Yah but it seams like when i put the 400hps 400w light closser to them at max power even the top of my hand fills really hot isnt that bad for the plants bc i dont wanna fry thier leaves. Wats the height distence for a 400w hps light with out burning the plants up. And yah im sorry when i wrigh messages i type alot
LED light
- Thread starter festus59
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Ganjagrowergu
Well-Known Member
I'm with T.S. fans, lots of fans, and then I say add one more.. I run in a 48"x32"x60" tent. When I was searching for new inexpensive lights I was going to go with a 400w hps. However I was warned that my limited ceiling would give me serious heat problems.
I spent an extra hundred on QB's that I didnt have, got an electricity shut off notice, but plants are happiest I've ever grown. (The bill is now caught up after a little anxiety)
I spent an extra hundred on QB's that I didnt have, got an electricity shut off notice, but plants are happiest I've ever grown. (The bill is now caught up after a little anxiety)
Well, it's all relative. There are a lot of places around the world where the sun's light, at local noon, can feel pretty hot - like the equator at sea level. They grow cannabis there, lol. I try to be reasonably careful with "baby" seedlings, but that's more because they don't have the leaves required for proper transpiration, nor do they have a sufficient root system to ensure that they can uptake enough water to transpire.
With air-cooled reflectors, I've had plants grow right up to the glass without burning (although I did see some minor bleaching here and there). With open reflectors... The problem with the "back of hand" test is that your hand doesn't use the same scale that mine does, neither of ours uses the same scale that someone else's does, etc. The usual general recommendation seems to be 10" to 18", with 14"-15" being most common. You'll tend to see leaf-curl if the bulb is close enough for its heat to be a factor.
Again, fans are your friend.
I figure a 400-watt HID is more or less adequate for about eight square feet unless I'm growing a 100% sativa - in which case I'd like to keep its footprint at 6 square feet or slightly less - or auto-flowering plants, which I can illuminate for 18 hours per day in flower instead of ~12 and, therefore, have a decent DLI with slightly less intense light. So I feel that it's wasting light to have my fixture high enough that its light is producing a larger footprint than that (or a significant amount of its output is shining on the tent's walls instead of directly onto the plants) is, by definition, too high. Other people may have different ideas in regards to what a light of this wattage is capable of, of course.
There's also the inverse square lighting law to consider - if you double the distance to the bulb, you haven't cut your intensity hasn't decreased to half, it has decreased to one-fourth.
I've been known to type a lot for one post, too, although I think the largest I ever posted here was only around 35,000 characters. I wasn't complaining about the length. It's just... I've seen threads peter out when a person decided to skip little things like punctuation, paragraphs, et cetera. With some, it's probably because the annoyance level crosses their personal threshold. But others (myself included) have really poor vision, and the lack of things like that can make a post difficult to read - especially if they use their computer's "magnify" function and end up having to move the window back and forth several times in order to read the whole thing. In the greater scheme of things, I don't suppose it matters all that much; there are lots of members who have good vision, and many of them might not notice such things.
Ok thank u so ill move the light down to 18" it doesnt have a glass casing arount the bulb but i have a small black fan that pritty power full i turn to medium facing up towards the light to let the air hit it and i have a ceiling fan on in my room 24/7 and 2 windows open 24/7 through out the entire night snd day i even check on them like every 2 ouwers to make shure thier okay but like i said thiers 12 plants in that tent all vents in tent are open and i leave the door to tent open all day to
If I only had one fan in my grow space, I'd probably blow it upwards through the canopy. Or across the canopy. It's not likely that you'll significantly cool the bulb - but it's possible to do so for the plants (relatively speaking).
Yah thats wat i started doing every night. I just set the fan facing up where its hitting the done and airs hotting the light bulb to so it cools it down throgh out the nigh bc i couldnt amagizin not using a fan the hps light put of thr most heat i ever felt it fills like a heat bulb u by for ur reptiles
Well, for the most part (as it applies to indoor cannabis growers), a watt of HPS light produces the same amount of heat that a watt of any other electric light does. Which is to say that 400 watts worth of those little 13-watt CFL bulbs in the same space would produce the same amount of heat - we just tend to notice it more with the HIDs because it's all coming from one place. It's kind of like... how you can cook dinner over a campfire or over birthday candles - if you happen to have a great many of them, lol.
1 watt = 3.412141633 BTU/hr. Therefore, a 400-watt HPS bulb, driven at 100%, should be producing ~1,364.86 BTU/hr. of heat while in operation.
1 watt = 3.412141633 BTU/hr. Therefore, a 400-watt HPS bulb, driven at 100%, should be producing ~1,364.86 BTU/hr. of heat while in operation.
Yah now i no wat u mean when u said ur plants will be really tall having them 28in away bc out of 12 plants i got 6 that are doing alot better then the other 6 not to ssy the other 6 arnt doing good they are hust half of them are growing a little bit faster then the others bc i got one plant its a lemon skunk its doing fantastic but its stem is getting pritty long its probly 5inches long b4 it hits the leaves so im lowering the light like 3 to 4 inches a day so its not to much for them all at once from 28in to 18in
I hered u say ur limited cieling would give u seriousious heat problems but the good thing i got about my grow room bc when i moved in my apartment i had 1 bed room thats big and another bedroom thats a toodler size room u could put ur first born child in it well it that room its got 2 windows i can open up to give the plants new co2 and if it gets to hot in the room i have a dehumidifier the one that bliws cool air not hot and a ceiling fan but i can only run it on slow 24/7 bc i got old house when i turn it all way up it rocks like its gonna come out of the ceiling so i run it the lowest u can run it got fans got windows i think ill be good for the heat problem i hop bc its turning into to 40.s the rest of the week at night so cracking each of the 2 windows 3 4in should cool it down in the room plus i leave door open through out the day
Hey just letting u no u were completly right about sticking the plants 18in from the plants my plants are doing fantastic right now i cant believe how good thier doing i thought itll be to close but the plants are growing super fast and great thanx
