why is my cab so hot? 400w CMH 200CFM S&P 97F

[ahhhavalanche!]

so this guy i know has this new cab, the grow space is 18" 40" 41" tall from the top of the (35 gal) res up. there is a 400w philips cmh in a cool tube with 197 CFM worth of S&P TD-125 pulling on it. There are currently 4 plants which were germinated 1 month ago in it... they are in a temporary set up with all 4 near the middle so that i can concentrate the light , just upgraded from 42w of warm white (broke my third daylight) --

IMPORTANT CFL DISPOSAL TIP - side note but this is important... you can not throw away CFLs they need to be disposed of properly, i know ace, and the local light store, will take your cfls after they have served their time (put the broken ones in a ziplock bag {quickly... if you cant you should evacuate the room for 15 min to avoid murcury inhilation}),

-- and 46w of daylight. After they get bigger and start to fight for space i will spreed them out evenly in the cab.

pictures worth 1000 words right... so enjoy these next 7000 word essay:

plants with light (any ideas to the sickness on the 3 of 4? cut off the worst leaf on the worst plant today... i think i heat stressed them when they were young cuz its only on the oldest fan leaves... the front right one is in perfect condition and their all in the same water (ppm~ 600 using 200ppm tap, and ph 7.6)

reflector and fan (S&P TD-125, 197 CFM in high mode)

filling the res:

res and grow plane:

ghetto rigged outside air pump

exhaust (will have a scrubber soon further decreasing airflow)

back with intake and seams showing

plants with light (any ideas to the sickness on the 3 of 4? cut off the worst leaf on the worst plant today... i think i heat stressed them when they were young cuz its only on the oldest fan leaves... the front right one is in perfect condition and their all in the same water (ppm~ 600 using 200ppm tap, and ph 7.6)

i cant get the air temp below 95F!!! right now the ambient in the room is 84, but i have a powerful house fan in the window ghetto rigged to positive pressuring 73F out side air into the 4" inlet. I have a small 4" fan blowing directly on the cool tube from like 1.5' below, and a 8" oscillating fan sweeping across the plants. Im eventuality going to have 2 4" inlets on the bottom with 3" s-tube pvc in them, but this is a master piece in progress (will be done before moms weekend next week), and right now the back has a lot of seams that air can get in (the front is 100% light tight... took a lot of love and care)
Why is my temp soooo high? what can i do to cool it short of tuning the AC on?

 

[FreezerBoy]

the 4" inlet.

You're choking the cab. Cool air has been locked out. Intake should be double the exhaust at minimum.

For a more exacting formula fan-intake calculator

 

[MHHSP]

Yeah looks like heat stress.
You need to get some bigger fans and create some directional air flow. In addition to the cool tube... Maybe cut a hole near the bottom with an intake fan (at least 250 cfm) and another one near the top with an out take fan (at least 250 cfm)
Your system is not getting enough ventilation. Passive ventilation will not do it with a 400 watt light in that sealed cab.
Ventilation is a key factor in the success of MJ, or any other plant.

 

[AndreNicky]

You're choking the cab. Cool air has been locked out. Intake should be double the exhaust at minimum.

For a more exacting formula fan-intake calculator

Im guessing this is your problem i run a 400watt in a similar size area and i keep my temps around 75-80f with 1 171cfm exhaust fan and a table fan for air movment

 

[KUSHEATER1]

cut some intake holes and get a nice exhaust fan next would be to keep ambient temps around 75 or so I run a 400 watt hps with room temps of 78 lights on 70 lights off.

 

[greenhead]

cut some intake holes and get a nice exhaust fan next would be to keep ambient temps around 75 or so I run a 400 watt hps with room temps of 78 lights on 70 lights off.

How many CFM's is your exhaust fan?

 

[hoosierdaddy]

Your exhaust fan outlet is 6", and you have reduced it to 4" with the flex duct. That is OK because your cool tube has less than a 4" orifice to begin with, and the intake end of the tube is choked down even more due to the restrictions of the bracket and light fixture. The ~200cfm that the fan can produce, is not going to happen unless you can provide at the very least the same amount of intake volume as the exhaust.

The laws of physics actually states that the volume of exhaust air through a port is equal to the volume entering. A top notch HVAC man will add at least 10% to his intake air supply to properly satisfy the air supply of even the best designed system.
We get the recommendation to double the intake size (from that of the exhaust). however this is just a rule of thumb that we use in our sport. It is not really needed to have double the intake volume, as you can't get better than Ms Physics says you can, but it is a good rule to follow, because many of us will fail to recognize the little nuances that are actually restricting the airflow from original specs. An example is the 197CFM fan you have...with the current set up, it is NOT able to produce it's rated CFM's because it is being starved for air supply. SO it is really not a 197CFM fan any more.

The area of the holes is how to figure the air flow volumes.
A 6 inch hole has about 28.25 inches of open space (radius x radius x Pi(3.141) = area of circle). If you were to use 2" holes for the intake, (1 x 1 x 3.141 = 3.141 sq in), you would need to use about 9 of them to double the exhaust size.

One fast move you could make and not change much, would be to add a bit of the flex ducting to the intake side of your tube, and then flex the duct to the top of the cab. This would allow it to suck the hottest air in the cab out.

 

[KUSHEATER1]

How many CFM's is your exhaust fan?

