Madmax
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So this means you will have to increase air temp seem lst has dropped to 73 ..ideal leaf temp is 76-77f ?No. leaf temps drop.
Water acts as a coolant. If proper VPD is maintained and respiration is high, it's like sweat evaporating from your skin.
Bear with me...
Lets say you measure your leaf temp at 75* and ambient at 78*. But RH is too high to allow for proper respiration.
Adjust RH down.
Respiration goes up
Leafs get cooled by water
Now you are at 73* leaf temps but ambient has not changed. You now have to recalculate VPD.
Its the leaf temp that matters, not the ambient. And LED is way different than HPS, most LED have no iR to heat things up radiantly which HPS has lots of.
The other day was 110f in the shade @ 30% rh, leaf temp in the sun was 90; 85 in shade. Plant is thriving.Most underrated tool for growing and its cheap.
Evaporative cooling is huge
Yeah but that is for a short period not all day and night every day and night. Plants have no issues tokerating stress for short periods.The other day was 110f in the shade @ 30% rh, leaf temp in the sun was 90; 85 in shade. Plant is thriving.
Correct, dli is very low. It gets 5 hrs direct sun on a clear day. My point was the huge diff in leaf temp. 25f is huge.Yeah but that is for a short period not all day and night every day and night. Plants have no issues tokerating stress for short periods.
Eg. Lux ranges from 2000 to 130,000 lux over a day and day to day. I have not seen a plant survive or even close to that for 18-24hrs a day exposure.
Cant compare outside to a grow room because its just not comparable
OK, so here is what I do - but there are more than 1 way to skin a cat. Lets assume that you have a garden in Veg and want to get the setpoints dialed in, but not sure where you are.So this means you will have to increase air temp seem lst has dropped to 73 ..ideal leaf temp is 76-77f ?
Ahhh yes extremely and bang on brotherCorrect, dli is very low. It gets 5 hrs direct sun on a clear day. My point was the huge diff in leaf temp. 25f is huge.
Same thing i doOK, so here is what I do - but there are more than 1 way to skin a cat. Lets assume that you have a garden in Veg and want to get the setpoints dialed in, but not sure where you are.
I set my AC to my desired ambient temp. Lets say 82F.
I would then figure a 4 degree drop in leaf temp because LED
So leaf temp = 78F.
Head over to @PulsePeet VPD calculator
VPD Calculator
Solve For: Temp RH VPD Temp (F) Temp (C) RH (%) VPD Air (kPa) Leaf Offset (F) Leaf Offset (C) VPD Leaf (kPa)pulsegrow.com
Enter my data, solve for RH
View attachment 1263609
So this means I set my dehumidifier for 55%. I always round down on the RH because the time it takes to remove the water from respiration around the leaf.
Now, let that thing run for at least a full light dark cycle. Now come back and measure leaf temps mid day using an iR gun.
Now plug that correct leaf temp number back in the calculator. Assuming you are looking for VPD of 1 (this changes throughout the grow) - the end result will be a stable RH number to set your dehumidifier to for the remainder of this stage of grow.
So in short, set your temp, pick your VPD, calculate RH then put that setting into the Dehuey. Bob's your uncle.
Now where this gets tricky is when you are using a lung room and air exchange to get your temp. In that case, you need to adjust the incoming RH via a dehuey in the lung room to give you the set points you are looking for, and it takes a few more days of adjustments and measurements to get it dialed in.
45RH is getting to the limits of a dehumidifier. The efficiency drops WAAAAAAY off as the amount of water in the air decreases. Not even close to linear.I run 1000w hids in a 4x4x6.5 tent. I have had a weird issue for almost a year now, like reveg symptoms. .lots of one finger leafs up top mid flowering.
I was running a vented room with around 60rh due to all my hydro systems.
Ive narrowed it down to vpd or genetics. My next plant to flower is a mimosa evo from barneys farm. I added a 50liter per day dehumidifier to lower my rh, in hopes that was my issue. Sad thing is the damn thing puts off heat while its running and basically runs 24/7 if i try to go lower than 45rh. Im in a sealed room now but i guess my point is this. . i get 0 leaf burn from the light. I do get other issues but yea. . ive never had the too much light issue.
Dogs and cats love the laser too.Most underrated tool for growing and its cheap.
Evaporative cooling is huge
Didnt realize that. I turned it up to 50. I guess i want it as low as possible. I should have gotten a bigger one fml45RH is getting to the limits of a dehumidifier. The efficiency drops WAAAAAAY off as the amount of water in the air decreases. Not even close to linear.
In this case, I would set it for 50 or 55 and adjust my ambient temp.
For me, under 50RH is reserved for second half of flower if I have bud rot concerns.
I run 1000w hids in a 4x4x6.5 tent. I have had a weird issue for almost a year now, like reveg symptoms. .lots of one finger leafs up top mid flowering.
