Three lead tester

[Ben Butcher]

Hello Everyone,

This is going to sound like one of those tin hat questions! I have just bought a Seaward Multi Tester and duely had it calibrated. It replaces a much older 2 wire tester which I was quite happy with, but has 3 leads. This confuses me a little as I cant think where I may need three, for example doing a Ze test on a house I recently rewired it said to piggyback the green to the black (reading of 0.15 Ohms) so what was the need for the green? Also it has a standard plug top lead for doing Zs testing at sockets so am I testing the circuit including the Ze if done live? Thanks for any comments, Ben.

 

[telectrix]

generally, most testers use 3 leads for testing Zs on no trip. i am not familiar with the seaward. have you not got the user manual? if not, sure you can download it.

 

[Deleted member 9648]

Hello Everyone,

This is going to sound like one of those tin hat questions! I have just bought a Seaward Multi Tester and duely had it calibrated. It replaces a much older 2 wire tester which I was quite happy with, but has 3 leads. This confuses me a little as I cant think where I may need three, for example doing a Ze test on a house I recently rewired it said to piggyback the green to the black (reading of 0.15 Ohms) so what was the need for the green?I'm not familiar with the tester but to carry out Ze test you would connect each lead to it's respective separate pole/earth....with a 3 lead tester you would only piggy back the green to the black to test PSC (line-N). Also it has a standard plug top lead for doing Zs testing at sockets so am I testing the circuit including the Ze if done live? All Zs testing includes the Ze....and it is only possible to test Zs live............can you give a little more info on your testing sequence please?Thanks for any comments, Ben.

.....................As I'm not familiar with the tester concerned happy to stand corrected.

 

[Jimmy Boy]

This took a bit of digging for it may provide the correct download

Download Seaward Literature Including Manuals, Datasheets and Software

 

[Ben Butcher]

Thank you Jimmy Boy, That's very kind, I have had a look but with everything in my life the info is for stuff not as old as that that I have! I will still have a good peer through it all. Cheers.

 

[Guest123]

Some installation testers require the 3 lead test when conducting a 'no trip' loop test on a circuit protected by an RCD for instance.

I know the Metrel range of insruments require 'piggy backing' of the N+E leads when conducting some tests also.

 

[Jimmy Boy]

There will be a legacy download somewhere, if it's used make sure it's in calibration still before use.

J

 

[MarkieSparkie]

Thank you Jimmy Boy, That's very kind, I have had a look but with everything in my life the info is for stuff not as old as that that I have! I will still have a good peer through it all. Cheers.

What model of tester do you have Ben? SBS7671 maybe? If you don't know the model name and/or number, just post a photo of it.

 

[Ben Butcher]

What model of tester do you have Ben? SBS7671 maybe? If you don't know the model name and/or number, just post a photo of it.

Hello, it is a Seaward CMB-S, quite old I think but calibrated with no probs! Thanks, Ben.

 

[Guest123]

Download Instruction Sheet: Seaward Combi Compact Installation Tester User Manual for: RSCAL(3752007),CMB-S installation tester. Part No 278A937. Manufactured by Seaward

 

[MarkieSparkie]

With the Seaward Combi Compact (CMB-S) you should be testing Rloop and Rline in a 3 wire test ie. Red lead to Line, Black lead to Neutral, Green lead to Circuit Protective Conductor or Main Earth Conductor as appropriate. There should be no need to use a psuedo-2 wire test with Black and Green leads piggy-backed, as the lead switching is done internally within the MFT when selecting Loop or Line on display.