In ,
ransley wrote:

I have an exterior light fixture, possibly low pressure sodium
standard screw base 30w bulb, someone put in 100w standard incandesant
bulbs years ago and it works fine. I wondered what would happen if I
put in a cfl, would I blow the cfl circuitry.

The voltage across the CFL's base, after voltage drop of the ballast,
may cause the pulse starter for a usual HPS fixture to actuate. The
pulses are something like 3-3.5 possibly 4 kilovolts.

Although the CFL's impedance will probably be enough to load those
pulses down to pretty much nothing, I would not count on it. I would not
want to explain this to my homeowner insurance company if a fire resulted.

- Don Klipstein )