High-pressure (aka "true") aeroponics - nutrient schedule?

The system I am planning is a 30-nozzle system, and I was planning on having every other nozzle run by a different of the two pumps, in other words 2 pumps, each pump handles 15 nozzles, and they're alternating throughout the system.

In order to accomplish this, I was going to have two separate 1/2" PVC matrices in the box, almost identical, but one would be slightly offset in all three dimensions so that you don't have like a stretch of pvc blocking a nozzle underneath.

That way, if one pump dies, there's still tons of mist being blasted into the box, and hopefully I can get the other one fixed, or maybe I keep a spare kicking around.

I was originally going to have both pumps feed into a single pvc matrix, so that even if one died you would still have full 30-nozzle flow, but then I realized that the pumps would "fight" against each other, pump A would try to drive the nozzle and also jam a bunch of water down pump B's throat, and vece versa.

Now that brings something else to mind. What if I have two pumps feeding into the same nozzle matrix, all 30 nozzles, and I have a check valve between each pump and the nozzles. Would that stop the two pumps from fighting one another?

You can hook two pumps into one line via a tee, some household water pressure boosting systems use this type of arrangement. It will increase the output flow (GPM) but wont affect the pressure and effectively doubles the cost of your pump

I did a few calculations using your 30 nozzles and average 90psi pressure in an accumulator system, I assumed the nozzles were the MNW white superfine and used a 10gal accumulator.

With a 3 second on/ 3 minute off timing cycle the 30 nozzles deliver about 76ml per cycle. The pressure in the tank drops from 100psi to 80psi taking around 56 minutes. The drawdown volume on the tank is about 1.4L
The pressure switch turns on the pump to recharge the tank at 80psi taking a little over 3 minutes (assuming a 0.4LPM flowrate) to get it back up to 100psi. The 30 nozzles deliver about 1.5LPH to the root chamber,which equates to about 36L/day or 9.44 us gal.

Just for comparison, with a 30 sec on/3 min off timing cycle you get 760ml per cycle. The 100-80psi drawdown time is now about 6.5 minutes with the same recharge time as before at just over 3 mins. The 30 nozzles deliver about 13LPH to the root chamber, which is 313L/day or just over 82 us gal.

Great news!

I just got off the phone with Shurflo Tech Support. The guy told me that the only issue with component wear would be a pressure switch, like in the demand pumps. If you constantly turn these on and off the pressure switch will die on you.

A bypass pump should have no trouble power-cycling 500x per day. The motor can handle it, and there's no pressure switch to wear out.

YAY!

Hi there
been reading the thread - good stuff.
Actually spoke with Steve from Cloudtops a few months ago, I was thinking of this same set up. Glad to see I'm not the only one crazy like that.
Here is the thing I have been wondering:
Is it worth it?
For now I am running a hybrid Aero/NFT set up, (AKA "Stinkbud" System), and the results are rather spectacular. Setting up a true high pressure set up as discussed will require significant more money and effort.
Those speaking from experience, would you say the yield is proportionally better, equal to the amount of effort put in? Or is there a different less obvious benefit?
I certainly don't lack the desire or dedication, but I can't help but wonder- are we fixing a problem that isn't, making a simple thing more complicated?
What's your take?

I can't speak about results from experience, but coming from DWC, I will be building this from scratch, is it really that much more expensive than a low pressure aero / nft?

1. lights, circ fans, exhaust fans would be the same
2. pumps will cost around $300 bucks, that is two pumps, both running together, so you never have a hit on your system if one of your pumps dies. So what would the equivalent cost be in low-pressure aero? $150? $200?
3. reservoirs, air pumps and stones, all the same cost as LP-aero
4. filter for the water, same as LP-aero
5. nozzles - what, $50 instead of $20?
6. cooling, whether that's air conditioning, or res chiller, would be the same cost as LP-aero, because this is based on your room and setup and won't vary between LP-aero and HP-aero
7. and the container itself for the plants, would be cheaper than using 6" or 8" pvc, but let's just say you build a custom box/table in either case, so the costs are the same.

