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ferdb · 11-14-2004, 11:07 AM

The Sunon 2123xst are a 120x38mm fan so they handle backpressure better than 25mm fans. They are superior to every 120x25mm fan I have by a large margin, and I have a lot of fans (Adda, Compuman, Zalman, Nexxus, Globe motors, Globe Fan, T&T, NTB, Papst, Panaflo old and new, Sunon DC, Silenx, Bi-Sonic and some others I can't remember). They have almost no bearing noise. As far as I know they are the best 120mm fan for airflow/noise that's available. Just dial them up to your rpm/noise preference.

At 120V (125Vac in my case here) they run at about 1200rpm down to about 650rpm at the minimum pot setting. I find 1200rpm is more than sufficient for me as an upper limit. If you need higher rpm than the Sunon's run stock at 120V then put a 2.2uf capacitor in series with the fan and it will boost the top speed considerably to a brisk 2500rpm. At this point it is no longer even remotely quiet but it is moving a serious amount of air (about 85CFM free air). a 4.7uF cap will boost the top speed to around 2100rpm, adds less heat to the pot than the 2.2uf, and fan rpm is less sensitive to line voltage fluctuations. Unless you need the speed though I would not put any cap in as it increases the heat dissipated in the pot. Don't forget to use a non-polar cap that's rated for the voltage. These fans never get more than slightly warm running at any speed from 2500 down to 0.

The fans are here http://www.alliedelec.com/Catalog/pf.asp?FN=551.pdf stock number 997-2123 at $9 ea
Pots are here http://www.alliedelec.com/catalog/pf.asp?FN=1233.pdf Stock number 522-0049 at $5 ea
2.2uf caps are here http://www.alliedelec.com/catalog/pf.asp?FN=1127.pdf stock number 612-0553 about $1
4.7uf caps are on the same page stock number 613-0500 about $2
Fan cords are here http://www.alliedelec.com/catalog/pf.asp?FN=549.pdf Stock number 609-5642 for 3' cord straight connector for $1.2

Allied has a minimum $25 order, but 2 fans plus parts covers that.

Note that the pots are rather large but they will fit into a 5 1/4" drive bay panel.

I have designed a fairly cheap and simple circuit that allows me to control my AC fans with the programmable T-Balancer fan speed controller (or any speed controller for that matter). It works well but it's a linear solution with about 4 watts dissipated in it worst case so I'm working on a switched mode design to see if I can avoid the heat without generating an unacceptable amount of noise in the fan. It's neither as elegant nor as noise free as I'd like yet.

Currently I use a Criticool pump relay to turn the fans on and off with the computer
http://www.criticool.com/Powerplant.html
This one is convienient since I just glued some perf board to the card and added my extra control circuitry for the T-Balancer. You could also just leave the fans on all the time.

I would love it if somebody else besides me would try out these 2123xst fans and leave some feedback on their experiences.

11-14-2004, 11:07 AM	#21
ferdb Cooling Neophyte Join Date: Sep 2004 Location: texas Posts: 68	The Sunon 2123xst are a 120x38mm fan so they handle backpressure better than 25mm fans. They are superior to every 120x25mm fan I have by a large margin, and I have a lot of fans (Adda, Compuman, Zalman, Nexxus, Globe motors, Globe Fan, T&T, NTB, Papst, Panaflo old and new, Sunon DC, Silenx, Bi-Sonic and some others I can't remember). They have almost no bearing noise. As far as I know they are the best 120mm fan for airflow/noise that's available. Just dial them up to your rpm/noise preference. At 120V (125Vac in my case here) they run at about 1200rpm down to about 650rpm at the minimum pot setting. I find 1200rpm is more than sufficient for me as an upper limit. If you need higher rpm than the Sunon's run stock at 120V then put a 2.2uf capacitor in series with the fan and it will boost the top speed considerably to a brisk 2500rpm. At this point it is no longer even remotely quiet but it is moving a serious amount of air (about 85CFM free air). a 4.7uF cap will boost the top speed to around 2100rpm, adds less heat to the pot than the 2.2uf, and fan rpm is less sensitive to line voltage fluctuations. Unless you need the speed though I would not put any cap in as it increases the heat dissipated in the pot. Don't forget to use a non-polar cap that's rated for the voltage. These fans never get more than slightly warm running at any speed from 2500 down to 0. The fans are here http://www.alliedelec.com/Catalog/pf.asp?FN=551.pdf stock number 997-2123 at $9 ea Pots are here http://www.alliedelec.com/catalog/pf.asp?FN=1233.pdf Stock number 522-0049 at $5 ea 2.2uf caps are here http://www.alliedelec.com/catalog/pf.asp?FN=1127.pdf stock number 612-0553 about $1 4.7uf caps are on the same page stock number 613-0500 about $2 Fan cords are here http://www.alliedelec.com/catalog/pf.asp?FN=549.pdf Stock number 609-5642 for 3' cord straight connector for $1.2 Allied has a minimum $25 order, but 2 fans plus parts covers that. Note that the pots are rather large but they will fit into a 5 1/4" drive bay panel. I have designed a fairly cheap and simple circuit that allows me to control my AC fans with the programmable T-Balancer fan speed controller (or any speed controller for that matter). It works well but it's a linear solution with about 4 watts dissipated in it worst case so I'm working on a switched mode design to see if I can avoid the heat without generating an unacceptable amount of noise in the fan. It's neither as elegant nor as noise free as I'd like yet. Currently I use a Criticool pump relay to turn the fans on and off with the computer http://www.criticool.com/Powerplant.html This one is convienient since I just glued some perf board to the card and added my extra control circuitry for the T-Balancer. You could also just leave the fans on all the time. I would love it if somebody else besides me would try out these 2123xst fans and leave some feedback on their experiences.