Sunday, November 18, 2012

Installing an Automated Greenhouse Misting System

It works! 

I have long envied the Curbstone Valley folks their propagation misting system and wanted one myself. Well, now I do! I completely copied their setup for the misting heads, pressure regulator, and filter, as described here, and it works great. 

In addition we added valves and a propagation timer, so that the mist will automatically go on for n seconds every n minutes, during a time window from n o'clock to n o'clock. 

Here's what we did, starting with the misting heads and working back along the system to the valves, and thence to the timer.

mister, anti-drip device, and barb to stick in the pipe. Fittings just press together.
Like CVF, I purchased individual parts from To assist you in your explorations, here are links to the mister parts, as shown above, from left to right:
The anti-drip device prevents drips happening after the water is turned off, which could damage delicate plants. I also got the hole puncher which is definitely worth it.
We didn't need to build a framework to support the misters. The wire top shelf supports the pipe, which I secured using small cable ties. 

The black drip-system irrigation pipe is capped off at the end of the shelf near the door,  and swoops down at the back.
To figure out how far apart to put each mister, I put in one mister and turned on the valve (see below) by hand. It seemed to wet about a four foot circle. So I punched a hole every two feet and poked in the three-part assembly. It's a bit hit and miss, figuring out the coverage. I figure a 50% overlap means that everything gets about the same amount of water and there are no gaps. It seems to be OK.

Below the propagation bench, the black piping is joined via an elbow connector and other standard connectors to the filter, then the pressure regulator, which screw together. 

A valve with pressure regulator and filter, and pipe going up to the misters.
Here are the links to the regulator and the filter. Use the fine mesh filter - 200 mesh screen. We installed them as shown on the Curbstone Valley Farm post, with the filter closer to the mister end of things:
Installing the Valves and Controller
For automation, you need a valve to open and close the water flow, and you need a timer to specify the duration of the flow and the interval between each. For propagation you need just a few seconds every so many minutes. I'm still figuring that part out - it depends on what you're growing, and how cool and damp the weather is or how hot and dry. I'm finding that a few seconds every 45 minutes is enough - maybe more than enough - for late fall.

Curbstone Valley Farm has not yet (or hadn't when Town Mouse and I enjoyed a visit recently) set up the automation side, but it is important to me. Maybe they can emulate my set up - or improve upon it.

So I ordered these from Mr. Drip (
I went overboard. I figure if we are doing this we might as well install six valves and a timer that can control six different zones. So the rest of this post would apply whether you are setting up your garden irrigation or a propagation mister. I want to use this system for both. If you have one or two valves, your job is that much simpler.

The completed valves, wired up. Three sets of two preassembled valves, plus two "snap wire boxes" (provided) which link the valves to the sprinkler wire.
I can potentially use up to three zones in the greenhouse, and three in the south garden. Sometime. Right now we have set up just one zone, for one propagation bench.

The propagation timer (I'll show the wiring hidden by the lower panel in another photo)
The special thing about a propagation timer is that it lets you control duration in seconds, rather than minutes.

I called on the services of Mr Dusky Footed Wood Rat to do the plumbing that brought the water to the valves; to install the valves; to connect the things of one diameter to the things of a smaller diameter using reducer whatsits; to mount the timer; and to run the sprinkler wire between the valves and the timer. 

Bet you thought I was joking about the dusky feet!
The valve documentation was OK for Mr Rat, but was Greek to me in places. Maybe I'll write a plain language version for the inexperienced installer. Or maybe not. 

A snapwire box all set up, showing the "common" wire and four colored wires. The plugs on top go to sprinklers 1, 2, 3, and 4 - counting from the left. The colored sprinkler wires go in corresponding slots.  
Sprinkler wire has four wires inside, and we needed to set up six valves, so Mr. Rat ran two strands of the sprinkler wire from the valves to the timer. I finished the job by connecting up the individual strands that are hidden cunningly within the outer sprinkler wire coating. First you strip back the outer sprinkler wire covering for about 4 inches, to reveal the five coated strands inside. Then you strip back each separate strand about half an inch, using a wire stripper, to reveal the metal inside. This was all sort of new to me, but I managed just fine.

Finally you poke one strand of wire inside each soft rubbery area at the bottom of the snap wire box, while pressing down the plastic bump that opens a gate inside. Letting go traps the wire. It doesn't matter which wire goes in which hole - the important thing is that whatever wire you shove through slot 1 in the snap wire box goes to position 1 on the timer, and so on. It's all just common sense.

There is one"common" wire from each sprinkler wire (we used the green strands) and four other strands to go to each numbered position. For six valves we needed two wires. We didn't need two of the strands from one of the wires so we folded them back and wrapped them. .
Confession: I have no idea why for each snapwire box there is one connection called "common."

Just to reiterate: make sure you match up the strands, using the color to help you put them in the same order you did on the valve snap wire box. Because we were using two wires, we put a bit of tape round both ends of one wire so as not to get mixed up. 

Here's another tip I came up with because I did not do it: start at the bottom and work up.

I found it was hard to squish the lower wires in after I had screwed in the higher ones. It would be better to start at the bottom and work your way up (remembering to start with the wire corresponding to valve six, of course!)
At this point, we were all done except the programming. If you've never set up timing for an irrigation system, be prepared to go over this a few times. Read the manual. These manuals are not great, in my experience, but if you persevere you'll get it. I wonder if there are dummy's guide type manuals or YouTube videos that are easier to follow. The logic of it is pretty simple - you just have to sort of get it into your head. I'd rather have an interface to a computer, where you could have a more intuitive UI, but those types of systems are not so common.

I'm just thrilled to have this system in place. Every time those little misters come on by themselves, my heart leaps up.

I hope to post updates about the amazing cuttings I manage to propagate - but we shall see what reality brings!

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