Then isn't the only increase, in the cost of the pumps? and a couple of bucks for the nozzles?

If you're going from LP-aero to HP-aero, you're right the increase might not be worth it, but if you're building from scratch, I don't see how it's that much more expensive. I could be missing something.

Sounds like you`ve got it sorted
Most demand pumps use really cheap and nasty switches that pack up in short order, the pressure settings drift a bit too.
I use a good quality 3-12 bar external switch, more reliable and has a wider adjustment range.
Don`t forget to include a pressure gauge after the pump to keep track of the system pressure, one that reads upto 11bar (160psi) would be ideal.
In my case system cost was $70 pump, $80 accumulators and $50 pressure switch ($200) excluding plumbing,nozzles timer,filters and pressure gauge...its all the little things that add up

I did forget about the gauge. Does anyone know if they make pressure gauges that can hook up to computer via usb? I google'd for it, couldn't find them, and i'm usually pretty good at finding stuff on google!

You can buy a basic 160psi pressure guage for as little as $7, for better quality maybe $30.
The Shurflo 8000-812-639 (115 VAC) looks like it should fit the bill quite well for your setup, $179 from these guys.
http://www.pumpagents.com/ShurfloPumps/8000-812-639.html

Wow, not sure how you found that pump, because it isn't even on Shurflo's website! It's a great pump, but maybe overkill, since I would like to buy two of the and have them both running together to prevent a pump failure from destroying the whole crop.

I was thinking of this one, found it for $127 here (by the way these guys seem to have the best prices around, the 812-639 you mentioned, they have it for $147).

I looked at that one (812-280) but in a worst case scenario if it has to run 30 nozzles by itself it wont have quite enough flow (1.4LPM@100psi versus the 30 nozzles @0.9gph which is 1.71LPM @100psi)
The 812-639 has slightly more flow than you`ll need (2.1LPM@100psi) which is a good thing as you`ll lose some to losses in the plumbing. The upside is it will run 30 nozzles by itself, the downside is the extra cost

The first link is the 812-280 is a bypass pump and the second is the 812-288 which is a demand pump with 80psi bypass

Atomizer said:

I looked at that one (812-280) but in a worst case scenario if it has to run 30 nozzles by itself it wont have quite enough flow (1.4LPM@100psi versus the 30 nozzles @0.9gph which is 1.71LPM @100psi)
The 812-639 has slightly more flow than you`ll need (2.1LPM@100psi) which is a good thing as you`ll lose some to losses in the plumbing. The upside is it will run 30 nozzles by itself, the downside is the extra cost

Click to expand...

The thing is, I am going to have the two sets of nozzles in separate PVC lines, to avoid the pumps "fighting" each other. So if one pump dies, the other one will (hopefully) still be running, but it will only be driving 15 of the 30 nozzles. I won't have any way of hooking it up to the full set, it will juts buy me some time to get the bad pump replaced without totally destroying the entire crop. But it will never need more than 1LPM.

Atomizer said:

The first link is the 812-280 is a bypass pump and the second is the 812-288 which is a demand pump with 80psi bypass

Click to expand...

Nice catch, yet again Atomizer.

Here's another site with a good price on the 280.

Atomizer, question for you.

The 280 bypass pump says it does 100psi, but that it has an 80psi bypass. What does that mean? Does it only go up to 80psi and then start to bypass? Does it start bypassing at 80, but keeps building pressure until 100? I'm finding that a little confusing.

Thanks!

As promised, here's the last answer on the droplet size for these nozzles, this one from Stephen at cloudtops (super helpful guy):

"the mfg has never been able to supply droplet size data. Ive asked on multiple occasions throughout the years and as recently as a couple of weeks ago. They are made by Tefen Plastics in Israel if you would like to contact them directly."

So now I have sent an email to Vann at dripworksusa asking why the hell they are posting droplet size data on their website when the manufacturer hasn't done the testing, as confirmed by three other websites!

