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Old 08-28-2010, 03:13 AM
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Default recirculating fan questions

I've finished installing the fan box on my plywood paludarium and wanted to get some opinions about the fans. The L-shaped fan box runs along the top of the front and side that have viewing panels. It is 2.5" tall (so sized for 60mm fans) and has openings for 4 fans on the front (60" span) and 2 fans on the side (28" span). The plan is that the fans will draw air from the top of the viv and blow it down the glass viewing panels, providing circulation and hopefully helping to keep the glass clear. I've attached a basic cross section of the box to illustrate the principle.

Anyway, here are my questions. What kind of airflow do you think is appropriate in a circulation system like this? Is there a general air turnover rate rule of thumb analogous to aquarium filtration? The emersed portion of the paludarium will be around 200gals or around 23 cubic feet. Does it seem seasonable to have 6 fans running at 15-20cfm?

Secondly, what kind of noise level do you think is appropriate? Are 32dBA fans an acceptable level of noise?

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Old 08-28-2010, 03:53 AM
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Default Re: recirculating fan questions

All I've really got in mind is that some FF proof screening on both ends is beyond necessary. But I'm sure you've got that covered. And maybe make it so you can change out said fans w/ ease, b/c you never know how well they'll hold up in that environment.

All these tanks are very different, from the enviroment that they are in, basement, bedroom, etc; to the environment they create within them (lighting, airflow, etc). You're gonna have to play around with it to get it "right". I know that's not what you're looking for, but I hope it helps. Maybe go w/ a couple more fan setups and then you can always seal them up w/ a cover if it's too much. But I know from experience that if you ever have to modify something after the fact it's a huge pain in the a**. Good luck and I"m sure you'll nail it.
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Old 08-28-2010, 10:42 PM
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Default Re: recirculating fan questions

Yup, I've got fiberglass window screen installed across the back and lower openings of the box. The access hole on the top is a hole with a lid that I can open to replace or clean the fans, or if I want to pull in some fresh air. I figure I'll use the 6 fans and have them connected to a fan controller to regulate the flow.

Still looking for thoughts on the sound (are 6 fans @ 32dBA each acceptable in a large viv?)
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Old 08-28-2010, 10:53 PM
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Default Re: recirculating fan questions

It's been my experience, that a circulation fan pulling air up across the front glass is more effective than blowing air down the glass. The humid air in the tank naturally wants to rise, and by pulling the air across the glass--you're working with the natural flow.

As for the noise of the fans: if you are in a completely quiet room--you will notice them. That being said, I have a total of 22 fans currently running in my living room ranging from 28-34dB, and my air conditioner is louder. Heck, the misting pumps I use run around 45 dB, and aren't any louder than the sound of the water flowing through the nozzles.
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Old 08-29-2010, 04:13 AM
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Default Re: recirculating fan questions

A fan at full speed can be a bit loud, audible anyways, and might disrupt something very quiet, like some frog calls. Turning the speed down a bit turns the volume way down though, and provides a gentler breeze, which is what I think you want. You can do that by placing around a 50ohm resistor in line with each fan, which is also accomplishable with two 100ohm resistors in parallel, and they're super cheap. Or you could just use a 9v power supply, I'd test it with a 9v battery first to see if you're getting the kind of airflow you want.
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Old 08-29-2010, 03:22 PM
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Default Re: recirculating fan questions

I use variable voltage power supplies. Unless I'm "drying out" tanks, I rarely run my fans at 12v, they're usually running at 9v.
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Old 08-30-2010, 12:13 AM
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Default Re: recirculating fan questions

Thanks guys. The fan controller should let me adjust the speed. Alasdair - thanks for the tip about reversing the direction of airflow.
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