DNO Issue !!!!

[stuart569]

Me also.I assume the readings would be the same?I think the 3 wire testers automatically display the higher reading of L-E L-N??

 

[Zeno]

Could someone explain how using a 3 wire tester would give a different result for Ze. I have a 3 wire tester but only use 3 wires when I don't want to trip the RCD, if I'm measuring Ze I just use 2 wires.

It is possible to get different readings by changing from a 2 wire to a 3 wire test on Ze or Zs.


Example from a real fault, (Megger 1552)
Tested a socket for Zs with plug, got a reading of 2.8ohm, tested another socket, 2.7ohm, maybe a broken ring or something? But continuity and readings OK on ring.

Go to another ring, high readings there as well.

Maybe Ze is high, so I did a two wire 20A bond test at the board, got a reading of .2ohm ish.

Strange I thought, get 2 wire Megger 345 no trip out, and do Z tests across the board all low readings?


Turn board off, do ohm test across MCB's check other circuits all OK?


Test across Neutral contact of double pole RCD and get 2 ohms ish FFS


Three wire testing uses the neutral as well.



Also on Hager RCDs and MCBs, always test for contact resistance they they burn easy, I have had around 5 cases of this.


Hope this helps.

 

[stuart569]

On a Ze you should be testing L-N anyway!Really? I have installed hundreds and hundreds of Hager boards and never had or heard of anyone having a burned out main switch or breaker.Had a couple dodgy rcd's and that's it!You must be buying fake stuff

 

[mogga]

ombusdman are sill to get back to me about S.P.s extorsionate charge for fitting an isolator as they dont cut and reseal any more only fit isolators at £150 ffs I told them Id pay no more than £50 as 1 hr and £15 for isolator but they have monopoly

 

[stuart569]

ahahahaha loving the sig mogga