I have had the same problem. I think it is due to the center retaining bracket. I have 2 96W bulbs, one with the center retaining bracket and the other with. The one with has burned out twice in 2 months, the one without is still going strong.
What brand are you all using? When you are said a middle spacer, are you talking about that little plastic clip that goes in between the 2 tubes on the bulb?
I have a 2x96W Brite Kit (retro) from AH Supply. I have been using this kit since Juanuary 2001. Lights are about 6-7" above water (no glass cover) mounted in canopy with fan blowing over bulbs. About 6 weeks ago, I put a 175w MH in between the 2 bulbs with about 5 inches between each pc bulb and MH. About 3 weeks ago, one PC bulb burned out. Last week the other PC bulb burned out. They were only 10 months old, could this have to do with the heat of the MH (fan blows over MH) or do PC bulbs burn out like that? Ballasts are working fine.
Lee1- no I mean the center retaining clip in the fixture that holds the bulb. In my hood there are three metal clips that hold the bulb in place- one at each end of the bulb and one in the center. On one of the fixtures in my hood there are only two- one on each end. That bulb is fine. The the fixture with three clips has lost two bulbs so far.
