2 wire and three wire loop tests

[Paul117]

Bit of an odd one but was doing a EICR today and got some weird loop test results. All low current 2 wire loop tests were around 7-8ohms whilst doing three wire loops on the saner circuits gave more to be expected readings around 0.6-1.2ohms. Overhead supply with a DNO PME head. Any thoughts?

 

[oldtimer]

Yea get rid of the 2 wire test I take it you are using a Megger 1700 ? Megger brought this out as a time saving measure ie instead of climbing steps you can do the test at the switch ie 2 wire only problem was everybody was saying no you need to test at the light point and measure Zs through the switch that way ie measure through the whole circuit . Instead nobody said boo to Megger and the 1700 has a mind of its own lol

 

[Guest55]

2 wire loop test is rarely accurate , use only as last resort.

 

[Paul117]

Yeah megger 1720. Just got it as a replacement for seperate testers for each function. My megger 2 wire lwt320 doesn't seem to have this problem though.

 

[oldtimer]

I honestly dont know why theu bother after several recalls and software updates but nothing new here Seaward have the same problem with their new Apollo PAT tester I think this is called re inventing the wheel

 

[MarkieSparkie]

Yeah megger 1720. Just got it as a replacement for seperate testers for each function. My megger 2 wire lwt320 doesn't seem to have this problem though.

Amen. Megger have yet to explain why their LTW separates produce valid results and their MFT 17xx and 18xx do not.

 

[telectrix]

i'll stick to my trusted 1553. one day i might even take the plunge and try to fathom out the bluetooth function.