I drew a bunch of things, crushed my head in all directions and not helped much by my level of English … I’ve not yet found a way to vulgarize the static pressure game. At one point a lot of specific parameters enter in game :
- temps (winter/summer/averages) : it set the average density of air to deal with
- height and barometric factors
- torque of the RVK and climate (barometric pressure)
- also the house insulation and exposition (winds)
For obvious reasons i can’t enter too much in details, and it’s damn hard to explain the things this way.
Better to show, and i’m sorry for the others, keeping the details external discussions. I don’t give up, i will find a way without falling in a tutorial barely practical.
Forget the RJ45 cable on right.
So, here we have the basis of the main problem with the static pressure. More clear without the tent.
- 1st error : The twos “massive” structure (lung closet + tent) eat a good amount of cubic space in the same spot. It was voluntary and based on bad habits : to generate the maximum “free air volume” possible, to maximize the air exchange and its stability. Now considering what I’ve learned on static pressure and its cumulative aspect for our use, it was hard to be more wrong in fact.
My house is not specially tiny and most of walls are 10 feet high, but on insulation and energetic efficiency i’m a bit crazy. So a single filtered 400CFM RVK is enough to put the whole house in negative pressure, and to open the cat trap if i open/close the front door at the other side of the house.
That’s the main static pressure rate to deal with, and when you reach the “grow room” this static pressure is increased by 4. So it create another layer of increased static pressure around the mouth of the ducted intake that was sucking in the same negative pressure bubble. Then increasing the static pressure in the tent, without improving the air exchange for the plants (too much velocity for optimal goals and straight ballistic from the duct port to the parabolic side-effect).
- 2nd error : also based on bad habits (considering my project, i don’t say it’s bad) : using the duct ports of tent. So in the photo you have the front left and the rear right, D125/5" each for an unique D125/5" mouth sucking air in the parabolic reflector.
What you’re seeing in the photo is an unwanted genius idea. I’ve build this platform to elevate the plant from the ground mostly for pest (gnats to name them). Just because I’ve saw that plants on shelves at this height was never colonized, simply.
But in opening the horizontal vents of the tents … thx Jah, i got the key directly. Leaves was dancing and the negative pressure inside was more close to the goal with passive intakes.
At this point, i built 4 prototypes of RVK box with different angles + different tests. But on static pressure it’s the final version that will stay until the end.
As you can see, in term of space used it look like i was drunk. But in term of static pressure it’s the heaven. Considering the three horizontal vents used, the equal space all around the tent is acting like big “U” for the negative pressure. And the space under the platform is acting like a buffer for the three vents. Sometimes complicated tests that turn like a nightmare, look very simple.
The red tape is the marks for the 5th prototype (it’s a “good” failure i will show) of insulated box for the RVK, that is replacing the “lung closet”.
The insulated RVK box
Nothing fancy or exotic. I’m used to build them and it was not so an headache for me. The more difficult was to scavenge in the house all planks and wood panels i can to build in chain these damned prototypes.
This is the box of the deadly “lung closet”. Compact, silent and pretty simple. If you want to make one good, don’t get mad it’s more cheap and fast than most of “overkill” tutorial are showing.
You need to make a cube in the thickest panel you find, any type of wood but never with empty space inside (like honeycombed) or you get a subwoofer amplifier ^^ Make it perfectly hermetic inside with acrylic sealing (not silicone), even if you don’t use it as “lung box”. Then use the cheap bubble insulation for the garage inside with a double face tape. Far enough, you don’t need to waste your money on expensive foams. Last but not least, duct your RVK inside the box with insulated duct and plan a minimal space of 6 to 8 inches on the “blowing side”. This little margin will kill all residual noises like a magic trick.
Then the ugly 5th that was not so bad in term of torque/noise ratio considering all the others and their respective strategy. It’s made like a “lung box” including the filter, with the intake at 90° in plain middle of the length. The final version of this one (that never born) was planned with thicker panel, and insulated. Problem : the weight. Almost 1,5 wife.
