Serious Cooling Issues - Flower Tent

[rkymtnman]

@rkymtnman - it's about 6 in from the vortex on the outside of the tent, in, another foot through the cooltube, and then another 2.5 - 3ft to the window exhaust nearby. I'd say no more than a 5 FT run from the vortex to the window. Before I attached the exhaust end to the window, I could feel the full force of the 449 CFM blowing through there, it doesn't seem very diminished, if at all.

yeah, that's not much at all. i was picturing a 20 ft run which would be hard for a fan to push that far.

 

[SPLFreak808]

Hi all,

I've been running a flower tent (2' x 4' x 5' high) for about a month, and am constantly on the verge of it overheating. I've done a ton of research, built out all my fans/ductwork in the best way I can think of. yet I still constantly feel like my plants will overheat any minute I step out of the house. Here's the setup:

The tent is in a closet. The closet doors are removed, so it is very open, almost as if it were just sitting in the room. There is air conditioning in the room, and while it can occasionally get up to as high as 77F in the room, it is generally about 72-74F on average. My understanding is that with proper ventilation I should be able to keep the tent just a few degrees warmer than the room. I would be happy with a constant 80-82 in the tent, however it keeps broaching 84, even hitting 86F on occasion. That really makes me nervous for my plant's health.

The tent is run at a constant 40% RH for flower. This is maintained with a humidity sensor/controller/humidifier combo, as the room RH has been 25-30% outside the tent.

The tent is running one 600W HPS bulb, hanging about 2.5 Ft above the canopy. The ballast has a dimmer switch with settings for 50%, 75%, and 100%. As I'm having these temperature issues, I've never been able to run it on 100% (full 600W), and have been running it on 50% (a little over 300W draw) just to keep it from overheating. Even at that setting, it gets too hot too frequently for my comfort zone.

The cool tube is a 6" diameter. I have a 449CFM vortex fan hanging just outside the tent that is pushing. It pushes through about half a foot of the 6" duct work into the tent to the cool tube, through the cool tube, and out the other side of the tent. It then has about 3 more feet of the 6" ducting out the other side, with no major bends, to a window where it exhausts. That window also houses my AC unit, so the venting happens on the side next to the AC. I have this fan turned to max (the full 449 CFM), though I would love to be able to turn it down slightly on the dial for noise purposes. I have checked all the ductwork and the seams from the vortex to the window, and no air is leaking from the system.

Additionally, I have 2 carbon filters mounted to the ceiling of the tent, a 6" iPower, and a 4" iPower. The 6" does most of the filtering, the 4" is just a backup because I had it lying around. The 6" is pulled (after the carbon filter) with a 240CFM can fan, also on a dimmer but set to full. The 4" is pulled with a tiny little 100CFM can fan that barely moves any air after the drag from the filter, but does still push a little clean air. As I said this is just a backup for me, I know I shouldn't expect much from such a tiny can fan. Each of my carbon filter lines run about 2.5 - 3ft of duct work total, and vent back into the room. While their exhaust is the same temperature as the tent, they don't move enough to warrant window exhaust IMO, and don't add much to the room heat that the AC can't take care of. The tent uses passive intake through all the flaps by the floor, and does retain negative pressure nicely when I have the 240CFM can fan on full (it always is!)

Aside from all that, I have 2 small clip-on fans inside the tent that are keeping the air moving in there, and blowing between the canopy and the light.

Even with all that running on full, and my poor 600W light dimmed to ~300W with the ballast switch, I'm still seeing 75F in the room and 85F in the tent right now.

One more thing, I have a mesh bug screen on the vortex that keeps dust from collecting on my light. The bug screen does fill with dust about once or twice a week and I slurp it out with a vacuum because it does drastically reduce the vortex performance if left dusty for multiple weeks. I make sure to maintain this, as well as my AC filter at least once a week with the large volumes of air being moved.

So my question is, what gives? Why are some people able to bring their tent temps down to within just 2-3 degrees hotter than ambient? Moreso, how are they doing it with smaller inline fans and less air being moved? I've been constantly making small improvements as I notice issues, but at this point I don't see any obvious change I can make to get the temp to drop those 5-6 precious degrees. I will say that when I was running this as a veg tent with far higher humidity for young growth (60-70%RH), I was able to keep the temp no higher than 82F. Of course this is a function of the humidity, so having a dryer 40% for flowering does mean a hotter tent. I'm hoping that someone has advice or improvements that will help counteract the higher temps. Thanks!

