earth fault loop impedance zs

[jamiep93]

im currently studing my level 3 electrical installation and just need someone to clarify the earth fault loop impedance zs procedure because something in my notes doesnt add up

 

[ajkend]

EFLI is a live test you perform once you have got satisfactory results doing the "dead" tests.

Best to speak to your college tutor seeing as there is a shock hazard doing this test.

 

[Technician]

The live test must be done because even though it might

look in order with (R1 + R2) and Ze the test is not complete

because without the live test you have not proved that the

entire fault loop exists.

HTH

 

[Megaohm7]

im currently studing my level 3 electrical installation and just need someone to clarify the earth fault loop impedance zs procedure because something in my notes doesnt add up

What is it in your notes that don't add up? Have you seen any live testing done in the workshop at college?

 

[Andy™]

The live test must be done because even though it mightlook in order with (R1 + R2) and Ze the test is not complete

because without the live test you have not proved that the

entire fault loop exists.

HTH

there is no requirement for a live Zs test, you can calculate it from R1R2 & Ze

personally, i always do a Zs test, just to make sure you havent got something wrong after R1R2 / Ze like not putting an earth back etc

 

[Doc Hudson]

The live test must be done because even though it mightlook in order with (R1 + R2) and Ze the test is not complete

because without the live test you have not proved that the

entire fault loop exists.

HTH

This is clearly incorrect information, as by proving Ze and proving R1+R2 you have proved the entire earth fault loop path as described in guidance note 3 .and as Andy quite correctly points out, one of the acceptable methods for obtaining Zs is by calculation. This can be found in the initial testing section of GN3. mis-information such as this does not help our student members to gain a full understanding of BS7671.

Doc H.

---------- Post Auto-Merged at 22:00 ---------- Previous post was made at 21:53 ----------

im currently studing my level 3 electrical installation and just need someone to clarify the earth fault loop impedance zs procedure because something in my notes doesnt add up

Welcome to the forum as a posting member, What part of the Zs testing are you having difficulties with? (Please ignore Technicians post #3 as that information is incorrect.) Is it describing the earth fault loop path, understanding what are acceptable max Zs values, what range to put your meter onto, where to put the meter probes, other?

Doc H.

 

[philbas]

As I understand it

You must measure R1 + R2 a dead test.

Ze can be obtained my enquiry or measurement.

Zs can be measured or calculated.

So the only test actually required is R1 + R2, and even that

 

[Electroglow]

Do you know what Zs is for?? What's the difference between Ze and Zs... What do both test prove...?

Yes there is a shock hazered on all live testing so the correct equipment should be used. All ways be carefull when testing live...

 

[philbas]

Do you know what Zs is for??

Was that directed at me ?

 

[Electroglow]

No the op

 

[Technician]

Doc; I apologise if you think that I have placed incorrect

information on the forum.

I omitted to state that the live Zs test was not ALWAYS

necessary (avoidance of live working for example).

I have always understood that live Zs testing should be

done wherever possible because live Ze and (R1 + R2)

tests can be done independently of each other. Only a

live Zs test would PROVE that the EFL exists.

Once again, apologies to you and the forum.

 

[Doc Hudson]

For many years BS7671 has suggested that Zs by calculation is a perfectly acceptable method, as such with this question being raised by a level 3 student, it is prudent to stick to the factual guidance of BS7671 that jamiep93 will most probably be tested on. Again your assertion that only a live Zs would prove a EFL path exists is misleading. If a Ze has been read and R1 + R2 has been read and an accessory on the end of this circuit has been confirmed to have correct polarity and earth continuity and is live and working, then clearly the full Zs path must be present. Also there can be many situations where installations have a lot of exposed metal parts and extraneous metal parts and have a lot of persons present in the building, where if doing a live Zs test could impose hazards and dangers to persons you have no control over. These would be some of the facts that a student needs to be aware of not an incorrect statement that only a live Zs can prove EFL.

Doc H.

 

[septiclecky]

im currently studing my level 3 electrical installation and just need someone to clarify the earth fault loop impedance zs procedure because something in my notes doesnt add up

It might help us answer your question if you gave a bit more info by what you mean by "something in my notes doesn't add up?

 

[Sidewinder]

I would prefer to do Zs however, it is acceptable to calculate.

You will however, often see differences between calculated R1+R2 + Ze and measured Zs values for a multitude of reasons.

A measured Zs will almost certainly be lower, so the calculated value will probably be a more onerous situation.

 

[ADS]

As I understand itYou must measure R1 + R2 a dead test.

Ze can be obtained by enquiry or measurement.

Zs can be measured or calculated.

So the only test actually required is R1 + R2, and even that

 

[batty]

Trouble with calculating Zs this will not tell you if you have lost a neutral.

 

[Andy™]

thats usually obvious when the kettle doesnt work

 

[batty]

But you could put an installation into service and then find a fair bit doesn't work or even one bit.

 

[Doc Hudson]

[quote name='Andy

 

[Andy™]

But you could put an installation into service and then find a fair bit doesn't work or even one bit.

i know, it does seem odd that you can pass a circuit without checking the neutral

maybe if neutrals were checked as thoroughly as L&E, there would be less burnt out neutrals?

---------- Post Auto-Merged at 21:13 ---------- Previous post was made at 21:11 ----------

Is that the first functional test after energising the circuit, make a cup of tea.Doc H.

not for me, since i rarely have hot drinks unless its cold. and i have a kettle in the van anyway