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kruser
Premium
join:2002-06-01
Eastern MO
reply to tschmidt

Re: Interesting article about the state of lighting.

How about the T8 size 4 foot LED tubes, anyone mess with those yet? They don't use a ballast at all. One end socket is rewired directly off 120 volt line voltage and the other end socket is just left in place to hold the lamp but all wires are cut.

The lamps I've seen have an internal reflector strip as there are no LED's on the backside of the tube so you lose any reflector properties from your fixture.
The lamps claim to draw 12.5 watts at 120 VAC input. Not cheap though at $50+ per lamp.

Of course you can use them to replace T12's or T8 tubes.

I don't know who made the one I saw but I don't think I'd like it for direct lighting except maybe above a test bench or something. Used in a fixture with a diffused reflector lens may be ok.
It was bright that's for sure. I noticed it also said "not dimmable". I took that as the lamp must contain some type of electronics that can't handle a conventional dimmer.

Are standard 4 foot T12 or T8 bi-pin sockets even rated for line voltage? I know the old T12 single pin 8 footers used line voltage rated sockets as they often used one socket to interrupt power to the ballast when the lamp was removed but I'm not sure about the typical bi-pin 4 foot sockets found in the old shop lights you could buy for 10 bucks (or less with lamps even) at your old hardware store. I tried looking at my spare sockets but did not have any old bi-pin sockets for some reason.
I'm thinking I remember seeing them stamped with a 600 volt rating but something tells me my memory is wrong.


tschmidt
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join:2000-11-12
Milford, NH
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AFAIK the bi-pin sockets are rated the same as ordinary wire 600 volts. Florescent start-up voltage is pretty high and some industrial florescent operate at 277V.

The T8 ballasts I have (not sure if it applies to all) are instant start, they do not use the heater. You need to bridge both contact together in each socket. Failure to do so causes the arc to migrate to one end of the filament, rather then the center, reducing tube life.

I am intrigued by LED lighting but think that tubular form should use a different connector then standard T8/T12 bulbs since they are not compatible.

/Tom

kruser
Premium
join:2002-06-01
Eastern MO
said by tschmidt:

I am intrigued by LED lighting but think that tubular form should use a different connector then standard T8/T12 bulbs since they are not compatible.

/Tom

I agree with that fully. Not sure what happens if you plug a standard T12 or T8 tube into a socket that has been re-wired for direct 120 volt line voltage!
The only thing good about it that I could see (other than the cost savings) was the fact that the LED lamp would simply not light if you insert a new one backwards.
I guess you could wire both end sockets with line voltage so it would not matter which way you insert the LED tube. The tube I looked at had dummy pins (still brass pins) on the non powered end. They did not go to internally.


tschmidt
Premium,MVM
join:2000-11-12
Milford, NH
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said by kruser:

I agree with that fully. Not sure what happens if you plug a standard T12 or T8 tube into a socket that has been re-wired for direct 120 volt line voltage!

If the LED tube is fed with 120 volts at one end and the other is simply a mechanical attachment plugging a florescent tube puts 120v across the filament. That would probably be prettying exciting.

quote:
OSRAM SYLVANIA’s LED T8 Commercial Grade replacement lamps are an energy saving LED alternative to traditional T12 or T8 fluorescent lamps combining innovative optical and mechanical design features. These lamps have a dedicated internal driver (120-277V) allowing them to be powered with direct AC by simply disconnecting the fluorescent ballast. The long 40,000 hour life (L70) lamps are available in 11W, 2-foot and 22W, 4-foot versions saving up to 30% in energy costs over 17W and 32W fluorescent lamps, respectively. There are a variety of color temperatures 2700K, 3000K, 3500K, 4100K and 5000K to choose from and good color rendering properties with a 84-87 CRI.

»www.sylvania.com/en-us/products/···mps.aspx

Florescent tubes work by ionizing mercury. Once the filament burned out I assume line voltage would be able to maintain an arc, since we are only talking about a half inch between filament supports. With nothing limiting current (assuming socket is directly wired to mains) the end will get very hot very quickly and probably shatter. All this will probably occur at current and time-frames that will not trip circuit over-current protection. But that is just a guess.

Someone up for an experiment?

/tom
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