where to measure temps in grow box? (wild swings!!!)

Whats the proper way to measure temps in a pc grow box?

If I keep thermometer on the floor, I get temp reading of about 75 degrees (5 degrees above ambient).

If I measure toward the top (near the lights), I get reading of low 90s and mid eighties if I prop the thermometer up on a box in the middle. I have lots of ventilation (6 fans, 4 exhaust toward the top and 2 intakes at the bottom, plus two passive intakes)

Also, when recommendations of having temps in the 70s is given, does that imply "shade" temperature or "in the sun" temperature. (i.e. outside, on a sunny day, temp may be 80 deg in the shade but if you put thermometer in direct sunlight, it will be above 100 deg)

Thanks you! I posted before, lots of views but not reply. Not sure if people don't know the answer or don't care but seems important to me.

with proper ventilation your temps should only swing 10 degrees from the bottom of the box to the top of the box. you want canopy ~75 , 80 max. and roots less than 75 deg day and down to 65-60 at night (using soil thermometer)

i mean of course right near the light is gonna be hot but the fan should move the upper canopy enough so the heat doesnt have a chance to soak in (if u design it right)

If just one zone for temp control make it your canopy temps. The rest are like so much fart gas and cannot be controlled at the same time.

Nizza said:

with proper ventilation your temps should only swing 10 degrees from the bottom of the box to the top of the box. you want canopy ~75 , 80 max. and roots less than 75 deg day and down to 65-60 at night (using soil thermometer)

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Thank you Nizza and Hotrod for the input!

No canopy yet. Just 1 inch seedling. I am attaching pictures of my setup. All the fans are exhaust except the two at the bottom right. As you can see, there is a lot of air moving there... I don't know how people keep their plants several inches from their cfls without having temps in the 90s. They just put out to much radiant heat...even if the air temp in a box is 70 deg, a thermometer 2 inches away from a cfl will read min of 85 deg.

My main concern now is about how close I should keep the plants to the cfls... raise them up (and get more lumens) or lower them and get better temps?

Also, any comments on my fan configuration?

The two fans at the domes and the on the very top at the side put out very warm air and seem to be doing the brunt of the cooling. The larger 12cm fan on the side puts out mostly cool air.

Thanks again!

Sorry, forgot to include the pictures!!

you should be able to get it 3 inches or so away from the cfls with an oscillating fan that makes the foliage move almost constantly. this way you know air is taking the heat instead of your plant

Nizza said:

you should be able to get it 3 inches or so away from the cfls with an oscillating fan that makes the foliage move almost constantly. this way you know air is taking the heat instead of your plant

Click to expand...

Will do. Thanks! have you seen any good solution for oscillating fans in a pc? I know most of them are large.

Also, do you think overall 7 CFLs (23 watt each) is a bit too ambitious for a PC grow?

For a fan make sure it's not constantly blwing the leaves around crazy, you want the leaves to just constantly shake a little, some people with fans too big point it at the wall so it's not too much air

Was thinking, create a streamline of air going past the bulbs with two fans at the same height of the bulb, one in one out. Then put an extra intake at the bottom where your oscillating fan would be