Correct Hieght for HID

I keep getting mixed reviews about how close you should place your HID above your plants...

I understand the problems with Heat and how that should be a factor and all but, I keep reading contradictive or non conclusive advice.

I usually start my seedlings under flouro, and move them under my MH then HPS... all the time gradually moving the lights closer day by day until they are as close as the Heat will allow, however, this time I'm starting them directly under the 400mh, I've read where some people say 2-3ft, some say as close 1ft 1/2 or less, the faq says it shouldn't be closer than about 4ft

It's my first time going from straight germ seed to under 400, so I don't want to Nuke the Girls... I know they should be able to handle the light as they pop up and adjust, but I'm unsure and don't want to fuck this Up, I'm already streseed with the PH problems I had before, so I'm trying to reduce the room for Error,

Thanks N advance for any Advice/Help

i was always told about 18 inches

I just started a round of seedlings bout a week ago with my 400w MH. Its about 3 1/2 feet from the plants right now. They are working on their 3rd set of true leaves and are about 3 or 4 inches tall. I'll gradually work the light down so that it about 20 inches above tops at the 2 1/2 week marker. Good rule of thumb is to use the bottom of your forearm to gauge the heat from the light. If it feels past comfortable after 45 seconds at a given distance, its too close.

Ok, thanks guys. I'll just start it around 3 1/2 and Work it Down like normally to about 18" or less using the hand under light test method as usual. I just didn't want to have it closer than needed and cause unneccessary stress.

Thanks for Your Input ++rep

If you had them under floros or they are seedlings, you'll want to keep them a few feet away at first until they're adjusted to that intense light, and gradually bring them closer to the light. Seedlings can handle 400 watts, just not too close the first two weeks.

Brazko said:

I keep getting mixed reviews about how close you should place your HID above your plants...

I understand the problems with Heat and how that should be a factor and all but, I keep reading contradictive or non conclusive advice.

I usually start my seedlings under flouro, and move them under my MH then HPS... all the time gradually moving the lights closer day by day until they are as close as the Heat will allow, however, this time I'm starting them directly under the 400mh, I've read where some people say 2-3ft, some say as close 1ft 1/2 or less, the faq says it shouldn't be closer than about 4ft

It's my first time going from straight germ seed to under 400, so I don't want to Nuke the Girls... I know they should be able to handle the light as they pop up and adjust, but I'm unsure and don't want to fuck this Up, I'm already streseed with the PH problems I had before, so I'm trying to reduce the room for Error,

Thanks N advance for any Advice/Help

Click to expand...

This might help...

nice charts gohydro. I've never seen any like those before.

Yep those Charts are pretty Useful (printing them out Now), Knowing what is within Optimum range was exactly what I was looking for. Now I know exactly how far I should start my lights (a few have already suggested some of these ranges) and how close I should be able to work them down too as the Girls begin to Mature... Great Help Thanks, and 2 All

for seedlings.... i would figure they are good and ready. I would think if you can keep your hand close to the bulb without being uncomfortable you will be good to go. especially with flourescents. want to keep them close.

grobofotwanky said:

nice charts gohydro. I've never seen any like those before.

Click to expand...

You're welcome! Just remember that those refer to lumen output and have nothing to do with the heat generated. Ventilate those HID fixtures, keep em cool and you're good to go.

HID's do wonders when you can get em close......these are at 23 days of 12/12

The sun is a lot more intense than that Metal Halide and marijuana loves it. I'd say put it 1ft away and not any closer because of the heat... not until they are big enough and then u can put it as close as you can. Generally i keep the lights close until i notice leaves closest to the lights starting to change a little, then i move them a few inches away and keep them at that distance once i know what the plant can handle.

Redeflect said:

The sun is a lot more intense than that Metal Halide and marijuana loves it. I'd say put it 1ft away and not any closer because of the heat... not until they are big enough and then u can put it as close as you can. Generally i keep the lights close until i notice leaves closest to the lights starting to change a little, then i move them a few inches away and keep them at that distance once i know what the plant can handle.

Click to expand...

