Trying to do the math on an affordable HPA system
- Thread starter Larry3215
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Thanks guys.
I have an in-line filter already - actually two. The intake inside my rez is a length of PVC pipe with lots of holes drilled in it. That is wrapped in two layers of silk screen cloth - I think its 150 or maybe 180 mesh. Then the water runs through another inline filter that is 150 mesh. I can change that to 200 mesh if needed.
The Hypro's listed before come two ways - one includes the 200 mesh filters. They are the almost the same price on-line as far as I can tell, but there are only a few sources in the US.
I was thinking (there I go again) the filters added to the nozzles would be easily removed/cleaned/replaced if they did clog up. Seems like that would be better than throwing away the nozzle if it some crap got past the filters? The nozzles themselves dont look like they can be cleaned easily, if at all.
Im not worried about my nutes - much. Im using Mega Crop, and it looks to me like it dissolves completely. Im more worried about other crap accidentally getting into the rez during normal operations that might get past the in-line filters. Those nozzle screens look like they just push into the back of the nozzle.
Am I way off in left field again?
I have an in-line filter already - actually two. The intake inside my rez is a length of PVC pipe with lots of holes drilled in it. That is wrapped in two layers of silk screen cloth - I think its 150 or maybe 180 mesh. Then the water runs through another inline filter that is 150 mesh. I can change that to 200 mesh if needed.
The Hypro's listed before come two ways - one includes the 200 mesh filters. They are the almost the same price on-line as far as I can tell, but there are only a few sources in the US.
I was thinking (there I go again) the filters added to the nozzles would be easily removed/cleaned/replaced if they did clog up. Seems like that would be better than throwing away the nozzle if it some crap got past the filters? The nozzles themselves dont look like they can be cleaned easily, if at all.
Im not worried about my nutes - much. Im using Mega Crop, and it looks to me like it dissolves completely. Im more worried about other crap accidentally getting into the rez during normal operations that might get past the in-line filters. Those nozzle screens look like they just push into the back of the nozzle.
Am I way off in left field again?
My chamber is 23" tall, but only 170 liters, so not quite the optimum shape. Still, the hypro's are a much better fit than the netafims. I will start with 4 firing up and see what it looks like.You have the answer from the "someone" who suggested the hypro model number. If it was off limits they wouldnt have posted the numberHypro`s work well firing upwards in 16" deep chambers and firing downwards in 39" deep chambers, they are short throw (around 12"), hollow cone. Four upward firing nozzles will service a 2.5ft square chamber (~225L) . Netafim coolnet and coolnet pro`s are long throw ,full cone nozzles, more suited to long narrow chambers like 16ft x 2ft (1500L). At the end of the day, you need to decide if a particular nozzle type will work for your chamber or application, then you spend the cash and see if your right.
I can re-work the chamber if needed.
Thank you.
I am having soooo much fun. Hypro is out of stock on all the anti-drip misting nozzles. Lead times vary from 2 weeks to 12 weeks depending on who you ask. I have only been able to find one suppler in the us who has some in stock - or so they say. They have some of the worst customer service reviews I have read in a long time, so my confidence is not good.
Im hoping someone can help with a new question.
I have run into some radically conflicting information on how much air pressure to pre-charge the accumulator with.
The RO guys say to put 7 - 10 PSI in the tank when its empty.
The well pump guys say to pump it up to 2 PSI less than the cut-on pressure of the pump.
Water heater guys say to set the pressure to equal the water pressure or 40 PSI minimum, but not over 80 PSI.
Those are radically different recommendations. What do you guys recommend?
My plan at the moment is to run the pump with a cut-on of around 85 PSI and a cut off of 100 PSI. The pressure reducer is set to send 80 PSI to the nozzles, but thats adjustable.
I have run into some radically conflicting information on how much air pressure to pre-charge the accumulator with.
The RO guys say to put 7 - 10 PSI in the tank when its empty.
The well pump guys say to pump it up to 2 PSI less than the cut-on pressure of the pump.
Water heater guys say to set the pressure to equal the water pressure or 40 PSI minimum, but not over 80 PSI.
Those are radically different recommendations. What do you guys recommend?
