Heat issues after changing lighting!

[tokeycones]

Hi guys, i recently changed from my Low wattage LED for vegetative stage to the 600w hps in my 4x8 tent since im going to 12/12 now, i anticipated a huge spike in temps however i simply changed my light cycle to turn on during the night instead which i thought would balance it out however on a warm night i can still hit temp's of 30 even 31c when the max During teh day with the LED was 27c. im using passive intake with a 150mm extraction fan and carbon filter , the room my tent is in is the hottest in the house however i can get away with having ducting to a window for an intake fan but both these windows are open 24/7 anyway. just wanting to know if investing in a intake will actually decrease my tent temps much or just increase airflow.

 

[TorturedSoul]

Not unless your extraction fan is too small (in which case the proper solution is to get an adequately sized exhaust fan, not add an intake fan).

Is this an open or sealed (air-cooled) reflector? If an open one, you may have much better results with a sealed one, set up on its own ventilation run. You shouldn't require a carbon filter for that, because you would be bringing in air from outside of your grow environment, passing it through your reflector, and then directly out of the grow room. In other words, in such a way that it cannot interact with your grow room air, therefore cannot pick up any odor. Additionally, some air-cooled reflectors have "insulating covers" available for them which will further segregate the heat produced by your light from the grow room environment.

The above has a side benefit: Since the vast majority of the heat would be a separate thing from your general grow room environment, you'd be able to make do with less airflow through your grow room in general (in other words, you shouldn't need as high capacity of an exhaust fan for it). That means you'd be moving less air through your carbon filter, which would tend to make it last longer. Probably significantly longer, since the air that you were moving through it would no longer be so hot.

Speaking of carbon filters, make sure that yours is rated for at least as much airflow as the rating of the fan you're using to move air through it. And make sure it's not an el cheapo fan that will be incapable of moving anywhere near its rated capacity of air when forced to do so through an obstruction (aka "your carbon filter," lol).

I hope and assume that you have the ballast to your HID fixture located outside of your grow room, because that's a heat source that has no useful purpose inside the grow area.

BtW, the formula for determining how much heat your light is producing is: P(BTU/hr) = 3.412141633 × P(W) , so...

A 600-watt HPS (or any 600-watt light, for that matter) bulb produces approximately 2,047.285 BTU/hour of heat. Be sure to factor that amount in when figuring your cooling requirements (IOW, if your grow is in a room that is more or less adequately cooled by a 6,000 BTU air conditioner when you aren't running a grow, you'll need an 8,000 BTU one to reach approximately the same temperature target when you are running a grow).

EDIT: A 4'x8' grow tent is, of course, an area of 32 square feet. I hope you have more lighting in there than just a single 600-watt HPS, lol. If not... that's a pretty good light for a square meter, lol, so a smaller tent might be warranted.

 

[tokeycones]

Not unless your extraction fan is too small (in which case the proper solution is to get an adequately sized exhaust fan, not add an intake fan).

Is this an open or sealed (air-cooled) reflector? If an open one, you may have much better results with a sealed one, set up on its own ventilation run. You shouldn't require a carbon filter for that, because you would be bringing in air from outside of your grow environment, passing it through your reflector, and then directly out of the grow room. In other words, in such a way that it cannot interact with your grow room air, therefore cannot pick up any odor. Additionally, some air-cooled reflectors have "insulating covers" available for them which will further segregate the heat produced by your light from the grow room environment.

The above has a side benefit: Since the vast majority of the heat would be a separate thing from your general grow room environment, you'd be able to make do with less airflow through your grow room in general (in other words, you shouldn't need as high capacity of an exhaust fan for it). That means you'd be moving less air through your carbon filter, which would tend to make it last longer. Probably significantly longer, since the air that you were moving through it would no longer be so hot.

Speaking of carbon filters, make sure that yours is rated for at least as much airflow as the rating of the fan you're using to move air through it. And make sure it's not an el cheapo fan that will be incapable of moving anywhere near its rated capacity of air when forced to do so through an obstruction (aka "your carbon filter," lol).

I hope and assume that you have the ballast to your HID fixture located outside of your grow room, because that's a heat source that has no useful purpose inside the grow area.

BtW, the formula for determining how much heat your light is producing is: P(BTU/hr) = 3.412141633 × P(W) , so...

A 600-watt HPS (or any 600-watt light, for that matter) bulb produces approximately 2,047.285 BTU/hour of heat. Be sure to factor that amount in when figuring your cooling requirements (IOW, if your grow is in a room that is more or less adequately cooled by a 6,000 BTU air conditioner when you aren't running a grow, you'll need an 8,000 BTU one to reach approximately the same temperature target when you are running a grow).

