Quantum Board LED & Temps

Hi all. I have started my first legal recreational grow using LEDs. You can check out my journal here: First Legal Recreational Grow - Canada Eh!?

So I have been running some temp/humidity tests over the past few days while my seeds are sprouting. I want to get a sense of what variances my plants might experience.

Currently I have a 240W QB288 3500k with Cree 660nm deep red. Bought this from KingBrite. When I have the LED on my temps are getting to about 34C and Humidity of 35%. With lights off I am getting about 19C and 55% humidity. I am running my exhaust fan with light off at very low speed today which seems to control humidity well, prior to this I had everything inside the tent turned off and humidity spiked to 83% and temp of 17.5C. A tricky science.

My question to you experts is this. Based on my setup(check journal) do you think adding an intake fan at the bottom to pull air from outside in will help temps?

Also, where is the best placement for my hygrometer. I’ve moved it around to see what my temp and humidity is at and wherever I move it I get different readings, significant differences. Above the LED verses below LED, sitting next to plant base? Mounted to wall of tent? I have tried all this positions and can’t seem to get a consistent reading to be able to say, this is the temp and humidity of my tent.

Any help is appreciated.

Outside the tent or from outside? If from outside, it depends on your temps. If I were to pull in air from outside I’d be pumping in 35c air. If you have outdoor temps in the 21-23c range it should help. You would want to make sure to add a filter of sorts if pulling air from outdoors.

For the hygrometer, keep it at your canopy level. Just keep moving it up as the plant grows.

I also wouldn’t run the carbon filter until you need it (when it starts getting smelly). You’ll greatly extend the life of it.

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I agree, canopy level is where you want to monitor temp and rh.

Best scenario your exhaust fan would run all the time. 34c is too hot for lights on temp. What is the temp of your intake air?

Hi @Bobbydigital. Sorry to confuse you. I want pull air from outside the tent, not outside from a window. My room hosting the tent is my basement and it is relatively cool, 20C. so I thought if I drew air from the basement it would add a bit of humidity to bring things just below 50% and decrease temps to be below the 34C. Would you suggest no exhaust until plants become smelly? Carbon filter and exhaust are connected.

You’ll want to keep the exhaust going. That will help remove humidity and hot air. If you can’t remove the filter then just run it with it.

I just leave my vent flap open and pull air in that way. I also have my carbon filter disconnect as Bobby mentioned as to not wear it out to soon.

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@dbrn32 I currently do not have an intake fan setup. This is what I am thinking will solve some of the issue. Setup and Intake fan drawing air from the basement into my small tent. Basement stays around 20C. Currently I have a 195 exhaust fan running which is connected to a carbon filter.

Any issues with light loss when you have this flap open?

I’m in veg no worries for me. But I am gonna create a box on the outside of the tent that will not allow for light leaks. Or you can use elbows/flex tube for light leaks and use one of the round port holes as well.

I would definitely run an intake with temps like that. Wish I could find 68* air to pump into my grow spaces

Me too! I have to pump AC in from a window unit!!! :face_with_symbols_over_mouth:

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@Jbum @Bobbydigital Welcome to Canada I guess? Where I am located can get pretty low temps -40C in winter time. I have a feeling come winter I will have the reverse problem and I’m going to be pumping heat into this tent.

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I started growing in my basement around 2012 and have never needed an intake fan. You do need a way for fresh air to get in though, that’s why passive vent was mentioned above. It’s not a big deal to have light leak in veg, but you will need a light trap for flowering. Probably the same as if you use a fan, they aren’t light tight.

Same for my garage tent. Would be a hell of a lot cheaper if I could just use a fan to pump in air


Nice! We have the same tent. Great products so far from them!

They do their job. I just hate the stupid windows. Those Velcro flaps are just asking for light leaks. I have a king size comforter that I throw over the entire tent.

Any thoughts on this idea. Getting a wall vent louver placed on inside of tent attached to ducting that goes out the tent in an S shape attached to the intake fan? This should prevent light leaks wouldn’t you say? I’ve read it’s best to have the inside of the ducting matte black to reduce reflection of light. I think the matte black inside along with a louver would help light leaks and almost like a cheap prefilter?

We should hear more about your setup. I wonder if something is sized or set up incorrectly.
What size tent (all 3 dimensions) do you have?
What size fan (diameter and CFM) do you have?
Is your fan hooked up to an exhaust port at the top of the tent?
Is your inlet opened on the opposite side and at the bottom?

You can check out my grow journal for more info. But my tent is 36”x20”x62”. I have a 4” fan that’s 195CFM. Exhausted out top of tent. I currently don’t have an inlet vent or passive air vent setup as temps when lights were off changed drastically. I was trying to lessen the factors involved.

Wait - no inlet vent? Then there’s no cool (or fresh) air coming in!

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