What is the optimal distance from 400w HPS?Hi temps up top.Expert help/opinion needed

i have a 6 foot high grow tent (3 x 3) and a 400 w HPS ballast light in a cool tube reflector. I am using 5 gallon bucket, DWC.

my plant is 3 week veg. i had the bucket on a shelf so she has been 6 inches from the light. she has grown to touch the light. i lowered the shelf so the top is 6 inches from the light.

The temp under my light, if i put the thermoter there, is sometimes 95, even 100! I have a cool tube and a dedicated 6 inch home depot in line duct fan pulling air. I also have a 6in and 4 in exhaust fan. the temp in my tent is OK, just right under the light.

In the past grow I used a 40 gallon rubbermaid rez so My plant was far from the light. i noticed a strectch and less full plant. My plant is now VERY FULL, i like this.

1. Is keeping the plant closer to the light causing the plant to veg better and faster?

2. Should I continue to keep the bucket on the shelf (i can adjust 1 inch increaments) 6 inches away?

3. What about the high temps? The only way I can keep it at 85 max up top to to open the tent and have a 24 inch fan blowing on it, this makes it not hidden (not exactly the reason i bought a tent!).

Put an air conditioner in the room if heat is a problem. I know this chart I'm linking is on this site, but I can't find it, sorry RIU mods:

http://www.thctalk.com/gallery/data/500/MH_Light_Distance_Chart.jpg

Put your hand over the highest part of your plants, if the becomes uncomfortable, it generally is for your plants too. Good luck!

the attached chart shows 11 inches away equal to sunlight levels unless you have CO2 enhancement you are not able to gain as much advantage eceeding sulight levels, if your bulb is old then that should be OK.
The temps are to high, photosynthesises ceases at over 95 F, grow in a basement or crawlspace in the summer or buy a room air conditioner.

I bought a cooling tube for my 1000 watt and now i keep my plants only a few inches away from the light.

I have no experience with cool tubes, but I know 400w HPS would absolutely torch almost any plant 6 inches away, or touching the bulb.

+rep all, thank you

VILEPLUME-my last grow my main bud touched the glass and it worked out well. just smoked some, and it is great. With the coolTube have you used a fan? i think the high temps registering on my thermometer is due to the heat from the bulb (not the increased heat in the tent). Which means it still worked out well. I have a dedicated 6in fan and the air coming out of the fan is hot. temps shoot up to well over 100 if I dont use it.

threeandahook said:

+rep all, thank you

VILEPLUME-my last grow my main bud touched the glass and it worked out well. just smoked some, and it is great. With the coolTube have you used a fan? i think the high temps registering on my thermometer is due to the heat from the bulb (not the increased heat in the tent). Which means it still worked out well. I have a dedicated 6in fan and the air coming out of the fan is hot. temps shoot up to well over 100 if I dont use it.

Click to expand...

The trouble with taking temps above the canopy is you get alot of radiant heat which heats up the THERMO GAUGE, whenever taking canopy temps place the thermometer just under the top of the canopy so that it isnt in direct light.



J

jondamon said:

The trouble with taking temps above the canopy is you get alot of radiant heat which heats up the THERMO GAUGE, whenever taking canopy temps place the thermometer just under the top of the canopy so that it isnt in direct light.



J

Click to expand...

ok. i did that and temp was 5 degrees less.

thank you

dude...400w cool tube, you shouldnt worry about a darn thing as far as heat goes...although it depends on the cfm of the fan blowing the air through the tube. i have a bat wing reflector, and 400w about 10-12" away with an oscilating fan keeping it cool for my girls. as your chart suggests though isnt 12" optimal?

I'm having the same exact problem with 400 watt with cool tube. Temps are 107 without cool tube, 97 with cooltube. Same 6" home depot inline fan for carbon filter and another strictly for the light. It's in my basement. Temps are about 65-70 without light on. I'm going to try to take the temp with the thermometer out of the light and see if that helps. I'll try and let ya know tomorrow.

I use 2x 600w. Air cooled, and keep the glass 6-10 inches from all my tops. 6inches for plants directly under it and the plants on edges are more like 10-12 away.

get a good inline 400cfm or better and then drop that god damn light on those plants. I go as close as 6 inches and they love it

Optimal distance is as close as you can get the light to the plants without burning. use the old hand test method. put your hand just above the highest plant, if you feel heat, then its too close, move the light up and down to get best distance.