Help with insulation resistance testing on a lighting circuit

[soar]

bit late to this party but L-E IR test should not be impacted by a bulb present. L-N will impact if a bulb is present and the reading will be low.
If you cannot isolate everything and there are sensitive equipment then connect L-N together and just do IR across E and L-N connected together. If the reading is above 1m then ok but if low further investigation is required.

very good explaination
thanke much