EFLI in 2391 land.

[La Poste]

Howdy folks.

I have just been reading the exam success book and according to the book the best way to conduct an EFLI test on a TT installation is to isolate at main switch, close all circuit breakers remove main earth terminal and then connect earth lead of tester to disconnected main earth conductor, neutral to consumer side neutral IE isolated side of main switch and also line to consumer side line IE isolated side of main switch then switch on the main isolator and test.
This makes sense from a safety stand point as you will not be sticking your fingers near any live conductors.

My question is if I were to do an EFLI test at a remote lighting point would I isolate the supply with main switch. close all circuit breakers, close board and lock it, walk back to lighting point, attach my tester, place loads of warning signs around it then walk back to the board and switch on, walk back to my tester test then walk back to the board switch off then walk back to my tester and remove it.
I mean this seems more dangerous than just connecting my tester to the live connections inside the lighting point IE inside the ceiling rose or whatever.

What do you think would be the safest way to do an EFLI test at a remote lighting point?
Surely walking backwards and forward to the board or even a lighting switch and leaving your tester, ladder , exposed conductors would be more dangerous than just working live in this instance.
Maybe if you put on a pair of insulated gloves or something when connecting your test instrument, maybe this would make them happy.

Any thoughts on this one.

Thanks.

 

[tommy76it]

You isolate supply when measuring efli at origin ze because you are disconecting main earth.If your measuring efli on a lighting circuit you leave the circuit on.

 

[La Poste]

The point of the previous post was to show that when City and guilds do an EFLI test on a TT installation they connect the probes, line and neutral to the consumer side of the main switch.
I understand the need to isolate I am just saying that they make a point of connecting to line and neutral to the isolated side of the main switch to avoid working on any live conductors.
They then switch the main switch on to energise the line and neutral conductors to provide the power to complete the test.

I mean in their way they have isolated the supply, removed the earthing conductor, switched all circuit breakers off, then switched on the main isolator and tested.
They are making a point of not connecting the test leads to any live conductors whilst connecting them.

I just wonder how this same logic would be applied to conducting an EFLI test on a remote lighting point where in reality a person would have to connect the test leads of their EFLI tester to live conductors as it would be safer to do it this way than to run back and forwards to a switch or the DB.

 

[tommy76it]

it def does not apply to a lighting point.You need to poke the probes into live terminals to get reading.I would have said isolate the main switch and test main incoming side for ze.You dont connect the leads if its probes your using,only the earth has a croc clip.So you connect the earth lead to earthing conductor and insert the probes into the live terminals on the main isolator.

 

[brucelee]

Hi mate
they are referring to ZE which on a TT is RA using a earth fault loop impedence tester switch off remove all loads ie switch breakers off you can test at supply side
C&G as you say prefer you to say switch off remove all loads and connect on load side switch supply on carry out test
switch off and disconnecting reverse order always connect earth first then neutral if needed Ie fluke needs neutral to power meter megger doesnt line last after test remove in reverse
or you can do it at the rod with the main earthing conductor disconnected and use ground spikes and a earth electrode resistance tester
ZE or Ra is the external earth fault loop impedence Ie suppliers side
ZS is a different test in C&G and REGs land and is carried out at sockets or by calculation
If you want to test ZS on a lighting circuit supply is left on and warn people ,Erect barriers and warning notices
connect earth lead first then neutral if needed to power meter ie Fluke if megger just 2 lead test line and earth
then connect line carry out test disconnect in reverse order on a lighting circuit
You dont switch of supply for ZS

think you are mixing 2 tests up mate C&G speak is another world lol

 

