Learned something new today and thought I would share

[Wiimote]

I've been running a 4ft x 2ft x 6ft closet for a few months now. About 2 months ago I switched from 2 150 hps' to a 430w Hydro Farm Sunburst (with 160cfm fan for exhaust). For the last month I have been fighting a yellowing problem (which fit perfectly the symptoms of N def in the infirmary sticky) which has decimated my yeilds. I've flushed, changed nutes, checked pH 100 times (always within .2 of 6.5), checked air temps (never above 82 and never below 75) and just about gave up on this run.

Finally yesterday I borrowed a friend's IR camera (to get before and after shots of our house) and decided for shits and giggles to see how my girls looked. Well I was shocked. The air temps in the closet is in the "good enough" range, but the leaf temp was well over 100 degrees!!!! Ack! No wonder I am having problems! Needless to say I spent the rest of the day adding and adjusting fans to get the leaf/bud temp down. I finally got the leaf temp down to within 3 degrees of air temp, and within 2 hours the girls looked MUCH better.

So a word to the wise from the hoping to be wise one day, air temps are not the only temps you have to watch for. A (relatively) strong light will heat up your leaves even if the air surrounding them is cool.

 

[Berry_Coughin']

Thanks for the info......

 

[Sammet]

Cheers!

 

[dreamgreen]

nice thought

 

[Blunted22]

actually man i think i might have the same problem. I just set up a new system with new 1000w under them. They bleached at first so i raised lights but ever since then they have been yellow. At first i thought it was a N Def but i went to fix it and didnt really change. Then I was thinking it was from switching to bloom as soon as we turned 12/12(not even sure if we did) but this would make alot of sense too. Do you know of a way to do this without a IR camera?

 

[Maj.PotHead]

yes i find in my cab and it's 400w hps air cooled hood placement of the fans inside for proper air circulation is critical just a inch or 2 one way or another. this can mean the difference of 2-4 degrees inside ive allways used the back of my hand method before my air cooled hood. if the back of my hand can take the temps for few min's then the plants leafs should be just fine. another thing i noticed with my setup is anything w/in 6inch of bottom of light gets bleached yellow. everything over 6 inch from light stays nice and green untill final flush, just wondering how close was your light and what part of the plant was effected upper or lower ???

 

[Wiimote]

Actually it was both parts. The tops bleached a bit from about 8in and up. I didn't think the tops were too close since I could (and have) held my hand there for over 10 mins without feeling any real warmth. Also, the chart I found floating all over here says 6in is the cutoff. So I assumed that the tops were having the same issue as the lower leaves. Since heat rises, I assumed the lower leaves were cooler.

What I finally found out was that the tops were bleaching and the lower stuff was burning. Using the IR camera, i found the tops were only hitting 82F, but 2-3 inches down, where there was no fan moving air, the leaves were hitting 104F. I raised the light so the closest tip is 10in away, and added an ocsillating fan blowing up under and through the canopy. Now the leaf temps are all under 84F and the bleaching should stop. They look much happier tonight. I'll still be lucky to get 1/2 from the two of them, but it's all about the journey.

 

[Guest]

Very Interesting, Cheers For The Heads Up

 

[Guest]

A lazer thermometer is a growers best buddy,zap a cola or upper fans,check temps of cubes in a dome,you name it.Ambient temps and plant temps I've found to be two different things.With ambient temps of 75 in flower the upper fans may read 75-80 degrees for a couple hours,then check plant temps at the end of the day without adjusting ambient temps,they've been sitting under the lights all day and are maybe 90 degrees.(all examples to make a point).Transpiration will only cool the plant to a point,ambient temps normally need to be adjusted throughout the day.

 

[randude]

I got one of those thermometers that soilman is talking about. It is an infrared thermometer sold at Sears, less than $100. The laser is just a pointing device so you can see where you are taking the temp from, it is not part of the monitoring part of the device.