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Project: Cooling Fans

In order to help control the considerable heat which will be created by the light rack, I decided to install a cooling fan system. My plans called for installing the fans on both the right and left sides of the light rack. I wanted to be able to use my ACIII Pro (now Apex) to turn the fans on and off based on the water temperature - so their installation was foreseen in the wiring when I built the rack. I wanted to keep noise in the fish room to a minimum, so I thought I'd try 12V PC fans. I've used fans from the Austrian firm Noctua in the past. I found them to be both powerful and quiet - and probably more important - I've never had one of them go out on me.

I decided to use six 120mm fans - three on each end of the light rack. This is what they look like:

I wanted the fans to be mounted on to the light rack itself, so that when the rack was slid out of the way the fans would move with it. This meant I would have to build some kind of box to hold them. I started looking for some material that wouldn't corrode and was as light as possible. I finally decided on expanded PVC sheet. It's basically just like normal PVC sheet, but (from what I understand) has had microscopic bubbles of some gas injected into it during production. The bubbles are so small that you can't actually see them. Their effect is that the sheet is very light. It doesn't have the rigidity of normal PVC, but is more than adequate for my purpose.

Before I go into some of the details of the build, here is a pic of the (mostly) finished fan box - so that you'll have an idea what I'm talking about as I describe the build. The back plate is rather large so that it can serve two purposes - it holds the fan box, but also blocks light from entering the fish room. Its bottom edge will be flush, with 1/4" to spare, with the top of the tank:

What is missing here are the grills (guards) that go over the fans for finger protection. They hadn't yet been delivered when the picture was taken. Also, the bolts holding the box together will be exchanged for nylon bolts as soon as they are delivered - that will eliminate any possibility of corrosion.


The first thing I did was make some mounting plates out of scraps of 3/8" black acrylic sheet that I had laying around. These would be riveted to the frame of the light rack and have threaded holes where the fan box back plate could be mounted using 1/4-20 nylon thumb screws.

Whenever I'm threading acrylic, I like to leave the protective paper on the sheet. I find it helps prevent chipping. Also , when you're threading the tap into the acrylic, remember that the material is very soft compared to metal. Always back off a turn for every couple of turns forward.

This is what the mounting plates look like mounted on the light rack (please excuse the fact that I didn't bother to clean up some of the edges).

Here are the individual pieces of the fan box. These are made out of 1/4" expanded PVC sheet. This material is very light, easy to work with, and sufficiently durable:

And this is the back plate:

I routed the 4 1/2" holes, for the fans, using a 1/2" upcut spiral flush trim bit and an MDF template I had from a previous project.

If you can, use a 1/2" bit instead of a 1/4" bit. The 1/4" bits can tend to vibrate. Also, a 1/2" bit will leave a smoother edge than a 1/4" bit. Add to that, the fact that 1/4" bits have been known to break when routing thick acrylic.

I attached the MDF template the the PVC sheet using double sided tape:

This holds the template securely to the PVC, but is easily removed when the work is completed.


So after all the cutting, drilling, and routing was done, I started putting the pieces together:

Using a thickened PVC glue, I attached the fan box sides to the front of the box.

I used bricks covered in duct tape as weights to keep pressure on the parts while the glue set up. An easy solution compared to trying to find metal weights.

After the glue dried, this is what it looks like, from the front:

... and from the back:

Three fans go on each back plate:

And then the box front is added:

The finished product is mounted on the light rack with 1/4"-20 nylon thumb screws:

Each bank of three fans will be connected to a 12V 1000mA power adapter. The adapters will connected to the central power distribution box on the top of the rack. There will also be panels along the back of the light rack (if you look closely you can see the mounting brackets - same as for the fan boxes). They will stop light - and cooling air - from leaking into the fish room.



Terry says...
That is sick! You got some talent there man! Just wondering can I use carpet tape to hold the templates? Thanks.
GlassReef: Thanks, Terry! Glad you like it. Smile

Yes, just about any double sided tape will work fine. Make sure you use enough to hold the pieces together well. You don't want them to split apart while your routing!

6th October 2010 11:31am

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