EDIT: A 4'x8' grow tent is, of course, an area of 32 square feet. I hope you have more lighting in there than just a single 600-watt HPS, lol. If not... that's a pretty good light for a square meter, lol, so a smaller tent might be warranted.

I have 1/2 of the tent under 600watt hps and 220 true watt led so i think im ok for watts per SF, good quality extractor and carbon filter which was suggested by the shop owner knowing my tent dimensions. I do not have an air cooled reflector as from what i could find online you get a voltage drop and definitely lose some efficieny but willing to try it HOWEVER wouldn't that involve not only buying another intake fan but also the air cooled shade? would probably tripple the total for that one light and im on a budget hence why i'm trying to find out if an intake is neccesary

 

[tokeycones]

1307 150mm Temp/Speed
80 Watts,460 cubic metres per hour is what im using for exraction if that gives you an idea to recommend if it's doing the job or to go bigger im a first time grower here

 

[TorturedSoul]

I have 1/2 of the tent under 600watt hps and 220 true watt led so i think im ok for watts per SF, good quality extractor and carbon filter which was suggested by the shop owner knowing my tent dimensions. I do not have an air cooled reflector as from what i could find online you get a voltage drop and definitely lose some efficieny but willing to try it HOWEVER wouldn't that involve not only buying another intake fan but also the air cooled shade? would probably tripple the total for that one light and im on a budget hence why i'm trying to find out if an intake is neccesary

Well, you wouldn't get any kind of "voltage drop." But you could see up to a 9% attenuation of your light output due to it having to pass through the glass.

However, I don't know if it would provide any major benefit, since you'd still have one light in there that isn't air-cooled (by that I mean the LED panel most likely doesn't have provisions to hook directly to ventilation ducts), so you'd still be producing heat "in the general grow room environment". I was sort of hoping you'd reply that you actually had TWO 600-watt HPS fixtures, lol, one for each side (which would probably be pretty adequate for the space, assuming you weren't growing equatorial sativas). At which point I would have wholeheartedly recommended you upgrade the pair of them to air-cooled reflectors.

if an intake is neccesary

If your exhaust fan is undersized, at best an intake fan will "push" it. It's like... If you're running along at your maximum speed, and someone else grabs hold of your back and starts running at their full speed, you aren't going to end up suddenly going twice as fast, lol. The best you'll end up doing is either getting pushed (slightly) by the person behind you, or pulling (slightly) that person. If that makes any sense.

1307 150mm Temp/Speed
80 Watts,460 cubic metres per hour is what im using for exraction if that gives you an idea to recommend if it's doing the job or to go bigger im a first time grower here

Hmm... It's been a while since I did the calculation for ventilation. Assuming your tent is 8' high (adjust as necessary), that's 256 cubic feet. 460 cubic meters per hour equals 16,244.7 cubic feet per hour equals 270.745 cubic feet per minute (again, assuming it is not being restricted by your carbon filter). I've seen recommendations to size one's fan so that it can replace the air once per minute, but with multiple lights (IOW, higher wattage), I'd suggest going a little higher. Maybe... 385 cubic feet per minute (654.12 cubic meters per hour) or so. With all (three?) of your passive intakes open, you should see a slight negative pressure evident when looking at the walls - but it shouldn't look like it's actually trying to collapse into itself, lol.

The above is only my best estimate (translation: guess ). Be sure your carbon filter is rated at that capacity or higher, that it's a good quality fan that won't get bogged down by the filter, et cetera. Also make sure you're not simply recirculating the air (exhausting into the outer room, then drawing it right back into your tent) because if you are, then of course you'll be experiencing runaway heating.

I have always been told (and it makes sense to me) that it's better to size one's fan/filter setup too large instead of too small. One can always slow one's fan down with a proper fan speed controller, but trying to speed one up tends to result in a broken fan, lol.

And good luck! I also know what it is like to try growing cannabis on a budget (although these days I grow in a much smaller space than you do... because of my budget ).

