Inspection and testing

bks · Nov 2, 2013

why RCD trips when you do two lead low current test and doesn't trip when you use three lead tester. I am using MFT megger 1730 and less than year old. I am bit confused with it. I did RCD trip current test as well in case RCD is faulty and found 19ma trip current. tripping the RCD, is that meant there is fault somewhere or what. I did test insulation resistance which i got overall >2megha ohms and individual circuit > 200 megha ohms. There is fixed appliances like oven, washing machine and dishwasher etc. Love to hear more about it please.

telectrix · Nov 2, 2013

on the hi loop test you are shoving 25A test current L-E. this will obviously trip the RCD. using the lo loop test, a 15mA current is used. so as not to trip the RCD. because of the low current used, the reading is not as accurate as with a hi current test.

edit: misread OP. seems you are tripping on a 2 wire lo test. not knowing the 1700 series, can;t comment further.

GLENNSPARK · Nov 2, 2013

telectrix said:
on the hi loop test you are shoving 25A test current L-E. this will obviously trip the RCD. using the lo loop test, a 15mA current is used. so as not to trip the RCD. because of the low current used, the reading is not as accurate as with a hi current test.

edit: misread OP. seems you are tripping on a 2 wire lo test. not knowing the 1700 series, can;t comment further.

i think they had problems with thenm Tel...

this was sorted out....but it may be that the instrument he is using needs sending back to Megger for them to update the firmware...which i think they were offering free...