Can you post a pic of the thermometer location with the hid on? I run my setups very similar to yours and my canopy sits at 79-82f with NO A/C just outside hot humid hawaii air, at night of course.

Takes me about 300cfm per 1kw hood and 250cfm per 5x6x6 room. As long as my outside air is below 72f, my canopy never rises past 82f.

 

[riffraff8]

I just drew a diagram of the full setup. Hopefully this will help you all visualize what I'm dealing with. @SPLFreak808, I have 2 acurite thermometers on the floor of the tent (my plants are still small, so they only rise maybe 6" above the termometers. I also have a thermometer/hygrometer sensor on a wire that's sitting on the tent floor next to the plants that hooky up to my temp/humidity controller. All 3 of these read the same temp, +/- 1 degree, and are all a couple inches lower than the top of the canopy (though right in the middle of the tent directly under the light, and not shaded by any leaves.

 

[rkymtnman]

that pic helps.

i think my idea might work. would be worth a try. so put the 6" next to the AC and blowing right outside. undo one end of your cool tube. now you will be sucking cool room air thru the bottom vents of the tent and eventually into the light and then to the outdoors. that make sense?

 

[rkymtnman]

i'd worry about your carbon scrubbers after you get the temps right.

 

[riffraff8]

@Resinhound, you could very well be correct! However since your first post sounded like you didn't read my OP at all and were just replying about pulling air off the top with passive intake on the bottom (which is what I described in my post as doing with my carbon filter exhausts), I got the feeling you were just answering for the sake of answering. I would love for you to be right, because ultimately it's about the plants being happy, not either of us knowing it all. If you have some links to valid reasons why pulling air is better than pushing (For cool tubes, NOT for actual tent air exhaust, because I totally agree with you that pushing air into a tent and letting it vent out of the seams doesn't do anyone good for preventing odors), or an experiment you or someone has done without altering any variables other than switching around the fan hooked up to the cool tube, I'd love to read about it. However you have to understand that my vortex took a lot of work to hang on bungees and deal with the noise issue, as well as hooking up the duct work and checking it all for leaks. Because of this, I can't completely flip it around just because one person thinks it will perform better, I need some kind of proof to warrant wasting the rest of my day trying something that may make no difference, especially when I've heard many people say it really makes no difference for cool tube air. Not tryna start a fight bro, sorry if it seemed that way, I just want happy plants.

 

[SPLFreak808]

I just drew a diagram of the full setup. Hopefully this will help you all visualize what I'm dealing with. @SPLFreak808, I have 2 acurite thermometers on the floor of the tent (my plants are still small, so they only rise maybe 6" above the termometers. I also have a thermometer/hygrometer sensor on a wire that's sitting on the tent floor next to the plants that hooky up to my temp/humidity controller. All 3 of these read the same temp, +/- 1 degree, and are all a couple inches lower than the top of the canopy (though right in the middle of the tent directly under the light, and not shaded by any leaves.

Do they actually show heat stress?
is your thermometer sitting in the light?
Can you vent the tent exhaust like the cool tube exhaust?
Bigger diameter room exhaust might help you out also, just vent it out the room. Recycling air can be a bitch to deal with when using hid's.

 

[Resinhound]

Well maybe the only "proof" you are going.to get is to try it yourself and see if it helps...if thats too much work then so be it I guess.Im not going to spend alot of time on a physics lesson to convince somebody an exhaust fan is meant to exhaust.

If you are pushing air into your cooltube you are warming that air and pushing it onto your plants...fuck man...

 

[riffraff8]

@rkymtnman that all makes sense to me, and would mean that the 449 CFM is pulling not only the air out of the cool tube, but also the air out of the tent, which would surely help with the temps. I'm curious about two things, however:

Obviously the first is smell. Since this negates my filtration system, I'd have to hook the 6" carbon filter up to the newly open end of the cool tube, so the run is (inside tent) carbon filter, little bit of ducting, cool tube, little more ducting out of tent (outside of tent) ducting run to the window, then the 449 CFM vortex, and maybe another couple inches ducting to get it out the window. Does that sound right?

