# How close is too close w/ a 600?



## Relentless999 (Jun 26, 2009)

My 600mh is 20" above the tops of the plants.. I havent raised the light yet ad they are ofcourse getting taller and love the light.. I know of the hand test, but overall how close is too close? should it be 18" at the closest?
 thx

edit: plants are 3wks old from seeds and are looking great. how close should it be now, but how close is the closest i should get to the tops throughout flowering?


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## smokybear (Jun 26, 2009)

Is your 600 watt aircooled? If so, you should be able to get within 12-16 inches or so with it. I would use the hand test and just keep a close eye on the plants for the first few hours to make sure they don't burn. I run a 400 watt about 10 inches away from the tops with no problems and it isn't air-cooled or have a cooltube or anything. Just be careful with it! Hope this helps. Take care and be safe.


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## phatpharmer (Jun 26, 2009)

I get my 600w about 5 inches from mt plants canopy, I use a 6 inch 449cfm Vortex fan with a cool tube to cool my light and I've never had any issuse with heat! The temps with the light on is 24c and with the light off its 20c it works out nice!

                                          Phatpharmer


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## zipflip (Jun 26, 2009)

smokybear said:
			
		

> Is your 600 watt aircooled? If so, you should be able to get within 12-16 inches or so with it. I would use the hand test and just keep a close eye on the plants for the first few hours to make sure they don't burn. I run a 400 watt about 10 inches away from the tops with no problems and it isn't air-cooled or have a cooltube or anything. Just be careful with it! Hope this helps. Take care and be safe.


 
wats ur square footage of ya space?


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## Relentless999 (Jun 26, 2009)

heres more specs on my setup. please tell me more. thx guys.
600mh going to swap in my 600hps in a couple of weeks
3.2'x3.2'x6.6' homebox large
the 600 is in a big easy cool 6 air cooled hood with a 6" 424cfm fan sucking from  one end exhausting out the tent, and of course hooked to the other side of the tent for fresh air.. the tent also has a 4" fan with a carbon filter for tent exhaust.
the 600mh is 18" above the tops..

I have a homebox small, 2.6x2.6x3.9 and i have a 400mh in it with the light about 20" above the week old plants. the 400mh is in a easy cool 6 air cooled hood with a 4" carbon filter and fan.


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## Relentless999 (Jun 26, 2009)

sounds like I can bring the light down some..


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## phatpharmer (Jun 26, 2009)

Yeah if I were you I would bring it down, just do it alittle at a time and see how the plants react, what I do is I put a thermometer that measures temp and humidity at the top of my canopy, and it gives me a high and low reading as well so I no the high and low for the light cycle which is nice.


                                          Phatpharmer



PS> Remember the closer the better!


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## jmansweed (Jun 26, 2009)

One reason so many of us have switched to using 600 watt set ups over 1000 is because we can lower a 600 closer to a plant with-out burning it. A 1000 at 1 foot spreads about 140000 lumens, a 1000 at 2 feet will spread about 35000 lumens, a 600 at 1 foot is more like 115000 lumens. A 600 at 2 feet away spreads about 30000 lumens. Lumens make those little girls grow so naturally the more effecient 600 is a good choice. Cooling any thing bigger can be expensive and dropping a larger light uncooled will kill your plants. 

Anyway, I dont want to confuse you. Drop the light close and keep it cool. More lumens, more weed. 1 foot over the plants = 115000 lumens with a 600. good luck

I just reread some of your stuff, dont drop a 600 like I just said untill your plants are older. Smaller plants can be sensitive to larger lights. Raising the lights on newbies will make them stretch. High intensity Flouros with grow spectrum allow you to get lots of lumens to your plants while eliminating the intence heat and extreme spectrum, and gives you the ability to drop the bulbs close to your ladies.


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## Budking (Jun 26, 2009)

this is way easier...... dont move the light...keep it put.   Let the plants grow up to to the bulb on their own, watch them closely as they start to get closer to the bulb. When the tops of the plants look anythig less then perfect then raise it up a bit and u have found ur Min height specific to your heat and cooling senario:hubba:


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## phatpharmer (Jun 26, 2009)

Budking said:
			
		

> this is way easier...... dont move the light...keep it put. Let the plants grow up to to the bulb on their own, watch them closely as they start to get closer to the bulb. When the tops of the plants look anythig less then perfect then raise it up a bit and u have found ur Min height specific to your heat and cooling senario:hubba:


 

IMO the light should be as close as possible to the plants, its stops stretching plus you get fatter tighter buds! And as stated earlier the futher the lights away you start losing lumens! A 600w at 6in to 1ft away gives more lumens than a 600w thats 2ft away! Just my opinion though!