My plan at the moment is to run the pump with a cut-on of around 85 PSI and a cut off of 100 PSI. The pressure reducer is set to send 80 PSI to the nozzles, but thats adjustable.
Air precharge needs to be 2psi below the pressure switch cut in pressure, so if thats 85psi you need 83psi air precharge in the accumulator. The 2psi ensures the tank doesnt run completely dry before the pump switches on. 80psi on the pressure reducer is ok. A 2 gal accumulator running 85-100 will give you about 1 litre of capacity,. most likely less given that accumulator stated capacities are nominal. When the pump kicks on at 85psi, you`ll have 150ml left in the tank assuming the 2 gal capacity is accurate
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Thanks, that was the way I was leaning.
I have a new issue now. The tank I ordered listed the max working pressure as 130 PSI on Amazon, but it turns out its really 100 PSI max.
Im thinking of returning it and getting a water heater expansion tank thats rated at 150 PSI working pressure. Its slightly less volume at 4.4 gallons instead of 5, but Im thinking the extra working pressure will give me more options.
I can set the cut off pressure higher and have more spread between cut on/cut off. That should lower the pump cycle rate - I think. Plus allow me to run at higher pressures if need be at the nozzles. The pressure switch has a max spread of 40 PSI, so the higher working pressure would allow me to use all of that.
I cant think of any reason a water heater tank would not work - it has a higher max pressure and much higher temp tolerance. Am I missing anything here?
I have a new issue now. The tank I ordered listed the max working pressure as 130 PSI on Amazon, but it turns out its really 100 PSI max.
Im thinking of returning it and getting a water heater expansion tank thats rated at 150 PSI working pressure. Its slightly less volume at 4.4 gallons instead of 5, but Im thinking the extra working pressure will give me more options.
I can set the cut off pressure higher and have more spread between cut on/cut off. That should lower the pump cycle rate - I think. Plus allow me to run at higher pressures if need be at the nozzles. The pressure switch has a max spread of 40 PSI, so the higher working pressure would allow me to use all of that.
I cant think of any reason a water heater tank would not work - it has a higher max pressure and much higher temp tolerance. Am I missing anything here?
The tank I have now is nominally 5 gallons. The water heater tank is 4.4 gallons and says the max 'acceptance' is 3.2 gallons. That sounds a little optimistic based on other tank numbers I have seen.Air precharge needs to be 2psi below the pressure switch cut in pressure, so if thats 85psi you need 83psi air precharge in the accumulator. The 2psi ensures the tank doesnt run completely dry before the pump switches on. 80psi on the pressure reducer is ok. A 2 gal accumulator running 85-100 will give you about 1 litre of capacity,. most likely less given that accumulator stated capacities are nominal. When the pump kicks on at 85psi, you`ll have 150ml left in the tank assuming the 2 gal capacity is accurate
Im going to have to see if I can figure out the math you're using to come up with those numbers. You have my curiosity aroused...
Make sure its designed for potable water. If it uses a diaphragm rather than a bladder i wouldnt run it too close to its max pressure if you want it to last.more than a year. Small tanks can be as much as 18% shy of the stated capacity. Larger tanks are better but could still be 11% shy. The math is Boyle`s Law
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It is for potable water, but it uses a diaphragm - Heavy Duty Butyl NSF/ANSI 61. The RO tank I ordered is also diaphragm, so Im not loosing anything there. The only bladder tanks Ive seen are the well tanks, but they kill my budget.
This tank is also slightly less $ than the RO tank.
If I run the nozzles at 80 psi, and a cut on at 85, the pressure switch limits me to a max cut off pressure of 125, because thats the max spread it can do. So I will be below max to some degree.
Thanks again for putting up with all these newbie questions. I really do appreciate the help.
This tank is also slightly less $ than the RO tank.
If I run the nozzles at 80 psi, and a cut on at 85, the pressure switch limits me to a max cut off pressure of 125, because thats the max spread it can do. So I will be below max to some degree.
Thanks again for putting up with all these newbie questions. I really do appreciate the help.
