Anybody know if there is such a thing as a 250 Watt HX-NPF mercury vapor ballast?

Hmm, Normal Power Factor..? Is that even possible?

Reason I ask, NEMA's came in 250 Watt mercury vapor versions, I don't know whether they were all 250 watt self ballasted merc's or they some how fit a 250 watt CWA ballast in them or what.

Mercury vapor ballasts can be made much smaller, at higher losses however. Ive removed a few 250w MV area lights (prob NEMA heads) which were identical in size to the 175w versions. The 250w ballasts in these were considerably smaller than usual, about the same size as a 175w metal halide ballast. If I remember right, they were HX type and without capacitor. They also got super ridiculously hot, I remember all those fixture's wiring insulation would just crumble and flake off when I would touch it. 

Sounds like they forced too many watts into too small of space lol 

I have a steber brand floodlight that has a Jefferson NPF mv ballast it's really a differece how fast the lamp warms up compared to a CWA ballast, although not as good for the lamp

Well i do know HX MV ballast do exist
They were very common sight in San Antonio , Tx
But they are long gone, There is a 250 watt jefferson
Nema ballast on ebay.

I have a 250W MV ballast that WAS "N" PF.To convert it to HPF just add the value and volt rating capacitor as specified on the ballast nameplate-Did that-lower power consumption.It is a High reactence ballast-not CWA.With NPF High reactence ballasts they draw high start current and the current goes down as the lamp warms up.With the capacitor the warm up draw and run draw is less.The cap compensates for the reactence of the ballast-and another bonus--the ballast runs cooler with the cap.Can't remember the brand of the ballast-was in a package for a 250W aquarium light.

I do have a 240v 400w MV HX choke ballast from a GE Powerbracket. I suppose in 240v it's easier to use higher wattage in less space since it's only one coil.