Efficient Sunritek T8-style LED

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naoki

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There have been LED light bulbs which can be used in place of T8 fluorescent light bubls. Until recently, the efficiencies of these were not so great. But there are quite a few new crops of bulbs with impressive specifications. I recently got one of the most efficient model (147 lm/W and very inexpensive), so here is the test report. I've been mostly using COB-type DIY LEDs (most recent types), which achieve higher efficiency than most commercial products. But this kind of T8-LED could be a game changer. In comparison, efficacy of T5HO and T8 is around 90 lm/W, and T5 (normal output) is around 100 lm/W.

The product is by Sunritek, model# ST-DTA12-12WC (3000K or 4000K) (the info in the website is a bit outdated, but they can send better info if you contact them).

Background:
There are mainly 2 (+1) types of T8 LED bulbs.
  1. The first type simply fits to the pre-existing fluorescent T8 fixture (like shop light) without any modification. This types REQUIRES working fluorescent ballast.
  2. The other type requires minor (super-simple) re-wiring of fixture (basically you are disconnecting the ballast).
  3. Then there is something called a "hybrid" type which can be used with or without the fluorescent ballast.
I personally prefer the 2nd type, direct-wiring, ballast-free models. The ballast wastes energy (so overall efficiency is lower with the first type), and if the ballast breaks, you need to replace the ballast. A lot of cheap shop lights have cheap ballasts which breaks over time, and I have 10's of broken shoplights. I'm actually glad I have saved those broken shop lights because I can get rid of the ballast and re-use it with direct-wire type LEDs.

Last week, I saw the first type with a relatively good spec. in HomeDepot (Philips InstaFit 4000K, $25, 1600lumen, 12W, 133lm/W). I'm not familiar with this kind, but this would be a very nice fit for people who doesn't want to do modification.

False advertisement:
There are lots of LED companies which advertise bogus performance specifications. Especially, you needs to be careful with those from ebay and Alibaba. But even from these sources, there are some decent companies. The following DoE "Lighting Fact" database contains many products tested by 3rd parties, so one can check the fact from false advertisement.

http://www.lightingfacts.com

By checking the database, Sunritek appears to be an honest company. Sunritek ST-DTA12-12WC(4000K), which we are talking here, is almost at the top efficiency (147.09 lumen/W). This is seriously amazing efficiency. Also, DoE CALiPER report for Linear (T8) LED is a good read, and contains the data from the previous Sunritek model as the top performer.

Cost
I initially contacted the company via Alibaba, but I think you can use the email which is listed here. The only way to get these at this time seems to be factory direct. I got 20x 4' bulbs ($10 each), and the shipping was $95 with UPS. Then WesterUnion Transfer fee was $30. So $325 total for 20 bulbs ($16.25 per bulb). It is a whole-saler, but they sent me "samples" (no minimum order quantity). Since the shipping is expensive, it is only cost effective if you place a large quantity order (maybe a group buy?).

Customization/order options:
There are several customization options.

  • Wattage: 12W, 15W, 18W
  • Case style: Aluminum back (DTA series) or all polycarbonate case (DTP series)
  • Efficiency range: there are lower efficiency options, but you want to specify the top efficiency 140-150lm/W.
  • Diffuser: clear (no diffuser) or diffuser (which provide more even light, but reduce the total output)
  • Wiring: single-ended vs double-ended
  • Color temp: 3000K, 4000K, 5000K etc.
The person who helped me was really easy to communicate, and helpful to decide which option to tak(PM me if you want to get her email).

Comments about the options:
  • I went with 12W because it has the maximum efficiency. As you go higher, you'll get more total output, but the efficiency goes down. With 18W, the efficiency goes down to slightly below 140lm/W (still very good).
  • From my measurement, aluminum back DTA series seems to be slightly better than plastic DTP series.
  • I chose clear (no diffuser) to get maximum efficiency.
  • Single-ended is easier to wire than double ended in my opinion.
  • I went with 3000K (which is probably a slightly better option from my measurement below) and 4000K.

Measurement:
I measured at 12" from the tube (not from the LED surface) in the very middle of the tube. Each value for the T8LED is the average of two different light bulbs. I measured only once for the T5HO and 2 bulb T8LED setup. I used LX1330B for footcandles, and Li-Cor LI-190A for the Photosynthetic Photon Flux Density (PPFD, unit= micromol/m^2/s). I tested DTA (aluminum) 3000K and 4000K and DTP (plastic) 4000K. Room temp was 69F.

