First, be careful when using a megger (place cursor over link, then right click, select 'Open in new window'
http://s159.photobucket.com/user/brianj ... 7.pbw.html ).
Here is some good reading before purchasing and using a megger (place cursor over link, then right click, select 'Open in new window'
http://www.transcat.com/PDF/BasicInsulationTesting.pdf ).
Here is some more reading, not the best article, but informatice nonetheless (place cursor over link, then right click, select 'Open in new window'
http://ecmweb.com/test-amp-measurement/ ... ce-testing ).
Here is some more reading (place cursor over link, then right click, select 'Open in new window'
http://jmtestsystems.com/PDFs/megohmmet ... esting.pdf ).
And some more reading (place cursor over link, then right click, select 'Open in new window'
http://www.newark.com/pdfs/techarticles ... VCable.pdf ).
It is not something I would chose to do during a home inspection - while megohm testing is not necessarily designed to be used on NM cable, it could be, but it will be quite time consuming as all loads need to be removed from the circuits and all power needs to be removed from the circuits (remove the conductors from the breakers or you will be testing the internal workings of the breakers too, which could cause AFCI and GFCI breakers to go bad, not sure of regular breakers but if I were to presume something like that I would presume on the safe side - that regular breakers could be negatively affected too).