                                    Phatpharmer:hubba:


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## pcduck (Jun 26, 2009)

I have/use a 600 watt aircooled, my canopy is around 5" from the glass. I keep my light as close as possible to reduce stretch.

*phatpharmer* In order to get a true temperature reading shade your thermometer other wise you may be getting the temp of the heated plastic of the thermometer.


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## dman1234 (Jun 26, 2009)

the hand test is all you need.
if it burns your hand its too close.
 so drop the light a bit and put yur hand at top of canopy for 30 secs and you got it


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## dirtyolsouth (Jun 26, 2009)

Budking said:
			
		

> this is way easier...... dont move the light...keep it put.   Let the plants grow up to to the bulb on their own, watch them closely as they start to get closer to the bulb. When the tops of the plants look anythig less then perfect then raise it up a bit and u have found ur Min height specific to your heat and cooling senario:hubba:



Don't want to step on any toes Budking but IME this is a recipe for S-T-R-E-T-C-H-I-N-G  your girls... 

I'm with dman...   if you can put your hand at canopy level below the light and keep it there comfortably it's not too close.  If your hand gets too hot you need to raise it more and re-test.  If you keep your light close you'll have much better results.  Sure, every couple of days you gotta either raise the lights but you'll get not only better bud development at the canopy but much better light penetration throughout your plant.  That's why people love cool tubes...  heat control.  A Cool tube fixture/reflector is much more efficient to air cool and you can even keep a 1k safely at about 12 - 15" from your girls, especially if you're using an 8" ventilation system.  A fan blowing steady at canopy level helps keep things cooler for your plants too.  
 
R666...   jman speaks much wisdom...  let your babies get a bit bigger before you put them really close.  You can slowly get closer over time.  

Here's some info I've had on file for many years.  It's from Stonersforum...  The only thing that's not mentioned are cool tubes as the article was written in '04, before they became commonplace in the indoor garden.

Peace! 

Contributed by: *BobbyDigital*
Submitted: April 24th, 2004  

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.


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## PencilHead (Jun 26, 2009)

I'm with Phat and the Duck--I run 2 600watters and my tops stay about 5" inches off the glass.  I've scorched one on each grow slightly not paying attention during that fast stretch peiod.  

Actually, my problem is that I'd like to get them closer at finish but the lights won't cover that much territory down low once the plant has fallen open.  I usually end up around 8-10" from the top at finish trying to get those side buds some rays.  Peace and luck.


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## Timmyjg6 (Jun 26, 2009)

What i do to determine the height of my light from my plants is get a temp meter "usually one with a probe" and place it at the top of my plant. And i lower the light till i hit a temp i am comfortable with. Usually 75 for me... Good luck


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## JBonez (Jun 26, 2009)

my 1000w can sit about 10 inches from my canopy, but i have two vortex 500cfm fans, one pushing and one pulling on each side of the reflector.

So if your 600w is air cooled, i would expect to get at least 10" or so!


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## JBonez (Jun 26, 2009)

ps, i have not seen a difference in growth with mh over hps.

hps= more lumens, i wont be using mh for veg anymore. JMO


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## The Hemp Goddess (Jun 26, 2009)

jmansweed said:
			
		

> One reason so many of us have switched to using 600 watt set ups over 1000 is because we can lower a 600 closer to a plant with-out burning it. A 1000 at 1 foot spreads about 140000 lumens, a 1000 at 2 feet will spread about 35000 lumens, a 600 at 1 foot is more like 115000 lumens. A 600 at 2 feet away spreads about 30000 lumens. Lumens make those little girls grow so naturally the more effecient 600 is a good choice. Cooling any thing bigger can be expensive and dropping a larger light uncooled will kill your plants.
> 
> Anyway, I dont want to confuse you. Drop the light close and keep it cool. More lumens, more weed. 1 foot over the plants = 115000 lumens with a 600. good luck
> 
> I just reread some of your stuff, dont drop a 600 like I just said untill your plants are older. Smaller plants can be sensitive to larger lights. Raising the lights on newbies will make them stretch. High intensity Flouros with grow spectrum allow you to get lots of lumens to your plants while eliminating the intence heat and extreme spectrum, and gives you the ability to drop the bulbs close to your ladies.



