One of the things I am concious of with keeping tanks is the humidity they create. I have never experienced a tank as large as a 250G so I can only imagine the humidity it will create. I am trying to address this by exhausting the hood section of the tank out of the vicinity of the aquarium. Here I will have some photos and explanation of how I created an exhaust system in my unfinished basement that will allow me to exhaust the hot, humid tank air to 1) my furnace cold air return during the winter (improves heating efficiency and will help humidify the house during the super dry Canadian winters) or 2) outside using my dryer vent during the summer.
This system was put in months ago, before I started finishing my basement. To start, I had to put together the piece which will actually sit inside the hood and draw air. I am using a 120V 4" drive exhaust fan that was given to me as the first piece of hardware that will move air. I attached it to a 4" PVC elbow using some nails and construction adhesive. Once the adhesive dried, I wrapped it in duct tape to make the seal air tight.
The next step was to mount the assembly to a floor joist and add an electrical junction to house the electrical connections for the exhaust fan and the flow boosting fan (to come). I drilled a couple holes into the PVC elbow and screwed it to a floor joist and mounted a standard light junction to the joist so that the junction was flush to the PVC elbow. This will give me access to the junction in the future since it will be below the ceiling drywall.
In all honesty, at this point I figured I just hook up some more PVC, and the drive exhaust fan would be able to overcome the head pressure and move the air from the one end of the system to the other. Boy was I wrong. I had no flow, so I had to figure out a good way to boost the pressure. Walking through Princess Auto I noticed furnace duct boosting fans. What do you know, they had a 120V 4" fan. Perfect! So I mounted the fan at the elbow and wired it up to a 120V electrical cord. In hindsight, I should've placed the boosting fan at a different spot but it works pretty well where it is. Attached to the boosting fan is length of 4" PVC that runs the length of the floor joist.
If you are wondering, yes that is 14-2 standard wire. It has since been replaced with 14-2 flexible outdoor wire. I used duct tape again to seal the PVC connections to the boosting fan. The long run of PVC was secured to the floor joist at each end the same way the PVC elbow was secured. The 4" PVC run took me to the tricky part of the project. I had to get the air from my future rec room, across the whole basement to where my furnace and dryer duct are. I had already boxed in my furnace duct work so I figured I could run a line next to the existing duct work without any problems. I used a modified funnel to taper the connection from the 4" PVC to a 1.5" flex hose that would carry the air the rest of the run. The braided flex hose creates a bit of an issue in terms of extra head pressure but I really didn't have much choice at this point. Here's the funnel adapter and it attached to the PVC with duct tape.
I don't have any photos of the termination of the whole system but there is a T connection with valving on each of the branches that allows me to run the air to my cold air return on my furnace during the winter or to my dryer duct during the summer. The whole system doesn't move a lot of air but enough that I think the humidity in the main room of the basement won't get out of control and it should help cool the lighting a little bit. It may have just been an interesting project and not particularly useful, but I figured with this setup I might as well go for everything I can think of rather than get the tank going and wish I had this or that.