I have found so much useful information on here. The following is a detailed set of instructions on something I built. It would be easy to make modifications to fit your specific needs. Hopefully some of you will find this useful.
Since I wanted to have some plants in my viv that require some air movement, I wanted to build an air circulation system (2 of them actually…one for each side of my split 55 gallon tank). I’ve seen several builds that use PC processor fans, and since I work in IT, there is no shortage of small fans laying around at my work that would otherwise end up in the garbage. I use two 12 volt fans from some old HP server power supplies for this build. What always seems to be the issue is how to shroud the fans to duct the air. I’ve seen several difficult to duplicate builds, but I wanted to come up with something easy to build and easy to duplicate. Here’s what I came up with:
Here are all of the parts laid out on the floor. All of the straight pieces are simply short sections of PVC pipe that act as connectors for two other pieces – all of this is 2” except for the bottom 2 pieces on each side, which are a 1 ½” street elbow and short piece of straight pipe. The pieces just above those are 2” to 1 ½” adapters.
Here is the real heart of this system…what amounts to the fan shroud. It is comprised of a 3” to 2” reducer which my fans fit into well – this size reducer would work with several different fan sizes, as long as they aren’t too thick. What holds the fan in place is another piece that is designed to fit inside of a 3” piece and reduce it to 2” (Sorry that I don’t know the correct plumbing terminology for this piece). What it does for our build is hold the fan in place, and pretty much self-centers it as you can see in the following photos:
Once you’ve checked the fitment of your fan, you’re going to want to drill a small hole in the 3” to 2” reducer, for your fan’s power wires to route through. After the entire system is built, you can put a small blob of silicone over the wires to completely seal it off. I drilled the holes for mine on the angled part of the reducer, as seen in the photos below.
Once you are satisfied with the fitment of the fan, you can cement the circular piece inside the reducer, which will hold the fan in place permanently. Make SURE it’s how you want it to be, because once its cemented, it’s in there for good…until it fails at some point down the road. When you test fit the circular piece, you will notice that because of the thickness of your fan, the piece feels rather loose. This is because the PVC pieces are a taper fit and since the fan prevents them from seating all the way the fit isn’t tight. The PVC cement should make up for this when you cement it together though, so don’t panic. BEFORE cementing, make sure you are putting the correct end in first on the circular piece! In the first photo below it shows the side that you want facing outward. The second photo below shows what the other side looks like so you’ll know what piece you are looking for at the big orange or blue store.
After you are satisfied with the fit of everything, you can cement the two pieces together. Make sure you first prime BOTH parts, then apply cement to BOTH parts. This is how you should cement all PVC pieces, but it’s especially important in this case because we are making up some gap between these two pieces. Another tip – once you press the two pieces together, hold them together tightly to keep the fan captive, but also twist the two piece about ¼ turn to make sure you have good coverage and also to promote the melted plastic pieces to bond better. This stuff sets up real fast, so you really only need to hold the pieces together for about 20 seconds, so do it right!
The good news is that you’re done with the hardest part! Pretty simple, right? Next we will cement one of the elbows on – this will require a small length of 2” PVC that will fit inside of the circular piece and elbow. When preparing to cement the elbow on, make sure to pay attention to the orientation of your fan power wires so they come out where you want them to for your build. Besides the two pieces that we just cemented together to hold the fan in, this elbow is the ONLY other piece that I would recommend cementing until you are POSITIVE about the fitment of the finished piece. You don’t need to cement it for it to stay together – test fit everything in your viv and then test it again. Then and ONLY then would I cement ANY of the other pieces together. Here are some progress photos, basically just fitting the pieces together:
The last task necessary to complete this side is to put the screen on the end of the elbow (to keep frogs out, of course). This is simply a matter of starting with a piece of screen that is too large for the small piece of 1 ½” pvc that you will push into the elbow. When it’s wrapped in screen, it WILL be difficult to push the piece into the elbow. This is GOOD as it will hold the screen in place well. It doesn’t need to go in very far to be effective, either. I got the piece started, then put the spare piece on the floor and pushed the elbow down onto it to force it in a bit. You will then end up with a piece that looks like this:
Then simply (and CAREFULLY!) use a razor knife to trim through the fiberglass screen. This is easy as you will use the elbow’s lip as a guide for your knife blade. BE CAREFUL though as the blade will want to slip QUICKLY around that smooth slippery plastic! When you’re done, you should have a clean looking piece like this:
Now it’s just a matter of fitting the pieces for the other side together (I wouldn’t cement them until you are SURE of the fitment! There, I said it again). Here’s how the pieces all fit together:
And here is what it will look like fully assembled:
Here is what it looks like installed (mock) on one side of my viv. I didn’t explain it well, but the bottom elbows (1 ½”) come up through the glass and THEN attach to the rest of the unit. It takes approximately a 2” hole through the glass for the elbows to fit. A small bead of caulk around the elbow is advisable to seal it off. Make sure they are angled how you want them to be before you caulk them in place. Obviously, this is an enclosed system. Other thoughts that I had were possibly incorporating some type of valve that could be opened to allow some outside air in if desired. Another idea I had was to plumb in a hose from an ultrasonic humidifier into the pvc on the exhaust side of the fan, which would push the mist into the viv when the humidifier cycled on. That would be easy to add on. Obviously, this is PVC so any number of adaptations could be made to it suit different applications.
Hope this helps someone!