What kind of 600W bulb are you running that gives you 115000 lumens at 1 foot?  I have not seen a 600W bulb over about 90000 lumens initial output...


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## phatpharmer (Jun 26, 2009)

Yeah my 600w HPS is 90000 Lumens if there is a 600w bulb thats 140000 I'd love to get one! My 1000w MH conversion bulb is only 130000!


                                                     Phatpharmer


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## dirtyolsouth (Jun 26, 2009)

JBonez said:
			
		

> my 1000w can sit about 10 inches from my canopy, but i have two vortex 500cfm fans, one pushing and one pulling on each side of the reflector.  So if your 600w is air cooled, i would expect to get at least 10" or so!



NICE JBonez!  I can get my gals about a foot from my Dual Arc 1K and I increase that to about 14" when I used my HPS...  Oddly enough, it runs hotter than the DualArc even though my halides have always seemed warmer to me than my HPS lights...?  Due to space  I'm only using one Eclipse/Ostberg 630cfm fan and it's pulling air first off my filter and through the lights and my fan is suspended in a sound muffler box just above by closet ceiling in the attic.  The box helps a bit with the noise but of course most of the sound is air going *W-H-O-O-O-O-O-S-H* through the ductwork.  Next grow...  insulated ductwork and I might get some Pink Panther stuff to wrap around my existing duct in the closet between grows.... 



			
				JBonez said:
			
		

> ps, i have not seen a difference in growth with mh over hps.  hps= more lumens, i wont be using mh for veg anymore. JMO


This grow I experimented with using a Solar Max Dual Arc 1K...  it has a 600w HPS and a 400w MH in one bulb.  I used the bulb to let the girls veg in my bloom closet for about a week and on into blooming.  Unfortunately I've never grown this strain before for comparison but I've had very strong growth using this bulb and minimal stretch with very tight nodes and I've also saw earlier and more amounts trich development than I've seen with other similar Indica strains at that stage in the past.

Having read that marijuana needs more of the red spectrum the later in flower it is I opted to swap out my Dual Arc for a Hortilux 1k HPS late in week 6.  As soon as I did that my gals who were flowering along great shifted another gear and started putting on the goo all the more...   I'm hoping that the gals stress a bit about seeing the mh side of their spectrum reduced and the change in color temp will trigger the gals to finish up nice and amberlicious...

We'll see...

Peace!


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## JBonez (Jun 26, 2009)

right on dirty!

yeah, i just spent the cash cause of the summer months, now im doing ebb&flow which lowers my total vertical space due to the table and stand.

My res is outside of the tent and stays a perfect 70 degrees.

I went with the vortex fans on each side of the reflector and now im having a problem keeping the temps up in my tent!!!!! WTH

Its all good, my environment is completely dialed for optimum growth. I am not running co2 yet tho, thats going to be in the future when i build my closed system with no intake or exhast, crazy but im going for the best environment i can possibly give, that way i dont have to worry if they are growing right, lol.


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## dirtyolsouth (Jun 27, 2009)

JBonez said:
			
		

> right on dirty!
> 
> yeah, i just spent the cash cause of the summer months, now im doing ebb&flow which lowers my total vertical space due to the table and stand.
> 
> ...



Have you ever used a Speedster voltage controller on a fan?  They're only $20 and very well built and it gives you completely variable speed control of your fan.  It's grounded and I'm sure you could put a grounded mult and control both of your fans with one Speedster.  I really love mine.  In the summer I run my fan at max when the lights are on and drop it back to 30-40% at night (my day) to keep down noise and keep minimal airflow pulling the stank out of my closet since my filter is in my chain.  In cooler months I can keep it around 50-60% and my closet stays cool.  It makes it so you can really tweak in your temps by varying the amount of air you're moving.  I just wish they had a combo Speedster/timer so you could set different speeds for day/night but I guess it gives me something to do...

Peace!


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## zipflip (Jun 27, 2009)

thats neat dirty. i woulda never thunk of it. lol i mean i didnt knwo they made such a controle module for universal use for like wiring up to fans etc...
  i'm a keep this in mind if i ever approach the similar prob as jbonez. only thing is right now im workin on more airflow. im still only usin microwave fans atm til i can afford better but it works but not way i want. lol
  gonna have to go int here an starty slappinmy fans around an teach them a lesson huh? LOL jp.


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