My condition: 5 single lamp 4 ft T-12s in a dropped illuminated ceiling. It’s on a 3-way switch control.
What I’d like to do:
1) Replace all five w/ T-8 and ONE electronic ballast – can I mount the ballast anywhere and wire all 5 new lamps to the five fixtures? Be nice to save the cost of new 5 ballasts vs. one. I’m assuming 5 single lamp ballasts will cost way more than a single e.g. 5-6 lamp ballast.
2) Can I install a dimmable ballast and a dimming switch? Do BOTH switches have to be dimming? or can I not do dimming w/ 3-way switch arrangement?
Some of you are electrical wizzes, so I figured I’d check here.
Replies
Fluorescent fixtures are a bit spooky. "Igniting" a fluorescent lamp involves the capacitance between lamp and fixture, inductance of the wires, etc. You could try what you suggest, but it's not guaranteed to work, because you'd likely change the effective capacitance and inductance values in unpredictable ways.
Dimming on a 3-way is also tricky. There are different schemes for doing this (some pretty good and some pretty sucky), and you pretty much must stick with a given manufacturer's scheme once you pick one.
And of course you must make sure that you use a dimmable ballast and that the dimmer used is compatible with that ballast.
I don't know specificly about dimming t-8's, but you might want to look at radio controled switches like ceiling fans use. Then you could put your dimmer switches wherever you wanted.
Id use two ballasts, like a 2 tube version, and a 3 tube version. But they can also be both the same type with the unused output capped off. look at QTP2x32T8/UNV DIM, and 3-lamp QTP3x32T8/UNV DIM. They can be controlled by 0-10v dc, or line voltage dimmers.
This drawing shows a dimmer in line with the AC to the lamp, or with a 0-10v control. The nice thing about low voltage control is that it can be programmed with electronics to maintain constant light levels in the room.
http://www.goodmart.com/pdfs/T8DimUnv.pdf
That gives me a couple of good ideas to ponder. I like the notion of the two ballasts since then, I might be able to adjust light levels for what I like ... e.g. really low in the early morning and high for meal prep (which is why I wanted to go dimmable).
I know the basics, but don't know the specifics. I may have a chance to go to a lighting store this weekend, so may grill them for some options. I think I can reuse my fixtures/tombstones and simply rebalast and relamp if I recall. If I can leave my switches to provide power, maybe I can use the remote dimming to either turn 2 or 3 lamps off or dim them down? Or do I have to rewire in some way? ... maybe run switch power to the low voltage control circuit and then run the ballasts w/ dimmers? I need to study your link some more.
The reason I suggested two ballasts is that I dont think a ballast is made to operate 5 tubes. Since the t8 bulbs seem brighter, you could probably use a 4 lamp ballast and leave out one tube. I would operate all the lamps together when dimming. The drawing shows that you can use a traditional dimmer, or one with a 0-10v dc output. Here is a link to a 0-10v wireless dimmer. You would need a power supply, a dimmer and the receiver to operate the lamp. This looks like a great setup. Also, you can have multiple dimmers, and even a remote motion detector.
http://www.google.com/url?sa=t&source=web&cd=2&ved=0CCIQFjAB&url=http%3A%2F%2Fwww.leviton.com%2FOA_HTML%2FibcGetAttachment.jsp%3FcItemId%3D9mOBCapbQSJPQApx5RboOQ%26label%3DIBE%26appName%3DIBE%26minisite%3D10025&ei=RG9RTYzOBoKg8QO3wsHrDQ&usg=AFQjCNE50_7IqFJ2XO3iUJ1TkMxzQXHgPg&sig2=cSnzCBfhQt6zSKUopk-s3Q
They do make 5-6 lamp ballasts ... used for e.g. high bay fixture applications. I wonder about connecting wires together ... guess you would do that inside each fixture enclosure to provide a junction box w/ the connections in it. I'd eliminate a fixture, but they are evenly spaced above my suspended ceiling and I was a little leary about having the lighting uneven. You've given me some food for thought, so I'm going to check out some alternatives at a lighting store, maybe and see what I come up with.
I missed the part about the fixtures being single tube, but I think 2 ballasts will still work OK, allthough some ballasts are able to work remotely (outside of the fixture) and some others not so well.
There are some great deals on Ebay sometimes for ballasts, especially on used ones. They seem to get swapped out a lot.
You could buy several of these. http://cgi.ebay.com/Motorola-Rapid-Start-Gold-Edition-T8-Dimming-Ballast-/130454139513?pt=LH_DefaultDomain_0&hash=item1e5fac3279