Questions about CFLs...

[Josh]

Hey guys and gals,
After checking out some of your photos I have come to the conclusion that I should build a germination/grow chamber for the 2010 season. I was thinking about using CFLs. I guess my first question is how many lumens should you provide for a standard 72 cell tray? I keep seeing "initial lumens" in bulb descriptions. What does this mean exactly?
I was also wondering if it would be better to have multiple bulbs or fewer bulbs? My original thought was that multiple bulbs would be better because it would seem to more evenly distribute the light.
Any and all suggestions would be appreciated.

 

[TXCG]

I'd say go with the 42 watt cfls. Most lumens for your dollar.

They say "initial lumens" because light performance degrades over time. Same with any bulb really.

Don't know what to tell you as far as lumens for the 72 cell thing, but i can tell you about 40watts per square foot should be plenty to grow the seedlings pretty large.

 

[wordwiz]

Only a 72-cell tray? j/k

In time, those 72 plants, unless you plan on weeding out half of them, are going to require about 4 times the amount of space - I'm guessing about 24" x 27" minimum. Last year, I had a space that was about 34"x30" and I used four 23-25 watt bulbs - hung horizontally - and the plants grew very nicely.

YMMV,

Mike

 

[thepodpiper]

Josh, what are you trying to accomplish with your light setup? Are you just growing them to transplant outside or are you looking to grow all year long?

Dale

 

[Josh]

I'd say go with the 42 watt cfls. Most lumens for your dollar.

They say "initial lumens" because light performance degrades over time. Same with any bulb really.

Don't know what to tell you as far as lumens for the 72 cell thing, but i can tell you about 40watts per square foot should be plenty to grow the seedlings pretty large.

So I guess if you wanted 10,000 lumens your initial lumen output should be higher to compensate for the degredation?

Only a 72-cell tray? j/k

In time, those 72 plants, unless you plan on weeding out half of them, are going to require about 4 times the amount of space - I'm guessing about 24" x 27" minimum. Last year, I had a space that was about 34"x30" and I used four 23-25 watt bulbs - hung horizontally - and the plants grew very nicely.

YMMV,

Mike

I was planning on making the box larger than a 72 cell tray but I figured I could use that as a standard for the lighting and then multiply once I figure out the dimensions. At most I am looking to put 25 plants in this. I would then have backups growing much slower in front of windows.

Josh, what are you trying to accomplish with your light setup? Are you just growing them to transplant outside or are you looking to grow all year long?

Dale

Just looking to grow them until I transplant them outside in the middle of May.

 

[wordwiz]

I'm not sure initial lumens is appropriate to CFLs. They tend to get brighter after they are on for a couple of minutes. But as for degradation - that happens over a few years if you are only using them for a couple of months.

IMO, 100 watts of CFL bulbs, be them 23-25 or 42 watt will be plenty for your grow space, especially if you use reflective material on the walls and top or paint them flat white.

Mike

 

[Pepper Ridge Farm]

Josh there is lots good advise here already in this thread and I agree 100 percent that CFL's are the way to go if you plan to just grow them until they go outside. You need to get one of those light fixtures that goes in your bathroom that holds 6 lights. Why wait until next year still plenty of time to get some great plants started for 2009. You just have to find out what works for you. We all have a little different way of doing things, but we all want the same result. CFL lighting is the best way for someone as yourself just looking to get some nice looking seedling.

 

[AlabamaJack]

Josh...I don't know how much space you have. I agree with what others have said.

my 2 cents....

You need to decide which lighting you are going to be using first, then build your chamber to match the lighting. I use 2 standard shop light fixtures with T-12 40 watt 6500K bulbs in my germinator for the first couple of weeks. The chambers dimensions are 2' high X 2' deep X 4' long. You can fit four 72 cell trays in this chamber. I can grow seedlings to 6" in the chamber easily but after that height with the leaves, the plants need to have more room....IMO...CFLs create more heat than standard fluoros do so take that into consideration also.

After a couple of weeks, if I want them to grow slowly, I move them to a grow area with the same light available as the chamber. If I want/need them to grow faster, I move them to my grow box that is 4 feet square and has somewhere in the neighborhood of 60K lumens from 320 watts standard T-12 40 fluoros with a mixture of 6500K and 4100K bulbs and 756 watts of 2700K 42 Watt CFLs.

Make sure you build it big enough for a small fan to circulate the air and "rustle" the leaves. Movement of the seedlings by air (or even brushing your hand across them a couple times a day) will make the stems stronger. The movement increases cell stiffness in the stems.

