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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> ELI testing https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1119947508 Message started by akuk on Jun 28^th, 2005, 9:31am

Title: ELI testing
Post by akuk on Jun 28^th, 2005, 9:31am

Hi, done some testing on last job, continuity of CPC, Continuity of final ring , insulation resistance , RCD etc. I had no problems. My problem was with the ELI test for the lighting circuit, for the ring I removed all the 'loads' connected the Fluke 1653 using the plug and there is a reading in every socket. For the lighting (radial) I removed the bulbs and by - passed dimmers, I could not get a proper reading, I don't mean the value, but the process confused me. I looked at the GN3, Amicus testing book, OSG etc. they all talk more about the External loop (Ze) than Zs. Can someone explain the steps for this test, what to do before, where to connect the probs (which one of them) and in which part of the circuit, I probably know the procedure but I can't see it in practice. Thanks
Albert

Title: Re: ELI testing
Post by The_Trician on Jun 28^th, 2005, 10:31am

Which measurement method is confusing you mate?

Ze is straight forward enough - you are directly measuring the effectiveness of the supplier's Earthing facility, so main isolator 'OFF', disconnect the main 16mm earth, set kit for 'Ze' and connect one lead to the disconnected earth cable and connect the other incoming terminal of the main isolator and hit the 'test' button.

Or, it is acceptable to establish the Ze value by enquiry, which means determining the type/charactoristics of the supply by identifying whether it is TNC-S, TNS, or TT.
You then ring up the supplier and ask them to give you a value. I just take 0.35 for TNC-S and 0.8 for TNS. TT is a bit more difficult because the supplier doesn't have to provide the earthing - you do. So its back to the regs book for this one.

Measuring Zs - if you have checked polarity for the lighting circuit you can just take the r1+r2 values you got from this and add them to the Ze value.

Measuring 'live' Zs for lighting is a pain - one tip, measure at the ceiling rose and not the pendent - there's no earth terminal in there!

Lamps out, Supply 'on', Light switch 'on', and measure between live and earth at each switch and at each lighting point.

Hope this helps

TT

Title: Re: ELI testing
Post by L.Spark on Jun 28^th, 2005, 10:59am

Hi Albert

Assuming you're talking about Earth Fault Loop Impedance (EFLI), then it's really not that hard to do, obviously there is external impedance (Ze) and system impedance (Zs) which is the impedance of your circuit and external loop impedance..

Don't know what meter your using but most Phase-Earth Loop testers require a neutral to operate, you should have a 3-test lead set Red/Black/Green or similar, firstly the earth probe/clip needs to be clipped on to the earth, then using the neutral and phase probe, hold them onto the neutral and phase terminals in that order, you want to test at the furtherst point in the circuit as your looking for the highest reading, in most situations you will be unable to tell where the furthest point is and therefor you would have to measure at all available points in the circuit

If your meter has 20ohms setting, turn to this, if it doesnt it's likely autoranging and will set it's self to the closest ohms range

It sounds like you have all the books, the best one to read is the electricians guide or on-site guide, the guidance notes are good, but for basic testing the first two are probably what you need

Alternatively you can calculate the Zs by using the following values, Zs = Ze + (R1+R2), if you don't feel competent to do the live test then It's probably best you leave it until you feel you can do it safely, if you could find someone who can show you how to do it that would be even better.

The live tests can be quite hazardoures and pose a risk to persons and property if not conducted correctly, theres a risk of pipework becoming live if if the installation is not up to scratch

Title: Re: ELI testing
Post by akuk on Jun 28^th, 2005, 12:04pm

The_Trician and L.Spark many thanks for your replies.
I don't have any problems with the theory behined the testing, values required, calculations and where to find tables and so on, I think that I cracked most of the tests and have a good understanding of the procedures and results, but I stuck with this one. Zs on sockets with the 1653 is easy, remove loads connect the plug prob to the socket and press the test, for the ceiling rose I had to use the fly frobs, I used the earth and phase, and could not get sense out of it, than I started to suspect that the Fluke 1653 needs neutral for this test although the neutral does not take part in the fault path when using TN-S system (probably this is the power source for the tester or somthing like that), while you were thinking I went upstairs and opened a socket and tested it with probs instaed of the plug (to simulate ceiling rose), it seems that it works.
How the hell you hold 3 probs with 2 hands, (I know that the tester has a prob that have the test button on it), the crocodiles are too big for access the wires in the C/R, any ideas? There are 2 resons why I need to know this: 1) It is me and I need to know. 2) Coming Friday I have my 2391 practical test and it is about doing the tests.

Quote:

Measuring Zs - if you have checked polarity for the lighting circuit you can just take the r1+r2 values you got from this and add them to the Ze value.

When I am doing the Continuity of CPC I get R1+R2 (Phase to cpc), I belive that this is what you ment or I am wrong.

Title: Re: ELI testing
Post by L.Spark on Jun 28^th, 2005, 12:30pm

wrote on Jun 28^th, 2005, 12:04pm:

I think that I cracked most of the tests and have a good understanding of the procedures and results.

That's great news

Quote:

but I stuck with this one. Zs on sockets with the 1653 is easy, remove loads connect the plug prob to the socket and press the test, for the ceiling rose I had to use the fly frobs, I used the earth and phase, and could not get sense out of it, than I started to suspect that the Fluke 1653 needs neutral for this test although the neutral does not take part in the fault path when using TN-S system (probably this is the power source for the tester or somthing like that)

You've pretty much got it there Albert, the neutral is only for the instrument to work, it is not actualy used to conduct the test as such, the important thing is that you have 3-leads aswel as your 13A plug, you would use the 13A plug as you have done, on ring circuit's and the like, and then use the 3-lead test for testing at wiring accesories, consumer unit etc

Quote:

while you were thinking I went upstairs and opened a socket and tested it with probs instaed of the plug (to simulate ceiling rose), it seems that it wo
rks.

