This is a rewrite of a post I made on the Procooling forum. It's a summary of the things I've found out about using undervolted AC fans, which are the best, how to speed control them, how much they cost, and where to get them.

In my search for quiet 120x38mm fans for a BIP II radiator in a water cooling system, I tried and discarded all the available DC fans because of their excessive motor/bearing noise. There is no quiet 120x38mm fans like the 120x25 Nexxus or Globes. I wanted a 120x38mm fan because they handle backpressure better than the 120x25's and radiators are pretty restrictive compared to just case cooling. I turned to AC fans and after trying pretty much everything but Papst AC fans (they're just too expensive), and Orion (which I couldn't find any available in less than case quantities), I settled on the Sunon 2123xst 230Vac fan undervolted to 120Vac. They are superior to every 120x25mm or 120x38mm 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. They are even better than the Gold standard of 120x25mm DC fans, the Nexxus.

The 2123xst is easily speed Controlled with a 1K ohm potentiometer (see below for availability).
At 120Vac (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 that 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 a more reasonable 2100rpm, adds less heat to the pot than the 2.2uf, and fan rpm is less sensitive to line voltage fluctuations. Adding a series cap also increases the minimum RPM achievale with the pot. 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 diameter but they will fit into a 5 1/4" drive bay panel.

I have designed a fairly cheap and simple optically coupled 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 (per fan) in it's 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.

There are small 230v to 120v transformers that would allow those with 230V mains to run these setups as well.

I will add things to this thread as I finalize them such as control circuits and some real CFM/rpm numbers etc. (soon as my thermoanemometer arrives). Please feel free to ask questions.
For those watercooling who already have a pump relay these fans are not only a cheap solution, but may be the best solution available period.

I would love it if somebody else besides me would try out these 2123xst fans and leave some feedback on their experiences. I don't want to be the only voice in the wilderness.

This solution will bring you 2 problems:
- Introduction of high voltage 110 or 200 AC in your case, outside of the PSU, in conjonction with watercooling................
- introduction of 60hz inside of you case with possible electrical perturbation due to this AC.

Yes, it brings in 120V into the case like using an AC pump for water cooling does. This is not a problem if you properly insulate the connections with heatshrink etc. If you don't leave any bare 120V connections exposed there is no hazard, this is especially true when the case is closed. Having watercooling in the case does not increase the hazards in any way. This is not a bath tub you are going to drop a toaster in. On top of that if you have proper wiring in your wall and 3 prong plugs the case will be connected to Ground, this along with the fact that the pump relay card is fuse protected means there is no more hazard than a regular PC.

The impedance of signal lines on motherboards and drive cables is so low and the mechanism of coupling into these lines with 60hz ac is so weak that you wouldn't be able to generate any appreciable amount of interference in the system. Compared to the crosstalk from high speed digital lines 60Hz ac is like a candle in the wind. I suspect that Brushless DC fans put a great deal more noise into the system with their coil switching than AC fans would since they are connected directly to the power supply.. This is not a problem.

If people still have reservations about having AC in their computer a solution would be to plug the system into a GFI. That resolves any danger of a shock hazard they might have if they don't trust their own wiring/handiwork.

btw - thanks for raising these issues. Both good comments.

Wow, this is really interesting. I'd love to see SPCR do some tests in lab conditions with AC fans.

Well I finally started measuring the airflow through a Black Ice Pro II radiator with different types of fans at different rpms. So far I've looked at the 120mm Nexus, 120mm Panaflo L1A, and the Sunon 2123xst. The fans were mounted 1" from the radiator with a standoff shroud and set up to suck through the radiator.

All 3 types have a fairly linear relationship of RPM to CFM when running in free air. Double the RPM and you double the CFM. They also have a fairly linear relationship of RPM to Voltage. Halve the voltage and you halve the RPM. On the restrictive environment of the radiator however the CFM drops off more rapidly as RPM drops than is the case in free air. For the panaflo going from 1600rpm to 800rpm the CFM drops to about 40%. The Nexus is similar, for a drop from 1000rpm to 500 it drops to about 39%. The Sunon suffers an even worse rolloff. From 1200rpm to 600 rpm it drops to about 35% of the airflow.