Code: 
             watt  PPFD footcandle PPFD/W
DTA(3000K)   13    42.8     275    3.29
DTA(4000K)   13.1  42.0     294    3.21
DTP(4000K)   13.3  38.5     255    2.89
2xDTA(3000K) 25.8  82       485    3.18
T5HO(4100K) ~50    83       590    1.66
T5HO(5000K) ~50    85       625    1.7

The T5HO bulbs were brandnew Philips F54T5/841/HO/ALTO (4', 54W, 4100K) and F43T5/850/HO/ALTO (4', 54W, 5000K), which were about $10 from HomeDepot. After the initial output, the output of florescent light decays. I did use a regular 4-bulb T5HO fixture with reflectors. The energy consumption for T5HO is calculated from the consumption from 4-bulb fixture, which consumed 200W with all 4 bulbs in. If you put only 1 bulb in the 4-bulb fixture, the actual wattage is about 70W.

Interpretation:

Pretty impressive! Basically a shoplight with 2 of ST-DTA12-12WC(3000K) gives similar intensity as a single bulb of T5HO at 12". Note PPFD is the relevant column, and footcandles doesn't matter much. So 26W of LED is enough to replace 54W T5HO (about 50W energy consumption in reality)! Now from the luminous efficacy number of T5HO (around 90lm/W), T8 LED is about 63% more efficient. The additional advantage of LED comes from the fact that T5HO emits the light in 360-degree and some lights are wasted.

Also the bulbs doesn't heat up at all! When you touch, you can feel slightly warm. This is a great advantage for growing plants.

Technical spec:
Each tube consists of 120pcs of Epistar SMD2835, driven each at 35mA/each. 15W version uses same number of LEDs at 41.5mA (so slightly less efficient in theory). I checked the Epistar datasheet, and the efficiency number matches with the datasheet.

Step-by-step conversion of a shop light

Well, it is super simple to rewire, but here is how I did it. It actually makes it as if it is a complicated process, though....

  1. Here is how the bulbs are packed.
  2. Remove the 2 (or 3 screws) to open the shoplight.
  3. This is how it look like inside. The box is the ballast, which I need to remove. Left side of the ballast, you can see the "tombstone" (fluorescent lamp holder), the place where bulbs get attached. From the bottom of the fixture, you can see the AC-plug wire coming in. There are 3 wires from this AC-main in. Green is "ground" connected to the pin of the AC plug. Black one is the "Live/Hot", connected to the smaller blade of AC plug. White one is "Neutral", connected to the larger blade of the AC plug.
  4. First cut the Live and Neutral wires from the ballast.
  5. I'm using an Ohm meter to confirm that the black in Live and white is Neutral.

(continue...)
 
Last edited:
(Part 2)

  1. When you look at the end of T8LED, one end has "L" and "N" marks. Basically all you have to do is connect the AC power (Live/Hot) to "L" and AC Power (Neutral) to "N". The other end of the bulb has 2 pins, but these are not electrically connected to anywhere. That end is just to retain the bulb to the fixture. This design is "single-ended" because all of the wiring is done in the tombston of one end of the bulb. Sunritek can make "double-ended" (one end of the bulb is connected to AC Neutral and the other end is to AC Live).
  2. When you look at the tombstone, there are two blade which make the connection to the light bulbs. Below the blade, the two left holes are connected to the left blade, and 2 right holes are connected to the right blade. Currently two blue wires are going into the two outside holes.
  3. The trickiest part of the conversion is to remove the wires from the tombstones. I pushed in something like a paperclip (you need to use a pretty thick paperclip), then pulled the wire out. Sometime, I can get the wires out by twisting and pulling the wires gradually without inserting anything.
  4. After the wires are removed, I'm making sure the right and left blades are not internally connected. This is called a non-shunted tombstone. Most of them which I encountered are the correct non-shunted tombstones. But there are some shunted tombstone, where the two blades are bridged/connected. For the single-ended LED T8 bulbs, we need non-shunted, so you need to check it.
  5. This is how the finished wiring looks like. The AC neutral (white) is connected to one side of the tombstone, and AC Live (black) is connected to the other side of the same tombstone. Then you use the 2 remaining holes to make the connection to the second tombstone. This is basically a parallel circuit. I already removed the ballast in this photo.


    Code: 
    ASCII wiring diagram
            /----------------\
AC Live ------ L of bulb-1    \--- L of bulb-2
AC neut ------ N of bulb-1    /--- N of bulb-2
            \----------------/
  6. SMD2835
  7. Backside (label) of the bulb. The end with this sticker is the one which needs to get connected to AC.
  8. The one on the Left has the aluminum casing (DTA), the one on the right has the plastic casing (DTP).
  9. Comparison of DTA(3000K) (bottom) and DTP(4000K) (top). Note that the DTP has slight frosting.
  10. Because of the slight frosting of DTP (right), it looks brighter in this photo, but it is not the case from the measurement.

