Stealth cab design - opinions needed!

hello there RIU'ers

After building a semi-stealth veg & flower chamber into an existing cabinet, I'm wanting to build a whole system from scratch, which will be 100% light proof and have super-optimized ventilation. I am so concerned with the ventilation, that I'm building a whole separate space for it, planning to use a 530cfm 6" inline Tjerlund duct fan for everything (which has great reviews).

DETAILS:
Exhaust Ducting: 4" PVC with 45˚ arms going to a 6" to 4" reducer to the fan
Supply Ducting: passive - 4" PVC. I'm also building a cooler for the flower room air supply
Flower room: 12.5 cubic feet (2 plants) 23"x23" area 41" high
Veg room: 7 cubic feet (4-5 plants) 23"x23" area 25" high
Drying room: 120mm pc fan exhaust, passive intake (probably going to split this space in 2 for another exhausted room for ballast / electronics)
Return room: 120mm pc fan exhaust, passive intake (this is to block lighting for the veg room light box return, without buying more pvc)
Cool tube: 4" flex and pvc ducting for 150w HPS (want to move to 400w tho)
Exhaust Fan: Tjerlund 6" 530cfm inline fan - will sit on foam to reduce vibration and connect to rigid ducting via short amount of flex

after researching ducting principles, this system seems to be the most optimized system for the space I have to work with. (Least amount of turns, length, etc)

** in the images below, some walls have been hidden to show specific parts. The front doors are not shown.

The inline fan will be exhausting a total of 19.5 cubic feet of space, along with the cool tube, which will probably be filtered to dampen the strength on that arm. I think it should be able to handle this.

Experienced Builders/Growers: PLEASE comment and criticize! I grow with using LST, and may try scrog, so the space's volumes work for me.

cool air supply ducting is BLUE and hot air return is RED

Very nice, you have put alot of thought into this.

What types of lights are you using for Veg? I think 2' T5 HO would work good. I would go 400W HPS for flower, I did and have almost the same size rooms as you. What is the temp at your intakes?

With a little redesign I think you can increase your grow space by minimizing the amout of space your "Utilities" take up.

You've got a huge amount of room used up by utilities. I'd be curious to see this built but I think you're better off doing some refining and tightening up your design, possibly with one small utility chamber overhead for side by side flowering/veg/mother chambers and if you plan to use hydroponics another utility room below to house your reservoirs and pumps.

I like the design. Looks like it's more complex than it should be. But I guess it has to be if you're trying to incorporate all the equipment, functions and grow space into one cabinet. I like to keep it as simple and functional as possible. I would build separate cabs for each stage and maybe stack them if space is an issue. But I think that, you also have to keep it hidden from someone who lives w/ you.

What did you design your cabinet with ?

Thanks a lot everyone for the posts so far!
Questions answered in no order:
1. The extremely large amount of utility space is due to optimizing the air flow. For example, using 45 degree connectors instead of 90˚ T connectors really adds a lot of length to the ductwork (but really saves on CFM).
2. I'm using one to three 105w cfls in a little box - see it here: https://www.rollitup.org/cfl-growing/350409-1st-grow-stealth-all-cfl-3.html
3. I'm using all soil, for taste and simplicity
4. Using a 3d program called Rhino, but Sketchup is better for those with little/no experience (and free)
5. Intake temps range from 65˚-80˚, but I want to design for 85˚, as it gets that hot here
6. Grow spaces are set-in-stone because i'm using these light-proofing metal edge parts from my current cabinet, and I also want to keep it small.
7. It definitely is more complex than necessary! But, i'm straining to preserve the CFM.

Very nice description of ducting principles here: http://gekgasifier.pbworks.com/f/CincinnatiAirDuctingandEntrainmentData.pdf

that PDF drove my design, and is very informative. See page 9 "ducting design practices"

I really like the suggestion of utilities above and grow space under. I'm going to think more on that, although the fact that i'm trying to minimize the number of duct turns and entry at 45˚ really adds length, and there is more length in the vertical direction, hence that orientation as of now.

my question: Does anyone have experience with this sort of inline fan, and do you think this is overkill?

