3 Phase Testing.

Tuco88

Howdy folks,


I have a question in regards to RCD/Earth Fault Loop Impedance testing of 3 Phase outlets of the kind, that have no Neutral.

I am using a Fluke Multi-tester 1652 (3 wire unit)

Is it ok to place the Neutral and Earth lead of the meter to the Earth Terminal of the outlet for testing? I have tried this and my values were good, I am aware of the fault current I will be creating in the Earth but it will be in mA, I made sure it was safe at the time to carry out. I have an awful lot more to test tho.

I am aware I could test the RCD at the board, but id be happy testing the cabling also. I'm trying to avoid the R1+R2 way of working out the EFL also :rolleyes:

2011

Tuco88 wrote: »

Howdy folks,


I have a question in regards to RCD/Earth Fault Loop Impedance testing of 3 Phase outlets of the kind, that have no Neutral.

I am using a Fluke Multi-tester 1652 (3 wire unit)

Is it ok to place the Neutral and Earth lead of the meter to the Earth Terminal of the outlet for testing? I have tried this and my values were good, I am aware of the fault current I will be creating in the Earth but it will be in mA, I made sure it was safe at the time to carry out. I have an awful lot more to test tho.

I am aware I could test the RCD at the board, but id be happy testing the cabling also. I'm trying to avoid the R1+R2 way of working out the EFL also :rolleyes:

Here is a short video showing how to carry out an EFLI test:

....and here is a short video showing how to use an RCD tester:

It has been a while since I have carried out this test, but I would normally have carried out this test by plugging into the socket outlet as shown in the video.

Tuco88

Force of habit of using the plug on single phase systems I think...

What do you thing about the EFL test no neutral?

2011

Tuco88 wrote: »

Force of habit of using the plug on single phase systems I think...

What do you thing about the EFL test no neutral?

The neutral is not part of the "fault loop".

2011

Risteard81 wrote: »

But you shouldn't be testing the cable. An RCD test is about testing the RCD, therefore all loads should be disconnected.

The cable is not regarded as a load.

So ideally test on the outgoing terminals of the RCD without the circuit connected.

This can be done, but it is not as convenient and can carry a degree of risk.

brightspark

Tuco88 wrote: »

Force of habit of using the plug on single phase systems I think...

What do you thing about the EFL test no neutral?

Ideally you need a 2 wire tester (such as the Fluke MFT 1700 series). Perhaps you could hire a 2 wire EFL tester?

Or the R1+R2 method which would take a little longer.

I think the 1652 allows you to do the phase to phase impedance testing.

2011

Risteard81 wrote: »

Many people seem to mistakenly try to carry out an RCD test on the end of a circuit so that the complete circuit is under test

Although this is not strictly necessary the test is valid.
Most people carry out an RCD test by plugging the tester into a socket outlet and pressing the button.

I agree that the loads should be disconnected but with a socket circuit this generally means nothing more than a bit of unplugging.

Are you suggesting that the RCD tests shown in the second video above are incorrect?

Bruthal

Risteard81 wrote: »

Many people seem to mistakenly try to carry out an RCD test on the end of a circuit so that the complete circuit is under test - this is not a valid approach to RCD testing as the RCD and not the circuit is what is under test. This can also result in loads being left in circuit which can give misleading results for the test.

I dont think testing at the end of the circuit is a mistake.

Just because its the RCD under test, does not make it invalid if the test also shows the circuit is capable of performing such a test.

If it passes the test, then all is good. If it fails, test at RCD terminals, and now more in depth tests have been done, while also validly testing the RCD, imo at least.

Bruthal

Risteard81 wrote: »

and such a belief demonstrates a severe misunderstanding on what the purpose of the test is.

O yes, the elevation of one's own electrical greatness in the testing of an RCD. Dont let it overwhelm you, you will be attempting continuity tests next.

Bruthal

Risteard81 wrote: »

I'm just curious as to what benefit you perceive to exist from testing the end of the circuit as opposed to the device itself?

Well I myself would prefer to test through the circuit, to the RCD. Not disconnect it and test at the RCD terminals.

But, my point was, that it is not a mistake to test on the circuit, or invalid. I did not say the test needs to be done on the end of the circuit.

On a side note, if someone causes a neutral-earth short on the circuit before you do your live tests, will you be finding it?

2011

Risteard81 wrote: »

I never stated that it was invalid.