I take the bet to reinforce the roof to make it a “chinesed gorilla like”, we even made almost the publicity with my big son. Over 400 pounds like chimps ^^
The torque was good and i got the central port like i wanted. Straight duct and gain of height. But i was too much addicted by the luxury of the silence, and it failed for that. It’s a nice compact configuration i regret to don’t have tried in some previous space but from the reflector you can see directly the carbon filter, and ear the increased noise from it amplified by the duct. The noise reached 60 decibels in the space, at one meter of the tent opened.
So, i’ve unmounted again the whole thing to build the final version. And i’m proud to say that this one rox for all the goals to achieve.
Almost 1 inch thick MDF panels (22mm). Planned to be a bit big for specific reasons (static pressure and torque curve again).
First the support inspired from the cars, i use a foam for soil.
For the carbon filter, my “universal technic” using the same things ever. Double face tape, short wood screws, eventually duct tape.
Then i place the filter with a mason leveler on its support.
Now the pain in the ass sequence … insulation.
Each step i apply an acrylic sealant, it’s even more important for this one because it act like a “lung box”, no leak permitted.
Etc … until the ducting.
This manner to duct can appear weird at first glance, but far more good for silent and torque with the right proportions. Don’t do it without insulated duct, it generate a “V8” sub bass because it create a bubble of negative pressure on the back of the carbon filter. It totally disappear when it’s no longer running “full tube”.
The beast is ready ^^ Less than a wife in weight.
Now it’s time to plan the all duct ports. For the exhaust points i’ve over 5 chimneys in the house. All “condemned”. Of course i’ve one brick-duct in the grow space.
6" duct directly linked.
Acrylic, double face tape , acrylic again.
For the tent, the credit go to my wife that have found a trick. It’s not that easy here, the shops have near nothing in term of choice and tools … even the specialized ones. French style, to accomplish something you have to reach a bunch of different people and shops.
In bonus i get nice white plant tags for my breeding notation in the pot.
And this now, full throttle noise 
:
Now that I’ve unmounted the previous deadly space to produce pollen, I’ve to set a contaminated line.
Not so simple, and it have to suck the smoke of my blunts on demand in bonus. With plants or not inside.
So it start with the exhaust point that i can’t joint with the 400CFM box, because i will use a little RVK of 264CFM with barely 75% less torque. The 400 will blow in the face of the 264, that will make a positive pressure in the pollen box … that will be sucked by the passive intake of the 4x4 tent.
No one will believe me if i say that this red circle was remotely set by a guy that make sport exhaust for cars ^^ But it work like a charm. Too much below, and the pollen grains will “levitate” and at this point it can escape in using the 400CFM pressure. Crazy to handle intellectually i find but it work heavenly.
Then the mount point, 90° elbow turned to the ground. It permit to lower enough the pressure applied to the little RVK, but also on the anti return valve. The pollen finish its travel almost only with gravity and sucked by the thermodynamic of the exhaust of the 400CFM. Best phone call I’ve made during the whole process.
Acrylic on the metal, cyanolite on the rubber.
Now the RVK scavenged in the bathroom, this little thing impress me. It turn all the time since … 2016. No pity. Poor little thing, it was the time for a maintenance.
And again a RVK box, because one time you taste to a quiet grow space … you never come back.
Ready to fire and to handle my blunts, on light two basic 20W domestic CFL. Far enough to produce a ton of pollen. Negative pressure is enough to secure the space, and not enough to kill the plants ^^
It’s now the time to handle the passive intake of the 4x4. And my very recent love for these horizontal vents I’ve never used before.
And why it’s a bit complicated to explain too ^^
I will not show all the prototypes maded and tested, there is a bunch. “Just a toke for the taste” :
And the final version, not the smaller but the better of all in term of airflow/light leak/noise/gravity trap.
Now i’ve a better RH (for me it’s lower-faster after a spray/watering) that is totally passive, the plants are vented as if I had placed a fan inside, the lamps are cold, and the negative pressure is just impossible to believe. For now i can’t get used by this mirage, it’s like my brain refuse to process the sensations. Strong outside, barely neutral inside. And total darkness even in a sunny day (night of my plants are always in daytime).