HPS radiant heat problem, cabinet design

Hello everyone. I have a few questions for the more experienced than me. Lets say i have a grow cabinet that is 5 feet by 4 feet by 3 feet or so. Its split 3ft and 2ft for flower and veg. I then have a 8 inch spot in the top of the flower with plexi to keep the heat out. This worked well with 8 150w CFL but now that i have a 400w HPS i am having problems with heat getting to about 90 if i keep the cabinet door closed. The heat is a radiant heat problem i think. The upper part with the light has no door (removed) and i have a fan blowing air (also tried pulling out) and the lower cab still gets to 90+. The lower chamber has a 6 in round duct fan pulling air out of the box. The room temp is around 75 or so (basement). I am thinking about pulling outside air to cool the upper part but i don't know if it will help with the radiant heat problem. Also does anyone know if negative air pressure vs positive air pressure is good for the plants or more efficient. I have included some pictures.

p.s.

Left side is Haze mother, and two unkown seed plants one is weird with 3 main stems (Both pre flowered as fem). The right side has 3 haze that where done with CFL (lolly pop looking) and three new clones. Also some unknown that are pre flowering etc.

Perhaps insulate your flowering section, as to protect the veg one, other than that get a cool tube on your hps.

actually the left side (veg) is fine. Its the flower side that has a cooltube type setup that has the problem. Here is a quick text picture. The middle = is plexi glass. The x is a light

I think you may have oversized the light for that small a space. 400 watts produces over 1300 BTU's, enough to heat a small room. Not sure there is a solution other than increasing the airflow in the bottom cab. What is the exhaust temp from the cool tube?

Not sure of the air temps from output of the light side. I guess i can increase the airflow to the bottom half and pull outside air to the top. It was 40f outside last night so i think that would cool the light down. More work.... I guess i could also get a 250w HPS and dump the 400.

Anyone? I know some of you are smarter than me.

Also positive vs negative air pressure on plants. Is one bad?

i prefer positive air pressure on my plants, I just don't like the way they look if I flip the fan. though I have no idea if negative is bad or not, I don't think it should matter just a preference.

I have air cooled lights but I don't even need then now that I have my new 10'' Vortex fan it has totally made all the differance in my room. I got it cuz I bought a carbon filter also amazing and I would recomend to anyone to get one

i think you need to set up a vent system for the 'top part' or where the light is. if you just have a fan blowing into a box with a light in it you are still going to get a lot of radiant heat. reinstall the door and seal the light area. venting the light area with an active exhaust and a passive intake would be the next step. Im not sure if you are doin this already. I read that you have exhaust for the grow area but you should vent the light area as well. its much more effective than aiming a fan at it. (which is what i see in the pic)

The top part is actually sealed at the plexi and the door. I have a small (computer) fan pushing air into the top part from the back. I just picked up a squirrel fan from the local rehab shop and i will be setting that up to pull cold air from outside the room into the top chamber. I am hoping that will work. The lower side closed got to 100+ and the one plant burt bad. I am also going to get some mylar in the next week or so to improve the light in the lower areas.

The cabnet sides and top are actually 6 or 8 inches longer than the inside area. This gives me a hollow spot in the back that is not noticible from the front or sides for fans and vents etc. So i can keep it a inch or two from the wall and everything is hidden.


Also on a side note. I read it on other boards but I have my lights set to 10/14 (10 on) because with 12/12 the Haze plants don't flower or it takes them forever. With 10/14 from clone 2 to 3 weeks old moved over to flower they start to show in about 4 weeks. Is this normal. The single haze is the only seed from the 10 i got from nirvana that germed. I also got 10 top 44 that never germed. The others are some that this american indian gave me from down south USA.

same situation as you, what i did was like some are suggestomg. keep the heat as high as possible. feed cold air at bottom area and have a small fan sending it towards the light. and i think you are, but make sure the temps you take are from near tops of your plants. why are some of your plants so damn tall?

anyways, i managed to get my temps at around 85- which is max allowed so i been told, so im trowing in the towel and aint shooting any lower. whats your humidity? you could add a fogger (about 40 bucks at petsmart) to up the humidity and cool the temp inside the cab. i couldn't my humidity stays around 75 % sometimes my temp reach 90 for like an hour reason why my plants get a little droppy but not to bad

That's very close to my custom-built cabinets. My two larger cabinets are 6' tall, 4' wide, and 3' deep. I use a 600w light, with the (digital) ballast inside the cabinet bolted to the top. No plexiglass. I use a 440 CFM 6" centrifugal fan and two Doran 8"x8" darkroom louvers for intake (one wasn't really adequate with a 440 CFM fan). Also, there's a tiny fan in there on the screen in the back right, just to move air around. No real heat problems at all. The intake louvers are at the bottom in the back, can't really see them. bhphotovideo.com sells them. The reflector itself is air-cooled and has a tempered glass pane, so I guess that's my version of a plexiglass divider. And yes, that's a small window AC unit behind the cabinet. That definitely helps in the summer.

Those plants aren't actually flowering yet. The timing on the three cabinets was getting too compressed, resulting in too much work in a short period of time at harvest time, so I've been vegging these for a few extra weeks in order to space out the harvests a bit better. (If you were wondering why there are no buds showing.) I'm generally able to keep temps between 70-75 degrees F, except in the midst of summer, when it gets up past 80 on some days (but the lights are on at night when flowering anyway).

I'll add a pic or two so you can see it, in case that helps.

