my grow cab setup.. is it flawed?

[biffmcnielly]

hi
I am really new at this but thought it would be nice to grow my own meds.

I started with a dwc tote, the aquired a metal storage cabinet bought my self a hps light, built a carbon scrubber and put my plants into individual buckets.

cab is 39x20x72 with a shelf 18 inches from top

I lined the interior with mylar.

hung my 400w hps

ran a 4' exhaust near top and cut a 3x10 intake on opposite bottom

got to the point of sealing up the big light leaks.

Day 1...cooked the plants got to 116 inside while in the 70's outside. took out the hps and rigged some cfl's
I then rigged some cooling on the light. 4" in and 4" out.
got it into the 80's but I think the light was still too intense for the plants. my 240cfm fan also fryed, so now I am running a 185cfm booster for now until I get the funds for a new fan.

right now with 2 100w cfl's and 1 300w cfl it is 75 in the box with the fan going and no scrubber, it is in the 60's in the room.

is a metal cab a bad idea?

where did I go wrong???

PLEASE NOTE THE PIC WAS BEFORE CAB WAS COOLED

 

[FreezerBoy]

400 is a little big for that cab but, you didn't say what type of fan you used. I'd think with a scrubber you'd want 300-400 CFM. A duct booster is for boosting your real fan, it's rather useless on it's own.

The most obvious problem is the intake duct on the fan. Heat rises. You're sucking out the cold air, trapping in the hot. Remove the duct or point it the other way.

 

[TheMonarch]

I think the scrubber may be too small.. If it helps, my 21"x34"x54" wooden cabinet with a 400w HPS inside stays at 75-78deg (3-5 over ambient) with a 140cfm dayton blower cooling the light and a PC fan running at half speed (20cfm, tested with trash bag with door closed) providing the plants with fresh air and filtering the smell. . So there must be something wrong with your setup, is the temp sensor in the shade? I think its just hanging about 6" under the light

Also I think your bulb/reflector will leave the sides of the cab kinda dark. Freezerboy has a drawing, I think

 

[BLUNToPOTomuss]

Remove the mylar and paint the walls flat white.

Does your light have the ballast connected to it? tons of heat pours from those types of lights. I think you need more exhast than just a 4'' hole.

Intake at bottom exhaust at top, If your light is NOT air cooled you need a fan blowing across and right under your light with a STRONG fan exhausting out of the BIGGER than 4'' hole.

IMO your Cab is a little small to run an UNCOOLED 400, I have a 24x24x48 with a 400 cooltubed and a 265CFM blower pulling through my Cooltube and pushing into my scrubber. ad I can stay at any temp I want lights on. I just adjust the room temp.

You got to exhaust the hot air at the top of your cab FIRST to reduce teps the most!

Good luck

 

[biffmcnielly]

exhaust is at the top, and I air-cooled the light... also made a remote balast for the light due to the heat

 

[BLUNToPOTomuss]

Ok I was confused By the pic, the duct that runs up from the ground, into your fan above your light and out somewhere..... what is that for? thats where I was confused......

Anyway to pull air from under your light with that duct? Or move it to the top off the cab to suck out the upper air?

Boosters suck once any resistence is added to them, I mean like a minimum of 50% loss!!

I have a veg cab that is 12x24x48 with 98w of cfls and I have 2 80mm pc fans (45cfm ea) exhausting that. Thats an exchange rate of 12x's a minute, I think you gotta go a bit more on the exhaust..... The faster the rate of exchange the cooler you will be.

Cheap 120mm PC fans push 75CFM ea and only run about $12. Put one or two of those on the back top of your cab if you can. Im sure that will help.

IMO noobs like us are better off having WAY more exhaust than needed to assist in cooling. Screw that 3-5x ratio, I think noobs should look at minimum 10x exchange!!! (where applicable)

 

[FreezerBoy]

Ok I was confused By the pic, the duct that runs up from the ground, into your fan above your light and out somewhere..... what is that for? thats where I was confused......

