EFLI in 2391 land.

[brucelee]

Hi mate think its in exam success but he may be mixing a few things up for External earth fault loop everything is isolated and testing is done at supply side set on High loop if testing Zs on the load side of a RCD then he should be using the No trip setting if its a 1552 1553 I think the new megger 1720 and 1730 you ca do the High loop with 2 leads on the load side of a rcd but ot deffo as i have 1552

 

[brucelee]

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.

Hi mate
the circuit is energised and you connect the earth first the the Neutral then the line and carry out test whe done take leads off in reverse order the eutral is needed if using a Fluke as it needs it to power the meter
if using megger then just the earth lead and line lead


yes C&G questions are very vague and hard to read between the lines there is to much ambiguity with regs and building regs

 

[telectrix]

might be wrong here, but i think with the megger 1720/30 you can do the no trip with 2 leads. the 1552 needs 3 leads for no trip, but only 2 for hi.

 

[brucelee]

Hi tel

think your right again mate with regard the new meggers for no trip fuction only 2 leads unlike the 1552

 

[malcolmsanford]

Hi tel

think your right again mate with regard the new meggers for no trip fuction only 2 leads unlike the 1552

Don't know what is happening here Karl, the Tels as just pulled me up on another thread, is he on drugs, and if he is can I have a few

 

[brucelee]

Hehe

think he is overdosing from the regs but I am glad he is as this helps me and others greatly lol

 

[telectrix]

now that's not fair. malcolm's knowledge of the regs is superior to mine. i have to look things up. i can't even remember the values to put in the adiabatic. i am quite good at sums though.

 

[brucelee]

yes I have also benefited from malcolms knowledge of the regs and there numbers which is very helpful to me as i cant remember them

 

[La Poste]

Sorry for the confusion in this thread.
The book answers come from the 2391 exam success book and some study aids past papers I have been doing.

Personally if I was to conduct a Ze test I would use the line and neutral on the supply side of the switch with the installation isolated but for some reason City and guilds or at least the exam success book does not like it done this way.

They prefer you to isolate each circuit, isolate the supply, connect your test leads to line and neutral on the consumers side of the main switch and also to the main earthing conductor (disconnected from the MET of course).
Then switch on the supply and press your test button and record results.

This method that they prefer so much would not work with a 100ma RCD as the main switch and one of the study aid answers did not take this fact into account when giving me a suggested answer.

Basically all I am trying to do is find the best way to answer questions so that City and Guilds give me the most marks.

 

[brucelee]

just answer if asked at the supply side and for ZE its between line of supply and disconnected earthing conductor with main switch isolated and locked off also all cbs,loads removed

and you are right it would not work on rcd main switch so would have to be supply side

 

[La Poste]

also all cbs,loads removed

Why would all loads need to be removed to do a Ze test?

 

[telectrix]

in the real world it's always a balance between theory and practice. in theory, it's been proved that a helicopter can't fly.

 

[La Poste]

in theory, it's been proved that a helicopter can't fly.

And a Bumble Bee

I have to say I really appreciate all the help here.
It's a great attitude you people have.

 

[brucelee]

everything is switched off loads are removed by switching CBs off

 

[VMan]

ill throw another question thats going through my head..

Earth fault loop paths, on a 3 phase system with a single phase sub main.
Now when i get out the crayons to draw this fault loop path, should i include the 3phase DB as well as single Phase DB?

so i would draw with my new crayons :

Supply transformer,
Supply line,
Origin of supply with supply cut out
Main DB (3 Phase)
Sub main Circuit r1
Single Phase DB ( Sub Main )
Load Circuit r1
Load
Fault
Cpc r1 (load)
Single Phase DB MET
Submain Cpc r1
Main Earthing conductor
PEN / Supply earthing conductor / general mass of earth ect...
????