My megohmmeter is reading "OL" or "I"; is this a good reading for the heating cable insulation resistance test?

If your megger is reading "OL" (over load) or "I" (infinity), these are commonly used readings on megohmmeters, when the measurement exceeds the maximum indicated value of the tester.

For a successful test, the insulation resistance measurement must be equal to or greater than 1 Gigaohm (1 Gigaohm = 1 G ohms = 1000 Mega ohms = 1000 M ohms). We recommend that you always check the megohmmeter instruction manual as each manufacturer can use different symbols or values for their testers.