Although the Sunon is a 38mm fan it seems to be at a disadvantage because of the more open 5 blade design compared to the 7 blade Panaflo and Nexus. The Sunon also has a large motor hub than either the Panaflo or Nexus. If you look at pictures of the various fans you'll see that the Sunon has much larger open areas between the fan blades. This hurts it even more as the rpm falls off and the CFM falls off faster than the other fans.

You can see the effect of the thicker fans though when comparing the airflow on the radiator to the free air CFM. The CFM of the Nexxus fan is reduced to roughly 50% of it's free air CFM when put on the radiator, the 38mm Panaflo and Sunon only drop to about 65%-70% of their free air CFM. Clearly the Nexxus takes a hit in restrictive environments.

From a subjective listening the Sunon's still have a bit of an edge over the Nexus for an equivalent airflow, even though it has to run a bit higher rpm than the Nexus at the lower airflow rates. The 5 bladed design means the noise tends to be a bit lower in pitch than the 7 bladed Nexus, and the Nexus tends to generate a bit more wind noise. The advantage over the Nexus however is not that great.
The Panaflos do better than either the Nexus or Sunon in a CFM to airflow department, but the motor noise is so overwhelming at any RPM that they get the big thumbs down.
It's unfortunate that the Sunon's are saddled with the 5 blade design they have, they certainly have the lower bearing and motor noise of any fan I've seen.
At this point if you are going for a radiator fan my recommendation would be the Nexxus. The Sunon has a slight edge on noise but it's probably not worth the extra effort required to hook them up.
I'm going to try some more measurements and comparisons when I get a chance and the background noise levels around here go down, but these are my preliminary findings. I'll also try and see how the Globes do on the radiator, although my guess is they should be close to the Nexus at the same RPM.

Thanks ferdb, sounds like the Sunon could be the one to go for. I'm going to get one and I'll let you know what I think.

On a sort of related note, it would be nice to share some ideas on building speed controllers with potentiometers that are both effective and above all safe. Working with mains current requires care and attention. My initial thought is to build the pot into a small plastic box, to keep all the wires securely hidden away. However, I was wondering if anyone knows anything about dimmer switches? I once saw an inline dimmer switch, which would seem to be ideal if it's just a simple pot.

Dimmers are not usually pots, but pots controlling Triac circuits that chop the line voltage up. Unfortunately Triac circuits don't take very kindly to Inductive loads like fans and they tend to freak out, not work, or make the fan buzz loudly. You can design a triac circuit that will work, but you have to take special measures to get it to behave nicely. At the moment the pot works very nicely, is cheap and simple, and doesn't introduce any switching noise into the fan.

Altogether now: It seems to me...

ferdb wrote:

....60Hz AC is like a candle in the wind

ne-na-ne-na-ne-na-neee-naaaaaaaaa

But seriously, this is a great thread, ferdb, some useful stuff in here for anyone interested in AC fans. It seems a bit too much work for too little gain in my opinion at the moment, but if you can come up with a simple and safe solution for using these fans there should definitely be a niche in the SPCR community for it. Especially if there are any other quiet AC fans out there or Sunon comes up with new designs.

I vote for a sticky for this thread!

I put a link of this thread in the main post of the "Top 120mm SPCR fans" thread under the Sunon section.



Bummer the Sunon doesn't come out the leader by a more significant margin. I wonder if it would hold its own more than a little better than the Nexus if used on a 2" heatercore. It's still the baddest boy in town, but it might not be worth the trouble.

I may still use the Sunons in my quasi external rad box since I'll be putting my Iwaki MD20Z in there, but I don't know now as it seems the speed controller is more trouble than it's worth. However, I be running the Sunons at a nonsilent noise level for when I'm gaming and overclocking (I'm a headphone gamer), so in this higher RPM regime in addition to the use of heatercores, perhaps the Sunon will shine more significantly. And of course, I'll still have the potential for a silent, even quieter than the Nexus setup, for word processing and such.

