lights

[twinkle]

hi guys,thinking! of using 400 watt hid? in my new growbox,the size is [4ft high x3 ft wide x2ft 6"deep] ok,all still with me,is 4 ft high enough for a decent crop?also what type of light would give me the max grow height,ie one with a ballast outside ,and a flat kind of reflector?and most important of all what distance would a 400 watt lamp be kept from the tops of growth ,a bunch of ? guys i could do with a bit of good advice from some of our more knowledgeable and senior peeps,grateful as always, regards twinkle

[skinny d]

just hold ur hand at the top of the plant for 2 minutes and ur hand should be comfortable. of course youll feel warmth, but ur hand should get HOT. i have a 150W hps and keep mine about 4 inches from the top

[Wilbur Nutsack]

Hi Twinkle

hang 1000w and 600w HID's 24-36 inches from canopy

hang 400w HID's 18-24 inches from canopy

and smaller HID's to 6-12 inches away

From the pinned topic at the top of this forum

Hows your ventilation?

You'd be able to get closer with a fan either clipped to the reflector or blowing upwards over the bulb.

A sheet of tempered glass in between the bulb and plants would help tremendously.

For lights, i'd think the fastlight lowbays are a little large. Gary/Hydrotechno does 400W which i'm guessing is no more than 3-4" in height. I'm not at home so can't measure one for you, but they are £100 with a remote ballast. Have a look here. The pic isnt the reflector you get BTW. Its much thinner/lower.

Wilbur

[Guest cali-trap]

Hi Twinkle

hang 1000w and 600w HID's 24-36 inches from canopy

hang 400w HID's 18-24 inches from canopy

and smaller HID's to 6-12 inches away

From the pinned topic at the top of this forum

Hows your ventilation?

yah, ventilation is going to be very important in a space that small.

i'm still amazed at how bright even the 400's are, 9 months and 4 lights later, and the heat... in a space that small, you need a goodly amount of airflow to keep from bleaching and burning buds.

[Fazered]

I second that. You just don't realise how bright and hot the 400w is. I upgraded and old 250w security light which ran hot but I was still very surprised. I have a 2.5ft x 3ft x 6ft growroom and the heat from the light was killing my temps as it is a proper walled closet which really holds heat. I have a 400w Lowbay and due to the design they push nearly all of their heat (and light) down directly onto your plants. I did a very simple but effective lowbay conversion which really helped. You lose some light but can have the lamp much closer where the intensity is much higher. However the biggest difference came when I ran the ducting from the fan directly to the reflector. It sucks out most of the heat and I am able to get my 400w to 12 inches without any problems so far. It has also resolved all of my temp problems, I rarely look at my temp gauge now when I used to be checking it every half hour.

- Remember that MJ can take much higher radiant heat than air temps. Make sure that your temp gauge is not in direct light from your lamp as it will not give you accurate readings.

- Remember that light intensity decreases exponentially. Eg. If your light intensity at 1 foot is 400 (just an example figure). At 4 feet the light intensity will be a 1/14th of the intensity at only 28.57!!

The closer the light without damaging the plant the better. It is also helps your lower bud sites. They can easily be 3 feet lower than your main cola so distance becomes even more critical.

[twinkle]

hey there,what a great bunch of peeps on this site,all these answers,all this knowledge for free,great guys thanks,my growbox is in my garden shed,plenty of air.

,but maybe a 250 would be better in such a confined space,and i may be able to get them to about 3ft 6" finished flower,and get a reasonable crop,i suppose the heat would be less with a 250w lamp as against a 400,i/ll see how my venting works,if i can get this setup right its haaaaaaaaappy days forever more,many thanks guys,regards twinkle