Zs.... 3 Lead Vs 2 Lead results

[JamesBrownLive]

Is it to be expected that a Zs test carried out using 3 leads (No Trip) will return a different result from one using 2 leads?

If so, can someone kindly explain what causes this.

Cheers

 

[Sparky Ninja]

The no trip setting applies a lower test current under test and so is more susceptible to 'noise' during the test.

 

[daiplayer]

My meter wont even allow measuring with out the three leads connected.

 

[keniff]

Also if your using 3 leads it's because there is a rcd you don't want to trip, the rcd changes the reading slightly to, try doing a ze either side of the rcd terminals and see what you get with your tester

 

[ian.settle1]

Think you will find that the only difference between a 2 and 3 lead test meter is that the connection for the neutral to allow the meter to work is that on a 2 lead meter is made internally in the meter where a 3 lead it is not and you need to make a physical connection to the neutral.

 

[JamesBrownLive]

Also if your using 3 leads it's because there is a rcd you don't want to trip, the rcd changes the reading slightly to, try doing a ze either side of the rcd terminals and see what you get with your tester

Well when I say 3 leads, what I was actually doing was using the Plug adapter on a socket, and switching between the Hi and No Trip settings. The circuit in question doesn't actually have an RCD protecting it. I was just wondering what was causing the differences in the readings.

Cheers

 

[jbrown1989]

i have recently finished my 2392-10 course and have my 2391-10 course booked for the end of september. when undertaking r1 and r2 vaule on a ring circuit at my workplace all the sockets have fly leads and are all connected via steel from the back boxes in the sockets, is it possible to just measure l-l n-n e-e and divide by 4 instead of the figure of 8 method because it will take to much time to dissconnect all possible paralell paths?

 

[telectrix]

as widdler says, noise can cause the difference. i find it's worse if you have radio 1 on. the best results are obtained when you tune your radio to classic FM.

 

[jordachus]

i have recently finished my 2392-10 course and have my 2391-10 course booked for the end of september. when undertaking r1 and r2 vaule on a ring circuit at my workplace all the sockets have fly leads and are all connected via steel from the back boxes in the sockets, is it possible to just measure l-l n-n e-e and divide by 4 instead of the figure of 8 method because it will take to much time to dissconnect all possible paralell paths?

No . A
full test with cross connections must be done- otherwise you will not find if you have a ring within a ring

 

[jordachus]

Well when I say 3 leads, what I was actually doing was using the Plug adapter on a socket, and switching between the Hi and No Trip settings. The circuit in question doesn't actually have an RCD protecting it. I was just wondering what was causing the differences in the readings.

Cheers

A test with two leads is using a higher current therefore is more accurate and because of that you should use when possible ( when you do not have additional rcd protection)

 

[telectrix]

or spurs

 

[daiplayer]

- by cross connecting at the board ( l-n...n-l) you also confirm polarity at each socket outlet,
- When you measure l-l , n-n, e-e, .....e-e will return different results as its a smaller csa ( usually 1.67 times the live conductiors value)

- cross connecting l-e , confirms the cpc is connected to each socket outlet

- also , in my tution of the 2391 ....we got hammered for calling it an earth....' its a cpc ( circuit protective conductor)



Hope im right, and it helps

 

[oldtimer]

Just to throw a spanner in the mix we were all told that you had to test a light circuit at the the ceiling rose or light point all of a sudden Megger bring out their 1700 series tester and say you can do it with a 2 lead set up at the switch and now they are in discussions with the registration companies to get an agreement