172mm Fans

Syncore · 08-28-2002, 03:09 AM

Long time reader of this forum and I finally have a reason to post. I recently started watercooling and I am now hooked. I started simple with a Maze3, BIX and Via Aqua 1300 closed loop setup. but I am already yearning for bigger and better. First thing I am going to do is upgrade the BIX to a nice large heatercore which leads me to my question. I was going to use the Comair Rotron 172mm fan that caseect.com sells but when looking for a better price I ran across these for $2.95:

http://www.mpja.com/product.asp?product=13243+FN

For that price I gambled and bought 5 of them since there is a minimum $15 purchase there. Now since they are 24v I am wondering if they will run at 12v just by wiring and hooking them up to a molex connector. If they do run then any idea what the 205 CFM would drop too?

-Syn

gmat · 08-28-2002, 06:28 AM

First, welcome to this fun, money-hungry (and wet) experience !
For your question, usually DC fans work at half their rated voltage, though it's about the limit. The only way to know is, to try and see

At this price i'd order 10 of them and build a crazy wind tunnel just for the fun of it !

jtroutma · 08-28-2002, 04:52 PM

What you could try and do is use a 12V rail and a 5V rail together so you can get the fan up to 18V ......... that is if you are shotting for some realy nice CFM scores yet fairly quite operation.

bigben2k · 08-28-2002, 05:22 PM

Quote:

Originally posted by jtroutma
What you could try and do is use a 12V rail and a 5V rail together so you can get the fan up to 18V ......... that is if you are shotting for some realy nice CFM scores yet fairly quite operation.

Actually, that would be 17V... but details, details...

In order to do that, you'd have to use the -12 and +5, or the -5 and +12 lines. Double check the power ratings of your PSU on those negative lines, because they're usually pretty low.

Since the +5 line is critical, I'd go with the +12 and -5 option.

If you want 24V, you could go -12 with +12, with the above caution.

Let us know!

jtroutma · 08-28-2002, 05:26 PM

Ok ok ok My math skills are not completely up to par.. (maybe that is why I cant pass Calc.3

) Anyways....

Ben... your saying that if he gives those fans a positive 12V line an a negative 5V line, then that would produce a 17V line?????

Sorry that I dont follow you but that doesnt sound like it will work.. can you please explain...

bigben2k · 08-28-2002, 05:49 PM

Quote:

Originally posted by jtroutma
Ok ok ok My math skills are not completely up to par.. (maybe that is why I cant pass Calc.3 ) Anyways....

Ben... your saying that if he gives those fans a positive 12V line an a negative 5V line, then that would produce a 17V line?????

Sorry that I dont follow you but that doesnt sound like it will work.. can you please explain...

I'd be happy to!

The standard mod that we all do, known as the 7V mod involves wiring a fan to the +12 and +5 lines (which are available on the Molex connectors). The difference in voltage between those two lines is: 7V!

So if you want 17 volts, you'd wire a fan to the -5 line (you'd have to tap into the mobo connector) and the +12 line.

I never believed that it worked, or that it was a good idea, but it does seem to. I saw an issue where the 7V mod would actually feed current back up the +5 volt line, through the regulator and I thought: that can't be right... but what's actually happening is that the current comes from the +12 line, is dropped to +5 (because the other components keep it at +5) and it feeds another component, and actually relieves the PSU on the +5 line. (Actually, in electricity everything is backwards, where the electrons, negatively charged, travel from the low point (GROUND) to the high point (+5 or +12), but that's too theoretical).

If anything, wiring something that way might make the PSU voltages shift a bit, so if your system is sensitive (highly OC'd), and/or you have a cheap PSU, check your voltages before and after.

bigben2k · 08-28-2002, 06:02 PM

Actually, it's possible to check this on-the-fly:

Typical -5V line is rated for 0.5 amps, max (may vary)

This fan is rated for 24V@ .75amps, which gives it roughly a resistance of 32 Ohms.

If we ran that fan at 17 volts, it would draw 0.53 amps (I know it's not accurate, but rough enough!), so it would overpower the -5 line.

With the +5 and -12 option, the -12 line is typically rated at 1.0 amps (may vary), so that should be OK.

The -12 to +12 should work too.

(If any ya'll try this, it's at your own risk, OK?)

aabtek · 08-28-2002, 07:57 PM

or you could use one of the small powersupplies, you know for the discman/printer/hubs ... I am sure you could find one rated at 24 volts .... power it from the same mains/strip/relay as the waterpump, so that it turns on with the rest of the watercooling.

I would be a lot less worried with that scenario than pushing a stressed powersupply where it is weakest.

bo v

pHaestus · 08-28-2002, 10:56 PM

Those fans work quite well at 12V (have one myself) and there should be plenty of 1A PSUs around at surplus stores that are 24V if that is your thing...

Syncore · 08-28-2002, 11:15 PM

Thanks for all the replies. Some were out of my technical range but I am glad to know they should spin at 12v.

