if you take two tubes out of a four tube fixture, is there any current flowing through the unused ballast? (assume two ballasts, one for each pair of tubes.) Any downside to doing so? I'd only like to leave this like this for a week or so until I can wire up two switches.
thanks,
nate \\
Hi, Quick answer, No. Usually inside two and outside two are paired. You can remove either pair. Current can't flow on open circuit!
If the fixtures are 4/40 T12, there's two ballasts. Just leave one ballast disconnected when you wire the fixture. If the fixtures are 4/32 T8, it's usually one ballast. Just leave out however many lamps you don't want lit
I already wired it up, is why I asked, and it's a PITA to get back to the wiring after you put all the tubes in. you pretty much have to take all the tubes out, then open up the wiring cover, then reassembly is the reverse... I am going to have to do this again in a couple weeks anyway, I just temporarily wired up this one troffer so I can have light while demo'ing the old crap. That sucker is bright with all four tubes lit! my eyes hurt... I think I'm going to wire up two of them, with two switches and 14/3 so that one switch will turn on a pair of tubes in each fixture, that way I can have normal light, and bright light if I need it to do delicate work or something.
nate
It depends on the design. Generally you would need to disconnect the ballast to totally shut it down. They generally don't use full power if there are no lights in them, but they do draw current. I would guess about
50%. For two weeks I would not bother worrying about it.
Get rid of all that hardware and install some sockets with compact fluorescents.
I'd rather not do that; this is a basement with a low (7 foot or thereabouts) ceiling with a drop ceiling below it. Any decrease in headroom will be an invitation to bonk your head, and I don't want to go to can lights because they'd probably be less efficient.
Plus, the troffers were FREE. Free is good.
nate
Can lights are definitely less efficient. Also, keep in mind that compact fluorescents tend to overheat in can lights, unless you get ones that are known to be good for such heat hellholes.
In general, compact fluorescents have about 2/3 the efficiency of T8
4-footers, don't last as long as 4-footers, and cost more than 4-footers. Use T8 when you can.- Don Klipstein ( snipped-for-privacy@misty.com)
But you can replace the compact fluorescents with Super Bright LED's as the price comes down without rewiring. They run cold and can give you 40 incandescent watts at 7 watts usage and last 20,000 hours.
Are you talking about the E27-CW8?
I don't see a 7 watt one, and this one is closest at 8 watts. Claimed light output is 385 lumens for the cool white, 365 lumens for the warm white. Color rendering index is 77 for the cool white and 76 for the warm white. Price is $49.95. And that one is some sort of floodlight or spotlight.
Compare to a 9 watt CFL, which produces 440 lumens, has CRI of 82, is rated to last 7,500-10,000 hours nowadays, and costs about $4.
Meanwhile, a T8 32 watt fluorescent produces about 2500 lumens, even in "average age and condition" when used with a ballast with ballast factor of .9, with power input to the ballast typically 28-30 watts. Color rendering index is 84-86 for the higher of the two common color rendition grades, average life expectancy is 20,000 hours, 24,000 for longlife ones, and they cost about $2-$3 apiece.
It's going to be quite a while before LEDs make T8 fluorescents obsolete. It looks like a few years before they get competitive with compact fluorescents even.
- Don Klipstein ( snipped-for-privacy@misty.com)
Just for the record, the fixture I am using holds four F40 T12s. Again, it is sort of the "fixture of opportunity" as they were free, and I needed to do something to replace the horrible mess hiding above my ceiling. I was originally planning on using three 2x2 troffers but the
2x4s were free so I will use two of those instead.nate
Probably a good move!
4-foot F40 T12 with magnetic ballasts of 30-plus-year-old technology still has energy efficiency ahead of compact fluorescents, as long as the ballasts are at least "commercial grade" so as to give a full 40 watts to a "true 40 watt F40", and your F40's are "true 40 watt". With favorable temperatures and if the ballast labels explicitly allow for 34 watt "energy saver F40" (or are rated for both F30 and F40 T12), you can use 34 watt "energy saver F40" to get a little more energy efficiency still than with "true 40 watt" F40 lamps. Just beware that those tend to be more intolerant of cold than "true 40-watt F40", and to some extent or another to be "generally a little more cranky" than "true 40 watt F40", and to be mainly available with lower color rendering index. The USA legislation that partially bans "true 40 watt F40 T12" has an exemption for higher color rendering index. Color rendering index near or above 90 generally necessitates a compromise in energy efficiency, but there is something that has fairly high color rendering index to be allowable as "true 40 watt F40" without compromise of light output and energy efficiency: Philips Ultralume! The "cool white color" is referred to as 4100 or 41 (nominal correlated color temperature 4100 K). The color rendering index of these is 84. Furthermore, these are upper color rendition grade triphosphor ones whose color distortions tend to be majority in the direction of "colors more vivid". Fluorescent lamps withy CRI near 90 or from low 50's to close to 66-70 tend to have their color distortions mostly in the direction of "colors less vivid".- Don Klipstein ( snipped-for-privacy@misty.com)
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