Temperature/Cabinet Concerns

:) The cabinet is 3x3x5 or 45 cubic feet. The lamp is a 430 hps with cool vents. I have a 240 cfm fan hooked up to the lamp. I also have two 80 cfm to vent out the cab. I have passive intakes for both the lamp vent in and the cabinet vent in(one each). The duct work comes out of the passive intakes and connects to a "y" which then goes to a single duct tube which then goes to the outside to draw the air into the box. Even though it is a nice 65-70 degrees outside the temps in the box are runnning 85+ . I have a digital thermometer hanging inside the box and the screen to read it on the outside. Is there a wrong place to put the thermometer in the box?? Also having the duct work connected to a "y" effecting in any way? I am just trying to get the temp down to the low 70's. :)

what size of duct tube are you using on your passive intake?

I have a similar cabinet with same problems too.

My cab is 2Lx4Wx5H with a total of 40 cubic feet with a bathroom fan rated at 70 CFM thats connected to 3in tubing, I have two passive intakes which are grills cut into the back of the cab.

My lamp is a 250w HPS

same probblem as kind67 the temp for my cab jumps almost to 90F when i turn on my HPS, I have been keeping my seedlings under two T5 2ft 24 watt and one 20w 2ft fluoro.

the room the cab is in stays around 75-80 but the cab jumps almost to 90. i know i defnitely need a better fan, im not sure rated for how much CFM. i was wondering if there are any other tips for keeping the temp down or how much should i get my new fan?

Well I got my exhaust fan off of an air hockey table. It's a squirrel cage fan and it moves alot of air. It's probably a little louder than most the other squirrel cages you can get from a hydro store but hey it was free. Right now I have that fan with 2 4" passive intakes with a filter over both and 4 cfls and it's staying right around 74-77 F. Basicaly the temp of the room it's in maybe only a couple degrees warmer. I have a 400w hps on the way so I'm not sure how much the temps will jump when I put that in. Oh my cab is 4x4x2. So That's one idea.

The intake into the cab is 6 inches and the intake to the lamp is 4 inches.
The exhaust for the lamp is 4 inches and the two exhaust for the cab are both 3 inches. I read where to use a smaller exhaust to create more velocity
and to create a force airflow to the exhaust. What about the thermometer location any idea if I am getting an accurate reading or is it just being run up buy the lamp. I to had my babies on cfl's and have transplanted to a larger pot and the hps.

Cactusman I love your location" from the basement of the alamo" that made my day.-peace:D

I try to prop my dig thermometer as close to the top of the plant that is closest to the light. I also move it around a couple times a day to monitor the different temps in the box.....less hot spots...

Work on the fans! you should be able to get it cooler than 85 in there!

you may have to separate your intakes or just have the single intake. From what I've read around here is that you want a negative static air pressure in your cab, especially if your running a carbon filter. Its hard for me to explain what it is, but I understand why and how it works. Try the search forum for static air pressure

More info:D
I switched my intake to just a single tube and not coming off a "y". The temps still hovered above 85. I was worried about negative pressure so I did a test. I turned off the lamp and the temp was 88.9 on the thermo. Within 90 seconds the temp was down to 73 and at two minutes 71. This also was about a degree above the ambient(outside) . Also I tried both fans on the lamp duct the 240cfm and the 80 cfm-Same result????? So suggestions suggestions suggestions please. :dance: Do I need to add another intake? Do I need to make a cool tube and do away with the cool vented hood? or what ?

A recap.
I have a 240 CFM and a 80 cfm duct fan for the exhaust. The exhaust size holes are 3" and 4". The intake into the cabinet is 6" and receives fresh air from outside. The lamp has a 4" intake and a 3" exhaust-there is a 80 cfm sucking the duct work from the lamp and the getting fresh air from the outside as well. OH the box is 45 cubic feet 3x3x5.
Peace to All -:dance:

Just some more info- I checked the ladies and the ironic thing is they look great. Leaves are green and full figured- new growth coming out the top?? Is it possible for the lamp to be reflecting off the mylar and cause a false reading on the thermometer????:)

I had a simlar problem in a box that was 5' tall, 30" across and 28" deep. Had a 250w hps and a daytona 150cfm fan. Temps soard into the 90's. First I made sure that the box wasn't pushed up against a wall. This helped giving more free flowing cool air, but still the temps were mid to upper 80's. So then I got an idea. I screwed a couple furing strips just below the lamp, and dropped a piece of clear tempered glass in there. I wasn't a tight fit, and you don't want it to be so you get good air circulation around the plants... but it isolated the lamp and the ballist enough that my temps dropped down to the mid 70's then.

Just a suggestion....

Jaxxx

is your vented light setup a sealed light setup. Any pics would help.

:thumbsup: Cactusman I attached a photo of the setup. It is sealed but only by gravity and weight. The glass slides into an opening on one side and has a metal tab that swings down to hold in place. There is 4" flexible duct going into one of the vents and the same size coming out. Then the duct goes to the active exhaust where I have had a 80 cfm and a 240cfm fan. Still the same temps???? Also there is a 6" passive intake going into the cab with two other active exhaust going out. I have each of them with 80cfm duct fans sucking as well. If you are facing the cab the lower right side has the intakes and the top left side is where all the exhaust are located.

Is your hood drawing air in from the cab or is it connected to an intake that draws in air from outside the box?

are y'all having this problem with the ballast nearby? those suckers get hot. I have a cabinet that is smaller than the ones listed here, and my temps never go higher than 85, even when I cover the top where the light is with a towel so light doesn't leak out the window. my ballast doesn't effect the temperature because it doesn't share air with the grow area. I have a segregated area that I was going to use for dark teatments so I lined it with black foam. but it currently houses the ballast and temps in there are around 90, but the grow shelf stays around 80. not bad for only being separated by a wall of plastic

Yeah I added my 400watt hps yesterday to my cab and my temps are at about 90 when the light is on and 74 in the dark. I moved the ballast to outside of the box and it didn't seem to help that much. I'm getting a new exhaust fan tomorrow so that should help alot...at least I hope.

I was just reading about similar problems in another thread. From what I just learned you maybe getting false readings by having the thermometer directly in the light.
Try making a small cover for your thermometer out of cardboard. Place the thermometer so it is at the level of the plant canopy with the cover keeping it shaded from the direct light. See if the reading drops any.

Hope this helps.