See your quote below that conflicts with this statement.
I have highlighted the relevant part in bold.

Risteard81 wrote: »

Many people seem to mistakenly try to carry out an RCD test on the end of a circuit so that the complete circuit is under test - this is not a valid approach to RCD testing as the RCD and not the circuit is what is under test.

Risteard81

2011 wrote: »

See your quote below that conflicts with this statement.
I have highlighted the relevant part in bold.

What I meant was that the belief that it must be conducted at the end of the circuit was invalid - not that the test couldn't be presuming that there were no loads connected.

2011

Risteard81 wrote: »

What I meant was that the belief that it must be conducted at the end of the circuit was invalid - not that the test couldn't be presuming that there were no loads connected.

Fair enough, but that is a million miles away from what you actually said

Bruthal

Risteard81 wrote: »

That is the function of an insulation resistance test - not of an RCD test.

And if the cable is nailed after the de-energised tests? Lots of work happens during that time.

2011

Risteard81 wrote: »

But you shouldn't be testing the cable.

I have just notice that this post is also incorrect.
Although it is not a requirement there is nothing wrong with having the cable in circuit when testing an RCD.

@ Risteard81 there is so much confusion about testing as it is that I think it would be best if you would delete / edit your incorrect posts on this thread.

If not I will do it when I'm in front of a PC.

Bruthal

Risteard81 wrote: »

That isn't incorrect. It is not the cable under test, nor should there be the perception that it is. That is not the same as stating that it cannot be in circuit.

But no one is saying the cable is under test.

I dont usually quote sites, but here is one from a uk site. Id guess its electrical common sense though.....

Tests are made on the load side of the RCD between the line conductor of the protected circuit and the associated cpc. Any load or appliances should be disconnected prior to testing.

Now its a uk site, and this is ireland, but you have to look at the idea behind it, rather than simply saying thats the UK, this is ireland etc.
But either way, testing via the circuits own cpc wont be happening properly at the DB with the line and neutral of the circuit disconnected.

Some insight required to look past the name of the test.....

2011

I very rarely delete any non spam posts from this forum.

However when it is in ration to a technical matter that already causes confusion with many experienced electricans and the posts are inconsistent I think it is for the best.

Tuco88

2011 wrote: »

The neutral is not part of the "fault loop".

You are very right, but the Fluke multi-tester that I seem to have is a 3-wire tester it will not allow me to test unless I have a Neutral.

2011

Tuco88 wrote: »

You are very right, but the Fluke multi-tester that I seem to have is a 3-wire tester it will not allow me to test unless I have a Neutral.

Yes, it needs a neutral so that the instrument itself can operate.
Connect the neutral to the earth. This should allow the instrument to be powered.

Tuco88

brightspark wrote: »

Ideally you need a 2 wire tester (such as the Fluke MFT 1700 series). Perhaps you could hire a 2 wire EFL tester?

Or the R1+R2 method which would take a little longer.

I think the 1652 allows you to do the phase to phase impedance testing.

You are on the ball Brightspark! I do need a 2 wire tester...

As you have happen to say there is a line Impedance two wire test on the Fluke between N - L. What do you think if I use this function but place the Neutral prob on the Earth of the Socket and Red probe to Live to get my Earth Fault result?

Sorry for the questions on this I am just not used to using the meter on 3 phase situations like this and don't want to damage it.

Tuco88

Thanks for the info so far lads, for the record the company is asking for the "RCD field test" in Ms on the test sheet so I have to test at the circuits, and I have also made up a 3 Phase Plug to a single phase socket (for testing purposes only) so I can plug in the tester with ease (good ol laziness the mother of invention) ha.

Lastly If you have on Views on the EFL test I would appreciate it. Its a dose doing the R1+R2 measurement way.

Test meter is a Fluke 1652C if any of you lads have one.

Bruthal

Risteard81 wrote: »

No problem with the quoting of a UK site. But then look at Guidance Note 3, Inspection & Testing, published by the Institution of Engineering and Technology (who form half of the joint IET/BSI committee JPEL/64 which writes the IET Wiring Regulations). It clearly states that the RCD shouldd be tested without loads connected, and ideally at the terminals of the device.

Without loads has nothing to do with testing on the circuit being correct or incorrect.

You are fundamentally incorrect to tell people that testing out on the circuit is invalid, and telling them that testing on the end of the circuit is a mistake.

Its confusing, and bad advice, even though you moved the goalposts later.