Sorry for the slow reply - Ive been in and out of the ER and dr offices the last several days - more dang (huge) stones!
Ok, I have another questions or two.
If the nozzle is directly connected to the solenoid, then pressure drops in the tubing is not the issue - at least not the way I thought at first.
You have an accumulator tank, and the pressure in the system is 7 to 8 bar, but I need a few more details.
Is that 7 to 8 bar the pressure in the tank itself or the pressure feeding to the solenoid? In other words, is the pressure in the tank the same as the pressure feeding the solenoid? The question Im trying to ask is - are you using a pressure reducer between the tank and the solenoid or is it a straight feed between the tank and solenoid?
What is the volume of the tank, and is it a metal tank or plastic?
Do you have a pressure gauge hooked up between the tank and the solenoid? Preferably close to the solenoid end of things? If not, can you add one?
Next question is about the nozzles - are they anti-drip?
Here is my current thinking on the large drops. It could be two things.
- It sounds like your nozzle does NOT have an anti-drip valve built in, or it isnt working. The first sets of nozzles I bought had bad anti-drip valves.
I think one thing that may be happening is the nute water in the down facing nozzle is draining out during the OFF cycle. That will cause a delay in the start of the mist while the nozzle fills up again, and cause the pressure to build up more slowly during the start of the ON cycle. That will cause the large drops at the beginning while the pressure is too low.
- The next thing is if you are NOT using a pressure reducer, and/or you have a long tube between the accumulator tank and the solenoid, the pressure in the accumulator tank will drop a lot during the first part of the ON cycle. A long flexible tube between the accumulator and the solenoid just makes it worse.
A pressure reducer will help keep the pressure more uniform - especially if its mounted close to the solenoid. The only way to know for sure is to put a pressure gauge right at the solenoid or as close as you can get. Then you can actually watch the pressure fluxtuate up and down during the ON/OFF cycle.
With no pressure reducer, I was seeing 20-30 PSI of pressure drop during each ON cycle. With the pressure reducer it is down to less than 5 PSI. Also, ANY air in the lines will cause the same problem.
Your chamber volume is huge for a single nozzle to fill. Im also guessing your nozzle is a wide cone shape. Do you know the angle?
If it is a wide angle cone, much of your mist will be hitting the side walls before it ever gets to the bottom of the chamber. A nozzle with a very narrow cone would be better for your situation.
I totally misunderstood the size of your chamber - it is much larger than I thought. Yours is almost 5 times as big as mine is, so you will need 5 times the volume of nutes for each ON cycle.
I was using 4ea 0.5mm nozzles in a chamber 0.17 cubic meters. Im guessing based on the specs for my nozzles, that your 0.3mm nozzles put out about 0.4 GPH. Mine put out 0.9 GPH.
So I have nozzles that have twice the flow rate yours do, plus I have 4ea and you have 1ea. plus your trying to fill a chamber that is almost 5 times as large.
That means you will need somewhere around 40 times as long an ON cycle as I was using. I think I was averaging around 0.7 seconds of ON time, so you may need as much as 28 seconds of ON time to truely “fill” your chamber from top to bottom.
I am on some good drugs at the moment, so no promises, but if I am doing all the math correctly - you may need as much as 28 seconds of ON time. That doesnt seem like its going to work very well for that tall a chamber and a single, wide cone nozzle. The plants at the top will get over watered if you run the nozzle long enough to get good mist at the bottom. Thats also where a narrow cone nozzles would help. Micro sized water droplets dont bounce - they stck to the first thing they touch, so a wide cone will waste a lot of mist on the upper parts of the chamber.
I would suggest you do some tests.
First, measure the actual flow rate using the plastic bag trick I described above.
Next - make any changes based on the questions I asked at the beginning about the anti-drip nozzles and pressure reducer, etc. Also the pressure gauge test.
Then, put a camera and light down in the bottom of the chamber and fire the nozzle. See how long it takes for a good level of mist to show up down there. Id start with that time as an ON time and adjust from there. Keep in mind that when the chamber is full of pots and roots, there will be more blockage slowing the mist.
No matter what you do, you are going to end up with a compromise situation if you only have a single nozzle in that tall a chamber, but you should be able to get it working much better.