Measuring Temperature Question?

Greetings,
I have just started growing 1 plant in my small closet (3 by 3 ish by 5 feet long). I have a 250 watt MH about 13 inches away in soil.
The light is on 24 hours a day.
The plant looks pretty good.
My question is temperature, or rather, where do you take the temperature? Do you put a thermometer in the soil near the stem? Do you put it on the wall and if so, how far away from the light? I have one thermometer in the pot and it is about 95 (seems hot) and another leaning against the pot that is about 78.
None on any wall.
Is it ambient temperature we are speaking of or the temperature where the plant is?
How can I lower the temp?
Do I have too?
I also have an oscillating fan (portable swamp cooler) that swings across the plant. I tried using the swamp cooler part but it really didn't seem to drop the temp that much and I figure the added humidity might not be that good either.
Thanks for any input.

Zitngrow

You're going to have to deal with the heat. The best way is to exhaust the hot air. A MH will put out more heat than a HPS, so in a closet it's best to aircool the lamp. Temps must be below 90.

Barring that, I would:
raise the lamp to 18 inches.
put it on a timer, on for 18 hours, let the room cool off.
put your thermometer hanging off the light, so it's above plant height.

HTH

Hey Potroast,
Thanks for the response. I raised the lamp, trade off of Lumens I guess, and put in a small bottle of yeast and sugar and water to add some CO2. Hope that was a good idea.
About changing the lights, should I do that gradually or just cut it back to 18?
I got the female clone as a gift so my "grow room" would not be completely dark if the lights are off. I am assuming that a little light seeping in during the veg state is not that important considering they were on for 24 hours a day, but obviously I could be way off. The lights are still on anyway cause I don't even have a timer yet. lol. oh well. tomorrow I will get one. It seems to have cooled down a little anyway. I am assuming I will have to add some kind of exhaust? fan in the next few days to get rid of some of the hot air. I wasn't really sure what you meant by aircool the lamp, or how for that matter. Any suggestions on a good cheap fan?
That's me. Good and cheap.
Oh well. Thanks again for the input.

Z

potroast said:

You're going to have to deal with the heat. The best way is to exhaust the hot air. A MH will put out more heat than a HPS, so in a closet it's best to aircool the lamp. Temps must be below 90.

Barring that, I would:
raise the lamp to 18 inches.
put it on a timer, on for 18 hours, let the room cool off.
put your thermometer hanging off the light, so it's above plant height.

HTH

Click to expand...

When you install a timer, just set it to what you want and go. Usually the dark hours are the hottest of the day. Light leaks don't make any difference during veg growth. But during flowering, she will require 12 hours of dark each night for 10 weeks.

A fan blowing out of the room will expel hot air and suck in fresh air. To aircool a light, you close up the hood with glass, and hook up air ducts to suck out all the hot air from inside the hood directly out of the room.

HTH

Be careful with that homemade CO2 I have had it fuck up my plants. I think I put too much in there or something Idk.

Greetings All,

I added an 8 inch inline duct fan in my closet today for ventilation and cooling. It seems to have lowered the heat slightly all though time will tell. The room seems cooler but the plant temp seems to have only dropped a few degrees.
My question is do I leave this duct fan running 18/6 same as the lights and the small fan that I have blowing over the plants or should it be on some kind of timer ie. 3 hours on 1 off etc.
Thanks for all your help,

Z

You should have the duct fan sucking air out of the room, and it will do a wonderful job. And you should run it 24/7.

You should run your oscillating fans over the plants during daytime only, so hook them up to the light timer.

HTH

Cool. I have the duct fan towards the top of the room with some ducting running out.
24/7 though huh? I would have never guessed that. Thanks for the info.

My fan doesn't oscillate. Do you think I should get one that does, or does it even make a difference you think?

Thanks again,

Z

You want the fan to blow air around, and jostle the plants, but not all the time. Blowing air on a plant constantly will dry it out, and suffocate it. That's why oscillating fans are good for growing.

take the temp at the top of the plant nearest the heat source

temp shouldn't get over 85 degrees

you have to lower the temp. with an exhaust fan

high humidty isn't good can induce the growth of mildew

Heyy, heres a little suggestion for you. My friend suggested it to me and now im using it too. There are thermometers that work like timer switches, only with heat. Have your exhaust plugged into this thermal switch and set the temp for, you know whatever (mines set for 28oCelsius) that way whenever your grow room reaches that temp, exhaust goes on, vents the room, goes off. Temp goes back up, exhaust goes back on... you get the idea. So ya, you might try it, who knows, its worked so far for me. Best of luck, also, my thermo switch is set right at the tops of my plants, and i just move it up on the wall with them as they grow. If you decide to try it, lemme know how it works for ya. It might not work for large size grow-rooms. Mines set up in a closet right now, though im currently outfitting an old gutted-out fridge.
Happy growin', Sarge