Temperature needs to be steady around 80-86F for best results so you want some way to control the temp. Depending on how well you insulate and "seal" the chamber, you may be able to keep that temperature using just the heat from the lights and not worry about an additional heat source. The most expensive single item I bought was a remote bulb thermostat which is a thermostat with a lead wire that you can put in your soil. Remember, it is soil temperature you are concerned with and not air temperature. If the chamber is sealed pretty good, once equlibrium is reached (air to soil), it is easy to maintain the temp you want.

Your main concern will be the timing of planting seeds to hardening off/planting out. If you plant out the middle of may, you don't need to start your seeds until the first to middle of march, the middle of february at the earliest or else you will run into the problem of you seedlings, especially annuums and tomatos getting too tall for your grow area.

 

[RowBear]

Josh-
Here is a couple of pics of my current setup. In the corner of my garage I mounted brackets for shelves and made a tent using 3 "Emergency Space Blankets." I have a window behind that acts as a solar heater. I made a small germination box out of scrap plywood that will hold two 72 cell trays. I have 4 CFL's mounted in the box along with a thermostat controlled heating mat. In my case I need this much lighting and heat in the germination box to keep my soil temp and air temps in the 85 degree(F) range. My garage is unheated. When my plants are a bit taller they will go on a shelf above the germination box and be under a 4 ft. 40 Watt Fixture.

 

[millworkman]

Rowbear, thats a pretty good setup. What size are your heating mats?

 

[RowBear]

In the bottom of the box, I have 300 Watt Water bed Heater(Overkill). The lower lights heat the top shelf.

 

[bigt]

I like the results from Cappy's 400w Metal Halide - but that setup isn't cheap and Cappy is probably right about just getting good looking seedlings to go outside. I've had decent results in the past with some crappy looking seedlings just barely surviving and going outside in May. But then sometimes you don't get pods until August-Sept. It would be nice to have some early pods in June for once so that's why a head start inside is good IMO. Anyway, saw this chart from a weed growing site:

CFL Lumens/Watt

105w - 65.714
85w - 58.823 (49.412)
65w - 52.308
55w - 65.454
42w - 66.667
40w - 66.25
32w - 65.625
30w - 66.667
27w - 64.815

-the 42 watt has the highest Lumens per watt value. My setup this year has one 40w grow light 4ft tube with 1700 lumens and that's not close to enough.

 

[AlabamaJack]

I knew I was using the 42 watt ones for some reason (other than that is the biggest I could get at homus depos )

 

[wordwiz]

I figure a minimum of 3500 lumens per square foot for seedlings. Eight sq. ft. needs 28,000 lumens. I really believe that all things being equal, such as I could by two 50 watt bulbs for the same price as one 100 watt (fixtures included) I would go with two bulbs so the light can be better distributed.

Mike

 

[bigt]

I like the results from Cappy's 400w Metal Halide - but that setup isn't cheap and Cappy is probably right about just getting good looking seedlings to go outside. I've had decent results in the past with some crappy looking seedlings just barely surviving and going outside in May. But then sometimes you don't get pods until August-Sept. It would be nice to have some early pods in June for once so that's why a head start inside is good IMO. Anyway, saw this chart from a weed growing site:

CFL Lumens/Watt

105w - 65.714
85w - 58.823 (49.412)
65w - 52.308
55w - 65.454
42w - 66.667
40w - 66.25
32w - 65.625
30w - 66.667
27w - 64.815

-the 42 watt has the highest Lumens per watt value. My setup this year has one 40w grow light 4ft tube with 1700 lumens and that's not close to enough.

Oops - I was wrong - it's actually 1900 lumens. Big deal. And the wrong spectrum for growth - 6500K - Promotes Overall Plant Growth, 2700K - Promotes Flowering and Budding.
Now I'm ticked off I even bought the damn tube. I going out to the garage and take down my dual tube shop lights. Maybe that will get the ball rolling. Can't be worse.

 

[Josh]

I'm not sure initial lumens is appropriate to CFLs. They tend to get brighter after they are on for a couple of minutes. But as for degradation - that happens over a few years if you are only using them for a couple of months.

IMO, 100 watts of CFL bulbs, be them 23-25 or 42 watt will be plenty for your grow space, especially if you use reflective material on the walls and top or paint them flat white.

Mike

Well I was looking at the 27 watt 6500k ones and it said 1,850 initial lumens. So I was thinking 6 of these would give me 11,100 lumens. It would draw 162 watts which wouldn't be too bad.

You need to get one of those light fixtures that goes in your bathroom that holds 6 lights. Why wait until next year still plenty of time to get some great plants started for 2009.