  11. The clear case part appears to function (creating a wider beam angle). This creates the stripy pattern you can see on the carpet here. But you can't see the pattern if the bulb is not too close to a flat surface and this isn't a problem in reality. DTP shows less pattern due to slight frosting.
  12. LX1330B lux/fc meter (left) and Li-Cor Quantum PAR meter (right). I think I was measuring 2 bulb per fixture setup in this reading.
 
Last edited:
Thanks, Tom. I hang out in some orcchid facebook groups, but I guess I could give a blog try. I've never done it, and I'm not sure if I have enough time to post lots, but it could be fun.

Here, these LED T8 tubes are deployed in my spare grow tent for quarantine/acclimation (4 LED tubes on the top and 2 at the bottom).


They are mostly from Bela Vista, Ooi Leng Sun and Malala imports from this spring/summer. I got very nice/healthy Paphs from Ooi (difficult to see but they are at the backside of the right most tray).
 
Thank you Naoki for your most informative thread!
I think there will be similar LED solutions for T5 fixtures some day...
 
Naoki I am using those + 1 year with good results,i grow a full room of 5 x 4 meters,with about 1000 plants inside(many miniatures and seedlings) from november to may more or less...results are great!!!Obviously you cannot grow everithing with those but nearly...
 
valenzino said:
Naoki I am using those + 1 year with good results,i grow a full room of 5 x 4 meters,with about 1000 plants inside(many miniatures and seedlings) from november to may more or less...results are great!!!Obviously you cannot grow everithing with those but nearly...
Click to expand...

I'm glad to hear that it is working well for you, Valenino! For a large scale operation, small increase in efficiency makes a big difference. Anyway, with the extra saving, I should have a couple hundred dollars extra every year to buy more plants! :)

Ray, one advantage of T5HO is the high density application. The skinny bulbs of T5HO can be packed to give lots of PPFD. 6-bulb T5HO fixture can fit in a 4'x2' grow tent (area) if the heat issue can be resolved. To get the similar total output, you need 12-bulbs of this 12W T8 LEDs. If you use a 4'x2' plywood as the backboard, and screw the tombstones tightly, you can pack T8LED (because it doesn't need reflectors). But with the modified shop lights, 6 bulbs are the max for 4'x2' grow tent. If you need more output, you could sacrifice the efficiency a little bit and get 18W version of Sunritek.

I'm going to place the T8-LED pretty close to plants, just like how it was with fluorescent T8. But we don't have to worry about burning (from heat). With T5HO, I have to make some distance between plants and the bulbs. So with T5HO, it is easier to water, and it can be easier to accomodate tall and short plants in the same shelf.

From the PPFD values, I'm pretty sure that I can grow most of the orchids by putting 6x 12W bulbs per 4x2' (4x is probably better with lower light plants like Paphs and Phals).
 
Is there any LED lights that I can just buy and use right out of the box without having to go through all this work?
It might be nothing for some, but for me, it is too much hassle to go through.

By the way, how much distance do you leave between your T5HO and the plants?

Also, is the difference (efficiency on plant growth) between T5 and T5HO significant?

What is the average life span of the ballast?
Shorter than the light bulbs or longer?
I heard someone saying their T5 light bulbs last over one year and some as long as three even? By then, I would think the efficiency is not too good anymore.

What would you recommend for 48"W x 24"D shelf?
I don't have any yet, but it will most likely be something I will try in the near future and I want to be ready before I get to it, so I don't rush or freak out with my plants not having lights in a new home. lol

Heat is the main concern for T5, hence I'm wanting to use LED.
 
Happypaphy7 said:
Is there any LED lights that I can just buy and use right out of the box without having to go through all this work?
It might be nothing for some, but for me, it is too much hassle to go through.
Click to expand...

How about Philips InstaFit 4000K, $25, 1600lumen, 12W, 133lm/W, which I mentioned in the original post?
http://www.homedepot.com/p/Philips-...-4000K-Linear-LED-Light-Bulb-453852/205807273

I don't have any experience with this particular T8-LED bulb, but the spec seems to be great (and Philips is a good LED company). To cover 4x2' area, about 4 of them are good (for Paphs). You can probably get a cheap T8 shop light to put them in, and no modification required. Initially it will be similar cost (about $120 total) to 4 bulb T5HO.

Happypaphy7 said:
By the way, how much distance do you leave between your T5HO and the plants?
Click to expand...

I think I keep around 15" with 3-4 bulbs. But I have only the higher light Paphs (P. philippinense, P. druryi) under T5HO now. Cattleya is within 12". For typical Paphs, they seem to be ok with lower amount (less bulbs or more distance).