Thanks again! keep the ideas coming! collective intelligence!

WOW, intricate as hell! Will come back to this later for sure

If you are not running a sealed room why can you not just locate your blower in an attic or hidden in a wall? The exhaust has to go out anyways put the fan on the other side. As a former stealth grower (I'm now licensed MM) I can tell you space is what you will be dying for, so EVERY usable extra square inch is worth fighting for. As far as inline fans go I would highly recommend looking at the panasonic whisper line if you can fit it whereever you end up putting(in the cab or outside), I dont see a DB rating for that and I would be very curious since I have seen similar designs in the 49-53db range whereas the panasonic is in the 30's. Also putting the fan outside will DRAMATICALLY decrease your sound level. When Air rushes into and out of the fan is the loudest noise you will have in that setup, putting it inside a wall or attic or as far away from where you can hear it will be paramount for stealth. Also you will want to insulate the venting.

Also 500CFM+ is a lot of air(I mean LOT of air) so if you plan on blowing it out the back and not going somewhere else with a vent tube, I suggest another plan unless you can deaden it somehow(possibly muffler like plates with holes in them located under the cab going from larger to smaller diameter). Someone will notice that amount of air being exhausted if they get anywhere near it.


As far as cooling power, for 1 400w HPS in a retardely small direct vent cab(much smaller than what you have here) 400CFM will do the job. I dont know about vented hoods and 2 lights but I think with cool tube/ hood you will probably be ok with what you have and you can probably go less.

One thing is if you can loacate it somehwere where there is some constant ambient noise that will help you, alot.

One other thing is that you can find a carbon filter that can handle the CFM requirements you are looking for and how large it is. FYI I have one rated for 450CFM and it is the long design (not short squat one) and it takes 31" of 10" diameter to run that kind of CFM. Filters for moving real air (not that 200CFM crap) are pretty large.


Another thing with as much extra space on the utlities side you might want to considered sealed room, you should be able to fit a scrubber in there and that would also allow you a smiple Co2 injection system using a small tank. Since you have a cooler, why not?

Also I notice the return on your veg room is not filtered? Why? Are you not going to veg enough to have enough biomass to start smellling much and can you efficiently seal the the top from the bottom even though you have a door that opens on that side?

Just my opinion and some ideas for you.

ok, here is my take. as you may know, i may not be the best grower, but i know how to build some shit!! everything sounds great, but here are my comments in red

Drying room: 120mm pc fan exhaust, passive intake (probably going to split this space in 2 for another exhausted room for ballast / electronics) i think 120mm may be too much. you do not want to dry them to fast so this may do just that. maybe like 15 CFM total, so if you get a fan speed controller (like $5 off amazon, just got one!) you can play with it.
Return room: 120mm pc fan exhaust, passive intake (this is to block lighting for the veg room light box return, without buying more pvc) veg rooms dont need to be 100% light tight. as long as you dont light stress them, meaning really screwing with the light cycle. you may be able to recup this space if you like for ballasts, or extra dry room.
Cool tube: 4" flex and pvc ducting for 150w HPS (want to move to 400w tho) if you angle your cool tube return at 45 degree angle up, you can place your cool tube in front of the filter giving more height. at the same time you may be able to eliminate that flex and use 1 90 degree PVC coupler coming out of the cool tube into a straight PVC which would connect to the supply cool tube. did that make sense? basically an S. that flex is loud compared to smooth PVC, and PVC flows better. And this may hurt your feelings, but I dont agree with the 400 watt in 12 cubic foot. I say 250, OR, add a 150 CMH to go with your 150 HPS so you have a broader spectrum in there. if it gets too hot with 300 watts at least you can remove one and rethink. if it gets to hot with the 400 watt, well we will be back on a thread like this helping you design your 400 watt flower cab.

i am not 100% on the cooler idea. not sure what your using for a "cooler", bet you might want to think efficiency. for instance, i once thought of placing an electronic cooler in my cab. it may have cooled it a little, but it would have ran its ass off and probably cost me more in electricity than it was worth. so I dropped the idea. i also tried a homemade peltier AC, so did jsgamber. they were not efficient. as others have stated most ideas are great on paper, but you may want to test your system first without certain things, like the cooler, to see if they are really needed.

no experience with your fan, but the CFM sounds good for what you have going. let us know when you got it built, it will be awesome!