I should post a link if anyone is interested.
https://www.amazon.com/dp/B001BNPSFW/?coliid=I2DDCFLVEJ2Q4C&colid=19CTNL8CVWP6J&psc=0&ref_=lv_ov_lig_dp_it
There are cheaper ones, and bigger ones, but this one seems to have the best specs and warranty for the money of the ones listed on Amazon.
https://www.amazon.com/dp/B001BNPSFW/?coliid=I2DDCFLVEJ2Q4C&colid=19CTNL8CVWP6J&psc=0&ref_=lv_ov_lig_dp_it
There are cheaper ones, and bigger ones, but this one seems to have the best specs and warranty for the money of the ones listed on Amazon.
Yeah, thats an issue for sure. I would love a larger well/bladder tank, but its just not in the cards for now.If the tank is a true 4.4gal, running it 85-125 will give you approx 1.26 us gal (4.77L). If its 3.6gal (18% less than stated ) it will drop to 1.03 us gal (3.9L). I dont like diaphragms because you have to buy a new tank when they go south
I was afraid it was going to be Boyles Law or something similar. I have not looked at, or even thought about anything like that in a few decades. Ok, ok, it was the late 60's. I will have to refresh my knowledge and play with that. If I remember correctly, I only got a c+ in chemistry 101. It was not may favorite subject.That will give me something to do in between programming the timer and waiting for the new tank and nozzles.
Thanks!
Well dagnabit, or maybe goshdarnit, or just I give up. I feel like I did the first day of algebra class when the teacher asked me to solve the problem on the board. I've filled up 3 pages in a note book, and I cant make the numbers workout to get the same answers you're getting.If the tank is a true 4.4gal, running it 85-125 will give you approx 1.26 us gal (4.77L). If its 3.6gal (18% less than stated ) it will drop to 1.03 us gal (3.9L). I dont like diaphragms because you have to buy a new tank when they go south
Given that P1V1 = P2V2, and using 85 and 125 for P1 and P2 respectively, I just cant come up with any numbers close to your values for usable volume. Its simple algebra, but its also been a looooong time since I solved any equations, so its very likely Im screwing it up somewhere along the way.
I am fairly sure you are not be using 4.4 gallons, or the less obvious 2.2 gallons for V1. If I start with 4.4 galls at 85 PSI, then V2 works out to 2.99 gallons for a difference of 1.41 gallons. If I use 2.2 gallons, then it works out to .74 gallons.
I finally worked backwards from your 1.26 number, and if I did the math correctly, came up with V1 of 3.11 gallons and V2 of 1.85 gallons - which I have no idea how you could have picked those numbers.
So, I am making a false assumption somewhere, dropping some decimals, or cross multiplying incorrectly, or???
On a plus note, I just got the shipping notice on the nozzles, so even though I feel like a dunce, Im in a much better mood
I remember the 60`s so age is no excuse lol.
All you need to know is P1 (cut-in pressure), P2 (cut-out pressure), tank volume (gallons) and atmospheric pressure (14.7psia)
Now to figure how much space the air occupies in the tank: ((P1 + 14.7) * tank volume / (P2 +14.7))
Example: ((85psi + 14.7psi) * 4.4gal / (125psi + 14.7psi))
Gives you (99.7) * 4.4 / (139.7)
which is 438.68 / 139.7
Final Result: 3.14 (gallons)
Now you know the air occupies 3.14 gallons of the tank volume and any space not occupied by air must be occupied by liquid. 4.4gal (tank) - 3.14gal (air) is 1.26gal (liquid).
Pretty easy, even for us old buggers
All you need to know is P1 (cut-in pressure), P2 (cut-out pressure), tank volume (gallons) and atmospheric pressure (14.7psia)
Now to figure how much space the air occupies in the tank: ((P1 + 14.7) * tank volume / (P2 +14.7))
Example: ((85psi + 14.7psi) * 4.4gal / (125psi + 14.7psi))
Gives you (99.7) * 4.4 / (139.7)
which is 438.68 / 139.7
Final Result: 3.14 (gallons)
Now you know the air occupies 3.14 gallons of the tank volume and any space not occupied by air must be occupied by liquid. 4.4gal (tank) - 3.14gal (air) is 1.26gal (liquid).
Pretty easy, even for us old buggers
Its been very eye opening playing with those numbers.
