How close could the light bulb be from top of my plants

[jiboia]

I have a 400 watt HPS, it is in a 6" glass cylinder. So the bulb is about 2.5 inch from the glass, how close could the plants get to the glass before they burn? I got a squirrel cage fan to cool the bulb.

thx

 

[senseless]

6 inches from the glass to be safe. i have a 400w light and a 6" cooltube and the plants diddnt get burnt untill they were about closer than 6 inches. 87 degrees is what you want to stay at or under.

 

[silent mystic]

I used to run aircooled lights, and would keep the glass cool to touch... I would let the plants grow right up to the glass... but be careful

 

[NiteTiger]

How close do they want to get?






Those plants repeatedly touched the glass, for days at a time, and loved it. And thats a 1kw there, so I can't imagine a problem with a 400? I cool two of those with about 250-300 cfm of fan power, so unless you've got a REALLY shitty fan,
you shouldn't have a problem.

 

[jiboia]

Thanks! Great help!

Will finish my growcloset this week!