I was thinking about getting those cheap porcelin lamps that mount to the ceiling. I have seen them used in basements. Only like $1.50 each. I would have to wire them all up but that is no big deal. I would love to build the box this weekend, but I don't want to rush into it. I figure take my time, think it through, and build it this fall/winter. That way I will be happy with the end result.

Josh...I don't know how much space you have.

You need to decide which lighting you are going to be using first, then build your chamber to match the lighting. CFLs create more heat than standard fluoros do so take that into consideration also.

Make sure you build it big enough for a small fan to circulate the air and "rustle" the leaves.

Temperature needs to be steady around 80-86F for best results so you want some way to control the temp. Depending on how well you insulate and "seal" the chamber, you may be able to keep that temperature using just the heat from the lights and not worry about an additional heat source.

Your main concern will be the timing of planting seeds to hardening off/planting out.

In terms of space, I will be building this in my basement. So I was thinking possibly 2' deep, 3' tall, and 3&1/2' long. I was originally thinking about using t5 tube fixtures but thought I could pack more power into a smaller area with the CFLs. I was thinking about using (6) 27 watt bulbs but if it turns out to not be enough I could always go bigger. The fact that the CFLs get hotter than the tubes is a plus. It is cool in my basement so hopefully like you said the lights in combination with a germination pad will be able to keep the box heated. the 3&1/2' length accounts for the room needed for the fan. Besides making the plants strong I figure the air flow probably also will help cut down on damping off problems.
If the plants get too big for the box I can always put them in my small sunroom.

Josh-
Here is a couple of pics of my current setup. In the corner of my garage I mounted brackets for shelves and made a tent using 3 "Emergency Space Blankets." I have a window behind that acts as a solar heater. I made a small germination box out of scrap plywood that will hold two 72 cell trays. I have 4 CFL's mounted in the box along with a thermostat controlled heating mat. In my case I need this much lighting and heat in the germination box to keep my soil temp and air temps in the 85 degree(F) range. My garage is unheated. When my plants are a bit taller they will go on a shelf above the germination box and be under a 4 ft. 40 Watt Fixture.

What are the specs. on your CFLs. I like how your box angles back allowing you to see the seedlings better.

Oops - I was wrong - it's actually 1900 lumens. Big deal. And the wrong spectrum for growth - 6500K - Promotes Overall Plant Growth, 2700K - Promotes Flowering and Budding.
Now I'm ticked off I even bought the damn tube. I going out to the garage and take down my dual tube shop lights. Maybe that will get the ball rolling. Can't be worse.

Thanks for the specs Tony. I am still not exactly sure what I am going to use. I have some ideas but I guess I need to crunch some more numbers and figure things out.

 

[AlabamaJack]

I was thinking about getting those cheap porcelin lamps that mount to the ceiling. I have seen them used in basements. Only like $1.50 each.

you mean like this? I have a 100 watt halogen bulb in it for heat and is what runs off the thermostat....

In terms of space, I will be building this in my basement. So I was thinking possibly 2' deep, 3' tall, and 3&1/2' long.

Just a recommendation...I assume you are going to use a couple 4 X 8 sheets of plywood to build this with...if you make it 4' wide, you will eliminate making waste of a few pieces of plywood and also reduce the number of cuts you have to make...(I'm Lazy)

 

[wordwiz]

Josh,

Last year, I was using a grow box that was about 2' deep, 3' long and 2.5' wide. Took a piece of plywood and a 2x6' piece of lumber that wan just under 3' long. Used screws so that it was attached - in the middle - of the plywood. I attached two outlets - the ceramic types you are talking about on each side of the 2x6, so the bulbs hung horizontally. I used 23-25 watt CFL bulbs and depending on whether I raised the plywood, I would get from 3200-6000 lumens at the plant canopy. During the dead of winter, when the upstairs temps were cool, I used Styrofoam on the sides and the chamber stayed above 85 degrees.

BTW, I also painted all the lumber with flat white paint which helped increase the lumens.

Mike

 

[wordwiz]

you mean like this? I have a 100 watt halogen bulb in it for heat and is what runs off the thermostat....


Just a recommendation...I assume you are going to use a couple 4 X 8 sheets of plywood to build this with...if you make it 4' wide, you will eliminate making waste of a few pieces of plywood and also reduce the number of cuts you have to make...(I'm Lazy)

And if you paint the walls white, use mylar or even staple white posterboard to cover the walls, your plants will get a lot more lumens.

Mike

 

[bigt]

Here's a good page with a ton of grow light options. http://www.expresslightbulbs.com/compact-fluorescent-cfl-grow-light-bulbs-p-2.html Might be worth checking out.