Yep, I don't use a 1652, but I'm getting my head around it slowly ;)

Quote:

How the hell you hold 3 probs with 2 hands, (I know that the tester has a prob that have the test button on it), the crocodiles are too big for access the wires in the C/R, any ideas? There are 2 resons why I need to know this: 1) It is me and I need to know. 2) Coming Friday I have my 2391 practical test and it is about doing the tests.

ooo you lucky thing, you're be getting assessed before me, frigging courses!

I can't comment much on the probes as I don't use the 1652, the green/earth clip is the one that goes on first, then you should only have to hold the 2 other probes

Quote:

When I am doing the Continuity of CPC I get R1+R2 (Phase to cpc), I belive that this is what you ment or I am wrong

The continuity of CPC can be done as just an R2 test where you connect a long lead to the earth block at the board, and then connect it to one probe, connect other to an earth point at a light or similar, it's alot of messing about, so we do R1+R2 which is where we bridge phase to earth at the board, or at a light, and then test between phase and earth at the other end, this is then our phase and earth value

Title: Re: ELI testing
Post by akuk on Jun 28^th, 2005, 12:42pm

wrote on Jun 28^th, 2005, 12:30pm:

yep, I don't use a 1652, but I'm getting my head around it slowly ;)

Me too I use the 1653... ;D

Quote:

ooo you lucky thing, you're be getting assessed before me, frigging courses!

Done my part 2 in parallel with 2391, my age I have to be efficiant with time...

Quote:

I can't comment much on the probes as I don't use the 1652, the green/earth clip is the one that goes on first, then you should only have to hold the 2 other probes

, I am not worried about the colours, I am asking how to connect 3 of them with 2 handa?

Quote:

what I ment was that cpc to phase at the furthest point will give R1+R2 and not r1+r2, and I'm sure that you know that...

Title: Re: ELI testing
Post by sparkyjonny on Jun 28^th, 2005, 12:51pm

wrote on Jun 28^th, 2005, 12:42pm:

, I am not worried about the colours, I am asking how to connect 3 of them with 2 handa?

The earth clip SHOULD hold itself, but most croc clips tend to fall off if you move the cable slightly. In a ceiling rose, you can often get away with ONE hand for the earth croc clip, and P & N probes...space the probes with your fingers...there's an art to it!! You need to do this if you need a seperate hand to operate the test sw on the meter (balanced on the top of your stepladders)!!

Title: Re: ELI testing
Post by akuk on Jun 28^th, 2005, 1:30pm

Is there any requirements or use for measuring the Zs for the whole installation, I know that the Zs at the end of the day, will define the disconnection time for a specific circuit with a specific mcb/fuse, it does not make sense to measure the whole installation or...you know something that I should know...? ???
Quote:

Thanks, I know that, what I am asking is whether there is a type of probs that could connect to a ceiling rose termination, as you know it is very small and not easy to get a good contact with a standard crocodile, yes the pointy ends can be used but than you nedd 3 hands...(one more and you can play poker)

Title: Re: ELI testing
Post by L.Spark on Jun 28^th, 2005, 2:32pm

wrote on Jun 28^th, 2005, 12:42pm:

what I ment was that cpc to phase at the furthest point will give R1+R2 and not r1+r2, and I'm sure that you know that...

Yes I'm well aware, read what I said again

Quote:

I am not worried about the colours, I am asking how to connect 3 of them with 2 handa?

The colours are just as important as using fused test probes correctly, as I've already said you clip the earth on first, if the earth doesn’t stay on then you're either not doing it properly, or the probes on the 1653 are really bad!

Sometimes the clips won't go on terminals, if this happens best thing to do is to disconnect the earth cable and clip straight on, however this could be difficult if you have 2-3 CPC's

Quote:

Is there any requirements or use for measuring the Zs for the whole installation

No requirements, we test circuit's individually for impedance, not as a whole

Quote:

but than you nedd 3 hands...(one more and you can play poker)

This is something you will get used to, I can't say it's easy because it's not always, but you're have to practice, the main thing is the earth crocodile clip, if this isnt working then you're wasting you're time

Title: Re: ELI testing
Post by akuk on Jun 28^th, 2005, 3:54pm

wrote on Jun 28^th, 2005, 2:32pm:

Yes I'm well aware, read what I said again

This was to ment to TT, don't jump... ;D

Quote:

The colours are just as important as using fused test probes correctly

I know it appears in the GS38, I ment that it is easy to sort out, the good ones always come in nice colours...Pink? :-/
Many thanks, I ask sometimes questions that I know the answer, but need reasurance, and all these discutions do it...Like in class 2 asking questions 27 look like they know the answer maybe 5 know the answer and 22 learn something...

Title: Re: ELI testing
Post by JerryD on Jun 28^th, 2005, 10:15pm

wrote on Jun 28^th, 2005, 12:04pm:

I had to use the fly frobs, I used the earth and phase, and could not get sense out of it, than I started to suspect that the Fluke 1653 needs neutral for this test

On my Fluke 1652 there are lcd indicators in the screen telling you what cables need to be connected to it for each particular test. This makes sure you always use the right test cables.

Title: Re: ELI testing
Post by akuk on Jun 29^th, 2005, 8:34am

wrote on Jun 28^th, 2005, 10:15pm:

On my Fluke 1652 there are lcd indicators in the screen telling you what cables need to be connected to it for each particular test. This makes sure you always use the right test cables.

In this aspect I think that the 1652 and 1653 are the same, now at least I now what it means, I looked at the manual, (very poor for an expensive unit), I could not find it, thanks for this input
Albert