The second is that since I'd be mounting the 6" carbon filter in the line of the 449CFM fan, I'd be removing the 240CFM can fan from the equation that currently pulls through that filter. Do you suspect that the improvement would still be sizable, even factoring in the removal of the 240CFM? It sounds like I'll be moving more tent air than before, but slightly less cool tube air (since there's now a carbon filter in the cool tube equation), and less air overall (but better placed movement)

 

[SPLFreak808]

Well maybe the only "proof" you are going.to get is to try it yourself and see if it helps...if thats too much work then so be it I guess.Im not going to spend alot of time on a physics lesson to convince somebody an exhaust fan is meant to exhaust.

If you are pushing air into your cooltube you are warming that air and pushing it onto your plants...fuck man...

@Resinhound, you could very well be correct! However since your first post sounded like you didn't read my OP at all and were just replying about pulling air off the top with passive intake on the bottom (which is what I described in my post as doing with my carbon filter exhausts), I got the feeling you were just answering for the sake of answering. I would love for you to be right, because ultimately it's about the plants being happy, not either of us knowing it all. If you have some links to valid reasons why pulling air is better than pushing (For cool tubes, NOT for actual tent air exhaust, because I totally agree with you that pushing air into a tent and letting it vent out of the seams doesn't do anyone good for preventing odors), or an experiment you or someone has done without altering any variables other than switching around the fan hooked up to the cool tube, I'd love to read about it. However you have to understand that my vortex took a lot of work to hang on bungees and deal with the noise issue, as well as hooking up the duct work and checking it all for leaks. Because of this, I can't completely flip it around just because one person thinks it will perform better, I need some kind of proof to warrant wasting the rest of my day trying something that may make no difference, especially when I've heard many people say it really makes no difference for cool tube air. Not tryna start a fight bro, sorry if it seemed that way, I just want happy plants.

Wow i didnt catch the direction of the fan lol, resin is correct.
Hid hoods seem to stay cooler when the air is pulled instead of pushed.
Not only that, inline fans are way better at pulling air through a duct instead of pushing air through it. I have some ugly green hydrofarms, they cant push air for shit but they can sure pull it. Gotta love those turbine style blowers.

 

[riffraff8]

@SPLFreak, no they do not show any signs of heat stress. I am concerned that their growth rate would slow, more than I am that they would actually shrivel up and die. But in either case, I always want to strive for optimal conditions, even if the current ones aren't killing the plants. My thermometers are sitting directly in the light, as the leaves would be. Do you suggest shading the thermometer to get more accurate readings? I also have a laser thermometer I can check leaf temps with. Will report back on that shortly. I could vent the tent exhaust out the window like the cool tube, but the carbon exhausts move such little air after the drag from the filters that it's really just kind of seeping 85-86F air into the room, definitely not affecting the ambient room temps more than a few tenths of a point max, with the AC blasting. the 449 handling the cool tube is move 95% of the air straight outside.

 

[rkymtnman]

@rkymtnman that all makes sense to me, and would mean that the 449 CFM is pulling not only the air out of the cool tube, but also the air out of the tent, which would surely help with the temps. I'm curious about two things, however:

Obviously the first is smell. Since this negates my filtration system, I'd have to hook the 6" carbon filter up to the newly open end of the cool tube, so the run is (inside tent) carbon filter, little bit of ducting, cool tube, little more ducting out of tent (outside of tent) ducting run to the window, then the 449 CFM vortex, and maybe another couple inches ducting to get it out the window. Does that sound right?

The second is that since I'd be mounting the 6" carbon filter in the line of the 449CFM fan, I'd be removing the 240CFM can fan from the equation that currently pulls through that filter. Do you suspect that the improvement would still be sizable, even factoring in the removal of the 240CFM? It sounds like I'll be moving more tent air than before, but slightly less cool tube air (since there's now a carbon filter in the cool tube equation), and less air overall (but better placed movement)

that might be tricky. if my idea works, what you could do is on the exhaust of the 6", add your carbon scrubber and then add the smaller 6" fan to blow that out the window. so you'd basically now have 2 fans sucking thru the whole setup and to outsdie.

 

[rkymtnman]

sometimes you just gotta try a bunch of things and hopefully one of them works.

luckily i have no neighbors so smell is no problem.

