T8 vs T5 HO vs (maybe) LED?

[FourOaks]

What kind of radius do the leds cover?


This topic has got me really considering leds to some degree. We have had so many gray days that my plants are really starting to suffer out in the greenhouses. Im thinking some kind of supplemental lighting in the future might be necessary.

[Greatgardens]

Originally Posted by Tiny Tim

Just bought one of these from Wally's. Never used this style LED before. If anyone has, how far from tops of seedlings?

This one?

https://www.walmart.com/ip/Lights-of...light/46808020

They have a zillion on their web site. This one looks very nice -- pull chain and everything!

-GG

[GoDawgs]

After reading some discussions online about T12's vs T8's and others, I decided to replace four of my six very old T12 florescents with T8's. It was a good time to do that as the tubes needed replacing anyway.

Then I read that some folks use two kinds of tubes in one fixture to cover a wide light spectrum so I did that too. Each fixture has a daylight bulb (6500k) and a warm white tube (3000k). Both are 32 watts.

I do believe that the seedlings are doing better but I have noticed I need to check moisture levels a lot more often as the T8's are warmer than the old cool whites I was using.

I also have detected a very very slight leaning of seedlings towards the daylight tube so the trays just get turned around. All in all I'm satisfied. Got everything at Lowes as Home Depot didn't have near the selection. Two fixtures and four tubes plus tax for the first came to $58.67 for the first two sets so I decided a few days later to just go ahead and get two more sets.

[decherdt]

I missed out on the whole T12 - T8 generation.
I've used a Kill-a-watt and a photometer app on my Pixel to check what systems I have. T5 and LED floods. <--these LED are not what I hoped. d'oh.
I prefer the results of the 12000 lux T5 over the 35000 lux LED flood.


Left
T5 12000 lux

Right
LED Flood 35000 lux

[FourOaks]

GoDawgs... you will be satisfied with the T8s. They are a leap forward from the T12s, thats for sure. Just watch out for leaf burn. I didnt think it was possible, but believe me, it is.


Im at that point where an upgrade is somewhat inevitable. T5s vs LED. Or even possibly HID lighting.


I need some supplemental lighting in the seedling house. Im looking for something to hang from the purlins. Whether its HID, T5, LED...

[FourOaks]

Originally Posted by decherdt

I missed out on the whole T12 - T8 generation.
I've used a Kill-a-watt and a photometer app on my Pixel to check what systems I have. T5 and LED floods. <--these LED are not what I hoped. d'oh.
I prefer the results of the 12000 lux T5 over the 35000 lux LED flood.


Left
T5 12000 lux

Right
LED Flood 35000 lux

Very interesting data you have there, with pics to back up. Thanks for posting. Im curious, did you take measurements of how close the lights were to the flats? Or could you take a guess as to the distance?

[Tiny Tim]

Al@NC I do run larger LED's. My Mars 300 watt I keep 12" from tops. My Mars II 400 watt I keep at about 24 inches for seedlings. It's the light spectrum that burns the plant not the heat with LED's. I've just never run this low watt strip type of LED. Thanks bower. this is a 5000k. I have it at about 8" and it has burnt the tips of my onions Other then that, the tomato's, peppers and eggplants look ok.

[Tiny Tim]

Greatgardens, that is the light I have. It's very well made. Extruded aluminum body, ends are plastic. Mine's on a timer. But, the pull chain works smoothly.

[Tiny Tim]

FourOaks. I have and run LED's and HPS. HPS runs HOT. Nothing like a LED or Fluorescent fixture. I need to run my exhaust fan constantly. They do penetrate a bit deeper into your canopy. Spread or coverage is about the same with my MarsII 400 watt, 190 actual watt LED and my magnetic ballast 250 watt HPS.

[Al@NC]

Originally Posted by Tiny Tim

It's the light spectrum that burns the plant not the heat with LED's. I've just never run this low watt strip type of LED.

Yeah, the LED I have doesn't put off any heat hardly, I was thinking the same thing..

Al

[decherdt]

Originally Posted by FourOaks

....did you take measurements of how close the lights were to the flats? Or could you take a guess as to the distance?

About 1 to 2 inches above the plants. Maybe too close for the flood light.
Had seen this http://www.tomatoville.com/showthrea...758#post534758 and got a few to fiddle with, but I may be done with flood light, no real need to reinvent the LED

[oakley]

Originally Posted by bower

4500 lumens is a lot compared to the typical fluorescent, iirc my 6500 k comes in at 3750 lumens for the pair. The LED lights I bought this year are 4000 lumens. I did have some ?? scorchy leaves ?? on certain brassicas under the LED but don't know for sure if that was the cause.

If it was me, I think I'd set up at least 8 inches to a foot above the seedlings, and wait to see the effects. If they're stretching to get closer, bring it down. But I'm only guessing.

Not a bad guess. I'm thinking some minor scorching is what happened here. Not on
the thick rugosas micro toms, but some of my micro sunflowers jumped up a bit
beyond micro and have some burn. I'm keeping all starts at 5-7inch, not 2-4.

[FourOaks]

Originally Posted by Tiny Tim

FourOaks. I have and run LED's and HPS. HPS runs HOT. Nothing like a LED or Fluorescent fixture. I need to run my exhaust fan constantly. They do penetrate a bit deeper into your canopy. Spread or coverage is about the same with my MarsII 400 watt, 190 actual watt LED and my magnetic ballast 250 watt HPS.

Question. What happens if you dont run an exhaust fan? Will it damage the bulb itself?


My use would probably be different then most folks. Im thinking hang the lights from the Green House Purlins. So, they are more or less out in the open. Not enclosed in a tent. I would think that I could benefit from the heat, as it would be captured inside the greenhouse.

These would only be during gray cloudy days when its cooler anyways, and during the dark days of winter, when its cooler and the days are much, much shorter.

[bower]

Wow... there is certainly lots to learn about tweaking my grow lights. The LED's are different for sure, even with the small increase in lumens. Just taking some pics for comparisons and looking for scorched leaves again - and I did find some, only on the plants that were just recently moved under the lights (too many choy, these were languishing on a windowledge until last week).

OTOH the bok choy that were scorched a few weeks ago have completely recovered, and grew right up to the lights, not a blemish to be seen on those leaves. Also the leeks have come back after their first haircut and are now growing up around the lights with no adverse effect.

Showing a pic of what I am thinking as "scorched" that is spots without chlorophyll. I don't know if the affected leaves can recover or not, because I nipped the bad bits when it happened first.

[bower]

Also thought I would compare the LED bok choy with the same generation under a fluorescent 6500 K in my cold window. This is west facing and does get afternoon sun when we have it.
First pic is how it looked a couple days ago with yu choy on the left. The light is some inches higher above the plants than it is in the LED row.
Second pic I brought the LED plants out - two on the left, compared with the three on the right which have been under the fluorescent + occasional sunshine. The LED plants are stockier with fatter stems. One of the plants under fluorescent is starting to bolt, another one has reached a leaf right up there. I've been thinking of this window as my 'coldest spot' but I'm realizing it is really my 'extremes' spot. Colder at night, for sure, but also the temp as well as the lumens can go way up there on a sunny day. Since bok choy is apt to bolt, the LED setup which gets a little morning sun at most looks like the better choice. Then again, the height of the lamps may have played a role too, with more growth focused on reaching for the light.

Last not least, getting a lot of mileage out of my second LED which is quite high above the plants on a white shelf. The chinese cabbage showing no stress reaching for lights. I could do better for the cut-and-come-again trays which have been bitten down numerous times already, but they aren't doing too bad in the circumstances, better than I would expect!