Cooling fan for electronics cabinet

Gdetrailer wrote:

You can power a 12V fan from 5V but it is going to run considerably slower than designed. While that is a good thing noise wise, it does a bad thing for actual air movement. These fans get very inefficient when run at a lower speed than designed so a fan rated at 50CFM at 12V running at 5V will result in at the best 20CFM. Same happens when you take a fan that is designed for 240V and run it on 120V, you will get CONSIDERABLY LESS than half the rated CFM.

CORRECT!

When running those fans on 1/2 Voltage you get 1/4 power, ~1/4 fan speed, ~1/4 air movement and 1/4 noise. It's a no-brainer.

Further noise reduction is done by using fans with anti-cavitation blades (whisper fans).

This is frequently done in broadcast and recording studios and the engineers that design this stuff know what they are doing.

Bill.Winegard wrote:
You want a quite fan like is found in a computer. Radio Shack has some 12V and 120V I believe but you will find many online. You can set them to run whenever power is available or you can add a thermostat so it only runs when the temps reach a certain level.

This is my favorite answer. When I was younger I built custom car stereos. My wife had one in her car and the amp would overheat and shutoff on a 100 mile trip. The amp had a clear plexiglass top so you could see the components. I bought a 2 inch computer style fan from Radio Shack and cut a hole in the amp cover to match. Glued in place so it would draw the air out of the unit rather than pushing it in. Wired it so it was only on when the amp was on. 3 years later and it was still going without issue till the day we sold the setup.

Gdetrailer wrote:

Kiwi_too wrote:
I took a 12v fan out of an old PC I had. I wired it to a USB cable and plugged that into a 120v to 12v adapter. Pulls quite a bit of air through the cabinet.

:h

Not sure as to why you would use a USB cable in between a 12V fan and 12V power supply.

Bad things will happen if someone decided to plug a USB device in using a 12V power supply.

USB ports (and USB wall charger/power supplies) provide FIVE VOLTS, not 12V.

You are quite correct. It is only a 5v fan and adapter. It is plugged in with a USB to 120V adapter.

Sorry about that.

I prefer to use fans as intakes, not exhausts & put filters on them. Then you have some airflow to cool the unit, minimal to no dust to clog the inner workings and act like a blanket on heat sinks, and with the filters external, when they turn from black to grey it is time to remove and rinse them off and reinstall them. In fusty areas you may need to clean them 2 times a week, in clean areas monthly. Before anyone complains about cleaning filters, external filters take less then 2 minutes to R&R, digging into a cabinet and blowing out the dust takes far longer, and there is no easy way to know when it needs to be dome.

Kiwi_too wrote:
I took a 12v fan out of an old PC I had. I wired it to a USB cable and plugged that into a 120v to 12v adapter. Pulls quite a bit of air through the cabinet.

:h

Not sure as to why you would use a USB cable in between a 12V fan and 12V power supply.

Bad things will happen if someone decided to plug a USB device in using a 12V power supply.

USB ports (and USB wall charger/power supplies) provide FIVE VOLTS, not 12V.

You can power a 12V fan from 5V but it is going to run considerably slower than designed. While that is a good thing noise wise, it does a bad thing for actual air movement. These fans get very inefficient when run at a lower speed than designed so a fan rated at 50CFM at 12V running at 5V will result in at the best 20CFM. Same happens when you take a fan that is designed for 240V and run it on 120V, you will get CONSIDERABLY LESS than half the rated CFM.

A funny story, my company builds some industrial products, we had some of the customers complaining about noise from the cooling fans.

The fans cooled a PC built into the device along with power supplies and other electronic parts. The fix for the noise was to buy a 220V fan to replace the 120V. Problem was our engineers discarded the fact that the 220V fans was rated the same CFM as the 120 fan but when running the 220V fan on 120V it barely moved any air.. Items inside the case soon didn't like the heat and failed more often..

Another point to consider, typical USB ports or USB chargers supply 500 ma per port or there are high power ones which supply 1A per port.

Please make sure the fan you select DOES NOT draw more than the USB port or charger can supply.

I took a 12v fan out of an old PC I had. I wired it to a USB cable and plugged that into a 120v to 12v adapter. Pulls quite a bit of air through the cabinet.

bwanshoom wrote:
This site has some good stuff. AC, DC, USB - if you have a USB port handy, that's the way I'd go.

x2. Coolerguys.com has a wide selection of fans. I went with a bank of 4, thermal-controlled AC fans & a set of USB fans.

I needed a fan to move some air around my PD9260C converter setup. went with one of those attic fan thermostat boxes. Set it for around 85 degrees. It runs a 6-inch muffin (axial) 12VDc fan pulling in fresh cooler air from the hallway to the wrap around seating storage cabinets where the converter is installed. I added some small round pass-thru vents interconnecting all of the wrap around storage compartments and blows back into the hallway on the other side of the trailer. Moves air pretty good through the storage compartment areas... Fan runs pretty quiet...

Roy Ken

tvman44 wrote:
Muffin fans are quiet and effective. (computer type) :)

I use two 220 Volt 5" Muffin fans and run them on 120 Volts.

They are super quiet and each one moves 25 cu. ft. of air per minute.

A sail switch can be used to kill power to the electronic equipment in case both of the fans fail.

Thanks for all the input, folks. I think I can manage from here.