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What distance should my light be from my plants?

TBayChronic

New Member
For 26-watt CFLs? An inch above established plants, with a fan placed so as to carry away the heat that they produce (yes, CFLs produce heat; for the wattage/light-output, quite a bit, lol).
What if I don't have a fan? And how high do I put the light while there sprouting
 

Siscokid

Member of the Month: Feb 2012
What if I don't have a fan? And how high do I put the light while there sprouting
Hope you got yourself a fan...it's important for them to have air movement around it..

I use Cfl's for sprouts and veg. I always put them real close to the light, sometimes they get a little burned from the bulb...no biggie.
 

risi

New Member
I have 1 Stage projector and 1 HPS Light looking at my young plants. They are so cute. Actually lights are about 1 meters away from plants I also have air-conditioner set to 25°C and fan that blows little bit. I don't know if fan and air-conditioner should be turned on. I check every day and my plants are still very healthy I guess I am doing right.

Please give me some suggestions if its ok to use fan and air-conditioner.
 

HighNoon

New Member
Need help from the Gyru's

I've been out of the game for about 6 years, a lot of change has happened. What's best, HID or LED, Specialized grow tents. I don't want to mess with paint, sanitize, light locking a room. So I'm pretty sure I'm going tent. I also like the SCROG method, lots of potential based on an old idea. I've got a $800 budget for my new grow room. All of my old supplies are 1200 miles away and scary looking I'm sure. This is a list of equipment I plan on buying (I don't feel like build stuff from 2x4 and space blankets)


Ulti-lumenx 400w Hps/mh High Pressure Sodium Metal Halide Electronic Digital Grow Lights System w/ Timer

16" Adjustable Pedestal Black fan

Broan Model 512 6-Inch Through Wall Utility Fan, 90 CFM, 3.5

Ambient Weather WS-0101 Wireless Thermo-Hygrometer with Indoor Temperature and Outdoor Temperature and Humidity

HM Digital TDS-EZ Meter/Tester, Water/ppm/Purity/Filter

Marina 75 Air Pump

General Hydroponics PH Down Qt. - ACID

General hydroponic PH CONTROL - BASE-

Belkin 6-Outlet Home/Office Surge Protector

Standard 3/16" Flexible Airline Tubing for Aquariums, 8 feet

Deluxe Bubble Disk® 5" Aerating Aquarium Ornament - Penn-Plax®

General Hydroponics GH1514 Ph Control Kit - Hydrofarm

Lux WIN100 Heating & Cooling Programmable Outlet Thermostat

General Hydroponics Eco Grower Max

GE 15153 Heavy Duty 24-Hour Mechanical timer

LED Wholesalers GYO1008 76-Inch x 48-Inch x 48-Inch Mylar Reflective Hydroponic Grow Tent

General Hydroponics Flora Series QT - FloraGro, FloraBloom, and FloraMicro - General Hydroponics

I like 400 watt HID, adjustable hood, 4' x 4' tent, and GH chems. I'm also a fan of their EcoGrower Max.

I need help on light height from plants as they grow, water/nutrient level in hydro system, air flow - this system will change the air every 1 1/2 min is that too much if such a thing. How often to change out water? I also saw "light movers" anyone use them, how do they compare?

Tell me I'm wrong, I'm missing something, or tricks. I'm hopping to start remembering what I used to do and ways to tweak it. I'm buying package fully Thursday so if I need more let me know. Everything in my list you can google to look at it to put it together in your head.

Thank you for your time.
 

StonerJ

New Member
My first hydro using some bag seed so low risk. 400W MH w/ integral ballast, air cooled with tempered glass lens. The temp is low enough to get the plant tops up to within an inch or two of the light, currently at 8" from top of larger plant. These two plants are 35 days from germination. The plant on the right is a week ahead of the one on the left which had pushed itself out of the rooting cube. After a week of fooling with it trying to get it to root in the cube while the other plant was taking off, I finally threaded the taproot directly into the hydraton and the next day it took off.

DWC 5 gal bubbler, Light cycle is 18/6, Nutes - Technaflora varying from 1000-1500ppm, solution temp @ 67 degrees, room temps 74 max (light on) min 64 (light off), pH @ 5.9, RH @ 55%. Drinking 1/2 gal of pH corrected distilled water daily.

http://www.420magazine.com/gallery/data/500/P3030003.JPG

:thumb:
 

HighNoon

New Member
I've got 2 fans, both rated at 370 cfm, one exhaust one intake, both variable speed. Temp seams to sablize around 79.5*F drip system running but I'm not going to plant until I get temps down a little. Wind meter says they are pushing close to what they say they can do.

What else can I try without getting a portable a/c?

Will the temps come down after I plant?
 

Spicy2na

New Member
I've got 2 fans, both rated at 370 cfm, one exhaust one intake, both variable speed. Temp seams to sablize around 79.5*F drip system running but I'm not going to plant until I get temps down a little. Wind meter says they are pushing close to what they say they can do.

