lightmaster-J,

There are several variations you can do with the 2-footers!

1) In any situation where you use a single 4-foot tube, you can substitute two 2-foot lamps in series.
        ballastwires ==[24"bulb]=[24"bulb]== ballastwires
Just make sure that you wire BOTH of the bulb-to-bulb pins together, and to one another. Connect the ballast-to-bulb pins as you normally would do for a 48" tube. This means that you can take a normal 2-lamp, 48" shoplight and create a 4-lamp, 24" fixture (with hardware modifications, obviously).

2) You can simply use two 24" lamps in place of two 48" lamps. This would require shortening the fixture. The 24" tubes would be overdriven a bit, and would be brighter.

BEST USE:
3) You can use the normal 2x overdrive method, but, instead of using a single 48" lamp, wire the two 24' lamps in series, as I mentioned above. That will overdrive two 24" lamps at the same time. They will be bright.

4) Wire up to overdrive a 48" lamp, except use a single 24" lamp instead. That is what you did. That is really bright.

Zink

I jumpered the pins and am overdriving 2 x 24" tubes with a single ballast (meant for 2 x 48" tubes). Been working great for a couple of months now. A little warmer but not much.
Tried the single 24" with the same ballast and just didn't see much difference, or at least not enough to warrant using a second ballast for the other tube.

Everything is growing and nothing has melted...success.

There is one thing I want to know.....

I am using a Sunpark SL15 ballast in it so I wired it like this:

[Lampholder]====2red/2blue wires==(BALLAST)==1red/blue/yellow wires====[Lampholder]

When it is running, I can see one end glow a faint orange and it turns off like a Metal Halide lamp. I can also smell the tube burning. It is the same with other F20T12 lamps I put in it, (Haven't tried T8 2 footers).

When I used a Sylvania 2 tube 4 foot Electonic ballast and wired it the same way (less wires of course...), It was about as bright but it didn't burn and I couldn't see any orange. I realized on the label that it can be used on F020, I am guessing that it means 20 Watt, 2 foot, T12.

I am also guessing that the sunpark SL15's can't really handle anything besides:

4'--F40T12, F34T12, F25T12, F32T8

-J-

lightmaster-J,

I am not sure what might be burning. Just make sure the OD wiring matches the diagram I posted at:
http://members.iglou.com/rons0z/lamps/ovdr.htm

The sockets should be wired like as in the
OVERDRIVING A 2-LAMP BALLAST >RAPID START >AFTER
graphic. That should work. If not, the ballast may be defective.

The lamps you listed are NOT the only lamps you can drive. I have used the Sunpark SL-15 ballast, in both normal and OD mode, to power a lot of different lamps. I have built fixtures which use the following lamps-
Medium Bi-pin Base:
F17T8, F30T8, F32T8, F20T12, F30T12, F40T12
Mini Bi-pin Base:
F54T5/HO
2G11 Base:
FT36W, FT40W, FT50W, FT55W

These are lamps I lit with the Sunpark SL-15, but did NOT build a fixture for:
F6T5, F24T12/HO, F48T12/HO, CFT13(T4), CFL26W(spiral), GE-F552D

I had a 26w spiral CFL with a bad ballast, took it apart, attached the SL-15, and VOILA, it worked fine - both normal and OD'ed.

Zink

I think I had the wiring as

YELLOW .
BLUE .
.
RED .

Does it really matter if the yellow is on the same side as the blue?

I know that when a normal T8 IS Electronic ballast's tubes go out, the burnt out end will usually arc an orange color before the cathode pops. Before I OD'd the SL15 I powered it with NEW 2 F20T12 and had the original wiring to it. It started up and began to arc at three ends, then the end-of-lamp-life-protection kicked in. I turned it off and it flashed. I turned it back on and it did the same thing. I don't have a problem when I use 4 foot T8's or T12's.

It may be defective because it is pretty noisy just like the other three out of the four SL15's; and last night I attempted an overdrive with 2 four foot tubes as a tandem.

---[LH] [tube] [LH]-Wire-[LH] [tube] [LH]---

It would light up most of the time, sometimes the EOLL Protection would kick in. I'll try the wiring of what the picture says and see what happens.

-J-

The RED and BLUE wire must be paired together on one side of the socket, and the YELLOW wire must be by itself on the other side!

This is a Rapid Start ballast. It sends a current through the filament to warm up the cathode before sending the starting voltage across the tube. That starting current goes from the RED/BLUE side, throught the filament, to the YELLOW side.

Pairing up the BLUE/YELLOW creates a SHORT! Been there - done that.

Zink

It was wired right and it was still doing it. I used another SL15 and it did the same thing. Could it also be that the tubes are cheaply made. They are a GE Chroma 50 and 3 Philips SPECT35. I decided to use a CE fixture with one SL15 and overdrive it. I put T8 tubes in it and hung it in my shop. It was way brighter than two of the slimline T12 75 watt fixtures.

