Two 315 watt cmh lights 3100k and 4200k

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Ironhead1970

Ironhead1970

I have another post up under RDWC Pvc and totes just more questions I read somewhere that you need to use two 315 watt CMH lights in a 4x4 tent? Had one I used in my last 2 grows in a 3x3 tent the light worked great.
I'm still in the setup and building phase even with one CMH the temperature was running around 77 degrees F. With 2 CMH one 3100K and the other 4200k now the temps are up to 88F I'm wondering how to get the temperature lower it's my 3rd grow first time using RDWC first two grows were in DWC. the Top 10" vent in the tent is right under a vent for the central air I'm thinking about putting some type of duct work to feed the air conditioner right into the top vent, but air is not on all the time? What about one of those Evaporative Air Coolers anyone try one with any success? My first time growing with RDWC going with autos don't have to worry about having it totally dark the only other thing I can think of is open up all the vents blow cool air into the bottom vents with fans, and add more inside fans have 4 now?
Any other ideas can I go with one cmh and put LEDs on the sides of the tent? How would I figure out the correct par? To much of anything is bad for all life.
 
Aqua Man

Aqua Man

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Leaf temps matter not air temps. Run a cool res a touch lower humidity and it will increase transpirations rates which increases evaporative cooling and pulls more cool water into the plant... it has it limits but will help.

Increase air exchange and don't put fans blowing hot air from the lights down on the plants.
 
Aqua Man

Aqua Man

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Not the most ideal but cheap and you would be surprised how much you can manipulate plant temps by the root temps and transpiration rates.

You will need to feed lighter to make up for the increased transpiration.
 
Ironhead1970

Ironhead1970

Thanks for the replies I'm still thinking about running the inline 6" Duct fan out of the top side vent Instead of the very top vent and use the bottom vents and the very top vent to pull in cooler air going to replace the small clip on fans with something stronger and I always have them pointed up from under the plants I have used a broken tower fan didn't rotate just had it on high pointing at the back corner of my 3x3 it made a nice breeze that didn't hurt the plants any had a Humidifier going
 
Aqua Man

Aqua Man

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Thanks for the replies I'm still thinking about running the inline 6" Duct fan out of the top side vent Instead of the very top vent and use the bottom vents and the very top vent to pull in cooler air going to replace the small clip on fans with something stronger and I always have them pointed up from under the plants I have used a broken tower fan didn't rotate just had it on high pointing at the back corner of my 3x3 it made a nice breeze that didn't hurt the plants any had a Humidifier going
So vent from the top.. intake at the bottom. This means cool air coming in goes to the plants as it's drawn up and the hot air from the lights is pulled out and never reaches the plants. 6" will do you well when you have that many btu's in a tent.

The clip on fans you want at or below the canopy not above. Mixing the incoming air and creating flow under and through the plants. Leaves transpire (call it breathe) from the underside. There is no benefit to air blowing on the tops of the plants.

This will mix cool air well distribute it to the plants well and the exhaust fan will pull it up and out keeping the heat from the lights away from the plant much more effectively.

You thermometer should be at or just below canopy level and out of the light and that can give falsely high readings.

Uts all about the leaf temperature. I bet if you grab an IR temp gun things aren't as bad as you think.
 
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CBDfutute4

CBDfutute4

My room temps have hit 91f already and mine are doing great

Lots of moving air has been my biggest reason for that I believe

How do u plan on keeping the water cool?
 
Madmax

Madmax

So vent from the top.. intake at the bottom. This means cool air coming in goes to the plants as it's drawn up and the hot air from the lights is pulled out and never reaches the plants. 6" will do you well when you have that many btu's in a tent.

The clip on fans you want at or below the canopy not above. Mixing the incoming air and creating flow under and through the plants. Leaves transpire (call it breathe) from the underside. There is no benefit to air blowing on the tops of the plants.

This will mix cool air well distribute it to the plants well and the exhaust fan will pull it up and out keeping the heat from the lights away from the plant much more effectively.

You thermometer should be at or just below canopy level and out of the light and that can give falsely high readings.

Uts all about the leaf temperature. I bet if you grab an IR temp gun things aren't as bad as you think.
I thought by having one fan blowing between light and canopy helps cool that air and keep air circulting round the buds and keep any mold starting if say get a humidity spike..
 
Aqua Man

Aqua Man

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I thought by having one fan blowing between light and canopy helps cool that air and keep air circulting round the buds and keep any mold starting if say get a humidity spike..
For HID... LED doesn't produce much radiant heat in comparison. Air movement through the canopy will cause air movement by the buds... you don't need direct flow on them just air movement. You should have good control over your humidity or you can have issues no matter the airflow. Buds don't give off water vapor like leaves do. Same as drying buds you don't want direct airflow on them... if it's to string it can even cause pistils to die back.
 
Madmax

Madmax

No its not blowing directly only on one at back on top bit of bud.i guess i still used it from when the de was running .shall i take it down.humidity gets to 60% max but is mostly betwee 47-57%.. overnites been real good this grow averaging 48%
 
Aqua Man

Aqua Man

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No its not blowing directly only on one at back on top bit of bud.i guess i still used it from when the de was running .shall i take it down.humidity gets to 60% max but is mostly betwee 47-57%.. overnites been real good this grow averaging 48%
It's not going to cause damage in that case... just more beneficial to have it providing air mixing onf the intake and through the plant.

If ya put your hand under the LED you will see what I mean. Those DE get hot at even 2 ft away .
 
Madmax

Madmax

Through the nite im not getting much air coming in through the extraction fan as i have the dehumidifier on and exhaust fan set right on low so i dont lose that warm air ..its gettinv down 0-7deg c here ..i sort of worry if the dehumidifier shits itself i will b in strife..quite a few times the exhaust cant get the humidity down when its over 70% outside.the dehuey is my savior lol..but you are right with the led ..no crispy leaves this time round and no nanners yet ..the ceiling was just too low to run the de..
 
St.Cloud

St.Cloud

6
3
I have another post up under RDWC Pvc and totes just more questions I read somewhere that you need to use two 315 watt CMH lights in a 4x4 tent? Had one I used in my last 2 grows in a 3x3 tent the light worked great.
I'm still in the setup and building phase even with one CMH the temperature was running around 77 degrees F. With 2 CMH one 3100K and the other 4200k now the temps are up to 88F I'm wondering how to get the temperature lower it's my 3rd grow first time using RDWC first two grows were in DWC. the Top 10" vent in the tent is right under a vent for the central air I'm thinking about putting some type of duct work to feed the air conditioner right into the top vent, but air is not on all the time? What about one of those Evaporative Air Coolers anyone try one with any success? My first time growing with RDWC going with autos don't have to worry about having it totally dark the only other thing I can think of is open up all the vents blow cool air into the bottom vents with fans, and add more inside fans have 4 now?
Any other ideas can I go with one cmh and put LEDs on the sides of the tent? How would I figure out the correct par? To much of anything is bad for all life.
Evaporation Air Cooler will increase the humidity. I use a portable a/c unit. Small. 6000bbtu in a 5x5. Fan setting low and constant. I have not done yet but the next grow I will have ductwork installed above lights then routed to blow a curtain of air across the area between the lights and top of canopy. This will keep temp down from lights but let the light beam thru. Currently my set up is crude looking but it is doing what it was intended.
 
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