removed from the outlets (fig. 2-14). If local lighting
should be made on each individual leg of dc circuits and
switches are double pole, the insulation resistance of the
each individual phase lead of three-phase ac circuits.
local branch circuit will not be measured when the
For lighting circuits, the legs or phase leads should
switch is open. In such cases, making an insulation test
include all panel wiring, terminals, connection boxes,
from one leg or phase lead to ground with the local
fittings, fixtures, and outlets normally connected. The
switches closed will determine whether grounds exist
on the circuits and fixtures.
lights should be turned off at their switches and all plugs
Figure 2-14.--Measuring insulation resistance of a lighting circuit.