DrCR

________

Sunon also seem to do a 7 blade fan (A1123/A2123 HST is the sleeve bearing variant, for 115/230V AC). Looks like it has about 25% better flow at 0.2in H2O pressure difference. I've managed to find the Sunon data sheet for all their AC fans from the internet (it's on google somewhere - can't quite remember where) which has pressure drop/air flow graphs for all their fans at both 50 and 60 Hz.
Air flow is rated at 112/124 CFM at zero resistance, and volume is 43/46 dBA. A bit louder, but I'm guessing most of that is probably air flow noise.

Edit: just realised that there are several other fans that could fit this model number. A2123-HST is the only detail it gives on the data sheet. It's got an Aluminium alloy frame, is described as "High Air Flow", and rated at 0.28/0.31 in H2O peak pressure.

You've caught me fighting a cold so I'll just address this one point for now. On a more restrictive radiator I think the Nexus is going to lose. It already suffers about a 50% drop in airflow on the BIP II, compared to 30-35% for the 38mm thick fans. If you are really going to use a bigger core though you may want to use a bigger fan. There are some nice AC fans in the 150-170mm category that are also 2" thick. The only DC fans I've tried in that category have terrible motor switching noise, the AC may be the way to go there.

I had found these fans earlier on Sunon's website, but I can't find anywhere to get them. None of Sunon's distributors have them in stock. But thanks for bringing them up again, I think I'll make another effort to obtain some.

If it helps, I just found them in stock on the RS components website in the UK. I'm not sure how much international delivery is however, but RS are a very reputable UK company so probably won't give you grief about it.
Stock number is 468-5582, website is http://rswww.com and cost is £12.23 for a single fan. UK delivery is free for account holders and £5 otherwise.

There is apparently no stock in the US. The best I could find was a backorder with a minimum order of 40 pieces for $450. A bit steep when you only really want 2 of them. RS's website doesn't like me for having a US postal code. They refer me to their US partner Allied Electronics, who don't carry the fans. I'll try and contact them directly and see if I can get them to send me some. bleh, what a pain.

It looks pretty promising so I may well order a couple of fans from them in the next few weeks (better still, I may be able to do it via work who have an account and so get free shipping - will check next week). If so I'm quite happy to send some on to you at cost.
The only issue is that they are designed as 230v fans, so may have problems starting. 70/110 is more than 110/230, but it may be an absolute 70v requirement - the .pdf catalogue suggests so

Edit: Exact statement is that 115VAC variant requires 60VAC to start. This implies the 230V variant would require 230VAC...

I'd love to have you ship them. I haven't had problems with any of the 230V fans I've got running at 120. The Sunon 2123XST start and run at 80V. at 120V they do about 1200 rpm. It turns out the 230V fans are easier to work with than 120V fans because of the higher winding impedance etc. it's also easy to boost the effective voltage on the fan with a series Capacitor to around 150-160V.

Please get me two of the A2123HSL (I'd prefer the HST terminal version but I don't think they have any in stock) and we can arrange something for me to pay for them plus shipping. Contact me at [email protected]
and Thanks for the offer

Will do - might take a week or so before I order as I'm naturally disorganised and am only just starting to get the components together for this build. I'll probably email you from work monday/tuesday to sort something out.

Sudden thought - is there anyone else in the US who wants one of these fans? I'm up to 4 fans already between myself and ferdb, and if I can scrape together an order for 6 they're a bit cheaper. If so, contact me by monday afternoon UK time on <removed to deal with spam robots> and I'll sort something out.

Tempting, but on a strict budget right now. Good luck to you guys! I'm looking forward to hearing how they perform.

DrCR
_______

How did turn out? Any update?

Thanks,
DrCR

I've not tried them in a system, but attached to a Thermochill 120.1 one of them pulling shifts a reasonable amount of air (several times what my Papst 92mm @7v does) while being virtually inaudible. The fans have a little bit of 50Hz hum (I think I can hear it @ 2m in free air, but only with a flourescent light @ 4m turned off!), and the rest of the noise is vibration. The fan bodies are aluminium (look like castings) so are fairly heavy, and that should help vibration when installed.
They are certainly by far the quietest fans I've ever come across (when set up two in series across 120v).
Waiting for a storm G4 (if I can get my paws on one) and for 939/PCI-E motherboards to become widely available in the UK before I actually try them in a system. Current plan is two of these sucking external air into the case through a Black Ice Pro 2, and two of the Sunon 25mm fans exhausting the air (in a TJ-06 - one where the normal back fan is, the other at the HDD bay).

