Temp problems NEED HELP CANT FAIL AGAIN!

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,
-X

so why dont you put the intake fan/passive vent on the other side of the box so its not pulling the hot air back in

Hot air out the top...cool air in through the bottom

I don't mean to sound offensive mate but I just don't see that setup working with a 600w LED. Even if you were to mainline that plant the tops would still be too close to that 600w led. For that setup I wouldn't run anything higher than a 300w.

You don't need to change your box.
Just get some ducting the diameter of your intake and outtake and extend them much further apart. Intake preferably from a window or a draught underneath a doorway!

Get your out take away from the back of your box and give the heat somewhere else to go - aside from sinking back into your box and the wall. You have a heat pocket there.

And lastly - if that's Tin foil you have in there and not Mylar - chuck it. Creates some pretty bad heat spots.

I know your going for stealth but that exhaust fan positioning is no good, I'd mount it on the outside of the cabinet as high as possible and just dump hot air into the next space making sure it has somewhere high to escape. How big is that cool air intake hole? If anything less than 4" open up another one. Worry about slight negative pressure later (or not at all) you need to move a ton of air. Personally I'd cut out the entire floor and go with a bbq or something grate to serve as a floor/intake and then cut a rectangular hole in the lower sides to draw cold air. Your intake air needs to be as low as possible and as far away from your exhaust as possible. Don't spend a single dime more on gear, you have more than you need.

Lastly, line the whole thing with mylar. That wood is holding heat.

I'm a first time grower however I've built well over 50 custom ATX/Mini/Micro style computers and the same principles apply.

Get all that wiring into the next cab too, just causes disruption in exhaust flow. Drop down to one fan (air movement, not intake). Something like this.

First buy a proper thermometer then place your thermometer away from direct light, just above the light line.
Take out your exhaust if you can. if not make sure your hot air is going out of the room entirely. try an intake pulling cool air in.
Some of these things may make it less stealth.
Personally I would send back your light and get your money back. Spend it on something efficient. Cheap LEDs will grow weed but will still put out a fair bit of heat. Build your own using efficient COBs, this will drastically reduce your heat out put and you will out perform a 250w hps with less wattage in COBs.
Move your thermometer!!!!!!

What is the black thing on top of the mass effect book?

coreywebster said:

What is the black thing on top of the mass effect book?

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Good catch, that looks like his thermostat and is nearly identical to mine. If it is, the vents are in the back for both temp and humidity so he's probably pulling temps trapped inside the actual t-stat since it's laying down.

Get that t-stat upright man, it doesn't "look" at a temperature to read it.

slow_grow said:

Good catch, that looks like his thermostat and is nearly identical to mine. If it is, the vents are in the back for both temp and humidity so he's probably pulling temps trapped inside the actual t-stat since it's laying down.

Get that t-stat upright man, it doesn't "look" at a temperature to read it.

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Something black in direct light is not a good way to measure air temp. Like wearing a black top on a sunny day is not a good way to keep cool.

coreywebster said:

Something black in direct light is not a good way to measure air temp. Like wearing a black top on a sunny day is not a good way to keep cool.

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Mine is the same, if not identical. I'd like to get something legit, anything bullet-proof you'd recommend?

slow_grow when I was talking about buying a proper thermometer it was because I saw the house hold one (white) in the back ground. I then noticced the black one directly under the light. The one you have is probably fine, except its black, so in direct light it is not ideal. No thermometer should be directly under the light but a black one will give a far worse reading than a white one. Just place them half way up the wall or just above the light line to avoid the radiant heat giving false readings.

Taken from another site.
In order to know you are providing the right thermal environment for you plants through ventilation, oscillating fans etc. you need to understand the physical nature of the 'heat' in grow spaces, how it should be measured, and the mistakes that can easily be made.

Essentially there are two aspects to the thermal environment that you need to be aware of:

1. The AIR temperature
2. The RADIANT temperature

Although obviously related, these are 2 distinctly separate phenomena and your plants have different tolerances for each.

1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.

Most thermometers are only designed to measure air temperature – growers often mistakenly place their thermometer in direct light; radiant energy will warm your thermometer and give a higher than actual reading.

*Assuming your air is well mixed up by oscillating fans, it doesn’t really matter where you locate your thermometer. The best spot is probably about half the way up a wall, with a piece of cardboard over it (To shade it from radiant heat), exposed to the mixed air in the grow room.

2. Radiant temperature
Radiant temperature is the result of heat transfer between objects at different temperatures without what's in between i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.

cut a hole in the top of the box so its perfect for the light to get through but not the whole lamp,all the heat from the lamp will come outside your grow area... then make another small box to go over your led with vent holes... the only prob is youll have to raise plant levels at times,(plant pot upside down works great)

@coreywebster Great info, thanks a ton man. I'm going to change the location of mine. As you can see from this photo I'm partially in the light/not high enough at all. My larger tent hits Monday so when I transition, I'll be sure to adjust. Thanks again.

Further info from same post.

Editor’s note:
[Cannabis loves high light levels/high radiant energy levels, but exceeding their tolerance for light can result in light burn and chlorophyll leaching out of the leaves. 600's & 1000’s put out a lot of light, and light burn can easily damage clones and young plants.

Light burn damage: initially the leaves look pale green (the edges may turn upwards, mimicking a Mg deficiency), then they turn yellow and finally yellow/brown as the leaves scorch.

This applies especially to high power LEDs, more chance of bleaching the plants. especially with blurple LEDs. Another reason why a COB light would be better than the existing one, it is a white spectrum and although bleaching is still possible it is less likely than with mono diodes with red and blue spectrum.
@Rednax you would find a cob light running soft wold out perform most things and more importantly you could have 64% light-36% heat ratio instead of the reverse of that with the hps you had and probably the same with the LED you have.

You need to exhaust outside the room and even the house if possible.

I tried and tried to vent in the house. I ended up with heat problems and mold.

Just mount a dryer vent in a window or something.

slow_grow said:

@coreywebster Great info, thanks a ton man. I'm going to change the location of mine. As you can see from this photo I'm partially in the light/not high enough at all. My larger tent hits Monday so when I transition, I'll be sure to adjust. Thanks again.

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Pop a bit of white card above your thermometer or raise it.
Just want to be clear. I'm not bashing blurple lights, they will grow you some weed. But the OP has a tiny space so a more efficient light would help him in the situation he is in.

@coreywebster ive never heard of a COB light. Can you send me a link to a good one? Thanks!

Sorry guys I never got an alert I was getting hits here. I've got more the problem worked out. Mostly it was the heat pocket I had in the back. Had to adjust where the exhaust was going, put the filter inside the box, and move my stats around. Thanks for the replies everyone I appreciate it!

Sound! Stuff just needed reorganizing then...reminds me of my grow