Matching physical size, wattage, hours/day etc.

14 years ago

I want to grow lettuces, spinach, and herbs, not necessarily at the same time indoors under light, hydroponically.

I am thinking about something like this 24" hex DWC system with a 400 MH lamp.

http://www.hydroponics.net/i/211142

http://www.hydroponics.net/i/133440

Still figuring it all out, but how many hours per day do these types of plants look for under artificial light, how far away should I be from the plants, and is 400 MH a good choice for this size system? I would almost think 250 watts would be better, but I don't see a lot of 250 watt MH "systems" (although they do sell 250 watt MH bulbs, I don't know if 250 MH bulbs go into these reflectors; it says they are compatible with 400 watt and up).

I am a little shabby on my geometry but I think a 24" hex fits inside a 48" square so it is about 16 sq ft including empty space, which seems to be the recommended size for 400 watt lamps. Using a square for calcs, since I can't obtain a hex shaped reflector, that gives me about 400 watts / 16 sq ft = 25 watts per sq ft.

On the other hand, 250 watts * 18 hours is the same KW/H as 400 watts * 12 hours, so same "energy" to me, but which is better for the plants.

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Comments (4)

art33
14 years ago
Hi pj,

Well, I've never used that type of lighting so I can't be much help when it comes to the wattage etc. (although it does seem like an awful lot of light just to grow lettuce and spinach). Anyway, my reason for answering your post is really in regard to your calculations :-) Maybe I'm just misunderstanding what you're saying, but the area of a regular 24 inch hexagon is 2.6 square feet. Even a square around it would be only 4 square feet. That's a long way from the 16 square feet you mentioned isn't it?

Art
pjcampo
Original Author
14 years ago
here is a link to the item. I do not know much about it.
http://www.hydroponics.net/i/211142

I believe it's 4 foot across at the longest point.

It holds 36 - 2" pots or 18 - 3". I was going to try 36.
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pjcampo
Original Author
14 years ago
I guess what I meant was that the sides are 24". I imagine the hex, while seemingly inefficient space wise, holds the water better structurally.
art33
14 years ago
Okay, I see what you mean now, and you could be right. If each side is 24 inches, it would be about 4 feet across. I was going by the dimensions they gave (24 X 24 x 24) and assumed they meant that the unit was 24 inches across and 24 inches high (each side being about 12 inches). Judging from the 2 inch grow cups pictured, that also looked about right. Nice looking unit in any case and hope you get all the info you need about it. Sorry I can't be much help but someone will probably come along who can.

Art