How far frome the plants should the light be?

[sumwhiteguy]

I have a 400w HPS in a cooltube in a 2x5x6 cabnet that is lined with mylar. the temp is between 70-75 when the light is on and 65 when the light is off. How far should the light be from the top of the plants?

 

[surreptitious]

the rule of thumb (men used to be able to beat their wives with anything as long as it was smaller than their thumb. *pointing at thumb* *in an irish accent* well, you cant do much damage with this now can you?) is if you can hold your hand under the light for a minute or so then the light is high enough.

my hood is air cooled with a 400 watt MH light. my plants are good until they are touching the glass. ur setup seems to be similiar to mine.

also, if you do burn them, it's quite noticeable, but they are usually quick to recover once the problem is fixed. but always better not to burn them at all.

bottom line, i suggest moving your light closer. the hand method works well.

 

[OldHippieChick]

The standard answer is: put your hand at the canopy level for a couple of min. and if it burns you it will burn the plants. You have very good room temps so I'd think you could easily manage 6" from the plants.... but I'd start at 10 and see if they stress.

:yeahthat: I type slow....

 

[Locked]

Bro I hve a 600w in a cool tube and i can get my light right down on my plants...the back of the hand test is what i use also...

 

[sumwhiteguy]

What about growth during flowering? I just started to flower so im wondering how much taller they will get

 

[surreptitious]

when the plants get taller then move the light higher. how long have you been flowering? have you not noticed any stretch yet?

 

[sumwhiteguy]

I just started 2 days ago. they havent started to bud just yet

 

[BBFan]

You should be able to get that light down about 10" or less from your canopy without any problems.

I grow with 400's and I keep them about 8" above the canopy without any problems.

Good luck to you. Nice looking set-up you have.

 

[surreptitious]

I just started 2 days ago. they havent started to bud just yet

depending on the strain you'll see some noticeable stretch. when that happens just move the light up. no worries.

happy growing.

 

[Mutt]

http://www.marijuanapassion.com/forum/attachment.php?attachmentid=6265&d=1149604828

 

[sumwhiteguy]

Thank u MUTT for the chart!! Thank you BB and surreptitious!! I will ower the light today when it comes on

 

[passafire420]

What about seedling a week old??? how far do you put the light above those??? i have a 600 watt hps light