 

[riffraff8]

@SPLFreak808 & @Resinhound - That's really interesting, I've heard anywhere from the contrary to them being exactly the same either way, to working better as pulling like you both said. I guess as with any aspect of growing there's so much misinformation floating around that trying it myself is the only way I'll actually know. Will report back later today with the results, and give you a formal apology, Resinhound, if it works better as you said. Sorry for my suspicion, but it's hard to trust a lot of information on this site, especially when someone just says it's better because it's better, and doesn't give my brain a reason as to why. But I'll try it!

 

[rkymtnman]

if you really want some asshole responses, put up a pic of a plant and ask how much it's gonna yield. or tell how great advanced nutrients are. lol.

 

[SPLFreak808]

@SPLFreak, no they do not show any signs of heat stress. I am concerned that their growth rate would slow, more than I am that they would actually shrivel up and die. But in either case, I always want to strive for optimal conditions, even if the current ones aren't killing the plants. My thermometers are sitting directly in the light, as the leaves would be. Do you suggest shading the thermometer to get more accurate readings? I also have a laser thermometer I can check leaf temps with. Will report back on that shortly. I could vent the tent exhaust out the window like the cool tube, but the carbon exhausts move such little air after the drag from the filters that it's really just kind of seeping 85-86F air into the room, definitely not affecting the ambient room temps more than a few tenths of a point max, with the AC blasting. the 449 handling the cool tube is move 95% of the air straight outside.

Well you are measuring temps at the foliage. The foliage is allowed to get a bit hotter then ambient temps but not too hot. 74-78 in the shade is good & should be near 80-84 at the foliage for hybrids/sats & a bit lower for indica's. Anyways i wouldn't run your setup like that. I'm not trying to shy you away from ryth's advice but if worse comes to worse put your blowers at the end of the ducts and vent it all straight out a window, use a scrubber for the room exhaust duct and keep your passive intakes where they are. Should drop you a few degrees. An easy way would be to build an air exhaust box built into the window and house your inline blower in there withthe scrubber in the room EVERYTHING gets pulled out.. Keep that shit from blowing back into the window.

 

[riffraff8]

Really appreciate all the suggestions! Will rework some things today and report back later with my results.

 

[dandyrandy]

@Konassure - those CFM numbers are WAY higher than I've seen anyone using for such a small tent (40 cubic feet). While I'm positive that a 1500CFM would solve my issue, my cool tube is only 6", so moving up to 8" or 10" ductwork for the cooltube run doesn't seem viable, does it? It would also probably sounds like a jet engine in my apartment taking off for 12 hours a day. Even the 449 CFM is pretty darn loud on full, even with it hanging on bungees. I'm not sure I have the space or can stealthily handle the noise of something that's THAT huge.

@dandyrandy, cooling a 1000w with 100CFM sounds like you must be working with air that's below freezing coming in, or some such insanity. How can that possibly even be working for you?? Is that a joke post to fuck with us, or is that really working out for you somehow? If so, I'm extremely curious...

@rkymtnman, I could theoretically run ducting right up next to my AC unit. Unfortunately this would mean an extra 4-5 ft of ductwork, and a more conspicuous-looking op. I think it's worth the trade-off, however, if it keeps my temps down low. I'll give it a whirl later today and report back with the temperature drop. This is the best solution I've heard so far. I'm still very curious, however, how so many people manage to get their tent just 2-3 degrees warmer than ambient just sucking in room air. Mine is always 9-10 degrees warmer than the room.

1000w of cob leds. Carry on.

 

[SPLFreak808]

1000w of cob leds. Carry on.

Sorry for the threadjack lol.

How big is your room?
What temps do you pull in?
Your cobs are running at 1kw? Or you have 1kw worth of cobs dimmed down?

Just curious so i would know what to expect.

 

[dandyrandy]

I usually run around 600w. I run 2 wireless thermometers 8" below the cobs. I see a 5° rise from intake at the bottom. Stealth not a tent. I never have heat issues as with the AC on in the summer and it being in the basement I may see 85° 8" below the cobs if I run full tilt, 945 watts or so. The plants are a foot away. The leds are mounted on 2 10" x48" heatsinks. No fans needed. The 100 cfm is probably 80 or so. It's my carbon filter setup. Very little noise and air movement. I would go with hid but stealth would be tougher. Good leds are not cheap.