-J-

sorry people but don't understand all this electrical jargon
How do you make a 48in fixture hold 24 in bulbs? why 24 in., why not overdrive 48in.?

derfy@sbcglobal.net

Home Depot has the following 4 foot two tube shoplights for $7.25 apiece.

Zink, do you know if these can be overdriven?

"ManufacturerÂ
Cordelia Lighting

Model #Â
HBSL-15

Color/FinishÂ
White

Ballast TypeÂ
Electronic, T8, MPF, Instant Start"

Well, I took the plunge.

I bought two of the HD $7.25 florescent fixtures and took them home.

Opened the box, and WHOO HOO ! Sunpark ballasts !

Needless to say, I have now joined the overdrive club.

And WOW, That's Bright !

The only downside is that I couldn't find Warm White tubes. So I got a Sunlight variety, and guess what, it's Warm White ! I hope to find regular warm whites in a box of ten somewhere, but HD ain't got 'em.

Tomorrow, I'm setting up my seed starter rack, and I'll probably go get another pair of Sunpark fixtures.

I did note that the two fixtures I got were off different assembly lines. Same ballast, fortunately, but different screw layouts.

Oh, and with these 'tombstone' fixtures, it's possible to pop off the back and more easily get the wires loose. I did try the wiggle-twist method but got only 50% success.

Jkirk...

I see I'm too late answering another one. I saw your post last night. I started to look up the info, mainly looking for an Instant Start version of that ballast, HBSL-15.

Is the info you listed above from the shoplights you bought, and overdrove? I was wondering if it was really an Instant Start ballast.

In any event, I'm glad you got it working. Try not to get addicted. I think some folks here have gone and bought 20 or more shoplights to OD. I can't remember who it was that did that many lights.

Zink

"Is the info you listed above from the shoplights you bought, and overdrove? I was wondering if it was really an Instant Start ballast."

A good point. I was expecting Cordelia ballasts, from the data on the HD webpage. Believe me, I was THRILLED to see Sunpark SL15 on the ballast.

And no, the wiring indicates these are Rapid Start, not Instant Start. I compared them to the page you linked to, and they ain't Instant Start.

But anyway, now anyone looking for Sunparks can mob Home Depot and clean them out before they can change suppliers.

Just keep out of the Mishawaka Indiana HD, I'm keeping that source for myself.

:)

And you might be right about addiction. I've been SAD for the last month or so. Sleeping late, and staring at the fire in our corn stove like it's a magic show. Can't get enough.

I plan to go get as many of these Sunparks as I can afford for my seedstarting rack and sit in front of it for an hour every morning until April.

Yesterday I pulled out the shoplights that I used last year for plants and I remembered that one of them was going out. It was a full spectrum I believe PHILIPS F40 DX. The left one was bluish and the one going out was orange in the center. Usually they are pink when they do that. Is it because of the spectrum?

-J-

So answer me this, I plan on overdriving a couple of my fixtures. Will one overdriven bulb produce more effective light than 2 bulbs that have not been overdriven? I just want to know so that I can overdrive a couple of 24" fixtures I have but I do not have a second ballast that I can put in there right now. So basically will the single bulb be more beneficial than to regular at least until I can afford to get a second ballast.

Cheers,
Sean

"So basically will the single bulb be more beneficial than to regular at least until I can afford to get a second ballast."

No, overdriving 2x usually gets you 170% output. So, two tubes are better than one.

However, the point of overdriving is being able to put the output of 6.8 tubes where you only have room for four.

If you only have room for one tube, then overdriving one would work, sure.

Technically, if you COULD pack in seven tubes into the same growing area of four that would be slightly better than over-driving four.

But doing that is pretty hard. Before I heard about over-driving I tried using reflective backing and thought about setting up three, two tube fixtures around a single tomato plant.

But even with these ideas, the plants I grew indoors in the winter were never happy.

I'm going to try again now that I know how to overdrive, thanks again, Zink.

To really pack in those bulbs, has anyone tried a setup like a stand-up tanning booth? You could have 360 degrees of tunes completely surrounding your plants. Wow, that would be bright!

Yes, I thought of that.

But with normal flourescents, a tomato plant can be almost touching the tube and still act as though it's in the dark.

So I decided to wait and see... and now I do !

I HAVE seen the Light !

> ....a GE Chroma 50 full spect tube...

This has a beautiful spectrum...for the human eye.

But the blue and red output slowly tapers off just before the "chlorophyll a" peaks (on the blue end, this is partly compensated by two blue mercury emission spikes). The GE Plant and Aquarium Wide spectrum bulb is a perfect complement; it peaks where the Chroma 50 dips and vice versa. The two together should replicate sunshine as the plant sees it.

I believe the Chroma 50 tube is identical to the GE "Sun" Tube, packaged in an orange/red cardboard sleeve, available at Wal-Mart (and in our part of the country, "Freddies").