If I use the 3.2 gallons they claim for ‘acceptance’ on this new tank, that works out to about .92 usable gallons or 3.48 liters. I had assumed that increasing the over all pressure in the system to say 95 – 135 for cut on/off pressures would increase the usable volume of the tank, but its actually the reverse. Going up to 95-135 lowers the usable from .92 gallons to .9. Lowering it to 75-115, raises the usable volume to .99 gallons. Increasing the spread does increase usable volume. Not huge differences at my scales, but still interesting.
There are two other things that I find really interesting as well.
First, you made this comment some time back. I forget where I copied it from though or how long ago it was, but Im curious to know if this still applies.
“In an ideal system, you would set the misting duration based on flowrate and chamber volume. For early growth, the misting duration would provide 0.02ml -0.04ml per gallon of chamber volume. For later growth, 0.06ml per gallon.
The interval between mistings is adjusted to provide the target daily throughput, which will be somewhat dependant on environment variables (light,heat etc). As an example, a 26 gallon chamber with one 1gph nozzle would need a 0.5- 1 second misting duration in early growth and upto 1.5 seconds for later growth. The interval between mistings for early growth would be 35-70 seconds (dependant on the misting duration setting) with a target daily throughput of 1.3 litres. For later growth, the interval would be around 50 seconds with a target daily throughput of 2.65L. The name of the game is to inject mist little and often to maintain an optimal aeroponic environment.”
If I adjust the flow numbers you have recommended to fit my root chamber – 45 gallons - I would be using roughly 2.25 liters/ .59 gallons per day in early growth, and 4.58 liters / 1.2 gallons per day in later growth.
If that all still applies, and we use the .92 gallon number for usable volume, my pump should only cycle once every 36 hours or so early on, increasing up to once every 18 hours or so later in the grow.
Of course, I still dont know if I can fill the chamber and keep the flow rates that low until I do some testing.
Are those flow rates still good targets to shoot for?
The second thing really boggles my mind. When I first read that post above, I was like “Huh. That seems like pretty low flow rates.” and then I went on my way without really grasping the implications.
But, now that I think on it some more, those are amazingly low flow rates! At least when I compare them to my last hydro grow. During the later stages of flower, my three plants were drinking an average of 1 gallon of nutes/day/plant for a total of three gallons a day. Some small part of that was surely due to evaporation, etc, but the bulk was sucked up through the roots.
With your flow numbers, the usage will be a little more than 1/3 of that number – BUT - it makes no difference how many plants I have in the chamber! On top of that, it seems to me that the majority of the mist is going to be lost on the sides and bottom of the chamber, or at least a large %. That means aero is somewhere beyond 3 times as efficient as traditional hydro – possibly a lot more than that - depending on how much mist gets stuck on the walls/ceiling/floor of the chamber, and how many plants are sharing the chamber.
But wait, there's more! You also said somewhere that EC levels in aero should be 1/2 to 1/4 of normal levels, so that makes it even more dramatic.
Im having trouble accepting that, but it sure looks like a worthy goal to shoot for, and is something that would (hopefully) justify the extra trouble and expense of growing this way.
Consider me boggled!
If I use the 3.2 gallons they claim for ‘acceptance’ on this new tank, that works out to about .92 usable gallons or 3.48 liters. I had assumed that increasing the over all pressure in the system to say 95 – 135 for cut on/off pressures would increase the usable volume of the tank, but its actually the reverse. Going up to 95-135 lowers the usable from .92 gallons to .9. Lowering it to 75-115, raises the usable volume to .99 gallons. Increasing the spread does increase usable volume. Not huge differences at my scales, but still interesting.
There are two other things that I find really interesting as well.
First, you made this comment some time back. I forget where I copied it from though or how long ago it was, but Im curious to know if this still applies.
“In an ideal system, you would set the misting duration based on flowrate and chamber volume. For early growth, the misting duration would provide 0.02ml -0.04ml per gallon of chamber volume. For later growth, 0.06ml per gallon.
The interval between mistings is adjusted to provide the target daily throughput, which will be somewhat dependant on environment variables (light,heat etc). As an example, a 26 gallon chamber with one 1gph nozzle would need a 0.5- 1 second misting duration in early growth and upto 1.5 seconds for later growth. The interval between mistings for early growth would be 35-70 seconds (dependant on the misting duration setting) with a target daily throughput of 1.3 litres. For later growth, the interval would be around 50 seconds with a target daily throughput of 2.65L. The name of the game is to inject mist little and often to maintain an optimal aeroponic environment.”
