Grow Room Temps

[bigweedo]

Hey Everyone,

Been playing around with my room temps, and have been wondering what everyone experiences. My growing area is 4x4x8.

For first three weeks:

Had plants in 1 gallon pots under a 450 watt MH. 6 inch inline 434 cfm fan running about half speed.
-Plants were 20 inches from light.
-Temp outside of room was usually 7-9 degrees cooler than grow room, maintaining 78 degrees on a regular basis. Had the door opened half way for intake.

Start of Fourth Week:

Transplanted plants into 5 gallon buckets and are still under 450 watt MH. Have fan on same setting.

-Plants are still 20 inches from light
-Temp outside of room is usually 10-12 degrees cooler than grow room, maintaining low to mid 80's.

This is starting to concern me, because when I turn my exhaust fan up, the degrees don't really go down.

What temps do you guys get in your rooms? Is this normal for a 450 watt MH?

Also any tips on keeping 25 foot ducting from rolling the whole 25 feet? I am only using around 5 feet of it at the moment, and it always unravels!


Any suggestions are much appreciated!

Thanks,

Big:icon_smile:

 

[Locked]

I don't get too worried till I go over 85f....my norms sit around 78f in my tent running a 600w HPS in a cool tube and a 400w in a standard reflector. I use a 6 inch inline (450cfm) to extract the air from my 4x4x6.5 tent. As for the ducting I cut mine to fit....usually cut a lil more then I need but not much.

 

[v35b]

Bigweed,No clue on ducting...However your temps are alright..I try to keep mine at between 75-80....

 

[dontknowmuch]

I say cut the ducting too, My veg temps are around 70 now and it will get colder out soon

 

[The Hemp Goddess]

I have never heard of a 450W MH. Are you sure it is a MH?

I don't understand what you are trying to tell us about the ducting?

 

[Hushpuppy]

I guess you are pulling air from within your home? growspace is walk-in closet? Where are you exausting to and how is the humidity. As the plants get bigger they will release more humidity into the air and they take up more space which makes it harder to move the air out. Also, if you are exausting air outside of the house, then you will need another way for air to come into the house or the exaust will be very slow regardless of the fan size and speed.

Where is the intake for the air going into the light? how many oscillating fans do you have moving the air around within the room? If you don't have good air circulation to keep the air mixed up, combined with bigger plants taking up more space and producing more humidiy, and if your air intake for the light is down low, then you will have a "bubble" to form within the room that doesn't get moved out of the room and replenished with cooler air.

I would pull air from about the mid level of the room and make sure there is plenty of air movement around the room to mix up the hotter air that tends to go up with the cooler air that tends to stay low.

I would also highly recommend that you cut some 2-4" holes in the door down low and make a little diverter on the outside and inside so that you are able to pull air through the door while blocking light from getting in during the dark cycle(assuming yu are growing photo-period plants). This way you can close the door and get a more efficient use of the negative pressure that it creates.

 

[bigweedo]

Already cut the ducting.. And yes, it is a walk in closet in my house. I have the exhaust fan (435 Cfm) and a 6 inch oscillating fan at the bottom blowing by the intake into the room.

My fan is midway up the room exhausting into the attic. I have a passive intake at the bottom of my room (i have black open up in bottom corner).

It's 75 in the house right now, with temps at 83, Humidity is in high 50's

And yes, the 450 MH, is really a MH. It's just a 600 dimmed to 75%, which is 450.

 

[Hushpuppy]

So you are exausting into the attic. That is pulling air from within the house, but is there a passive intake to allow air from outside the house to come into the house to replace what is pulled out by the exaust fan? If not then you have a "vacuum deadhead" that is preventing the fan from pulling much air into the room and out through the light.

The best way to test this is with one other person at a door or window to the outside. and something that produces a considerable amount of smoke. Put the smoke device at the door to the growroom and stand inside the room but as far out of the way as possible. watch how fast the smoke comes into the room, where it goes and how fast it goes out. Then have the other person open the door or window and watch it again and see if there is a big difference. If ther is a big difference with the door or window open then that is what is causing the heat buildup.

Also, that 6" oscillating fan doesn't sound like it is doing a lot of work, especially as the plants get bigger and slow down the breeze. you might want to get a couple more to move air both under the canopy and above it.

 

[bigweedo]

Thanks for the reply hush. Yes, i have my windows open in my room where the closet is located. I smoked a J in the doorway and noticed the smoke easily being taken from by the fan

Any one ever tried freezing milk jugs with water and putting them by the intake??

 

[Hushpuppy]

Yep, if you got a window open in the room for recirculation, then that should be enough to keep that problem from occuring. haven't tried the frozen jugs but it might be enough to bring it down 5-10 degrees. It would be worth trying it.

 

[Dr.Drow]

mj stops growing at 90f, 80 would be ideal lights on, 70 at night.

 

[The Hemp Goddess]

Any one ever tried freezing milk jugs with water and putting them by the intake??

Yes, it really does not work very well.

 

[river]

mj stops growing at 90f, 80 would be ideal lights on, 70 at night.

Where do you take the temp reading? At the top of the plant, middle or bottom?

 

[Dr.Drow]

I go by my gauge it sits above the plants. I prefer cooler nights too 65ish help purple come out. I never notice any bad things happening till 50f then phosperous gets locked out fast.

 

[Dr.Drow]

Soiless growers can add an aquarium heater to the rez, this will allow plants to withstand those cooler temps and get nice and purple without nute lockout problems.

 

[bigweedo]

I bought the little digital temperature gauge at radio shack for 20 bucks. It comes with a 5 foot cord with a white "receptor" end, which I put right by the tops of the plants. I'm going with 5 gallon buckets and LST, so I just lay the little guy right by the trained top of the plants.