Here is some math from ASHRAE. If I want the air inside of a 2x2x4 space to turn over 1 time every hour, then this means I want to remove and replace 16 cubic feet of air every hour. The formula would be; volume (2x2x4) x 1ACH = 16 cubic feet of ACH (air changes per hour). 16ach/60min = .267 CFM (cubic feet of air per min). That's a small amount of air for what we want to do...we want much more than 1 air change per hour we want several hundred air changes per min...but u see the math. Rule in building science says 1 CFM in should usually equal 1 CFM out, and that = balanced air flow my friend. Loved the video..Im about to flip a grow tent from bud to mining to manage heat in my 2 bedroom apartment! Good luck.
Absolutely. I am getting in to the warmer months, and I am no longer pumping the heat indoors, and now I need to be scrubbing the heat from the cards as fast as possible. I need change my setup to add cfm, and increase the rate of exchange. And you are totally correct about equal flow. Most videos I had seen on grow tent with crypto mining showed the walls caving in as the optimal setup, yet their cards were always running super hot. I've realized all that means is there is a choking point in your setup. Even pressure is good flow.
I love your thumbnail!! Awesome! Yeah, I am struggling to convince people that positive pressure is a much better way to exchange the air, but somehow most people revert back to a negative pressure (exhausting) system. In my "garage build" video and my "automating the cooler" video I actually mention the pros and cons, but still people ignore how important this is. Have fun!
Thanks my dude! I'm definitely going to go check out your channel! I'm excited to try some diffrent things for the tent this summer. But as far as a winter setup...this will be my go to.
I love seeing your channel. Especially in this bearish time. We're all in the same boat and Im looking forward to tagging along and hodl rigs with you good sir.
I have the opposite problem being in Florida. I might try add an intake fan because I have two exhaust fans and I cannot zip the tent up without the rigs getting wayyyy to hot and shutting down.
Yeah man it gets pretty hot and sticky here June-Aug. So I will definitely be changing the setup when this weather turns around. I think passive intake is fine as long as the walls aren't caving in on the tent. It's when the tent went into vacuum that my cards started getting too hot. Air doesn't exist in a vacuum, so every bit it goes negative below atmospheric, starts to lower the air flow giving the card fans less to push over their coolers. If I slowed the exhaust fan and let the walls settle it would actually lower the temps. I eventually just opened one of the ports and raised the exhaust fan gradually until I found the sweet spot. We'll see how this all pans out in a couple months!
My best ever summer temps was when I completely sealed off a spare bedroom (door, vents) put an exhaust fan in a window on one side, and left another window cracked open on the other. Negative pressure pulled air in from one window and across the rig and out the other. Any attempts to PUSH the air across the rig with fans increased temps a bunch. even with bigger box fans pushing. So from that experience, I'm not convinced that it's necessarily negative pressure vs positive pressure but rather is the air puled through/across the rig or pushed through/across the rig. probably something to do with turbulent flow vs laminar flow in combination with pressure? Fluid dynamics is way to complicated! Right now I'm running my tent negative, but with a LOT of flow. (3 exhaust fans - intakes outside air) 7k watts of rig heat, ambient in tent is 82 while it's mid 70's outside in Wisconsin, card temps are happy. They were definitely NOT happy with this negative setup until I added that 3rd exhaust fan.
Yes I completely agree. I think I've confused a lot of people by referring to vacuum as "negative pressure". I dont think that passive intake creates much measurable negative pressure, and I've also found passive intake to be very effective. It's when the exhaust overruns the capabilities of the intake, that I think the trouble begins...when the walls start caving in, and it is measurable. I've seen too many videos of tent setups where people show the walls caving in as evidence of a proper setup. In my experimentation it not helpful. Ideally you would increse the available intake, or just work within the limitation of it. In my winter setup I did not want maximum airflow, as I needed to scavenge heat to suppliment my furnace, so I had to work within the limitations of my intake. After discovering this, I adjusted my setup, and it was awesome. Now that the heat is here, I do need max airflow, and I'm going to have to change things around. I appreciate the feedback, and the well thoughtout comment! Thanks, and stay undead!
