In article , Pete C. wrote:
SNIP

They have big honkin' CFLs with mogul bases too. They're starting to
appear at the big boxes. You have to be careful though because there are
also some similar looking mogul based CFLs that are designed to directly
replace HID lights such as mercury vapor without removing the HID
ballast.

CAUTION - most of those mogul screw base ballastless CFLs get overpowered
in HID fixtures - should they work at all.

CFLs of wattage over 50 watts (and for that matter also most under
50 watts) tend to either have their own internal ballasts or require
ballasts specific to themselves as opposed to ballasts for mercury or
other HID lamps. Do not put a mogul base CFL into a 175 watt mercury
fixture unless it is rated for use in a 175 watt mercury fixture and also
has the ANSI "ballast compatibility" code of H39.
Other HID "retrofit lamps" have other ANSI "ballast compatibility" codes
on either the bulb or the package or in any inserted printed material.
Use those in HID fixtures only if the fixture and/or the ballast has an
ANSI "ballast compatibility" code same as one for the lamp (lightbulb).
Otherwise, there is probability or possibility of malfunction, including
significant chance that malfunction will occur "down the road" should the
lamp work "apparently OK" initially. Such malfunctions may include
hazardous ones.

Keep in mind that there is such a thing as ballastless mogul screw
base CFLs that lack any ANSI "ballast compatibility" codes. Those require
ballasts/fixtures recommended by the lamp manufacturer, which may be
proprietary ones. The best example that I can think of is Lights of
America "Fluorex" lamps, widely available at Home Depot.

- Don Klipstein )