(Under)Powering a D/C Fan

I just got a D/C fan that I'm going to hook up in my home theater
cabinet to vent the hot air generated by my htPC (home theater PC).
It calls for 24vdc, 1.7 A. As I understand it, I can get an a/c
adapter (wall plug) that provides more than 1700mA, but not less. Is
that correct? Also, this thing is unbelievably loud at 24vdc - is it
dangerous to underpower it with, say, 12vdc? I really don't need the
300+ cfm it provides at 24v, so I'd like to run it slower. Any
Thanks so much!
Reply to
J. Trout
Loading thread data ...
I've certainly derated replacement PC power supply fans that were unnecessarily loud and powerful, and run them continuously for years. With an ordinary DC motor I wouldn't even hesitate. The only issue that might exist is with a brushless DC motor that uses some electronics to do the switching - there's presumably a voltage below which the electronics won't function. You might want to put a suitable rated (slow-blow) fuse in series as a precaution.
Reply to
Sylvia Else
theater PC).
less. Is
24vdc - is it
need the
Skip the DC fan find a quiet 110 volt fan you can plug into the wall then maybe enlarge the vent opening is the home theater at top and bottom direct the fan at the bottom holes
Reply to
Phil Scott
Yes, your adapter needs to be able to supply at least 1700mA at 24Vdc. With the motor running on 12Vdc it might draw less than 1700mA. You could power it with the 12V supply from your computer if you are inclined and you know what you're doing. That is, assuming it's safe to power it with 12V, which I don't know one way or the other.
Reply to
operator jay
The 1.7A is hopefully its full load current and the fan will quite possibly take a little more as it ages and, of course, will anyway when starting up. So I would probably allow at least a 2A continuous rated supply. Some fans are designed to work against a specified air resistance and those fans will overspeed and make a lot of noise in free air.
It should be quite happy running with reduced voltage and no harm should come trying and seeing what voltage gives you the best effect. However, to be sure you could either post details of the make and model or look up the manufacturer's data sheets. These will probably have a graph of cfm against voltage, so you will be able to judge how much you can cut the voltage and the noise.
Reply to
Almost any DC fan can be run with a lower voltage, with exactly the effect you desire: reduced rpm and therefore lower noise. The current draw will also be reduced, though I'm not sure exactly by how much. I'd guess a 12 vdc supply that can deliver 1A would be about right, though of course a heftier one will not harm anything at all. Indeed, it might be better because the voltage might actually end up a little higher, and 50% might be slower than you actually want it to go.
Reply to
Floyd L. Davidson
You seem to have one of the 6.75" diameter fans such as the Rotron Patriot.
I use the nominal 24-volt fans all the time in 12-volt solar systems to ventilate restrooms. It will move about 120 cfm at 12 volts and draw about half of its rated current, be very quiet, and last many years.
There is no start-up surge on these fans, if flow is blocked the current decreases.
You will more likely have failures with the low cost power supplies. Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA snipped-for-privacy@pvri-removethis.biz
Reply to
Bill Kaszeta / Photovoltaic Resources
First off, thank you so much for all the responses, I really appreciate it!
Second, Bill, you're freaking me out! It is a Rotron Falcon, 6.75" indeed - well done!!!
Thanks again, everyone - I'm on my way :)
Reply to
J. Trout
But a wall wart on it about 12vdc at about 1 or 1/2 amp. I did the same thing to my cabinet, works fine, has been going full time for 2 years, I have a large filter in front to keep dust out. No problem.
Reply to
President Musharraf

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.