Need help. Temp problems not sure why

Hello RIU members. I'm a seasoned user here and have had a few failed attempts at growing in my stealth box I made a few years ago. Mostly my problem was temp, so after my last failed grow I decided to hang it up. However, not to long ago I wanted to turn my failure into a success and I thought since I had some extra money I could try again.

Long story short I had a 250w HPS that was running my box temps up to 98-97 so I sold it to a buddy and put that towards a 600w LED since I've heard really good things about them correcting heat issues.

I got it in last night and decided to give it a test run over night. After hooking everything up and testing it for 12 hours I was horrified to open the box up to the exact same temp readings.

I am looking for any help, advice, and suggestions to get this grow up and running. I've contacted my LED seller and asked him if I should try a 300w LED. Also I've got a 3.5 inline exhaust with controller but only a large CPU fan for intake. Both of them are in the back of the box for stealth (I believe this might be a problem as it pulls hot air out it sucks it back). My deminsions are 18 in x 32 in x 36 in high.

Again looking for any help here. Was really excited to get this up and successful till I saw the temps this morning. I've added some pics to help too.

Thanks in advance

My fan is rated 170 CFM also.

Rednax said:

Hello RIU members. I'm a seasoned user here and have had a few failed attempts at growing in my stealth box I made a few years ago. Mostly my problem was temp, so after my last failed grow I decided to hang it up. However, not to long ago I wanted to turn my failure into a success and I thought since I had some extra money I could try again.

Long story short I had a 250w HPS that was running my box temps up to 98-97 so I sold it to a buddy and put that towards a 600w LED since I've heard really good things about them correcting heat issues.

I got it in last night and decided to give it a test run over night. After hooking everything up and testing it for 12 hours I was horrified to open the box up to the exact same temp readings.

I am looking for any help, advice, and suggestions to get this grow up and running. I've contacted my LED seller and asked him if I should try a 300w LED. Also I've got a 3.5 inline exhaust with controller but only a large CPU fan for intake. Both of them are in the back of the box for stealth (I believe this might be a problem as it pulls hot air out it sucks it back). My deminsions are 18 in x 32 in x 36 in high.

Again looking for any help here. Was really excited to get this up and successful till I saw the temps this morning. I've added some pics to help too.

Thanks in advanceView attachment 3744314View attachment 3744316View attachment 3744317View attachment 3744319

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IMO Move your intake fan to the bottom of your box. Cooler air is more dense and its cooler along the floor. As you know heat rises. Also just my opinion but i would just use some bright white paint on the inside of your box as a cheap alternative for more light reflection. It beats messing with that mylar crap.

No expert here but arnt LED lights ment to be a fair way from the top of your plants? Unlike CFL's.

And I agree with what Venom said.

Lucky Luke said:

No expert here but arnt LED lights ment to be a fair way from the top of your plants? Unlike CFL's.

And I agree with what Venom said.

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I keep mine @24" for veg and 18" for flower.

Thanks for the replies guys. I've thought about putting the intake in the floor of my box but that would take up plant space and I think the light would shine through the bottom. I could def put the intake below the beam its currently sitting on which would lower it about 4 inches.

As for the LED yes they will be about 24 inches away from the plants at the start and since I'm going to run autos by the time they flower the should be around the 18 inch mark. As they get bigger I'm going to LST them to keep them low as possible.

Thanks again! Keep the suggestions a coming.

Rednax said:

Thanks for the replies guys. I've thought about putting the intake in the floor of my box but that would take up plant space and I think the light would shine through the bottom. I could def put the intake below the beam its currently sitting on which would lower it about 4 inches.

As for the LED yes they will be about 24 inches away from the plants at the start and since I'm going to run autos by the time they flower the should be around the 18 inch mark. As they get bigger I'm going to LST them to keep them low as possible.

Thanks again! Keep the suggestions a coming.

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Sorry for the confusion but i didnt mean in the floor of your grow box. Just a lot lower then it is now or you will never get cooler air. As for light leaking i would just get a piece of ducting and attach it to the back where your intake fan is and curve a 90 in it and throw a piece of womens nylons on the end of it to keep crap out.

I agree with everyone, the grow room side of the intake should be low, the intake side should be unobstructed and cannot be blocked by anything closer then the diameter of vent used. (eg) 6" vents need atleast 6" or more of unobstructed clearance.

Also, that aluminum foil isn't helping the heat situation.

Why is your exhaust duct going down? Warm air needs to go up.

ttystikk said:

Why is your exhaust duct going down? Warm air needs to go up.

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Lol im banging my head now.. I looked earlier and didn't notice the intake and exhaust is recirculating the same air behind the box.

@Rednax
Your exhaust should be far far away from the intake, point it out a window or up an attic. You are recirculating the same air in a tight little corner.

SPLFreak808 said:

Lol im banging my head now.. I looked earlier and didn't notice the intake and exhaust is recirculating the same air behind the box.

@Rednax
Your exhaust should be far far away from the intake, point it out a window or up an attic. You are recirculating the same air in a tight little corner.

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Ha me too i thought it was being ducted out of the room. Didnt notice that it was the fliter. I'm sure its really building the heat back there.

I'd scrap the cpu fan and run a passive intake. Use a filter inside on the exhaust side of the ducting so it exhausts filtered & scrubbed air. When the exhaust fan is on it will naturally draw fresh air into the box through the open inlet. As mentioned already, use the inlet on the lower side of the box and the exhaust up high. Duct the heat from the outside of the box away from the box entirely(like out a window etc) so you dont suck in the hot air through the inlet. Inevitably your grow box will only be able to achieve the temperature of the room that its in.

