On Sun, 13 Mar 2016 18:41:50 -0000, "Mr Macaw" wrote:

The problem is when there is more than one circuit in the box or when
people assume all white wires (neutral here) will be grounded. If you
open up that wire nut only one of those wires with be ground, the
others may be at full line voltage through the connected load.

Firstly, why on earth would you have more than one lighting circuit? Secondly, if you do, simply use a multimeter!


They tend to use the large ceiling boxes as junction boxes and there
may be a number of circuits radiating from there. We don't have loops.

The other problem is, as long as all the neutral wires are connected,
it will be near or close to 0 volts. It is when you open that circuit
that you see line voltages through connected loads.