around how far should a 400 watt bulb be from the tops of the plants?

[Tamerlane]

how far should a 400 watt bulb be from the tops of the plants?
using a ceramic metal hallide.

please advise
T

 

[Brooklynz Kush]

12 inches if you have an air cooled reflector 6 to 8

 

[patlpp]

usually 12 to 16 inches unless you are air cooled, than 6 to 9 inches (very general)

Put you hand just above the canopy and feel the heat with the top side of your hand, not your palm. If your hand gets significantly warmer after a minute, back off 3 inches and do it again until your hand does not get warmer. Ventilate well also

 

[Brooklynz Kush]

Ok like i didnt basically say that but in other words.

 

[woodsmaneh!]

If you feel any heat on your hand it's to close, move it till you don't feel any. Remember to move it all the time as your plant grows.

Peace

 

[Tamerlane]

thanks everyone.

 

[homebrewer]

I use 600's and even when the heat is not a factor, I'll get bleaching sometimes if I'm not careful. So other than heat, keep in mind that the intensity of the light can bleach the top leaves, though I'm not sure if that is an issue with the 400.

 

[Tamerlane]

I have some minor bleaching spots on a few of my plants... but is that really even an issue?

 

[Mr Bomb]

About 12-18 inches depending on ventilation.

 

[homebrewer]

I have some minor bleaching spots on a few of my plants... but is that really even an issue?

Minor spots? Not an issue. But best case scenario is no spots at all.

 

[purplehazin]

Ideally you want 10K lumens/sqft, which is 14-15 inches away from the canopy. With a piece of glass in between, I'd lower it to 12-13 inches from the canopy.

6 inches from the plant is too close.

 

[woodsmaneh!]

If you get bleaching just bend the plant over a bit.

 

[golddog]

Once they start growing, I put my 400 watt HPS or MH light 4 inches from the top of the canopy with a Sun Systems Air Cooled Hood with 4 inch fan.

I don't get any bleaching or burning. I get full size colas.