment apart from hand dryers and tea urns!!!
What are your thoughts ?


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