First thing I see is I would have the Cool Tube intake (passive right?) directly on the back wall. Too many un-necessary angles. Veg chamber too as I assume it's 3" or 4" from wall. As Gumball says, light proofing veg isn't a big deal. I also think a 120mm is overkill for that drying chamber. I think the area for timers/wiring and ballasts etc is good. Fan seems like plenty. A 400W isn't needed in that small a spot and heat is our enemy. I'll look more and give you a better view. Great diagrams BTW.
Daniels

@TheDude
- Everything must be enclosed inside the cabinet, unfortunately. I am moving to an apartment (w/ no roomates), so there will be people above and below me, but no balconies, (and no more cleaning lady to worry about - so I can have a bit of noise but not a hell of a lot - i'm getting more worried about this fan tho, as I already bought the Tjerlund 530cfm). Getting everything IN the cabinet is a big challenge.
- The air velocity is a challenge though, and I know I will have to keep the cabinet a bit away from the wall (want to put it on casters) but I like your muffler idea, although I'm having trouble visualizing exactly how it works. I fired the fan up for the first time the other day, and the air movement is LOUD. I need to try to dampen this. The way the air exits the fan needs some refining.
- Good point on the filter - the one shown is using a 10" long strip of carbon-infilled sheet from the petstore. I guess i'll need more, damnit, i hate messing with activated carbon!
- I didnt plan on filtering the veg room, as i didnt think smell would be an issue. Out of 2 strains i've already tried, smell hasn't been around during veg.

@Gumball
- With the veg room, i'm trying more to keep light from getting out - without a couple of turns, the light exits through the flex that i currently use pretty easily from that little cfl-box i built.
- I hear ya on the cool tube, i'll use as little flex as possible, and avoid a 400w (no feelings hurt!)
- with the cooler, i've designed one of those highly-debated ice chest coolers that circulate cold water thru copper piping. I have a medical ice bag for it, and I think it can work with the scale that i'm using it for, and since the box itself is outside the room, the ice should last longer. I really read up a lot on those diy a/c designs. I dont like real a/c cost and energy use.

@Daniels
- Well, with the angles, i'm trying to trap the light. I run my lights at night, so and leaked light is very noticeable. Hell, if i can eliminate some of those angles on the passive intakes, I will! The light traps i built for my current setup have 3 turns and still lets some light out! (but much less length though)

I'll have to upload some pics of my current cabinet, which hasnt been well documented. Its something of a prototype, but i can highlight the light escape issues i have.

thanks guys, very helpful feedback!

Nice software ya got there, what did you use?

As far as airflow and space, I found an 80 cfm more then enough to exhaust with but you already got the monster you may as well use it.
I assume you are using 4" to conserve on space. Have you seen those flat dryer ducts that go from round to square in my cab? I bet if you looked at using those you can save about 2 inches in width. You may want the dry chamber to exhaust through the carbon filter too or it will smell up the joint. I assume you are going soil as I dont see any space for a gravity fed res in your design. I understand you want stealth but a cabinet against a wall will need to be at least an inch away cause of the carpet and molding. Might as well make it two inches and run your flat ducting behind the cab. Nobody will notice it and it will give you a lot more room. Good luck at keeping any humidity in there during veg.

You know one thing I'm thinking is say you could put a long carbon filter under the box (is that a possiblity?) and push air into it (do you have an old dead filter you can use to diffuse the air?) that would allow air to go out all directions instead of being directed out in a jet which would be less loud.