My humidity is about 57 to 60%. I guess i could try to up it a little. Its getting colder hear so I am guessing soon i will be dealing with cold problems. It normally can get to 50 or 60 in the basement during the winter (no heat). So maybe that will be a good thing.

The tall plants are Haze Sativa. The three on the left side where done under cfl and all but the top died off. The other two where put there about 4 weeks ago and they where about 6 or 7 inches tall also under cfl on buckets though. They grew fast but switching to HPS and the heat slowed them down. Now that i have temps in check by leaving the door open they are growing again. Flowering takes forver for haze so I clone then put them to flower right away. I get about 3 foot out of them before they flower. I topped one and just bent the other over today. The third sativa is in the middle and i bent it and let it veg a little longer. Left alone they get very tall and push on the plexi glass. They all seem to have small stems and small leaves.

The two on buckets on the right are unkown indinca (I was told it was BC) and they stay short with big stems and leaves. The back ones are some that got burnt.

droogz said:

The top part is actually sealed at the plexi and the door. I have a small (computer) fan pushing air into the top part from the back. I just picked up a squirrel fan from the local rehab shop and i will be setting that up to pull cold air from outside the room into the top chamber. I am hoping that will work. The lower side closed got to 100+

Click to expand...

so open up ANOTHER hole in the 'top part' and use the squirell cage fan to blow or pull the hot air OUT of the area. dont use it to force air in the sealed box and expect all that heat to piss out a little hole. You need the fan suckin that hot fuckin air OUTTA THERE before you try and jam any cool air IN there.

you need 2 holes for proper ventilation. i didnt see you mention another hole in the top part. do you have just a fan blowing air into the top part? if so, open up another hole and use the squirell cage to suck the air out through that new hole. see where im going with this? you NEED 2 holes for proper ventilation. EXHAUST at the top. INTAKE at the bottom.

Nice rig Bongulator

Ventilation is paramount is smaller grow chambers. My flower box has a grow space measuring 39"w x 42"h x 30"d. At the moment I have 27 SOG type ladies flowering in there. I am currently burning (2) 400w HPS mounted in DIY cool tubes and (1) 24" Reptisun 10% UVb lamp. I cool both HPS lamps with a Stanley blower drawing air from the grow chamber across the lamps and out through a carbon scrubber. I also have 2 cheap Wallyworld fans inside the box for circulation and a 110 cfm bathroom fan to remove heat from the chamber(does not cool lights) The larger Wallyworld fan is mounted high and blows across the cool tubes and the smaller one blows across the canopy.
I know this sounds like alot of fans, but it's what I had to do to get the temps down to a reasonable level. With all the lights on my temps stay in the low to mid 80's at canopy level and I can live with that.
Some may say I'm overdoing it with 2 400's in tht small space but my girls would disagree. Since adding the 2nd 400, I have seen a significant increase in bud density and weight. However, this could also be due, in part, to putting my girls into flower sooner. They don't stretch as much so the canopy stays lower and doesn't grow to the top of the box where the temp is higher.
I've been reading about CMH lamps lately. From what I've read they radiate alot less heat than an HPS. If you can find a way to direct some cold air from your ac to your intake that'll also help.
Try not to laugh too hard at the construction of my box. I can cut and screw 2 pieces of wood together but I wouldn't call it carpentry.
Hope this helps.

chilly lizard

theres no way i would laugh at yer box. it looks really good to me! could use a little more stealth but thats just the way i like them to be.

you have 800 watts in that cabinet? thats nuts! i think if you got a quality hood (one that is air cooled and directs ALL light downwards) you would be better off with just 1 400 watt bulb.

fuck man, 800 watts in less than 4 feet of height, thats a shit load of light.

i like the hurricane tube setup. looks good. you must get ROCK solid nugs if you use 2 lamps in there! still cant believe your dimensions. good for you if you make it work. Ive struggled with temps in a bigger box with smaller lamps.

Thanks Khujo! I appreciate the compliments. She's not very stealthy but she doesn't have to be since I live alone.
I have been constantly upgrading since I built it. I started with a 150 HPS, then went to a 250, then a 400. At first I just had the lamp mounted with a fan blowing directly across the bulb and the fart fan handling the venting chores. That was ok until I went with the 400. Temps got a bit out of hand so I rigged the cool tube. That took care of the excess heat and the quality of my buds improved.
I don't use a cooled hood because, like a dummy, I built the thing only 4' high. With the limited vertical space I think a hood would need too much head room. I originally had a DIY reflector I made from a piece of 8" steel duct like the HVAC guys use.(I picked it up off a trash pile at a jobsite. I'm cheap. lol.) It caused hot spots like a madman so I scrapped it. I'm always making improvements to the box. Perhaps reflectors will be next.
I, of course, want to grow enough to be self-sufficient but am after quality over quantity. That's why I added the second 400 and the UVb lamp. My buds are nice and tight now....and tasty, too.
I know that with all that light in such a small space my setup is inefficient. I'll never see that magical 1 gram per watt everyone shoots for. But, like I said, quality over quantity is my goal.
I was going to add some pics showing some of the girls but I kept getting a message that my request couldn't be processed because a "security token" was missing. Whatever the hell that means. Oh well! Maybe later.

The main thing is getting the light in a seperate chamber and blowing shitloads of air into it. My 1000 watt hps in a easycool8 reflector is cooled by a 465cfm valueline blower and the glass is merely warm and the top stays cool enough where it dosnt bother you to keep a hand on it. Keeping a high enough airflow by the bulb (a comp fan wont do it) is huge in keeping your temps resonable. Switching from a "500"cfm suncourt duct booster fan my temps dropped OVER 15 DEG!!!