Awesome!

Does the fan look like this pic?: pic (from this link). Just curious. The fan blades of the pictured fans would seem suggest noisy airflow, at least I would think squared fan blades would (as opposed to reversed scimitar like blades).

I'm still tempted to pick up a few of these, but I'm thinking of selling my Iwaki MD-20Z and buying a pair of DDCs so I'm may want to stick with DC. Will have to think about it.

Question. About how long does it take nowadays for a G4 Storm to come in after ordering?

DrCR

_________

I've been caught up in other demands lately, but I did receive two of the A2123HST fans from pdf27 (thanks again). I mounted them on a Black Ice Pro II radiator and did some rpm/airflow measurements and comparative noise tests between them and a Nexus 120 and Sunon 2123xst at similar rpms. At the same RPMs the A2123 make a little more noise than the 2123xst but the higher airflow more than makes up for it and it comes out ahead on CFM/noise. At comparable CFM through the radiator the A2123 have a better airflow vs Noise ratio than the 2123xst or Nexus 120s. The A2123 have a 7 blade fan like the Nexus (although much different blade shape) and the CFM vs RPM is very close to that of the Nexus. The Fan noise is a higher pitched than the 2123xst at the same rpm because of the increase in fanblades (the 2123xst has 5 blades), and is similar to the Nexus in tone. The A2123HST has almost no bearing noise at all (in my samples).
For Radiator applications the A2123 comes out as the best performer but the advantage over the Nexus or 2123XST are moderate. Both the A2123 and 2123XST are heavy metal 38mm thick fans which 'weigh' against them from a mounting and weight issue. The AC fans also need to be mounted with rubber grommets or other vibration isolator methods to avoid the vibration noise they tend to couple into the chassis or radiator.

Bottom line is that the Sunon A2123 is the best airflow to noise ratio fan I've found for radiator use. If you want the ultimate performance you can achieve it with this fan. However the Nexus 120 is fairly close in performance and has the added convenience of being light weight and running on 12V.

Not really - it's got 7 blades and while they're not swept back the edges are very rounded - they look quite like flower petals actually...


Yeah, I've been wondering how best to fit them. How do you fit yours?

I'm using 1 inch standoffs and rubber grommets to mount them to the Radiator, but it would be nice to come up with something a little better in the way of support and isolation.

Cool deal, thanks ferdb.

Edit: I went ahead and added the A2123 to The Top SPCR Quiet 120mm Axial Fans Compared + 120mmAC Fans. thread.

Could you point me to one? I've got a largish core that just might like some 150mm lovin' ;D

It's not AC but Comair Rotron Patriots come in 172mm and run by default at 24v pushing 235cfm At 12v they're much quieter and still push lots of air. Mine won't run at 7v but I've never tried anywhere between 12 and 7.

OK I hate to reveal my ignorance about anything electrical/technical, but... this sounds great but I'm not sure I could make it all work without killing myself! Despite my misgivings, I'm thinking about tinkering around with the sunons and some potentiometers and the powerplant pci thing (it's only ~$20). First, though, I have a couple questions:

1. So do you hook up AC to the pci powerplant, and then hook up each fan to that, with the pot right in front of the fan?

2. Do the fan wires that end in terminals just hook into the pots and then into the fan wires that you mention are available from allied electronics?

3. You talk in-depth about your use of these fans with radiators. I'm still using oldskool air cooling for my components, so... how do you think the sunon would fare on a thermalright XP-120? I was thinking: 3 sunons: 1 on an XP-120, 1 for case intake, 1 for case exhaust. What do you think?

3. Honestly some pics of your set-up with some explanation would benefit me and I think others who are tempted to go down this path...

And thanks a lot for your work in this area, it sounds very promising! I think that maybe an article for SPCR is in order... perhaps you could moonlight as an SPCR article-writer...