T5 vs T12?

[Justin]

For many years I have used T12 shoplights to grow Paph seedlings. I have 4x4' T12 bulbs for each shelf. The lights are about 12" above the plants.

With T-12's phasing out of production i am looking to try a T5 for my next lamp. For the equivalent lumens of four traditional 4' shoplight bulbs should I try twoT12 lamps?

Are two 4' HO T5 bulbs 12" above the plants too strong?

 

[eggshells]

No. Should be good a good distance from your multis. On barbatas I find them a little bright that just one is enough.

 

[consettbay2003]

I assume you mean should I try two T5 lamps. 12" is much too close even for multiflorals.

 

[MorandiWine]

HO T-5s can get warm though, watch out for leaf scorch. Why not try an LED tube array? No heat and they last "forever?"

tyler

 

[Justin]

i will check out the LEDs.

what about T8? less intensity? So a total of 2xT8 lamps 12" above the plants? over a 2'x'4' shelf.

 

[tnyr5]

Two 4-foot, 54w HO t5's with parabolic reflectors will easily replace a 4 bulb t12 system. I would keep the plants at least 2ft away, though. You can get a 4-bulb t5 fixture with reflectors from Home Depot. At 2 feet away, you should be in the 200 par range (in the area directly under the bulbs) with that fixture.

 

[naoki]

Tony, did you really measure 200 micro mol/m^2/s at 2 feet? If so, what kind of bulbs are you using?

Here is my measurement:
Fixture: Hydrofarm FLT-44 T5HO
bulbs: 3x AgroBrite 6400K 54W (pretty old), 1x Philips 4000K 54W from HomeDepot

185 micromol/m^2/s (Li-Cor LI-190) and 1410 fc (with LX1330B) @ 12"

With 1 bulb, the intensity is about 1/2.6, so 71 micromol/m^2 and 542.3 fc @ 12".

So 2-3 bulbs are the appropriate amount. I tried to get about 100 micromol/m^2/s for Paphs (and slightly lower for lower light Paphs).

Efficiency of T8 is similar to T5HO. T5 normal output is a bit more efficient (and T12 is very inefficient, but it can produce fair amount of light because it can be 40W). So you can just compare the wattage. T8 is 32W, T5HO is 54W. So two T8 gives similar output as one T5HO. Ballasts in some T12 fixture can handle T8.

4 bulbs of T8 could be slightly more economical (even though people incorrectly assume that T5HO is superior) if you don't need to achieve high intensity.

If you can do a little bit of simple wiring, DIY LED is cheaper. Here is a link, but there are more efficient versions announced and should be available within a month. About 2x 50W Bridgelux Vero 29 will cover 2x4' area.

 

[tnyr5]

Naoki,
I was guestimating based on what I remember from using t5's over reef aquariums. Maybe the HD reflectors/ballasts aren't as efficient, but I know with the aquarium fixtures, particularly the ATI powermodules, these numbers, or at least something close, were possible. Since you've got real data, I defer to your numbers.
I agree with you, though, that building an LED array is probably a superior alternative.

 

[naoki]

Thanks for the info, Tony. My measurement was from ordinary bulbs. When I measured my "plant" bulbs (purple one), it gave much better PPFD. So I knew that bulbs can make a big difference. But the bulb selection of T5HO is a bit limited (or they are too expensive to be worth it), so I was curious what your bulbs were.

 

[tnyr5]

The reef bulbs that could get those numbers were usually made by ATI, Geisemann, KZ, and UVL. They typically cost 25-30 dollars a bulb.

 

[AdamD]

I use a 4 bulb (2') setup for my seeldings, about 16- 18" above, blue spectrum, and I'd say they have the best colored leaves of all my paphs.

 

[polyantha]

Two 4-foot, 54w HO t5's with parabolic reflectors will easily replace a 4 bulb t12 system.

I agree, I use 4x54W T5's in the winter months per 2sq m and it is enough to even bloom multies.

 

[fibre]

I agree, I use 4x54W T5's in the winter months per 2sq m and it is enough to even bloom multies.

What is the distance between the tubes and the leaves and do you use reflectors?

 

[Justin]

i ended up going with a single shoplight fixture with 2 x 4' T8 lamps.

 

[polyantha]

What is the distance between the tubes and the leaves and do you use reflectors?

Sorry for the late reply. With reflector, 55cm over the highest leaf.

 

[fibre]

Thanks for the info. The distance of your bulbs is about double the distance of my 54W T5 HO. I grow P. niveum there - with reflectors.

 

[naoki]

But isn't polyantha using plant bulbs (I remember his post about the PS experiment with CO2 sensor)? From my measurement, a crappy plant bulb can emit 40% more light (PAR) than a 6400K bulb.

Odyssea Plant, 2', 24W (new): 88 micromol/m^2/s @ 12" (30cm)
AgroBrite 6400K, 2', 24W (new): 58 micromol/m^2/s @ 12" (30cm)

 

[fibre]

The bulbs I use for about two years now are Osram 54W T5 HO. These seem to be quite efficient. Most of my Paphs got yellow leaves, but I thought that the yellowing is because of a change in my fertilizer and the new substrate. Too many changes at the same time. An addition of Mg and Fe greened up most leaves but not all of them.