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HPS or MH


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  #1  
Old 05-04-2016, 09:47 AM
Rye Rye is offline
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Default HPS or MH

I read through the light info page, Here but still have a question about which light, an hps or MH, that specific plants prefer.

Currently I am using 400w t5 jump starter light to grow my Kale. This system is only 3 weeks old at this point. I am looking to upgrade to a better light system, and found one for sale used locally. It's an apollo 1000w system. I have read where it's not advisable to use the dimmer function on this ballast as the lights don't work right when you do.

My questions are, given as lettuce type plants are low light, if I am growing Romaine, spinach, and kale, will a 1000w burn them? Second, given as MH, and HPS each favor one end of the spectrum, which end does lettuce prefer? Red or blue?

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Old 05-05-2016, 03:08 AM
GpsFrontier GpsFrontier is offline
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Hello Rye,
First, I could be wrong but I think your statement "I am using 400w t5 jump starter light" is wrong. Each 4 foot T5 bulb is 53 watts. 400 watts would mean your fixture has 8 bulbs. If you actually do have 8 bulbs and 400 watts of T5 florescent lighting, that's plenty to grow lettuce.

Quote:
if I am growing Romaine, spinach, and kale, will a 1000w burn them?
It depends on how close the light fixture is to the plant. Any bulb can burn the plants if the bulb is to close. If you can hold your hand near the foliage, and it doesn't feel to hot it should be fine. If it is hot, the bulbs are to close.

Quote:
given as MH, and hps each favor one end of the spectrum, which end does lettuce prefer? Red or blue?
Blue....
MH (metal halide) mimics the high summer sun and promotes more of the vegetative growth. Since the goal of growing lettuce is vegetative growth, and not the flowering/fruiting cycle, the better choice for growing lettuce would be MH (the blue end of the spectrum).

HPS (high pressure sodium) mimics the late summer sun. When the sun is lower in the sky. Because of the suns lower angle the sun's rays have to pass through more of the earths atmosphere. The atmosphere causes the change in spectrum. Plants have evolved over billions of years and know when the days get shorter and the light spectrum shifts towards the red side, summer is about over and it's time to fruit/flower before winter sets in.

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I am looking to upgrade to a better light system, and found one for sale used locally. It's an apollo 1000w system.
How much are you planing on growing? A 1,000 watt light is going to be expensive to run. Have you given any thought to whether you will be making your money back or costing you more to grow than buy. What's the point of growing your own head of lettuce if it costs you $6 to grow, and only costs you $1 to buy it at the store.

I pay 9.3 cents per kilowatt hour. National average is 10 cents. A quick rundown using what I pay, this is what it will cost:

1,000 watts for 18 hours a day= $1.67 per day to run.
$1.67 x 30 days= $50.10 per month

The ballasts uses electricity as well, typically between 8 and 15% of the bulbs wattage. Using 10% of the bulbs wattage for the ballets= 100 more watts
100 watts for 18 hours a day= $0.17 per day, x30= $5.10 per month.

Just the lights alone will cost around $55.20 to run (using 9.3 cents per kilowatt hour), and that is just for the lights. That doesn't include fans for air circulation, nutrients and pH adjusters, pumps etc... If your not going to be growing and consuming $100 worth of produce each month you'll be loosing money.
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  #3  
Old 05-05-2016, 12:23 PM
Rye Rye is offline
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You bring about some great points. With the lights running so much electricity, is it really worth it?
My first run with the kratky is just a learning evolution about what to do and not do. Several times in the setup of this, I've considered whether it was worth the cost, because running my 54w light( You were right, it isn't 400) and fan seems to burn a lot of juice.

I am going to order an apollo 400w light and hook that up and run it over my system. The kale is growing for now, but I get the feeling, and from what I have read, that my lighting is stunting or slowing the growth.

Thank you again for the informative answer to my questions GPS. I wish I could contribute more to the conversation to liven the board up.. but as I am 25 days into my first attempt, i don't have anything but questions right now.
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Old 05-05-2016, 11:23 PM
GpsFrontier GpsFrontier is offline
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Hello Rye,
Cost vs reward is always on my mind. For me growing hydroponically is first and foremost about being economical. I like to say who wants/cares about growing a $20 tomato when you can buy them for $3 a lb at the store. That's just a waste of time and money, and I'm not interested in wasting either. There will always be a learning curve for new hydroponic growers. Even if your used to growing plants in soil like I was before I started growing hydroponically. The first few grows for anybody growing hydroponically are always really just an experiment and learning experience (me included). In the beginning cost isn't really the main concern, the first grows are just a benchmark for future success (and failures). But as your success evolves and as you gain experience along the learning curve, focus begins to shift from simple success to economics. Once you know success is not only possible, it's able to be repeated and predictable every time, the question then becomes how to do it more efficiently and cost effective.

I don't know the wattage of the fan your using, but the 54 watt bulb running 18 hours a day costs about $0.09 a day/ $2.70 a month to run (using the 9.3 cents per kilowatt hour that I'm paying). I use this simple online electricity cost calculator to calculate/estimate costs. You just need to fill in what you pay per kilowatt hr, the wattage, and how long you plan to run it, then click calculate. Typically 4 to 6 "T"5' bulbs would be enough to grow enough lettuce type plants for a family of 4 (naturally that depends on how much they eat). If you make good use space, space the plants well, rotate plants efficiently (new seedlings in as you harvest), it could be well worth the money and effort to grow your own this way.

Six of these bulbs would cost about $16.20 a month to run. So it would be economical to do if they spend $5 or more on lettuce a week. You could even drop the cost to run by 1/3 (to $10.80 a month) using only 4 "T"5' bulbs. Growth may be a little slower, and spacing a little tighter, but if your not eating that much lettuce, you don't need as much space to grow it anyway. You can also run "T"8's, instead of "T"5's to even out the lighting over a larger space. You need more T8's to get the same light intensity, but their only 32 watts each instead of 54. So 6 T5= 324 watts, and 10 T8= 320 watts. While the 10 T8 gives you about the same light intensity as the 6 T5's, and the wattage is essentially the same, the extra bulbs can give you a couple extra sq feet to work with depending on the growth rate and spacing of your plants.

P.S.
Don't worry about it, just add whatever you have to share whenever you want, and if all you have are questions, ask your questions. That's what forums are for. All I had were questions in the beginning too. In fact that's exactly why I joined this forum, to ask questions. Unfortunately for me most of the answers I got were only from spammers trying to sell products or drive traffic to their blogs. So I did a lot of research on my own. You don't need to worry about spammers now, their usually deleted within 24 hours so they rarely even bother trying anymore.
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Last edited by GpsFrontier; 05-05-2016 at 11:41 PM.
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  #5  
Old 05-30-2016, 09:52 AM
Rye Rye is offline
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I ended up going with a 400 watt MH light and the plants took off immediately. Thanks for your help! Learning a ton here and hoping to move from my Kratky system to a 100 slot NFT at the end of the summer. Going to start building it soon.

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