is this too hot?

Hey RIU,

my new set-up arrived today and ive connected it all up and testing for the heat and humidity etc so far what im running is:

a 400W HPS (not vented hood)

6" Extractor fan attached to a carbon filter

4" intake fan bringing fresh air from outside in

and a standard fan inside tent circulating the air around

my highest my temps have hit after having everything running for a few hours are

30.6*C/87.1*F

im going to leave the kit on for another hour and see if it keeps rising but my question is, is this heat damaging to the plants?

imo, you're at the top end, depends though. If you're humidity is low (say 30-35%), that's high, if your humidity is say 45-50%, you're ok. It also depends on whether you're in flowering or veg. I'll let temps go 85'sh with 50-60% humidity in veg and the plants (most strains) respond well. In flowering I target 82 +-2F and humidity target @40% +-5%. Lower humidity is fine, just not optimum imo, anything higher and you're risking mold.

GroErr said:

imo, you're at the top end, depends though. If you're humidity is low (say 30-35%), that's high, if your humidity is say 45-50%, you're ok. It also depends on whether you're in flowering or veg. I'll let temps go 85'sh with 50-60% humidity in veg and the plants (most strains) respond well. In flowering I target 82 +-2F and humidity target @40% +-5%. Lower humidity is fine, just not optimum imo, anything higher and you're risking mold.

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there's no plants in the tent as its only just arrived and am yet to start a grow with the new set-up just messing around with the fan speed controllers trying to hit right temps so im ready for when i start, from the half hour ago when i posted this i fiddled around with the speeds ect and its stable around the 84-85*F area and humidity is around 41-42% Humidity

you should be fine, i run my lights at night, it helps a lot

ConnorTJ said:

there's no plants in the tent as its only just arrived and am yet to start a grow with the new set-up just messing around with the fan speed controllers trying to hit right temps so im ready for when i start, from the half hour ago when i posted this i fiddled around with the speeds ect and its stable around the 84-85*F area and humidity is around 41-42% Humidity

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You'll be good in veg, if you're using the same tent to flower you may need to drop your humidity when you get into flowering. I don't drop mine until after 2 weeks into 12/12 (after the stretch) as there are no buds to speak of, the plants are essentially in veg over-drive during the stretch so the higher humidity is a good thing.

Reason I say you'll need to plan to drop your humidity when you get into flowering is that as soon as you fill the tent with plants, your humidity will increase to around 55-60%, depending on how many plants, air-flow etc.

Usually it's just a matter of exhausting more, or bringing in drier air to drop your humidity, not rocket science, just need to play around a bit in your specific environment until you get it where you want it. Good luck!

ghb said:

you should be fine, i run my lights at night, it helps a lot

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THIS^^^^^^^^^^^^^^^makes a huge difference. So does having an air cooled hood in a tent : /.

It is fluctuations in temp and humidity that invite mold and powdery mildew NOT just high temps/humidity. Imagine condensation on a glass-when you get big fluctuations in heat and humidity condensation can form inside your buds. In fact, plants would love 50%+ in flower, but we as indoor growers keep it lower so we don't have to deal with it, however anything below 50% isn't optimal at any stage. That being said, I run it lower then 50% in flower and as high as 75% in veg.

You know what thrives in lower humidity? Spider mites. You know what still happens in low humidity? Powdery MIldew. It's more about air exchange and circulation then humidity.

Also, training your plant to have many more small colas rather than 2 liter sized donkey dicks helps big time to combat mold. I usually see people getting mold in those big fat colas.

ConnorTJ said:

there's no plants in the tent as its only just arrived and am yet to start a grow with the new set-up just messing around with the fan speed controllers trying to hit right temps so im ready for when i start, from the half hour ago when i posted this i fiddled around with the speeds ect and its stable around the 84-85*F area and humidity is around 41-42% Humidity

Click to expand...

85 with 40% humidity would be at the absolute ceiling for me-acceptable for a day or two, but no more.

If your vegging in that set up you might want to consider buying a cheap humidifier. Take a look at this VDP chart, something I have found really usefull and very accurate for cannabis. Plants thrive at these numbers, however it's not worth losing a crop to mold for us canna growers so we run them lower in flower. In veg you can run your humidity almost as high as you want-as long as it stays somewhat consistant and you have good air exchange and circulation pm or mold shoudn't happen. In veg at 85degrees the best humidity is 75%-80%. I don't run it that high but plants do thrive at those numbers. I find 60-70% the sweet spot for super vigorous plants in veg.

If humidity caused mold or pm then every plant and tree in my neck of the woods would be infected, lol.

We as canna growers like to keep it below 40-50% in flower because mold can't grow at those numbers(50% it can happen, but once you get to 40% it can't), it doesn't mean that is what's best for the plant, actually quite the opposite.