6 inch cap fan

 

[ahhhavalanche!]

i dont know if i agree that it is an intake area problem just because i had the positive pressure fan pumping a significant air into the cab. There is no way that that fan can be there all the time, cuz it puts the cab in the middle of the room and the landlord might notice if there is a large humming armiour in the middle of the room... i think i am going to downgrade to a ~350w cfl setup (stick with what i know) and turn the blower down to its low ~150CFM setting... i am actually a little disappointed with the blower cuz people in another thread said it was whisper silent (silenter then a panasonic whisper!) and mine is definatly not! go see my rant in the inline fan thread... also im not SO sad to see the CMH go, i got an amazing deal on it $40 (special ordered from a local light store) and i borrowed my friends 400w ballast so i didnt sink so much $$ into that part of the setup.

 

[threeeleven]

Sure... don't take the advice of people that are trying to help you....

What's the ambient temp of the room the cab is in?
Why do you have a positive pressure intake when you can use passive intakes?
Why do you ask questions and don't even give people's answers the time of day?

 

[ahhhavalanche!]

wow threeeleven thank you for your constructive post... no i will not blindly accept others answers as fact... i do believe that my reply was polite, conclusive, and appropriate (i wont say the same to yours)...

all your questions were meticulously addressed in my original post:

"What's the ambient temp of the room the cab is in?"
as you can see in the picture with the exhaust... the ambient in the room was 85, however the intake was being feed by the fan from the window with 73F outside air... turning the AC on to cool the whole apartment is not an option... im a hardcore environmentalist, and my roommate is trying to save money on the elec bill...the living spaces remain between 75-80... we dont switch the air on till it gets to like 82

"Why do you have a positive pressure intake when you can use passive intakes?"
the positive pres intakes was to compensate for the small intake by forcing air in instead of passively letting it get sipped in... after passing my fluid dynamics class (used to be a rocket scientist) i am confident that the size fan and kick ass intake i set up would counter any gasping caused by the small intake

http://www.icmag.com/ic/newreply.php?do=newreply&noquote=1&p=1908072# regaining civility

"Why do you ask questions and don't even give people's answers the time of day?"
i do appreciate the responses i have been getting (with one notable unnamed exception), and i hope that i didnt come off as rude by disagreeing with yall's conclusion... i hope that many a more civil dialogue can occur on this forum... and by the way its a little before 4:20pm where i am.

 

[threeeleven]

Well whatever you are doing isn't working, obviously. The ambient question was rhetorical... because you are running 85F ambient .. not gonna work. Piping in "cool" air with a shitty ass fan like that... obviously not working ... so why not listen to some of the other answers and try them out before dismissing them...

Sorry you got butthurt by my post, but when someone asks for answers then disregards them... we have a name for that... its called YUMMYBUD SYNDROME.

 

[FreezerBoy]

311 needs a timeout. That said, you're choking the cab and depriving it of cool air. Look here to see how others have cooled a 400 watter The 400 Watt Club

 

[bounty29]

The combination of 80+ ambient temperatures, a 400w bulb in a cab, and insufficient ventilation system will make it pretty hard to grow. A 400w bulb is going to warm up the room it's in, and if you don't have AC then your temps are going to be too high.

 

[darrinjefferson]

i agree with what everyone else has said. if ya want to take a look at a sweet 400watt cab look at the link in my signature.

late

 

[eyes]

your a hard core environmentalist and your roomie is trying to save money? 73 degree air ist gonna cool that cab.try waiting for temp drops in a month and youll be pullin in 40 degree air or so.if you are going to cool that cab,run that 192 cfm fam with its intended opening matched to the cool tube.also,run the air somewhere that cant be recirculated to ambient air being pulled back in to the intake.

thats a very ineficient set up.you have the intake end of the hurricane glass blocked essentially by the socket.how is it developing its true cfm through a half a@@ opening like that ?dont worry about blowing air into the cab...cut more holes for the intake and make it passive not active.one whole with the lame a@@ fan blowing in to a paper cone wont cut the mustard.youd be better off without that glass until you have a filter..just run the bulb without the hurricane glass and open up more intake holes and run that fan with its true opening.get that hot air out where it cant be sucked or mixed into ambient air.that way you box temps will be a few degrees over ambient.you can always push air over the bulb to see the difference as well.but,with that set up its not going to cut the mustard.

 

[ahhhavalanche!]

i finally got around to putting in the second intake today... i like eyes idea of ditching the cool tube... i will (if i can find time, lab report due on tues) try it like that hopefully tomorrow... if that doesnt work my plan is to throw it under some cfls, and when it does get hardcore cold outside throw the cmh on for maybe the last third of flowering... does anyone think that that will light shock them or cause any other adverse effects?

 

[FreezerBoy]

These things are built for the Sun. Nothing we can buy competes with that. However, training a plant to think CFLs are the Sun leaves them unprepared for stronger light. Hang the big lamp high for a day or three and move plants under it at "noon," so their first day under the big lamp is a half day.

 

[darrinjefferson]

i find that cool tubes in that small of space work best. in my 400watt cab I had one large intake. I think it was 6" x 12" and I had a 307CFM fan pulling through a cool tube. this was a perfect combination. If you need additional fans or a better one you should look into a stanley blower fan and mod it into a fan for your light. I have a friend who cools a 1000watt hps with his stanley. they are also only $30 so its really cheap.
hope this helps
late

 

[Bubble Puppy]

I like the idea of adding an air conditoner to your cab.I just did ,spent $200 and added 10,000 btu .No more cooling problems .You would only need a small one ,maby 5200 btu