Happypaphy7 said:
Also, is the difference (efficiency on plant growth) between T5 and T5HO significant?
Click to expand...
T5 normal output can be around 100lm/W while T5HO is about 10% less. But the total output of T5HO is about 2x of T5. T8 has the similar efficiency as T5HO, but the total output is similar to T5. The tricky thing about T5 type vs T8 is that they respond differently to the temperature. Under cooler condition, the efficiency of T5-type decreases more rapidly. Since all of them are fluorescent bulbs, effects on plants should be similar.

Happypaphy7 said:
What is the average life span of the ballast?
Shorter than the light bulbs or longer?
I heard someone saying their T5 light bulbs last over one year and some as long as three even? By then, I would think the efficiency is not too good anymore.
Click to expand...

The ballast longevity somewhat depends on the quality of ballasts. For example, there are quite a bit of variation in quality of electrolytic capacitors and resisters. When I disassembled broken ballasts, I saw these components blown. But the ballast longevity is definitely much longer than the longevity of fluorescent bulbs. I have used T5HO for only 3-4 years, and there is no failure in 3 units. With cheap T8, some fails early (like 2-3 years), but many survives for a long time. I guess Exponential probability distribution in action.

I think I posted a thread about fluorescent bulb longevity where I found out that the decay of T5HO output was faster than what I have expected. Now, I've been following the decay more closely. It appears that some of them decay much quicker than others. Or the operating environment may have a major impact. For example, Odyssea 24W plant bulbs appeared to have lost the output (in terms of PPFD) by 22% in 3-5 months. Agrobrite 6400K 24W lost output by 44% in 2 years. But these 24W bulbs were operating at a higher temp because it was sitting on a glass of the enclosure directly (not much air flow around the bulbs). I'm following with Philips F54T5/841 now, and it has lost 10% or so in a half year (I don't have the exact number now). This one is operating with free air flow around the bulbs. I'll eventually post the detail next winter or so.

But maybe 1-2 year is reasonable for T5HO bulbs.

Happypaphy7 said:
What would you recommend for 48"W x 24"D shelf?
I don't have any yet, but it will most likely be something I will try in the near future and I want to be ready before I get to it, so I don't rush or freak out with my plants not having lights in a new home. lol

Heat is the main concern for T5, hence I'm wanting to use LED.
Click to expand...

To be honest, most anything will work as long as you give sufficient amount of light (PAR). 4 bulbs of T8, T5, or T8-LED, or 2 bulbs of T5HO, etc. Some geeks (including me) like to discuss small details :p, but you probably don't have to over-think too much! Heat is an issue if you have lots of fixtures, or if you have them in an enclosure like a grow tent. For Paphs, I don't think you have to worry too much about the heat if you are growing on the open shelves. I personally like to minimize my environmental impact, but for a few fixtures, you might not need to worry too much about the efficiency. Also the LED technology is advancing pretty rapidly, so there will be always better efficiency stuff for the next couple years.
 
Thank you for nice detailed answer.
I love geeks because they do the thinking for me. hahaha

It is great to know that I could buy those lights at HD, and we have two here. :)

Regarding the distance between the plants and the light source, that is measured from the top of the plants to the light, not from the base of the pots to the light, correct?
I heard people saying 6", but that distance sounds great because for one, I don't like the appearance when the plants are too close to the light, and two I want space for the spikes and all.

I did not know about the impact of temperature on the light bulbs.
When you say cool, how cool are we talking?

For LEDs, I wouldn't have to worry about heat, and the longevity of them should be longer than T5, right?
 
Actually, the distance (between the top of the leaves and the bulbs) with T5HO was about 12" or less with 4 bulbs, and Cattleyas were more like 8-10" (I think they became taller). So it is probably around 180 micromol/m^2/s at 12". I usually try to get around 100 micromol/m^2/s (or slightly more) for typical Paphs. With around 12 hours of day light (I use a little longer), the cumulative amount of light (Daily Light Integral) is roughly 750-1000fc of "noon" time peak intensity in a greenhouse (you multiply micromol/m^2/s by 7.5-10). So to get 100 micromol/m^2/s with 4 bulb T5HO, you'll need to reduce the number of bulbs and use 12" or you need to give more distance. One of the reasons why I'm using 100 micromol/m^2/s is posted in this thread. But you can give more light before the leaf "burn" or something called "photo-inhibition" starts to occur.

With the temperature and T5 effieciency, this page might be helpful. I realized this when one student was doing a growth chamber experiment at relatively low (i.e. Alaskan temperature, I think it was 15-20C). The T8 system in the chamber broke, so I told her to put a couple T5HO fixture in it. But the total output became extremely low. With Paph conditions, I don't think you have to worry about it. But with high altitude cool-cold growing orchids, this could be an issue.

In theory, (well designed) LEDs should have much better lumen maintenance than fluorescent bulbs. But the fixtures driving LEDs hard (i.e. cheap crap) may fail earlier than expected, though.
 

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