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Topic Title: PAT test on 3ph + earth circuit
Topic Summary: PAT test on 3ph + earth circuit
Created On: 25 April 2009 06:31 PM
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 25 April 2009 06:31 PM
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tfyey1

Posts: 15
Joined: 05 March 2009

Would you please tell me how to carry out a PAT test on a 3ph + earth circuit (380V).
The PAT apparatus we have can do only single (220V).

Regards
 25 April 2009 10:03 PM
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deleted_1_Grizzly01

Posts: 250
Joined: 21 February 2008

Firstly, you need to make up an adaptor cable, 13A plug to 3-phase Ceeform socket. The earth pin from the 13A plug connects directly to the earth pin in the 3P socket (obviously!). The neutral pin from the 13A plug should connect to all 3 phases and neutral (if present) in the 3P socket. Don't connect the line (live) pin from the 13A plug to anything. With only the neutral connected, it guards against some numpty trying to use your test adapter to actually run 3P kit off a 13A socket.

On the 3-phase kit, the only tests you'll be able to perform with your PAT apparatus is earth bond and insulation resistance. Any test that requires mains voltage to be supplied (earth leakage, load etc) will not work, for reasons stated above.

For further info, see the IEE CoP (3rd ed.) section 10.2.1 (page 47) and section 15.5, Note 5 (page 76).
 25 April 2009 10:04 PM
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tfyey1

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Joined: 05 March 2009

Thanks for your reply.
At the moment I don't have an adaptor, so I'm asking how can the PAT test be carried out on this equipment (3ph + earth)
I assume that the 3 phases will be connected together, so I will use a plug and then connect the phases to one pin and the earth to the earth pin. There will be no wire connected to the neutral.
Is this the correct method.
Thanks
 25 April 2009 10:07 PM
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deleted_1_Grizzly01

Posts: 250
Joined: 21 February 2008

Originally posted by: tfyey1
I assume that the 3 phases will be connected together, so I will use a plug and then connect the phases to one pin and the earth to the earth pin. There will be no wire connected to the neutral.


See my post above, and do it the other way around. It shouldn't make any practical difference to the testing, but it is safer if the adaptor should fall into the wrong (ie. incompetent) hands!
 26 April 2009 12:01 AM
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ericmark

Posts: 329
Joined: 12 February 2008

To make an adaptor to connect three phase equipment will only test some functions and although tests like earth continuity may be tested OK. Insulation and leakage tests may not be possible.

An understanding on how the equipment works is essential. Contactors may not be energised and three phase motors could be single phased causing overload and other problems.

All sorts of leads and adaptors can be made to allow one to use the PATester with a host of items for which it was not originally designed to test. But since you ask the question I am not sure you have the skill required. Main point you say 3 phase not 3 phase and neutral and PATesters are designed for split phase and single phase at 55 to 230 volt and connecting them to a 400 volt supply is likely to cause damage.

There is no reason why a semi-skilled should not carry out the majority of repeat PATesting functions. But sorry to say there are requirements when inspecting and testing some items of in-service electrical equipment which are not always apparent to the semi-skilled operator.

The main problem is where timers are included as with washing machines, dish washers, vending machines, and fridge / freezer. And also where some contactor is required to close. If there is a faulty heating element which is not activated during the test then the fault will not be found.

Also there is the environment and why in University I found a cupboard full of Alan Bradley PLC's all with Pass stickers on which were designed to be mounted inside a panel and the IP requirements were clearly not met when used without being fitted in a panel.

While used by the university students I could not see any real dangers. Even if the live terminals could be accessed without use of a tool it was very unlikely a university student would be daft enough to try it. But same units were also used on open days to impress visitors and school children could well stick their fingers where they should not be touching.

There is unlike the PIR no halfway mark or Codes for non compliant parts. There is just Pass or Fail. And I would think the company doing the inspection and testing and the University would have been in a lot of hot water had any young kid done something daft. It seems the lads doing the testing had asked the lecturer for advice but the lecturer was an electronics engineer and hadn't a clue about regulations.

I have refused to test items because I have not the knowledge required. Coke vending machine for example and it was put on a maintenance contract and removed from PATesting list.

I think it is important to know the limit of your ability. And there is no shame in saying this equipment requires a specialist. This phoning up the office for advice does not work because it's not the guy behind the phone who is signing the paperwork.
 26 April 2009 12:26 AM
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sparkingchip

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I think eric said it is a job for a Electrician.

Andy
 26 April 2009 06:45 AM
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tfyey1

Posts: 15
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I think that you have misunderstand my query.
I have asked for advise on how a PAT test is carried out on a three phase and earth equipment as I have a single phase PAT tester and I'm not sure on how the adaptor will be made, is it by connecting the three phases to the phase of the PAT tester or to the neutral ?
 26 April 2009 08:20 AM
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electricalengineer

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Joined: 08 April 2009

The best way would be not to use the PATester and do all the relivent test's by hand (with test meters).
 26 April 2009 12:10 PM
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deleted_1_Grizzly01

Posts: 250
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Originally posted by: tfyey1
I have asked for advise on how a PAT test is carried out on a three phase and earth equipment as I have a single phase PAT tester and I'm not sure on how the adaptor will be made, is it by connecting the three phases to the phase of the PAT tester or to the neutral ?


