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Exit Sign Lit Without "EXIT" Stencils
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I was hopeing this was PL since I've always wanted a PL exit sign but oh well. If i were to get a PL exit sign i would want it ti be a side mount double-sided one with red letters and without battery back-up since that's how the ones in my elementary school were (well they still are). I always enjoyed looking at an EOL lamp and listenign to that high pitch "BZZZZZ" the exit sign gave off. The janitors typically waited until both lamps were dead before relamping them. Those exit signs were one of my favorite things to look at when i was in elementary school (i wasn't actually into lighting; i was into signs but i think exit signs were the bridge that made me interested in lighting as well). Of course now i look back and think how lucky i was to be in a school with 100% T12 lamps, PL lamps, and probe MH. Unfortunatly the cafeteria and library lights were replaced with T8s becuase the lights were falling apart.
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Using one ballast also saves money and energy as compared to using tow ballasts. Another benefit was that the U lamps ran on the same ballast as the F40 linear lamps which means a place with 2X2 and 2X4 troffers only has to sotck one type of replacement ballast.
Oh and I think U lamps have become less popular recently, most newer 2X2s use either 2-3 F17T8s or three PL 55 fluorescents.
Preheat F-40 was still, made all the way to the early 90s!
BTW, is 3X F32T8 an acceptable replacement for 4X F40T12 without noteable lumen drop or should a 4X F32T8 be used?
Anyways those 2X2s originally used 2 F40 U lamps but was retrofitted to use 2 F17T8s. Three F32s might be enough to replace four F40s but you'll probably have to get a high ballast factor ballast (120% output) instead of a normal ballast factor ballast. (88%)
Oh, and I heard that they made F40 tulamp ballasts and T17 ballasts as late as 2000 or so and I believe the LPF F40 preheat ballasts are still made (since they apparently never got banned go figure) .
I guess T12s have suffered most of the bans is because they are the most common magnetically ballasted lamp still in use today.
I guess a T17 ballast would be similar in size and weight to a modern VHO ballast eh? Oh and if you have a picture of the ballast label you or the people here might be able to date it.