I was running a vented room with around 60rh due to all my hydro systems.
Ive narrowed it down to vpd or genetics. My next plant to flower is a mimosa evo from barneys farm. I added a 50liter per day dehumidifier to lower my rh, in hopes that was my issue. Sad thing is the damn thing puts off heat while its running and basically runs 24/7 if i try to go lower than 45rh. Im in a sealed room now but i guess my point is this. . i get 0 leaf burn from the light. I do get other issues but yea. . ive never had the too much light issue.
Sounds like issues from too much HPS. All ppfd is not equal, symptoms of too much blue may be different than that of too much red, green, or whatever. Back off the light and the problem is solved.I run 1000w hids in a 4x4x6.5 tent. I have had a weird issue for almost a year now, like reveg symptoms. .lots of one finger leafs up top mid flowering.
I was running a vented room with around 60rh due to all my hydro systems.
Ive narrowed it down to vpd or genetics. My next plant to flower is a mimosa evo from barneys farm. I added a 50liter per day dehumidifier to lower my rh, in hopes that was my issue. Sad thing is the damn thing puts off heat while its running and basically runs 24/7 if i try to go lower than 45rh. Im in a sealed room now but i guess my point is this. . i get 0 leaf burn from the light. I do get other issues but yea. . ive never had the too much light issue.
But i want to add even more light lol. . . turning it down is an option, just the last one. Im going to do it just like this one more time on the mimosa evo from barneys. At least then if it still does it ill know its not vpd or genetics.Sounds like issues from too much HPS. All ppfd is not equal, symptoms of too much blue may be different than that of too much red, green, or whatever. Back off the light and the problem is solved.
You say your plants are suffering from too much light but youy want to give them more. OK glBut i want to add even more light lol. . . turning it down is an option, just the last one. Im going to do it just like this one more time on the mimosa evo from barneys. At least then if it still does it ill know its not vpd or genetics.
I actually am gonna try 1250w on the barneys. So if this problem gets worse and not better, I will know its too much light and will have to turn it down.
Cash is invested in making HPS work for good or bad.You say your plants are suffering from too much light but youy want to give them more. OK gl
I used a 1000w hps for decades, so I know a little. Some plants can be 1' directly under it and just make huge buds. Others get stressed and foxtail/reveg. I doubt adding more hps will improve anything-unless you have the perfect clone...Cash is invested in making HPS work for good or bad.
I'll be honest - I don't get it either. Heat problems already... UP THE HPS!
just playing around cashmeh, but you gotta look at this from our perspective... at least for a minute. Maybe?
yeah man, I've run 2 identical tents for a lot of years now, only difference was 1 with LED the other 2200W of HID/HPS. At least 50 grows. I feel like I know them pretty well too.I used a 1000w hps for decades, so I know a little. Some plants can be 1' directly under it and just make huge buds. Others get stressed and foxtail/reveg. I doubt adding more hps will improve anything-unless you have the perfect clone...
I will always use hps in the winter. Plants love the mix light; so no point in running solid led and a space heater.yeah man, I've run 2 identical tents for a lot of years now, only difference was 1 with LED the other 2200W of HID/HPS. At least 50 grows. I feel like I know them pretty well too.
I am now, as of this grow converted to 2 LED tents. I got HPS lighting for sale if anyone is interested lol. HPS stopped making sense hands down with the invention of bar LEDs.
I actually added a 250w led to the tent.You say your plants are suffering from too much light but youy want to give them more. OK gl
Im just waiting for 1000w leds to come down in price. My issues have never been heat until the dehu ran 24/7 which the 12000btu window unit couldnt even keep up.Cash is invested in making HPS work for good or bad.
I'll be honest - I don't get it either. Heat problems already... UP THE HPS!
just playing around cashmeh, but you gotta look at this from our perspective... at least for a minute. Maybe?
Have you hit 2lbs in a 4 x 4 yet?I actually added a 250w led to the tent.
Im going to run the evo, which is good genetics supposedly, and ill have my rh as low as possible. So this will eliminate vpd issues and genetic issues. So if by then im still having the same issue, ill turn the lights down. But atm, its a last resort.
Im just waiting for 1000w leds to come down in price. My issues have never been heat until the dehu ran 24/7 which the 12000btu window unit couldnt even keep up.
My issue is either genetics, vpd or. . orrr. . my massive bloom booster. I will run a grow without it before i turn the lights down lol. .
Again im not against the quality of light, just the upfront cost. Ill run one one day im sure, just not as big of a deal. Ive gotten pounds of a 200 dollar light, i wouldnt have if i spent 200 on an led.
Again one day sure. . but atm. . i am testing to see how much light can be absorbed without burning it, and its wayyy more that what im seeing with the average led user.
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