[gap30]

yes in real life you would at least warn others but about 75% of the time (in my case anyway) i am usually testing either with someone else or with builders around on site and most sensible people know if you are testing to exercise caution, but for example if it was in a busy office, you would have them email all employees on site telling them the testing is being carried out, then the general area you are working in you would let people in the immediate vicinity know also 9 times out 10 you would be standing on a ladder/leaving your test gear on the top of the ladder whilst you ran back to the db or get the hoppo to run to the db. In my own personal experience when most people see you are testing the electrics they tend to avoid you by a mile! lol

i am referring to a zs on a lighting circuit

 

[Des 56]

The fashion nowadays is to avoid live working
On that basis,they suggest dead tests to determine the Zs of the lighting circuits

 

[Deleted member 26818]

I think what is being suggested, is that all connections with probes and croc clips are made with the installation isolated, and then once the connections are made, the supply is then energised to allow the test to be conducted.
Would need very long arms when testing Zs, or another person by the CU just to flick the main switch.

 

[JUD]

My question is if I were to do an EFLI test at a remote lighting point would I isolate the supply with main switch. close all circuit breakers...

I mean in their way they have isolated the supply, removed the earthing conductor, switched all circuit breakers off...

Just an observation :wink5:

What's your definition of closing a circuit breaker?

To close a circuit breaker means to switch it ON.

Switching OFF would be opening the breaker.

 

[telectrix]

what a load of cobblers, testing Ze by connecting probes to load side of main switch then switching on. as soon as you switch the isolator on, your croc clips will fall off.

 

[La Poste]

Just an observation :wink5:

What's your definition of closing a circuit breaker?

To close a circuit breaker means to switch it ON.

Switching OFF would be opening the breaker.

That's a fair observation, sorry it was late when I wrote the post.

 

[La Poste]

Question:
Describe in detail how to carry out by direct measurement an earth fault loop impedance test on the workshop lighting circuit.

Answer:
secure safe area around last luminaire on the circuit.
Test instrument to be used is an earth fault loop impedance tester.
Leads to GS 38.
At the furthest point on the circuit test between switched line and CPC.
With the circuit energised test and record result.
Re-instate luminaire.

Now that all sounds a bit vague to me.
Test between switched line and CPC, what with the circuit energised, do I connect the leads with the circuit on or off.
It's a very vague answer.

Other question:
Describe the test procedure to determine the resistance of the installation earth electrode.

Answer:
seek permission to isolate.
Safely isolate supply and all circuit breakers.
select and earth fault loop impedance tester confirm calibration condition of leads to GS38.
disconnect the earthing conductor from the main earthing terminal.
connect the instrument earth lead to disconnected earthing conductor, neutral to outgoing neutral of main isolator, line to outgoing line of main isolator.
close main isolator.
check instrument set to 200 Ohms and carry out the test and record the result.
Open the main isolator and disconnect the instrument in the reverse order.
Reconnect the earthing conductor.

I always thought a person would do the test at least twice to check for voltage spikes or transients, maybe C and G don't like this method.

My point is in the second question the book answer makes a strong point of connecting the leads when the circuit in safely isolated but on the first answer, the light test there is no mention of isolating the supply to connect the test leads, that fact is brushed over if you ask me and the answer is very vague.
I just wonder what you guys who do this sort of test in the real world would do and what you would consider to be safe.

 

[Deleted member 26818]

If you conduct a Zs test at a light fitting, by connecting the probe to the switched line, you are including that conductor in the test, and by switching the switch, you will prove polarity.
Obviously, depending upon the type of fitting, your method of connecting your probes will vary.

 

[La Poste]

Have an assistant stand by the switch and operate it for you.
Connect leads to a dead circuit then ask your assistant to energise.
Chat up the security guard or better still the office secretary and her flick the switch.
I'm serious though, with this exam if there is anything that you write down that is potentially dangerous they penalise you for it very heavily.

 

[Deleted member 26818]

You can get adapters for testing light fittings, which plug in in place of the lamp, and you then stick your probes in.
You can then leave them there and go and flick the switch.
Of course you'll either need extra long probe leads, or leave your tester on the top of the steps.
Not much help with flourescent fittings though.