The bypass pressure will be adjustable usually via a small allen key, the factory setting is 80psi.
I guess you may get a buck passing kind of answer on the nozzles, something like "thats what the manufacturer told us

Looking at this system while having superior nutrient delivery, the obvious negative difference is "vulnerability". The cost issue is not that big, agreed, since existing gear can easily be retro-fitted
BUT: If your one pump craps out, you're running on whatever residual pressure you've got left, and then its up to you to catch it asap. Granted, they are high quality, but machines nevertheless.
With my current system, every unit has it's own pump. But nutrient delivery could certainly be improved, and there is something to be said for one large nutrient pool to maintain, vs. "x amount" (plausible deniability -)
So ideally one would have a system with a back up pump. Any thoughts on that one? I can't quite figure that one out.
Having this solved would make this pretty much the ultimate "high yield/sleep well at night" set up.

I have already outlined in this thread, how you can have a back up pump.

You have two pumps, each driving 1/2 your nozzles. Inside the box, instead of having one manifold, you have two manifolds. BUT you have both covering the entire box. So if you lose a pump, you're not dead in the water. You're still running, you're not going to lose your garden, but it isn't running at a reduced capacity, you still need to replace the bad pump asap.

And I would think the same applies to low-pressure aeroponics. You better have a backup pump handy, in case your primary pump fails.

I have attached a picture to illustrate. The black circles are the nozzles. Notice that they alternate between the red manifold and the blue manifold.

Atomizer, a couple of questions about your setup:

1. do you run a single filter for the whole system, or individual nozzle filters?

2. do you have air pump + stones oxygenating your res?

The pump failure issue is there with any system that uses a pump.
I have a backup pump, at $70 its not much expense for peace of mind but if it was $200 i`d think about it more carefully as its a big outlay on a maybe (optimistic viewpoint).
I`m 100% certain an accumulator based system is less prone to pump failure simply because the load on the pump and running time is minimized. Unfortunately an accumulator wouldnt be as effective with a long misting cycle.
I use bag filters instead of inlines because they have a large capacity, are cheap and washable. They don`t clog up completely without warning which can starve the pump of water.
The normal filter size recomended for aero is 200 mesh (75micron). I use a coarse filter to catch large debris followed by a 20 micron bag. For the supply res, a 5 micron bag will remove pretty much anything that might cause problems to the pump, pipework or nozzles. Anything smaller than 5 microns with 95psi pressure behind it.. isn`t going to stay put for long

I use a small airpump to keep the supply and return res water moving, its mostly to prevent it stagnating rather than actively adding oxygen. When you have gallons of water stored at 95psi in a sealed accumulator tank for hours at a time theres no easy way of adding any oxygen to it

Thanks.
This pretty much describes the system Steve from Cloudtops suggested to me, with a few variations.
I kinda liked quentins' approach, but it seems a little complicated.
When you work with accu tanks, it's a whole different deal, and it requires different thinking.

So what if you have just one line and two pumps, since it is "on demand" and we're working with accu tanks. Have a back up pump with a pressure switch set to kick in when pressure in the accu tank drops below acceptable.
Is it needed? Guess it's just what you're used to (comfortable with) coming from my current set up.

Not really having experience with this, it just takes some time and a few rounds of back and forth with someone like you who's done it and is there.
My real challenge is how to get all the right parts and information and set it up as it relates to my gear.
Besides cloud tops, who else do you recommend?

Quentins dual pump approach is ideal for a 30 second misting cycle,
Playing devils advocate for a second, if you use two identical pumps to run half the system each. Its logical to assume that if one pump fails they both fail, afterall both will have done exactly the same amount of work at that point
From a reliabililty viewpoint you can`t be sure how much mileage is left on your good pump before it too may fail. So perhaps you should be buying two more pumps when one fails... just in case?

The accumulator system is more complex to set up initially but could be cheaper than buying two powerful pumps.
On its own, my pump could run just 2 nozzles but upto 80 with the accumulator. Why use 40 pumps when one will do a better job The calculations are easy enough..if you have the specs for your nozzles.