Meizhi's and heat

Ok I’m running out of ideas.
Led is supposed to run cooler…not these
2 450 meizhis, 4x3 tent and 90degrees with 2 inside fans an intake 4" fan and a carbon filter at the top of the tent and a release valve at the top and sides
@Countryboyjvd1971 @Hogmaster @Majiktoker who has them?
What gives? How much more cooling equipment will I need to get the temp down? It’s not going to be cost effective.


@Oldstoner has those lights I have 3-300s and a 600 my temps are around 85 is the lights running that hott

@Fever @Hogmaster I’m using 2 900 watt Meizhis 85 -87 degrees except on the days they get watered then it’s about 80

I dont use that brand but looks like Hogmaster has you covered

I had to put a bigger cfm fan in my tent and now my temps stay at 77-81degrees. I went from a 4" cfm to a 6" cfm fan with my meizhi 1200w led and 4x2x6 tent. My lights only on bloom as the full spectrum brings temps up to 90+. Maybe a bigger cfm fan will do for you just my lil input

Are you running positive pressure with a intake fan only? No exhaust fan after the carbon filter?

You should be running negative pressure with the exhaust fan sucking air out the tent through the carbon filter, and you do this by running the exhaust fan a little more powerful than the intake fan, or no intake fan at all.

Also, if you don’t have the right type of 4" exhaust fan, like a centrifugal or “vortex” fan and are only using a plain inline duct booster fan, it might not have the ability to pull the air through any sort of restriction like the carbon filter.

Happy growing,



Yes I have intake cheap fan and an outtake vortex fan the negative pressure is rediculous! The tent is tighter than a drum but these darn lights don’t care they pump out heat faster than I can expel it!!

How big is the vortex fan and how many cfm?

Maybe the tent shouldn’t be tighter than a drum.

The side inlets I would assume are near the bottom of the tent and the top release valve is where the vortex pushes the hot air out?

What is the temp outside the tent?


It’s hot in the room as a result of the meizhi’s

I have intake at the bottom and outtake at the top

So it sounds like I need an air conditioner in the room which may not fix it but will help

Is this a room in your house? If so and it would normally be cooled like the rest of your house, the cheapest thing to do would be to get some duct to run the hot air out of the house completely.

Something kind of like this:

Interesting. It’s in the basement and I have a basement window that is depressed so I could conceivably put something in fra my if the open window and cut a hole in the center to run the duct through?


Sounds like a plan!


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Mine run a little warm and are the same as your lights . Is smell a issue for you ? I run the 2 450s and a 1000watt generic light and cant keep the tent closed up when the lights are on I just open the flap put a fan pointed in and crank the exhaust . @MacGyverStoner I would like to close the tent for the smell not that if it is a huge issue but if it was lessened that would be good to . My question is I have a a/c duct right over my tent but I am not sure what pumping the cold air in the bottom of the tent would do to the lights . Have you ever heard of this? Will it cause a fog or condensation on the light or tent ?


It is kind of standard practice to have cold air enter the bottom of your grow tent or grow room and have the hot air extracted through a carbon filter at the top of the tent or room, and as described above for @Fever – then have the hot air sent out of the environment entirely.

If you aren’t monitoring your humidity and making sure your ventilation is circulating the air effectively without letting humidity build up too high, then you are asking for problems no matter what. Of course you may need to have a humidifier and/or a dehumidifier to keep things in check anyway, and as long as you are not having the humidity get out of range for the growth period you are working with, you should be fine.

Clones humidity level
Growth Week 1: 70%
Growth Week 2: 70%
Flowering Week 1: 65%
Flowering Week 2: 60%
Flowering Week 3: 55%
Flowering Week 4: 50%
Flowering Week 5: 50%
Flowering Week 6: 45%
Flowering Week 7: 45%
Flowering Week 8: 40%
Flowering Week 9: 40%

Seedlings humidity level
Growth Week 1: 60%
Growth Week 2: 60%
Flowering Week 1: 55%
Flowering Week 2: 50%
Flowering Week 3: 50%
Flowering Week 4: 50%
Flowering Week 5: 50%
Flowering Week 6: 45%
Flowering Week 7: 45%
Flowering Week 8: 40%
Flowering Week 9: 40%

Happy growing,



Thanks for all the info bud will put the line to the tent in the next couple of days and finally close up the tent

I’m with @MacGyverStoner
@Fever you should exhaust heat /hot air completely out of house
I recycle my air in winter to keep temps up but this time of year you need to get it out and keep room temp cool I try to maintain a grow room temp around 74 and my tents normally stay around 10 degrees at the top higher then room temp but air at canopy level will be at or just above room temp
I read tent temp both high and under canopy as well
I run 3-4 leds in my tents at a time

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thank you for the RH data @MacGyverStoner good stuff bud!

Not working now I’m at 92 degrees

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That set-up looks like it has a lot of restriction. You need more force, or fan power the longer the ducting is as well as if it has any bends in it. You want to have as little and unrestricted or not so choked off bends in the duct to get best results.

What is the temps outside the tent now?

A pic of the inside top of your tent with the carbon filter and extraction fan might help us help you as well.

Plus, you’ve never given us the specs on your extraction fan, how many CFMs?


145 cfm and the lights just shut off
The tent gets to 74 degrees with the lights off and 92 with them on