I am swapping out an existing floodlight for this:
The existing light works fine. The new light works as long as it is NOT screwed into the electrical box. If it is touching the electrical box when the light comes on, the circuit breaker will trip (accompanied by a complementary popping noise and some sparks).
Some background information: My house was built in the 50s. I'm not aware of any outlets that are truly grounded. The power to the floodlight is controlled by a switch in my kitchen. Conduit runs from the wall just outside the switch to a carport fluorescent light and then out to the floodlight.
At the electrical box for the floodlight, there is a red wire (hot) and a white wire (neutral). The floodlight has three wires: black (hot), white (neutral), green (ground). I connect the two hot wires (red to black), the two neutral wires (white to white), and leave the green ground wire unconnected and capped. Again, it works perfectly when the wires are connected but the light is not screwed into the electrical box.
Any testing I have done with an analog voltmeter seems to be correct. When the power is on: red(hot) to white (neutral) reads ~110V. Red(hot) to the electrical box reads ~110V. White(neutral) to the electrical box doesn't register a reading. With the power off, there is no reading.
I originally assumed something was wrong upstream. I have verified everything is I would expect behind the kitchen switch (same testing procedure as above). I haven't pulled the fluorescent light fixture yet to check its electrical box, but the wiring at the fixture looks okay (nothing exposed).
I'm left wondering if something is wrong inside the new light, lol. That seems unlikely, but I guess it is possible. Hopefully, I've explained this well enough. I'm sure it's obvious I am no expert with electricity.