What else can I try without getting a portable a/c?

Will the temps come down after I plant?
What size room/tent are you growing in? I never force air in my grow rooms. Only use an exhaust and draw in air. You can actually do more damage with an intake depending on your setup. If its a tent, I'd recommend removing the intake fan or just use it as a circulation fan inside the tent.
 

vangs

New Member
For (artificial) light, there is a law that always applies known as the Inverse Square Law. It states that light diminishes exponentially in energy as the distance is increased from the source.

A good example is that you might be getting 1000 PAR Watts at 4" from your light source, but that would change to 250 PAR Watts at double the distance (8"). This law makes it EXTREMELY important for indoor plant growers to get their light source as close as possible to their plants. The amount of light your plant receives is directly related to it's yield/flower density.

The problem: Indoor lamps used for plant cultivation (HID - High Intensity Discharge) give off large amounts of heat, to such a degree that they could cause damage to the plant if put too close.

Indoors, there is an optimum distance/height between the plants and the light source. This distance fully illuminates the whole canopy with direct light from the source, but is as close as possible to the plants for maximum lumen intensity. This will be called the OLH, for Optimum Lamp Height.

Ultimately, to get the best light efficiency from your lamp, you want it at the OLH at all costs. But how can you get it there without causing harm to your plants with the abundant heat?

First, try moving your light to the OLH and see what it does to your plants. If they have no problem, then you're fine. If you have a high output HID, this probably won't be enough.

Next, try actively exhausting your light hood by hooking up a direct exhaust system to the hood, and then move your lamp to the OLH and see if the plants are O.K. If the plants still seemed affected by the heat, then you must add glass to your actively exhausted lamp hood. Glass will absorb/reflect/filter some of the light energy being emitted by the lamp.

The number would seem relatively low, around 2-3% of PAR wattage, but it will effectively filter out almost all of what little UV-B is emmitted by the lamp. UV-B is believed, and has been shown, to have a positive influence on the potency of Cannabis.

Overall, it would be beneficial for one to add glass if needed to keep their lamp at the OLH, due to the all-powerful Inverse Square Law; moving light farther away will greatly reduce the amount of energy being emitted and is reaching your plants (Light intensity is directly related to yield and flower density).

Almost all glass offered today for insertion in air-cooled lamp hoods is tempered glass, which is regular glass with low amounts of impurities. If one was looking for the most efficient glass for their hood, quartz glass will allow the transmission of UV-B, but is not made specifically for light hoods.

And also remember, that if you have a rectangular garden, it is important to position the longest side of the reflector parallel to the shortest side of your garden. (from FAQ by Head Rush)

Additional note: you should periodically inspect and clean your light hood and bulbs, especially after foliar feeding or underleaf spraying for insects. The dust and dirt that collects will definitely decrease reflectivity. Isopropanol alcohol, glass cleaner or water (and a soft cloth) can all be used to remove streaks, dust and spots.

Contributed by: MedMan

There are a number of factors which play a part in the temperature radiated from your bulb, watts, hood design and air circulation for example.

A simple method of testing for temperature is to use the back of your hand; if its too hot for your hand, its too hot for your plants. Good ventilation is the key to getting your light closer to the garden.

Editor's note:

Recommended typical OLH distances:

Flourescentsroximimty
400w HPS: 1 foot
600w HPS: 1.5 foot
1000w HPS: 2 foot

Author: BobbyDigital
i have 2 plants, first grow. the plants grew larger than i could estimate. i use a 1000w ups, and i cant raise it any higher. its currently about 8-12inches away from the glass.. im assuming the tops colas are too close to the light but idk what to do because the plant is over 4 feet tall. so if i reduce the 1000w to 600w im worried it wont reach the bottom of the plants... its a 4x4 tent... 3 plants but the 3rd is a runt, well over 2ft away so im not worried about that.. the tent is sealed and cooled with an ac and ket at 73F. but the top of the plants are taking longer to load crystals. it seems like the bottom of the plants are gaining crystals alot faster than the top of the plants.. both plants.. is it because the light is too close to the light??? i dont want the tops to burn. but i dont want to have no yield on the bottom. would u reduce the light to 600w or keep it at 1000w and just hope for the best???
 

BuckeyeFoodie

New Member
I need some help from the grow-light masters - I'm a veggie grower who has always bought my tricky plants (tomatoes, broccoli, basically anything that isn't a squash) established from a nursery and just planted them out, but because I'm bored with the standard varieties I'm going to try growing some wild varieties from seed. And I've spent upwards of $100 on seeds, so I really don't want to fuck this up...

I need your help badly.

I tried planting from seed last year and it was a complete disaster - leggy seedlings, nothing that established beyond the first leaves. I know now that I didn't have enough light last year using two 60 wt can lights that were too far up, so I've gone out and gotten a better set-up (4ft T5 fluorescents).