 

[tokeycones]

My tent is in my room which im in 80% of the time + have gaming pc + screens running ect so the ambient temp in room is significantly higher than other rooms or even the average house temp which i figiured might be causing this, i had initially planned to go full led had the cheap one to veg early stages while i waited for amazon to ship my 2 mars hydro's however they never made it here and i was issued a refund , i started with one 600hps in half my tent see what would happen before i bought two and holy crap am i glad i did as the heat is insane already (plant's are fine) but i don't want to get a crap yield or really fluffy flowers due to being too hot. my exhaust is venting to a window but not actually out the window about 15-20 inches away so the neighbours don't see the ducting as it's not exactly legal here yet haha. on the grounds of my led being unventable, it puts out almost no heat mate i can be at 23C turn it off and not go below 22c

 

[tokeycones]

with buying an air cooled hood can i just run it off my exhaust /carbon filter setup save me investing any more money than just the hood? If so and this sorts my temperature issues out i might invest in another 600 hps and utilize the space i have as i was just about to 12/12 them i can postpone that for another few weeks then spread my girls out more, either way mate appreciate the info !! cheers

 

[TorturedSoul]

Yeah, you can connect an air-cooled hood to the same run you've got your fan/filter on now. It's not as efficient (IMHO), and it won't prolong the life of your filter - but that's a worry for the future . You could do the same thing with two of them, and would probably see cooler temperatures (especially if you chose reflectors that had those insulating covers available - or just made something with duct insulation and some good spray adhesive, I guess). You might still have to upsize your fan, but maybe not, and you'd be looking at more gross light output than you have now so... more buds.

Hey, I just thought of something. Those crappy portable air conditioner units that are meant to be vented through a window... I don't recommend them, because even the "good" ones that I've seen seem to be rated at 14.4K BTU but only equal an 8,000 BTU window unit. But, anyway, the good ones have two hoses coming out of the back, one exhaust and one intake. If I saw an adapter in someone's window holding the ends of two 6" hoses, I'd simply assume they had one of those and think nothing of it. Maybe you could set up something like that, use one hose for your grow room exhaust (make sure your carbon filter doesn't... expire in the middle of your grow without your knowledge though, lol), and run another hose from the adapter to one of your tent's passive intakes. For this application, I might even suggest one of those cheap "in-line duct booster fans," the type that can't move air against any kind of real load, but can serve to move air when there's no restriction. That might... (it's late here and I'm trying to think on the run and probably failing miserably at it) mix enough fresh air in with whatever else will be coming through the passive intakes from the outer room to keep the temperatures in your tent at or below 86°F (30°C). Above that, and you'll probably start seeing issues if you aren't adding supplemental CO₂. And that's if you're maxing out the amount of light-energy that the plants can use (if not, your maximum temperature should be somewhat less).

Too bad you can't get your gaming PC and associated hardware out of that room. That's a fair amount of heat right there.

 

[tokeycones]

That idea with the adapter is worth a go i think i might give it a crack see how it looks, man i left a HUGELY crucial piece of information out on my original post, i set the hps up while still in veg as i wanted to give the plants 1 week or so to adjust to the big change in light . if i count the temps between what would be my 12/12 cycle .30c would be my max, 24c my lowest, 27c my average, are these temps workable ? the 32c i hit was due to the extra 6 hours earlier the lights turn on (4pm) the days heat isn't gone until 8-9pm

 

[TorturedSoul]

It's debatable, but I think so. Don't pick any "cold weather" strains, I suppose. You might see some extra stretching, maybe buds that aren't quite as dense as they could be. But it shouldn't impact your gross weight, I don't think. Temperature is only part of the equation; as I mentioned earlier, there is a relationship between temperature, the amount of light-energy, and CO₂ level. And that doesn't just mean that the plants can thrive under somewhat higher temperatures when there's more light - the plants can actually use more light at those higher temperatures. So if it's going to be hot anyway, lol...

Your choice in method of growing can make a difference, too. I used to do DWC hydroponics exclusively, and one time I had severe heat issues (Summer, enclosed space, generally hot building, and failed central a/c). I had temperatures a little above 100°F (37.8°C) for... longer than I wanted and, yes, my buds were noticeably airier that time, even though I was growing the same strain as the previous run. But that was basically it in terms of negative effects. I credit that to the DWC, along with strong airflow through the canopy and "mad" amounts of aeration in my (largish - 20 to 25 gallon) reservoirs. Now, when I was suffering the heat issue, the plants were already pretty big - I was in my "one plant per eight square foot scrog" phase - so those reservoirs were partially filled with root mass. If I remember correctly, they'd hold about 13 gallons of liquid, give or take - so imagine my surprise that first evening when I came home to find that they had mostly emptied of liquid, lol. The plants were transpiring that much moisture per day. But that was allowing the plants to self-cool to some extent. I don't think they'd have been nearly so healthy if I had been growing in soil.

They were Asian sativas, which would have helped.

Going back to bed now.