Where do you measure your temps from?

Ok, so I am testing out my new box lights/temperatures while my seeds are germing...

Right now I have rolls of tape stacked up about the height of my cups (that I will begin the grow in) and I have my thermometer on top of the tape rolls... So it is about 1 inch from the lights (about where my plant will be) *CFL grow btw*... Is this the proper spot to gauge your temps?

Do I just put the thermometer in the corner of the box? Do I put it right in the light? I basically have it in the hottest possible spot in the box....


WHERE DO YOU PUT YOUR THERMOMETER IN RELATION TO THE REST OF YOUR GROW??

where ever your canopys are, you should be good mang.

icurbyou said:

WHERE DO YOU PUT YOUR THERMOMETER IN RELATION TO THE REST OF YOUR GROW??

Click to expand...

you put it at the top of the plant canopy but shaded from direct light. if you don't shade it you will pick up the radiant heat of the lamp. the thermometer tells you if the air is too hot. you still need to test if the radiant heat is too great by placing your hand at the top of the canopy. if your hand can stand the heat, so can your plants.

i keep one on the rocks, in the light, i have a probe in the shade at canopy height, and i have a probe in the water.. using 250 hps i dont see more than a 2 degree difference in the one in the light. but i've got 265cfm in/out in a 126cf area

Well right now my themometer is 1 inch from the (3) 26w bulbs (I will be using for the seedlings) and with that 1 inch distance it's a solid 81.9*. It's also kind of enclosed by my light reflector (see signature link)...

Iunno, i think that will be a good temp. I mean 81.9* an inch from the light doesnt sound too bad at all. My hand can handle that for sure!

right? lol

icurbyou said:

I mean 81.9* an inch from the light doesnt sound too bad at all. My hand can handle that for sure!

right? lol

Click to expand...

the problem is that your air can be 82 f but the actual surface of the plant is much higher due to radiant heating. radiant heating is why you can cook things on hot pavement when the air is quite a bit cooler. that's why u need to use your hand to test radiant heat

When I put my hand down at the same place as the thermometer it feels warm but not HOT and definitely not scorching.

It just feels warm... Kinda feels good actually. lol

icurbyou said:

When I put my hand down at the same place as the thermometer it feels warm but not HOT and definitely not scorching.

It just feels warm... Kinda feels good actually. lol

Click to expand...

then you are good to go. good growing

listen to desert rat, i cant really help you when it comes to cfl, never used em for primary lighting.

There must be a minimum time one would actually have to hold their hand under their HPS and down above the canopy that would signal the light is in a good spot, or is too close? I mean, there certainly isn't any discomfort here when holding the back of my hand much, much closer to the bulb . . . but I suspect there would be in X amount of seconds, or minutes. This hand method just seems too vague.
For example, something like "try 20 inches with your hand for 2 minures" etc.

your hand is measuring radiant heat which the human hand will feel right away. if you are too close your hand will feel it witihin seconds.

hmmm so maybe ive been worrying about my temps for no reason i have my thermo beside one of my plants directly under 1000wHPS .

that's going to read too hot - try a small piece of carboard or similar to block the direct light. the temp is going to be within a couple of degrees of your general room temp if you have good enough ventilation

MrFishy said:

There must be a minimum time one would actually have to hold their hand under their HPS and down above the canopy that would signal the light is in a good spot, or is too close? I mean, there certainly isn't any discomfort here when holding the back of my hand much, much closer to the bulb . . . but I suspect there would be in X amount of seconds, or minutes. This hand method just seems too vague.
For example, something like "try 20 inches with your hand for 2 minures" etc.

Click to expand...

With an HID system, I think with time and experience you "know" when it's too hot with the "hand method".

So, IF you can feel any heat down by the canopy, it's too close? It seems a shame folks new to HPS seemingly must burn their projects in a few spots to tune the damn things in for the best over-all coverage and deepest penetration.
I suppose it's such an "individual case" type of thing that it's inevitable.

Desertrat knows his stuff... yeah I burnt a few leafs on my plant too just switched over to a 400 HPS too... gonna check the temp tomorrow... but I did pickup 15 LBS of Dry ice this afternoon that'll drop the temp and add me some CO2