My questions are how high from the surface of my planting medium should I start the lights? and then do I just keep raising the bulbs so that they're that initial amount from the tops of the seedlings? Or is there some other method to follow? I tried making sense of the initial post in the thread, but it just gave me a headache!

Any help you all could give me would be fabulous!
 

lykarckstar

New Member
I also just began my first grow from clones . Used diff bulbs : one for Veg and one for flower. I had my clones in Veg for 12 days until i saw each one had pistols forming. then changed the bulb and the timer to 12/12. During Veg I had the lamp ( air cooled 400 W ) 24" and they seemed to love it so I would do that OLH again. Now that I am in Flower I wasnt sure at first so I had it 24" but after reading more i moved it 12" and after 2 full Flower days and them seem to be very happy. On another note DO NOT OVER WATER espec in veg ... its easy to do.
 

WizHigh

Member of the Month: Dec 2012
I need some help from the grow-light masters - I'm a veggie grower who has always bought my tricky plants (tomatoes, broccoli, basically anything that isn't a squash) established from a nursery and just planted them out, but because I'm bored with the standard varieties I'm going to try growing some wild varieties from seed. And I've spent upwards of $100 on seeds, so I really don't want to fuck this up...

I need your help badly.

I tried planting from seed last year and it was a complete disaster - leggy seedlings, nothing that established beyond the first leaves. I know now that I didn't have enough light last year using two 60 wt can lights that were too far up, so I've gone out and gotten a better set-up (4ft T5 fluorescents).

My questions are how high from the surface of my planting medium should I start the lights? and then do I just keep raising the bulbs so that they're that initial amount from the tops of the seedlings? Or is there some other method to follow? I tried making sense of the initial post in the thread, but it just gave me a headache!

Any help you all could give me would be fabulous!

I would run my T5 about a foot over my dome since that what I use to germinate. And from there I wont adjust the light until they start to grow closer to it. once they get there 4th - 5th set of true leaves you can lower the light to about 5-10inches away. And adjust threw growth.
 

bmiles6

New Member
yes i believe so , ive grown with LED and they do work but it takes twice as long ... the best thing about them is that they r cheep to run and dnt cause much heat. i now grow with hps and LED to get the best of both worlds .
What kind of led light did you have? Do you think the ufo led light would do a better job?
 

Smoke2Js

Nug of the Month: Jan, May 2013 - Plant of the Month: June 2013
How high do you want your plants to grow? Set the light at that height, and leave it. when during veg the plant is 1/2 way to the lights, switch to flower, and double the amount of light. Look at BIG pro grows, all the real pros hang their lights high and don't move them. Their buds are just fine, in fact they are perfect. The plants won't over heat, spend less time transpiring and more time growing. You save water and electricity, and your plants will be better than ever. Nuf said, you can dispute this with grows of awesome buds with hella close lights and over stressed plants, but the plants are running from the light. Your fan leaves will tell you. If they are droopy and "everything is right" check your light distance. Better yet, place a clean piece of metal at the top of the growing medium( in full light if possible) during lights on, come back in an hour and touch it. Warning ,it will be hella hot!! And your tops are even hotter. if you want to grow under a 1000 hps, get a 400 watt bulb for veg, switch to 1000 watts for flower, you will be stunned at how much better your plants look, grow and smoke.
http://ga.water.usgs.gov/edu/watercycleevapotranspiration.html
 

Yblaster2k

New Member
Im using 600 watt MH right now... I have AC blowing through my house but my grow room seems to be hotter than the rest of the house... Im currently at 82 degreees Faranheit and my light is about 3 feet above my seedlings.... If i move it any lower it hits around 90 degrees,

I do have a fan hitting the walls and circulating... I have a feeling it's too hot and the seedlings will rot.


Please, anyone help!
 

Droseph

New Member
Im using 600 watt MH right now... I have AC blowing through my house but my grow room seems to be hotter than the rest of the house... Im currently at 82 degreees Faranheit and my light is about 3 feet above my seedlings.... If i move it any lower it hits around 90 degrees,

I do have a fan hitting the walls and circulating... I have a feeling it's too hot and the seedlings will rot.


Please, anyone help!
I've been dealing with a similar situation, but with a 1000w MH. There was a heatwave in my area recently so it's been a chore to keep the temps at leaf level under control.

Building an air-cooled hood with the exhaust going out of my room really helped, going from 90+ to 80! The more fans you can get pumping hot air out of that room the better. Putting the plants on the floor and bringing the light to them also helped. Even if doing something only helps you out 1 degree, you are closer to your ideal temp and it's worth it.

I would say 82 degrees is not the end of the world. Mine seem OK at a steady 80. Obviously lower is ideal. The the more sativa-leaning plants seemed to take the heat better than the indica. For a short period, maybe 6-8 hours my room reached 86f, that was enough to notice some curling and yellowing.

If you are just dealing with seedlings, I would just grab a couple of 100w cfls for now until I could dial in that large light.
 
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