Great video! Just like an engine, its an oxigen pump, if you cant suck air in your not going to be able to push air out, to make horsepower. Tent is the same way. You have to keep air moving. Make up air has to come from somewhere.
Awesome video! I'm starting the get the high temps in early spring. Similar tent setup, 8inch intake/exhaust but not having the air distribution manifold. Middle one top rack are getting really hot. My go pick up some 4" pvc today. Just have to figure how to split the 8 inch into those 4 inch pipe
The problem you might face is that you will need to split in to two 6" or four 4" to equal the volume of the 8" inlet as crazy as that sounds. You can get a rough idea of how they contrast volume wise by calculating and comparing the surface area of each circle (Pie X raduis squared). 4"=12.56, 6"=28.27, 8"=50.26. So on mine, the two 4" are approx equal to the 6" intake fan I am running now, which is turning out to be the choking point in my system. I either have to slow my 8" exhaust fan or open more ports in the tent to avoid pulling the tent in to vacuum. Also for the small holes on the manifold, you will need find out how many holes of particular size you need to drill to get the equivalent of the initial intake. I'm thinking if I end up upgrading I might go with 8" furnace ducting or something along those lines to keep it simple. I haven't had to face much warm weather yet this year with this setup, but I plan to keep things updated on this channel. If you decide to build something let me know!
@@theblockingdead1310 yeah, I was thinking about the size conversion after what I wrote. Got a few idea I need to look into this weekend. Like 6 inch rigid tee in 2 columns on each side with flexible tubing in between the 2 that I could easily pierce where I want. Or put up a main trunk in the middle and drill hole on 3 sides. Not sure it the pressure would be divided evenly on the last one. Any, I'll update you If I find a solution
I have 2 exhaust fan (6 inch each one) in the top of the tent, and 2 intake opened in the bottom (that take airflow naturally) and the temps are very good. Now I have both exhaust fan at mid power, but if I put the power of 2 exhaust fan at max power the temps go a little bit down, so for me negative pressure work better. What do you think? (I’m testing the grow tent since 1 week)
Passive intake seems to work fine. It's when the walls begin caving in and you are in the stages of drawing the tent in to vacuum where things get crazy. The word I probably should have used is vacuum, but the definition of vacuum can be a grey area. There is soft vacuum, then there is a void which is full vacuum, and everything in between. You want to try and stay close to neutral in terms of PSIA. As long as your intake is allowing enough air flow to keep up with the exhaust fans you are going to be fine.
How well is the pvc with holes cut working for you? I tried splitting my intake with 4 inch elbows and t's, but found that it was a failure. The air would just find the least resistance and come out of the first 1 or 2 holes and the rest nothing. Great video. I've had a hot box in the basement for years now, and learned the hard way that I need just as much intake as exhaust. Like sucking on a blocked straw. Now my hotbox is completely isolated from my living space and the house ac works great.
It seems to be the best way I've found so far. I also tried something similar to what you are describing and had the same results. I had to do the math to figure out how many holes it would take to equal (but not exceed) the 6" intake it is fed from. I just calculated the surface areas of all the circles. two 4" is equal to one 6" and then 24+ 1 1/8 holes are also equal to the 6" intake. The idea was to keep from having too much air flow out of one particular area. In practice though, the lower tubes do flow slightly more air as the pressure favors the bottom row. It might have been more even if I had had split the air coming in between the top and the bottom. I can also manipulate the flow a little by blocking some of the holes off.
Yeah, I think neutrol pressure is what you really want. And the negative pressure usually refers to actively exhausting more than you actively blow in, but still let air in passive through more openings around the enclosure. That's what's usually happening in negative pressure PCs. Not actually going towards vacuum, but just focusing more on exhaust-
That's exactly what I was finding in my experimentation. I was hesitant to use the word vacuum as there is differing ideas as to what the definition of vacuum is. As an auto mechanic we usually look at numbers in PSIA in reference to absolute pressure and it's difference to atmospheric. So there will be negative pressure measured in PSIA, and actual manifold vacuum measured in inches of mercury. Small amounts of negative pressure in a passive intake is fine, but towards a vacuum is where things get harmful.
