earth loop problems

[rammo]

can anyone help? i have been testing a 3p tt installation today Zs is fine 77ohms r1 + r2 0.24ohms fine but when i test loop at sockets i have had readings from 0.69 ohms to 849ohms at the same socket all connections checked nothing lose have retested earth stake and no change there????? There is a 30ma rcd on the main incomer which i am going to change to a isolator as all circuits are now protected individually with rcbo can any body help?

 

[SimpleSimon]

Wait is it your Ze getting 77ohms or Zs?
When you saying it's ranging are you using a digitAl or manual reader to get that range?

 

[KFH]

If you are testing Zs using a non trip meter they tend to be very susceptable to noise on the mains. Try disconnecting all other circuits if you have not already done so. I have not seen the differences you have when using my MFT 1552 but it does flag when it thinks there is too much noise on the line to give a good results and then the differences can be 10ohm or so compared with a full 20+ amp test.