How do you pass Insulation Testing when your load is low impedance?

This is probably a silly question but I read that for class I equipment I need to perform insulation resistance tests and it must be under 1 megaohm.

My understanding is that one of these tests involve checking the resistance between live and earth connections.

So if my supply is 240V and I have a 24W resistive load (let's say I am a heater). Then the resistance of my load will be about R=V^2/P = 240^2/24 = 2.4k ohm.

So essentially I have 2.4k ohm load between live and Earth. So during the insulation test I will fail because the resistance between live and earth is less than 1 megaohm.

Is this right?

• the load is not between live and earth but live and neutral Aug 19, 2021 at 9:11
• If your load is between live and earth, you failed the insulation test. Aug 19, 2021 at 10:30
• What if I wanted to measure the line voltages with respect to earth. Eg. Have a voltage divider. I suppose I need the voltage divider to have a total resistance of more than 1Meg Ohm? Aug 19, 2021 at 11:15
• You generally don't do insulation testing on live equipment. You isolate the equipment and then apply the test voltage between the L or N to E. Aug 19, 2021 at 14:48