@@theblockingdead1310 Yeah, theres often a lot of variation about what people mean when they say things I guess, specially outside professional settings. I'm gonna get a small tent for my 2 rigs now that summer is closing, and I intend to have 50-100% more passive intake space, than active exhaust space, so I'm hoping that'll do the trick and create a good flowthrough of air ^^
More air = more air molecules to exchange heat. Plus with partial vacuum the air is directly pulled from inlet with out stoping at the tourist attractions. Over pressure force's the air to in making the air to all over the place
Yeah it seems to me that keeping the pressure as neutral as possible helps with flow. It was pretty evident with the two diffrent temp probes, that I could not keep my hot/cold aisles separate in a vacuum, as every square inch was trying to equalize, and there was no longer a steady flow moving across the shelf.
@@theblockingdead1310 I appreciate the reply! I have a similar basement. Gotta love these Wisconsin root cellars! Lol I love watching the bigger channels, but I am never going to have 100+ gpus. I appreciate your perspective!
@@robertpiper6860 Oh that's what they're called! Always called mine the dungeon. Thanks my man. Yeah I'm almost out of power, and the electricity bill is getting out of hand. Thanks for watching. Got another one dropping soon on how to avoid hidden fees.
That's exactly my theory as well. Under vacuum you aren't doing the fans or heat exchangers any favors. Immersion is the thermal efficiency king when mining. But getting a big enough tank/pump/heat exchanger, and all the liquid can be $$$. I suppose the initial investment would pay dividends on power and equipment life/maintenance. Do you know of a good place that sells everything needed?
@@theblockingdead1310 sorry bro. I know ZERO! I just watch A LOT of videos on mining and when I finally came across immersion cooling, I thought it was a no-brainer. Not only the noise and the obviously the heat but honestly for me... the DUST!!! Already with the sound and heat you got me sold but supposedly when you're done with them, they come out of the dielectric in mint condition and squeaky clean! I don't really know anything about software and hardware so it'd be a steep learning curve for me... All that said, there's probably something I don't know that the big guys do. Maybe they're not worth keeping mint because they become obsolete and have to be replaced anyway 🤷 Who knows.... ✌
100% agree that I was limited by my intake. What I found along the way though is that if I overrun my intake, and draw the tent in to vacuum, that it has a negative impact on heat exchange. I just found that fascinating. If I work within the bounds of my intake it works excellent. Remember though that this was February, and I was trying to gather heat for my house. Now that it is summer, I am going to need more flow, more intake, and will be revisiting my setup. Just found it interesting that too much negative pressure causes problems.
LOL.... you dont have near enough cfm.. thats the only issue. im runnig a 10 inch 1600 cfm fan with 2 8 inch inlets. 95 degrees here outside wirth the same size tent running 50 degrees on cards. also you hae shelving for air to sit... you need to set your cards on the racks in a better pattern.
I agree that now it is summer and I will need max cfm and to alter my setup. When I made this setup it was February in Wisconsin. It would sometimes get below zero overnight. I was not trying for maximum cooling, as i was scavenging the heat to my house. Rather trickling in enough cold air, as evenly as possible, for as long as necessary to remove heat from the cards, and then pump it in to the ventilation. What I accidentally discovered in testing was that if I overpowered the cfm limitations of the intake, my cards would heat soak. But if I slowed the exhaust enough to match the limitations of the intake it worked perfectly, and my hot and cold isles would stay separate. The pressure difference between the two sides was naturally causing the tent to want to equalize, so the hot and cold isles would blend. And the vacuum was hurting anything else that relied on air pressure and volume (card fans, and heat exchangers).