If I adjust the flow numbers you have recommended to fit my root chamber – 45 gallons - I would be using roughly 2.25 liters/ .59 gallons per day in early growth, and 4.58 liters / 1.2 gallons per day in later growth.
If that all still applies, and we use the .92 gallon number for usable volume, my pump should only cycle once every 36 hours or so early on, increasing up to once every 18 hours or so later in the grow.
Of course, I still dont know if I can fill the chamber and keep the flow rates that low until I do some testing.
Are those flow rates still good targets to shoot for?
The second thing really boggles my mind. When I first read that post above, I was like “Huh. That seems like pretty low flow rates.” and then I went on my way without really grasping the implications.
But, now that I think on it some more, those are amazingly low flow rates! At least when I compare them to my last hydro grow. During the later stages of flower, my three plants were drinking an average of 1 gallon of nutes/day/plant for a total of three gallons a day. Some small part of that was surely due to evaporation, etc, but the bulk was sucked up through the roots.
With your flow numbers, the usage will be a little more than 1/3 of that number – BUT - it makes no difference how many plants I have in the chamber! On top of that, it seems to me that the majority of the mist is going to be lost on the sides and bottom of the chamber, or at least a large %. That means aero is somewhere beyond 3 times as efficient as traditional hydro – possibly a lot more than that - depending on how much mist gets stuck on the walls/ceiling/floor of the chamber, and how many plants are sharing the chamber.
But wait, there's more! You also said somewhere that EC levels in aero should be 1/2 to 1/4 of normal levels, so that makes it even more dramatic.
Im having trouble accepting that, but it sure looks like a worthy goal to shoot for, and is something that would (hopefully) justify the extra trouble and expense of growing this way.
Consider me boggled!
If you work out how many 50 micron droplets you can generate from a given amount of water and then distribute them evenly in the chamber volume it`ll make more sense. As for nute strength, if you have a res of nutes at EC: 0.1 and evaporate half the water the EC will double to 0.2. Droplets are effectively floating spherical reservoirs until they make contact with a root. If the diameter of a droplet halves en route, its water content is reduced by a factor of 8. The nutrient in the droplet cant evaporate and is left behind so the EC also increases by a factor of 8.
I didnt believe it at first, but after doing the math, I can see that it doesnt take much water volume to fill a chamber with 50 micron drops. That also made it clear why you're so adamant about no drips after each cycle. A few drips could easily double your usage.
I read your comments on drops evaporating before when I was researching this. Another thing that didnt click at the time, but makes a lot more sense now.
What I dont get is why roots would take up so much more water/nutes than they need from regular hydro, than they do in HPA? What do they do with all that extra water? Or maybe we should ask how they get by with so little in aero, and still grow bigger and faster? I wonder if all that extra water goes into (unnecessary?) transpiration?
I always hated biology, botany, and pretty much all the other 'soft' sciences. I like things that follow rules with as few exceptions as possible. I Like them to be predictable, and consistent. I like it when answers can be accurately calculated, or deduced from basic principals, and repeatable measurements. Im in 100% agreement with that guy in the movie "The Martian". To paraphrase: "Botany isnt "real" science."
Still, I keep finding things that are fascinating about growing this plant.
I read your comments on drops evaporating before when I was researching this. Another thing that didnt click at the time, but makes a lot more sense now.
What I dont get is why roots would take up so much more water/nutes than they need from regular hydro, than they do in HPA? What do they do with all that extra water? Or maybe we should ask how they get by with so little in aero, and still grow bigger and faster? I wonder if all that extra water goes into (unnecessary?) transpiration?
I always hated biology, botany, and pretty much all the other 'soft' sciences. I like things that follow rules with as few exceptions as possible. I Like them to be predictable, and consistent. I like it when answers can be accurately calculated, or deduced from basic principals, and repeatable measurements. Im in 100% agreement with that guy in the movie "The Martian". To paraphrase: "Botany isnt "real" science."
Still, I keep finding things that are fascinating about growing this plant.