Rednax said:

Thanks for the replies guys. I've thought about putting the intake in the floor of my box but that would take up plant space and I think the light would shine through the bottom. I could def put the intake below the beam its currently sitting on which would lower it about 4 inches.

As for the LED yes they will be about 24 inches away from the plants at the start and since I'm going to run autos by the time they flower the should be around the 18 inch mark. As they get bigger I'm going to LST them to keep them low as possible.

Thanks again! Keep the suggestions a coming.

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Obviously these guys haven't used a mars hydro light. by the time you get to flower you can run them closer than 8", but you battle heat when that close. I ran mine at 8" away, removed the glass from the unit, and had an additional fan that blows air across the heatsink through the side openings just to keep my canopy temps around 80.

Those mars lights run very hot, especially towards the end of their day. However, if you move it much further than 8" away during flower, you're going to have some wispy buds.

Your intake should be opposite your exhaust. since your exhaust is on the top left, your intake would work best on bottom right - this allows the air to flow through the box to cool the whole box. Plus, like they said above, you want your intake to grab the cooler more dense air near the ground.

SamsonsRiddle said:

Obviously these guys haven't used a mars hydro light. by the time you get to flower you can run them closer than 8", but you battle heat when that close. I ran mine at 8" away, removed the glass from the unit, and had an additional fan that blows air across the heatsink through the side openings just to keep my canopy temps around 80.

Those mars lights run very hot, especially towards the end of their day. However, if you move it much further than 8" away during flower, you're going to have some wispy buds.

Your intake should be opposite you exhaust. since your exhaust is on the top left, your intake would work best on bottom right - this allows the air to flow through the box to cool the whole box. Plus, like they said above, you want your intake to grab the cooler more dense air near the ground.

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8" from the canopy huh? I have two of the 600's and cant even go down to 12" without bleaching/heat stress. I guess different users have different experiences. I dont doubt what you are saying but 18" is good for me and "wispy" buds was not what i experienced. I guess to each thier own though.

Is the hot air exhausted just in the same room as the growbox?

If so then that would be your biggest problem.

Gquebed said:

Is the hot air exhausted just in the same room as the growbox?

If so then that would be your biggest problem.

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#1) you are just heating up already hot air to cycle through the grow box.

#2) that hot air air being reheated and cycling through the grow box will not have enough co2 in it for the plants to survive.

So you fry em and choke em out at the same time.

Gquebed said:

#1) you are just heating up already hot air to cycle through the grow box.

#2) that hot air air being reheated and cycling through the grow box will not have enough co2 in it for the plants to survive.

So you fry em and choke em out at the same time.

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Agreed. I think this is what happened to my last few grows. Unfortunately I cannot vent it outside, through the floor, nor through the ceiling.

However I made a few adjustments last night before I ran another temp test. I moved my exhaust fan outside the box and placed it on top of my filer and reducer. Also I took an oscillating fan and placed it outside the box facing the intake. Just by doing this I got my top canopy area to 91 and my lower canopy to 89. I left the door open all night as well since if the room is 90 then the best the box could be is 90.

Tonight I continued to make adjustments by lowering my intake fan to the bottom. Dropped it about 5 inches roughly. Also I've placed a large oscillating fan on top of the box to draw some of the heat away from the back of the box and push it out of the room.

I started another temp test about 30 mins ago and have my fingers crossed. I've got some pics too.

Thanks so much for the help so far guys! Special thanks to Venom Grower couldn't have done this without all of you. Hoping for a good temp result tomorrow morning. I'll let y'all know.

PS I was thinking I could vent it out a window in the fall/winter. Would I even need a filter if I did. I doubt i can do it now since it's like 100+ outside.

Thinking about ways to get that exhaust further I could take the filter off and run a line to the bottom left side underneath the left side shelving.

Or if I take off the filer and reducer I could run a 90 straight up and the large fan would disperse it.

as Hydrored said..can u remove the intake fan and make it passive and then use the removed intake fan as an extra exhaust fan?

then keep an eye on ur positive pressue and adjust the size of the passive intake to suit.

Another idea, using an esky (cooler) to run ur intake air from and have ice in the cooler. Just get a steady supply of ice happening using a freezer if u can. That should drop ur intake temp down by quiet a bit.

Rednax said:

Agreed. I think this is what happened to my last few grows. Unfortunately I cannot vent it outside, through the floor, nor through the ceiling.

However I made a few adjustments last night before I ran another temp test. I moved my exhaust fan outside the box and placed it on top of my filer and reducer. Also I took an oscillating fan and placed it outside the box facing the intake. Just by doing this I got my top canopy area to 91 and my lower canopy to 89. I left the door open all night as well since if the room is 90 then the best the box could be is 90.

Tonight I continued to make adjustments by lowering my intake fan to the bottom. Dropped it about 5 inches roughly. Also I've placed a large oscillating fan on top of the box to draw some of the heat away from the back of the box and push it out of the room.

I started another temp test about 30 mins ago and have my fingers crossed. I've got some pics too.

Thanks so much for the help so far guys! Special thanks to Venom Grower couldn't have done this without all of you. Hoping for a good temp result tomorrow morning. I'll let y'all know.

PS I was thinking I could vent it out a window in the fall/winter. Would I even need a filter if I did. I doubt i can do it now since it's like 100+ outside.

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I would suggest that you use some foam/or duct tape to fill in that gap around your exhaust port. It will increase your air flow and help pull the hot air out of the box and not pulling the same air back in. Also if you still have the old holes in your box i would patch them up so you only have air being pulled from one intake. I agree with the other posters that passive intake works well as long as the room your grow box is in is at a comfortable level. Best of luck to you with getting your grow box environment dialed in.