If your temps are staying below 85 degrees try switching your lights on at night and your should be able to get that down to at leat 80 degrees which is no problem-still on the high side but definitely ok.

Increase your humidity in veg to something over 50% and your plants will thank you for it.

GroErr said:

You'll be good in veg, if you're using the same tent to flower you may need to drop your humidity when you get into flowering. I don't drop mine until after 2 weeks into 12/12 (after the stretch) as there are no buds to speak of, the plants are essentially in veg over-drive during the stretch so the higher humidity is a good thing.

Reason I say you'll need to plan to drop your humidity when you get into flowering is that as soon as you fill the tent with plants, your humidity will increase to around 55-60%, depending on how many plants, air-flow etc.

Usually it's just a matter of exhausting more, or bringing in drier air to drop your humidity, not rocket science, just need to play around a bit in your specific environment until you get it where you want it. Good luck!

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^ I find with proper air exchange plants BARELY raise the humidity, maybe by 5% max. And that's with my waste rez sitting open in my tent.

The humidity in your tent should be almost exactly what your intake humidity is if you have enough air exchange.

Don't let the low humidity in flower scare you. In fact, it's really hard to get your humidity below 50 without a dehumidifier. I've always keep it at or under 60% and never had it in years of growing. Again, it's fluctuations in temp and humidty and spores, NOT humidity itself that causes it.

Once i realized this and bumped up my humidty I felt like an idiot for running so low for so long. Bump your humidty in veg over 60 and watch the magic happen. I run my flower tent at 45% right now, but my temps never go above 75degrees.

Also, get a fan on the light.

My 400w on a wing reflector has a small fan (4" blade 120v) that the built in stand grips right onto the reflector. (all my 125w CFLs do this as well) drops the temps a shit ton.

Heres my fan, tho my local store had them on clearance last yr for $8 so i stocked up lol http://www.amazon.com/Polar-Aire-High-Velocity-Fan/dp/B005OS4OOQ

Pic is actually of my 250w cuz its not in use atm. (I do this too all my fixtures now except the 2 in tubes)

Squidbilly said:

85 ... I find 60-70% the sweet spot for super vigorous plants in veg.

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This chart goes on the wall and makes me feel better about what I have going on. I assume we want to take the measurement(s) at the top of the canopy under the lights. ??

Your temps are at the top end, 75 is Ideal.

You may want to look at an air cooled hood.

Recommended humidity is around 60 in veg and around 40 in flower or there abouts.

Squidbilly said:

In fact, it's really hard to get your humidity below 50 without a dehumidifier.

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My humidity get's down to the mid 30's with out a humidifier.

While I'm in veg my last grow I ran a cool mist humidifier with ice in it it cooled my room down nicely I use cfl don't know how that would work with HID's

Squidbilly said:

85 with 40% humidity would be at the absolute ceiling for me-acceptable for a day or two, but no more.

If your vegging in that set up you might want to consider buying a cheap humidifier. Take a look at this VDP chart, something I have found really usefull and very accurate for cannabis. Plants thrive at these numbers, however it's not worth losing a crop to mold for us canna growers so we run them lower in flower. In veg you can run your humidity almost as high as you want-as long as it stays somewhat consistant and you have good air exchange and circulation pm or mold shoudn't happen. In veg at 85degrees the best humidity is 75%-80%. I don't run it that high but plants do thrive at those numbers. I find 60-70% the sweet spot for super vigorous plants in veg.
View attachment 3172448

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bravedave said:

This chart goes on the wall and makes me feel better about what I have going on. I assume we want to take the measurement(s) at the top of the canopy under the lights. ??

Click to expand...

Just an update...It did go on the wall.

bravedave said:

Just an update...It did go on the wall.

View attachment 3209426

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Remember, it's just a guidline and it's not plant specific. I still keep it under 50% in flower these days, just to be safe, but the chart is a great reference. In my experience, plants in veg really thrive in higher humidity.

Hello mate. Remember that those lamps cannot be to close also if you don't have a way to take some fresh air from out side and get some air out it will keep hot as a hell. co2 it cold be the best way...

but look hood so far.

Good luck Mate

ConnorTJ said:

Hey RIU,

my new set-up arrived today and ive connected it all up and testing for the heat and humidity etc so far what im running is:

a 400W HPS (not vented hood)

6" Extractor fan attached to a carbon filter

4" intake fan bringing fresh air from outside in

and a standard fan inside tent circulating the air around

my highest my temps have hit after having everything running for a few hours are

30.6*C/87.1*F

im going to leave the kit on for another hour and see if it keeps rising but my question is, is this heat damaging to the plants?

Click to expand...

there is no right or wrong temp as long as u are under 90F, it is ALL based on strain. Some strains will love 87 degrees, others will throw a fit and hate it. Basically just find a strain that likes the heat and u will do great. If you cant keep it under 90F u willend up having problems with most strains in flower.