Me too. Looks like he's pulling cold air out the bottom and leaving the hot air at the top. Where is the fan drawing air from?

 

[DiscoBiscuit]

hi

ran a 4' exhaust near top and cut a 3x10 intake on opposite bottom

The part you left out is you ran a 4" duct from the intake? to the exhaust. I tried to tell you this in the previous thread but figured you didn't agree. Give it a try, dude. You can always put it back on later but I don't think you will.

Any cool air coming into the tent is trapped in the duct, not circulating (thus cooling) the cab. Get rid of the duct running from the intake to the bottom end of your scrubber.

Another thing you can do is leave a couple of inches space between the scrubber and lamp housing. Your scrubber will be more efficient and it won't heat up as bad when it's not laying against another hot surface.

 

[guest 77721]

Hey Biff,

You're problems are caused by trying to remove heat and pass all the cooling air through a scrubber. The scrubber is a huge restriction to airflow.

Your growbox design looks good and to answer your question about the metal cabinet, it helps to radiate heat by conduction/convection.

Your 400 W HPS light puts out 75 w/sqft which is a good intensity to grow some nice medicine. Too cool a bare 400W HPS, you need 126 CFM of unrestricted air flow for 10*F temperature rise and 158 CFM for 500 Watts.

You can buy a great big centrifugal blower to force your cooling air through the scrubber with the existing desin.

Upgrading your hood to a ventilated style will work with your existing duct booster fan. All you need is 42 CFM for a 30*F exhaust temp and a few degrees rise in the box as long as the airflow isn't blocked up.

 

[FreezerBoy]

Until you lose the ducting to the fans intake, you will continue to bake your cab. Lose the ducting and you will lose the heat.

 

[severian]

Nice photoshop.

I think this is what Freezerboy is saying.

Same size metal cab, but using open cooltube.

 

[DiscoBiscuit]

severian, that little circ fan is one of the quietest I've ever tried. I even used it as an exhaust in another cab, it moves that much air.

 

[severian]

Yup, its a Lasko and whisper quiet.

 

[FreezerBoy]

I think this is what Freezerboy is saying.

Right-O-Rooney, severino.

Sucking cold air off the bottom causes heat build up. To remove heat, you have to, well, remove heat, which lives at the top of the cab.

....... add ........
Maybe this will hammer home the idea. What he's doing is on the left, what he wants is on the right.

 

[DiscoBiscuit]

FreezerBoy, Why don't you drop the tail duct and let the exhaust suck air outta the cab instead of the room it's sitting in?

Okay, now I get it. The north end of the duct isn't connected to the cab. Damn I'm thick sometimes. Another fine diagram, sir.

bif, that's what I've been trying to say but a pic is worth a thousand words.

 

[FreezerBoy]

The rectangle is the cab, not the room the cab sits in. The tail duct doesn't connect to the room. Intake from the room comes through the intake ports. The tail duct in both illos is sucking cab air only. On left, it sucks cold air out the bottom as fast as it comes in, converting the cab to an Easy-Bake-Oven. Turned up (or simply removed) the tail duct sucks out the heat at the top which, of course, draws more cold air from the room, through the intake ports thus, cooling the cab.

 

[DiscoBiscuit]

I get it, thought your duct was collared to the cab.

 

[FreezerBoy]

We be cool. I'm just that slow a typist. By the time I post it's often after the conversation has changed.

 

[mpd]

I had the same problem in my new stealth cabinet. I realized I wasn't pulling the air from high enough in the cabinet to control all of the heat I wanted to control. Freezerboy's diagram may be primitive but it is spot on. Nice cabinet project. The kinks will be worked out in no time and you'll be a happy camper. You wait and see.

 

[GrowerGoneWild]

Freezerboys diagram is correct.

Cool air is always denser, and will _push_ hot air out.

In my growcab, I've had to extend my fresh air intake so it reaches the bottom of my cab. And for those of you running hydroponics, it has the added benefit of cooling the res a few degrees.