FIGHTING TEMPS WITH NEW PLANTED SEEDLINGS , HELP !

Hey everyone,

Okay so this is my second grow BTW. Ill explain how my first grow went (complete newbie at the time). I went to home depot and bought a Bulb specifically for plants lolz and put it on a regular desk lamp and had it shining on my two plants at the time and they started pop out of the soil but I noticed they were getting too tall and flopping over. I then immediately purchased a grow tent with a VIPROSPECTRA BLURPLE LED light for my 3X3 grow tent and noticed I wasn't battling that issue any more(at that time I didn't have a thermometer to measure heat or humidity (again complete newbie) so I was never unsure of those measurements. Once the plants were in VEG state I then purchased a MARS HYDRO TS2000 with thermometer and and set it always at 100% since it does have a dimmable function. Well my last grow my plants grew so tall (because I left them in VEG for 3 months) and they ended up getting light burn.


Now this is a completely NEW grow, and I am doing this MUCH MUCH differently, however this is what I noticed yesterday after putting my newly popped seeds into the soil under the MARSHYDRO TS2000 at 30inch away from the light (manufacturer recommended for seedlings) Temps reached a staggering 84 degrees , while Humidity( I went and purchased a small humidifier) Humidity was 45-48%..

My question of the following is at this point do I raise the light more until heat lowers and leave it at 100% wattage?? Or do I dim the light wattage to maybe 75%? I actually jumped the gun and lowered it (I believe to 75%) hard to tell because you have to use a screwdriver adjust it so I am not 100% accurate of its true wattage , however the TEMPS did lower from 84 degrees to 79 degrees. Please advise on what I should do, I am trying to do things better this time , my first grow I had to throw A LOT of buds away due to "airy buds" and burnt ones also. Thanks Guys !

How are you ventilating the tent?

Nizza said:

How are you ventilating the tent?

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I’ve got two rotating fans. One at the bottom close to the seedlings and one at the top facing the top of the LED light where the ballast is which gets the hottest so I can cool the light system off since it doesn’t have a built in fan like some LED lights

Ilovegreenplants said:

I’ve got two rotating fans. One at the bottom close to the seedlings and one at the top facing the top of the LED light where the ballast is which gets the hottest so I can cool the light system off since it doesn’t have a built in fan like some LED lights

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so then, you have no fan taking air out of the tent? That is the reason you are having problems then. You need to get a fan to extract the heat from the top of the tent and send it into the room its in. You also need to open a hole at the bottom of the tent for fresh air to come into the tent, but don't need a fan there. You could use one of the rotating fans instead of two

I would go for a 4" inline fan for your extraction fan, with a speed controller. For the intake I would use one 6 or 8" pipe. Make sure when installing the ducting you try to give the duct 1-3' of straight duct off the fan before making any bends. Also, be sure to make light traps out of the pipe by bending them 180 degrees

Nizza said:

so then, you have no fan taking air out of the tent? That is the reason you are having problems then. You need to get a fan to extract the heat from the top of the tent and send it into the room its in. You also need to open a hole at the bottom of the tent for fresh air to come into the tent, but don't need a fan there. You could use one of the rotating fans instead of two

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Sorry I forgot to mention I do have an exhaust fan running 24hrs and I have to open mesh vents with the flaps open at the bottom the tent. I have the ability to leave another opening open and put an air duct to allow larger air to be drawn in if that’s what you are thinking?

how hot is the room that the tent is in getting?

Nizza said:

how hot is the room that the tent is in getting?

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About 76 degrees. I actually have a very large rotating fan I was using for my first grow to keep temps Happy during VEG/flower because I was battling heat at the time too. It Definitely helped by a few degrees. Grow tent is in a bedroom. But that room is small and for some reason gets the hottest/most humid out of all rooms

Ilovegreenplants said:

About 76 degrees. I actually have a very large rotating fan I was using for my first grow to keep temps Happy during VEG/flower because I was battling heat at the time too. It Definitely helped by a few degrees. Grow tent is in a bedroom. But that room is small and for some reason gets the hottest/most humid out of all rooms

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if the room it is in is 76, then the tent shouldn't be that much higher. 79 sounds right.
where do you have the thermometer located? Try putting it where the exhaust is at the top of the tent or out of the light. This will give you an accurate reading
80-84 isn't a bad temp under LEDS but you would want higher humidity, but that is going to make your bedroom uncomfortable
also if you want to save power drop the power down and get the light a lot closer. When you get more foliage you can raise it and increase the wattage to help with the light spread

Nizza said:

if the room it is in is 76, then the tent shouldn't be that much higher. 79 sounds right.
where do you have the thermometer located? Try putting it where the exhaust is at the top of the tent or out of the light. This will give you an accurate reading
80-84 isn't a bad temp under LEDS but you would want higher humidity, but that is going to make your bedroom uncomfortable
also if you want to save power drop the power down and get the light a lot closer. When you get more foliage you can raise it and increase the wattage to help with the light spread

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i though the temp probe has to be right by the plant soil to see what the accurate temp/humidity is? And when it’s in VEG state you put the Temp probe hanging in the middle of the tent? So 80 degrees under the LED is okay? Even though it is shining right on the seedlings?

yes 80 degrees is OK under LED.