How is your fan rated? I know the whispers are not meant to be run this way but is it possible to put a rheostat in to throttle it down? That might be something to think about.

Cruzer: thanks for stopping in! I'm using the 4" mainly because it is the most available and least expensive. I hear you on the 2" ducting, but I really want to keep everything inside the cab, and I'm ok with having so much space for utilities. I only want to flower 2 plants at a time anyways, just personal use and for a few good friends.

TheDude: That diffuser is a great idea. I dont have an old filter, but I can build something that can do this. I'm not sure how the fan is rated, just says 530 cfm on their website. I'll definitely get a speed controller to tone it down a bit. I'm going to email the manuf. and see if this fan can be run horizontally, thats a good point.

Well, these Tjerlund fans can be mounted horizontally or vertically, no problem. They can be speed controlled down to 50%, but anything under that, and they can start to burn out the motor.

After researching muffler devices, I think i'll build a little chamber in the bottom of the cab, lined with foam, to exhaust the air. Maintaining the high airflow:silencing ratio seems to be hard to balance.

Sounds like a good idea, maybe you could re-engineer the cabinet to hold the fan and exhaust the air in this same foam lined insulated muffler box? Just a thought to silence even further.

Well, taking more of these suggestions into consideration, I'm going to eliminate the flex altogether, and use rigid, fixed cool tube in the flower room, using adjustable shelving to move the level of the floor.

Here are a couple of new screenshots showing the entire system outside of the cabinet. The idea is to have the highly filtered flower room exhaust going directly to the fan, with the cool tube and veg room lines running as secondary branches. I may have to add filters to the secondary lines to balance the strength of the fan. With a controller for the 500+ cfm fan, this setup should be nicely customizable, but will require a lot of testing, I think.

Looking to start construction this saturday, so any more suggestions this week are very welcome!

Looks like an exhaust header!! My only suggestion, and this is only if you don't have experience with the PVC ducting, is to go into Lowes or Home Depot and test fit/measure a bunch of these pieces in the store. You will look silly, I did, like a kid playing with legos! But you will know what will and won't work. You could obviously buy it all take it home and fit it, but this could save you some trips. Plus we all know once you start building it you will want it done and may cut corners. Looks like a well thought out design

gumball said:

Looks like an exhaust header!! My only suggestion, and this is only if you don't have experience with the PVC ducting, is to go into Lowes or Home Depot and test fit/measure a bunch of these pieces in the store. You will look silly, I did, like a kid playing with legos! But you will know what will and won't work. You could obviously buy it all take it home and fit it, but this could save you some trips. Plus we all know once you start building it you will want it done and may cut corners. Looks like a well thought out design

Click to expand...

hah, well, i'm one step ahead of you, man! Not only did I assemble the whole thing in the store a few weeks ago, I was extensively measuring every piece, so in the 3d model, it is the actual size. People were definitely giving me weird looks. Well, I've definitely thought a lot about this design, but have yet to see how it will work in the end - - like everything else i've tried, I'm sure there will be some unforeseen surprises as I'm taking everything from theory, no experience.

yah, it definitely looks like something that should be on a car! If nothing else, this can be an RIU learning experience here...

I think it will work great, just don't use pvc glue, maybe a wrap of foil tape at the seams, but glue means permanent, sawing and major disassembly to modif), bad juju in my book!

The only thing I see that maybe a problem is smell. Your going on the assumption they don't stink in veg. And we all do. But some strains are fragrant throughout the grow. So you may want to consider a design which places the filter in the bottom after the last 90 degree turn and filter all your exhaust. This will also give you a touch more flower space, and may help dampen the overall exhausting air noise, as someone else pointed out will be loud. Still a great plan.

Take your weed out of the cab to dry it, don't dry it in there, even if you have a seperate chamber within the cab, the temps are too high, but your fan is massive, not sure if you've been using it already, but its gonna be one loud muther fucker, they're usually meant to cool several 1000 watters at once, I'd suggest investing in a control switch to regulate the speed of the fan.