The answers have been supplied in my posts above, to construct an adaptor lead so you can perform earth bond and insulation resistance tests on your 3P appliance using your 1P PAT tester, and references to the appropriate parts of the Code of Practice (which I hope you have access to a copy of, since you are conducting PAT). Please read them.

Eric's post contains some good points, and as he said, since you have had to ask the question, you may not be competent to carry out this sort of testing.
Please get someone who is competent to check your wiring, and supervise you.
 26 April 2009 12:14 PM
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deleted_1_Grizzly01

Posts: 250
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Originally posted by: ericmark
... Alan Bradley PLC's...


Ha ha!
That threw me for a minute. Allen, not Alan.
I had images of a northern chap who wasn't killed by a Blackpool tram after all, setting up an electrical control company
 26 April 2009 03:26 PM
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ericmark

Posts: 329
Joined: 12 February 2008

That episode of Coronation street was before my time. OK so spelt Allen wrong. But as I have said before the Portable Batching Plant I use to work on would take 3 Electricians the weekend to test this in-service electrical equipment although it included testing all safety switches as well. And there is no way one could plug this into a PATester. It needed around 10 tractor units to move the appliance.

Between that and the office toaster are many items which will require far more than plugging into a PATester. Once one leaves the 18kg limit normally considered as the limit for non wheeled electrical equipment then often some product knowledge and skill is required.

Hence to try to tell anyone how to make up test leads could very easy lead to someone doing inappropriate testing and I therefore take the attitude if you don't know this is not an appropriate medium to instruct you with.

I will agree the 25A earth continuity test which the PATester can do is very good and constructing a lead set to allow this test to be carried out is a good idea. However when it come to insulation testing then one needs to revert to the meters often used to test insulations.

Very few three phase machines are without some relay or contactor and as a result some dismantling is normally required.
 26 April 2009 07:23 PM
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deleted_1_Grizzly01

Posts: 250
Joined: 21 February 2008

Originally posted by: ericmark
Hence to try to tell anyone how to make up test leads could very easy lead to someone doing inappropriate testing


No, not really.
If my instructions were followed (or if someone purchased one of the ready made adaptor leads that are for sale by many manufacturers as Alectricity mentioned earlier) then an IR test between 'live parts' and earth can be performed. As this is no more or less than a PAT instrument would do in an IR test to a single-phase (Class I) appliance, I can't see the problem.
 27 April 2009 08:15 AM
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Patnik

Posts: 172
Joined: 25 June 2008

Hi tfyey1,

Our 'in-house' 3-phase PAT adapters are built as Grizzly01 describes (all phases and any neutral connected to BS1363 plug neutral: earth to earth) but we also remove the live pin from the BS1363 plugtop to further reduce the chance of abuse.

When I started PAT I was asked to test lots of 3-phase stuff including old workshop machine tools. As said above there is no way to do run or leakage tests with a normal PAT tester and in reality the insulation test is only likely to work as far as any contactor which is likely to isolate any manky old rubber insulated wiring etc inside the machine from the test.

After I realised I was the only 'system of maintenance' I made it very clear to the 'responsible person' that PAT wasn't sufficient in itself and all I could offer was a decent earth test and external visual inspect of wiring and covers. I also started using labels saying 'earth tested' rather than 'PAT tested' on these machines (again making the reasons clear to the boss in writing). After several years there are moves afoot to get these machines properly tested and inspected - it's going to cost about £75 for each of them to do it properly!

Sometimes PAT seems to be used as an excuse for management to avoid more appropriate (expensive) maintenance - I see it as part of the PAT role to make it clear when PAT is not a sufficient 'system of maintenance'. It's my initials on the label!

Nik
 29 April 2009 02:25 PM
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kt66se

Posts: 53
Joined: 22 May 2008

This is good advice on these posts - my second customer, having found I did PA testing through word of mouth had 2 3ph sewing machines that used to be tested by the local sparky. (His records show earth test only). I had posted questions on how to test on this forum and got some good advice which I stuck to.

Having agreed to make sure they were safe to continue using with the limited options a fluke 6500 offers, I advised the customer to get these machines onto a maintenance contract. I have returned to re-test other 6 monthly items and found the machines still are not on a contract for 2 reasons.....

1. Customer can't find anyone to take on a contract for 2 machines
2. Customer is happy that the checks I perform are adequate.

I have doubts and am currently looking into testers that will meet test requirements for 3ph items with the suspicion that this customer will not find anyone to take this on.

Adam
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