Sure Will, Right now I have them around 20", and will probably try to move them as close as a ft or less, I usually have them as close as a foot R less anyway but I always start them under CfL's until they are about 3-4nodes strong, then I begin to introduce them to the HID's.. I went overkill trying to adjust my PH (roller coasting), lesson learned, plus the PH solution I used (Spa time) I believe was very toxic forming (especially w/ my nutes), So I tossed that and went with a more conventional Hydro PH solution & everything is going fine Now.

Being the first time w/ going straight under the 400, I kind of had an understanding that being under the MH/HPS would probably do no harm and be great, b/c like said it's not close to being stronger than the Sun.. However, I was Traumatized , and was going to make every effort to check / recheck my information, in Which everyone has been helpful and I'm reassured I am on the right track once again, Thanks for your Input as Well, Every bit has been Useful..

Thanks

Personally, I've found my best plants were grown when they were each about an inch under a daylight 100 cfl for the first few weeks. They grow amazingly large fan leaves and are 2x as long across as they are tall (as in, 8 nodes by the time they are 6 inches tall). I've tried lots of plants under my HPS from start and it never worked out very well unless i had them close. It's only 150watt but i dont need much and it gets the job done. Anything more than 18 inches from the light stretches pretty bad(about 1 node every 5 inches). I'd say for your 400 watt NEVER put plants more than 2 feet away unless u want bad stretching. Personally, I'd say for a seedling keep them within 12-18 inches and you can't go wrong.

Also, basic physics means light decreases by distance squared. Your Metal Halide at 1 ft is giving just as much intensity to the top-growing part of the plant as a 100watt CFL at 2 inches. If you are keeping that Metal Halide at almost 2 ft, you might as well put them each under a 100watt CFL with less than 4 inches.


This was a 1 month old Strawberry Cough plant using only 2 100watt CFL's. It was an awesome plant. I've tried outdoing it by vegging under HPS and they never come close. The point is, CFL's work excellent for veg as long as you keep the distance small.

I hear ya, but I've never had problems w/ stretching, The Biggest Gap I've ever had while vegging was about an 1" 1/2 maybe, under flouros and that was b/c of blackouts most of the time. This go around I had them only a couple 2 a few cm apart . However, that was after I germed them until their first true set of leaves under CFL's. I was 4-5nodes strong on each, even topped them, I was a Happy camper...That was when I ventured into New territory and everything went to Shit .

So upon, tuning Up my knowledge on Fertilizing, I ran across how others were just germing and going under their Big lights... I had a pretty good understanding, but this was New Territory as well, so lesson was learned, and precautionary steps were taken..

Right now I feel comfortable with the lighting where it's at. So far only 2 have showed , Once the others pop and show, I'll begin to decrease downward until the Heat is unbearable.. I can already see a significant difference in the stem and germ leaves, usually this is where I have the most visible stretching to begin with, and it is quite the opposite, short/stocky as I can see the first set of true leaves beginning to open up .

Cfl's are great, especially for the Vegging cycle, I would suggest cfl's to any person, however, I''m jealous of others who have the thick, short, stocky, dark green plants going from day 1...I feel this method would promote better structure and allow the plants to have a better yield as the Outcome.. So after this rodeo, I definitely will be adhering to your advice and others which has been well noted, but right now I need 2 observe and gain the experience, and Right now I'm at an Optimum point of Comfort,

Thanks,

I believe the recommended max height for 400 is 18", I have my light @ 20", over naked baskets except 2.. I think they will be alright, No point in turning Back Now

If my Plant looked like that, I would probably already been within a foot.. Also, HPS are not good for vegging, they get the job done, but they promote upward growth.... MH and daylight Cfl's are what is needed for healthy vegging

gohydro said:

You're welcome! Just remember that those refer to lumen output and have nothing to do with the heat generated. Ventilate those HID fixtures, keep em cool and you're good to go.

HID's do wonders when you can get em close......these are at 23 days of 12/12

Click to expand...

I have the vented reflectors with glass and I can keep them10-12 inches from plants..
the difference of the vented reflectors in night and day..I turned my lights on before I hooked up the exhaust vent and they were too hot to touch..now hooked up, there just warm to the touch as most of the heat excapes