The intake air temperature is going to be a little lower than the grow tent temp. The exhaust temp and the intake temp will give you an idea of the actual temperature of the foliage area. Intake temp will govern the temperature of the soil. The leaf surface temp is usually -2% F of the room temperature.

Seedlings don't need much light so I would dim it down to save power and get the light closer.

There are lots of places you can take readings to get a good idea of the climate, but you do not want your temp/humidity sensor in direct light

Nizza said:

yes 80 degrees is OK under LED.

The intake air temperature is going to be a little lower than the grow tent temp. The exhaust temp and the intake temp will give you an idea of the actual temperature of the foliage area. Intake temp will govern the temperature of the soil. The leaf surface temp is usually -2% F of the room temperature.

Seedlings don't need much light so I would dim it down to save power and get the light closer.

There are lots of places you can take readings to get a good idea of the climate, but you do not want your temp/humidity sensor in direct light

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good to know ! You’ve been extremely helpful BTW ! So just so I am understanding this correctly.The intake you are referring to is the vents open at the bottom of the vents “ intaking “ fresh air ? And I should have the temp probe by there because that’s the actually air being drawn in? Just want to make sure I am understanding you correctly

Ilovegreenplants said:

good to know ! You’ve been extremely helpful BTW ! So just so I am understanding this correctly.The intake you are referring to is the vents open at the bottom of the vents “ intaking “ fresh air ? And I should have the temp probe by there because that’s the actually air being drawn in? Just want to make sure I am understanding you correctly

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I like one temp reading at the intake and one at the exhaust, from here I can figure out how much heat my fixtures are adding to the room. If the intake air goes up, too high, I am having heat problems, we don't want 80 degree air blasting at the soil. 76 is acceptable and when you water you are bringing that temperature down , Ideal root temp is 70 degrees or so, so you will be fine!

Glad to help, if you can sleep in the room your tent is in, I'd guess your temperature is just fine. Focus on using the light correctly you do not want to use too much, too fast. Seedlings will be happy with just a little light. Having enough light and controlling temps are going to help you avoid that "airy" bud this time. Be sure to check them each day and move things around to ensure optimal light coverage and you will have some nice buds

@Ilovegreenplants when you have a chance, scope this out. VPD is the road you're on right now. to know exactly how your girls are feeling, you need to measure leaf temps. you'll need an IR temp gun. if you dont have one, get one, you'll find all sorts of uses for it aside from this.

in order to grow dank nuggets, your girls need to be operating efficiently to allow best growth. based on above, you need to raise humidity quite a bit if you're running around 80F. High heat and low humidity creates high internal leaf pressure, which slows growth and causes the plant to transpire more (she drinks more water). this can also increase likelihood of nute burn even if not fed high ec/ppm because shes wanting more water than food, because its hot. if its not possible to get VPD in proper range, last resort is adjusting nute levels. in this case, if high heat and low humidity cant change, then feeding lower ec/ppm should be considered. happy growing!

visajoe1 said:

@Ilovegreenplants when you have a chance, scope this out. VPD is the road you're on right now. to know exactly how your girls are feeling, you need to measure leaf temps. you'll need an IR temp gun. if you dont have one, get one, you'll find all sorts of uses for it aside from this.

in order to grow dank nuggets, your girls need to be operating efficiently to allow best growth. based on above, you need to raise humidity quite a bit if you're running around 80F. High heat and low humidity creates high internal leaf pressure, which slows growth and causes the plant to transpire more (she drinks more water). this can also increase likelihood of nute burn even if not fed high ec/ppm because shes wanting more water than food, because its hot. if its not possible to get VPD in proper range, last resort is adjusting nute levels. in this case, if high heat and low humidity cant change, then feeding lower ec/ppm should be considered. happy growing!

The Ultimate Vapor Pressure Deficit (VPD) Guide

"Why devote an entire guide to VPD?" you might ask. The answer is that the vapor pressure deficit (VPD) is extremely important for growing plants. VPD helps you identify the correct range of temperature and humidity to aim for in your grow space. With VPD you can achieve the best results while...

pulsegrow.com

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I have dimmed the wattage on my MarshydroTS2000 to maybe 60-75% and now temps are 78.6 and humidity 49%

seedlings can’t function in 49% humidity?

Ilovegreenplants said:

I have dimmed the wattage on my MarshydroTS2000 to maybe 60-75% and now temps are 78.6 and humidity 49%

seedlings can’t function in 49% humidity?

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Looks like seedlings to VEG humidity can be 40-60%

Ilovegreenplants said:

I have dimmed the wattage on my MarshydroTS2000 to maybe 60-75% and now temps are 78.6 and humidity 49%

seedlings can’t function in 49% humidity?

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That's fine it's not perfect but I doubt if i will be able to notice a difference in 49% from 59% besides ln my monitor