Brad · 08-29-2002, 03:44 AM

but because it's using the -5v as a ground does it really matter at all what the -5v is rated at?

bigben2k · 08-29-2002, 08:31 AM

Quote:

Originally posted by Brad
but because it's using the -5v as a ground does it really matter at all what the -5v is rated at?

Well since the -5V isn't actually a ground, yes it will matter. Why do you think that there are so many wires on the mobo connectors that are ground?

The -5 line is regulated, the ground isn't.

bigben2k · 08-29-2002, 08:31 AM

Quote:

Originally posted by aabtek
or you could use one of the small powersupplies, you know for the discman/printer/hubs ... I am sure you could find one rated at 24 volts .... power it from the same mains/strip/relay as the waterpump, so that it turns on with the rest of the watercooling.

I would be a lot less worried with that scenario than pushing a stressed powersupply where it is weakest.

bo v

Just make sure that the PS you get has a DC output: many of them have an AC output.

bigben2k · 08-29-2002, 08:33 AM

Quote:

Originally posted by Syncore
Thanks for all the replies. Some were out of my technical range but I am glad to know they should spin at 12v.

If you're interested, I could come up with a diagram for a rheobus that would allow you to set the voltage, using the -12/+12 lines, so that you could fix the voltage anywhere from 0 to 24 VDC.

utabintarbo · 08-29-2002, 09:39 AM

Quote:

Originally posted by bigben2k
If you're interested, I could come up with a diagram for a rheobus that would allow you to set the voltage, using the -12/+12 lines, so that you could fix the voltage anywhere from 0 to 24 VDC.

That would be a great subject for a How-to! Do it! Do it now!

Bob

bigben2k · 08-29-2002, 10:13 AM

Actually, any Rheobus can do it, as long as the chip is an LM317 (rated for 1.5 amps). The LM317A is rated for 1.0 amps.

The difference would be the power connections, and making sure that nothing short circuits, since there would be no ground.

shaft01 · 08-29-2002, 12:22 PM

I have these very same $2.95 fans in the system I am currently constructing.......They work just fine on 12v with fairly good flow and VERY quiet......

Though as others have discussed it would be nice to have the option of turning them up a notch......Many of you may be intrested in the details of the system they are going in and that and pics can be found here: BlackMax

I also bought a 24v 6amp PS from the same vendor when I ordered the fans for $4.95 which I would love to be able to regulate from say 12 to 24v.......I am guessing a reostat would do the trick but am unsure of what exactly to get and where to get it.......

Guess I am STANK cheese here for a while lol

bigben2k · 08-29-2002, 12:30 PM

Welcome to Pro/Forums!

That's a really nice project. Where did you pickup your iPanel?

Like I said above, you can use the Rheobus design (easily found with Google), just make sure you use an LM317 or LM317A. It will work with 24 VDC.

shaft01 · 08-29-2002, 12:46 PM

Quote:

Originally posted by bigben2k
Welcome to Pro/Forums!

That's a really nice project. Where did you pickup your iPanel?

Like I said above, you can use the Rheobus design (easily found with Google), just make sure you use an LM317 or LM317A. It will work with 24 VDC.

Thanks! I believe I am glad to be here

......I will check into that.......I bought the Ipanel from BIG008.COM via Egay of all places......

EDIT: How about a LM317T with the following specs:

1.2 to 27VDC. Heat sink required for max. current rating of 1.5 amps. TO-220 case

toddalaska · 08-29-2002, 11:24 PM

Quote:

Originally posted by bigben2k
I'd be happy to!

The standard mod that we all do, known as the 7V mod involves wiring a fan to the +12 and +5 lines (which are available on the Molex connectors). The difference in voltage between those two lines is: 7V!

.

can someone walk me through how to do this standard mod.

im assuming that it can be done on a 12v fan (kinda over clock it)

no ground?
or do the 12 and 5 go together

i think you guys will get the idea what im asking.

WebMasta33 · 08-29-2002, 11:55 PM

Ok, you have 4 wires on the molex from the PS

yellow +12v -- ground -- ground -- red +5v

from the molex you have on the fan you have

red +12v -- ground -- blank -- blank

if you take the ground wire and move it to hook into the red+5 volt, you'll have a 7volt fan.

I'm currently running two 12volt Panflows at 5 volts, which is you just move the 12v line to the 5volt.

toddalaska · 08-30-2002, 12:12 AM

ok dangit, i was hoping to over volt the fan for more rpms

i take it this is done for quietness

pHaestus · 08-30-2002, 12:32 AM

Check the ATX spec; there are -5V and -12V lines on the PSU's ATX connector. Tap into those for the ground of your fan for 17 or 24V. Make sure the PSU has the A to handle this.

thebigNil · 08-30-2002, 12:48 AM

You could force feed the fans 17-18v I forgot how much exactly but you just need to get your hands on a old AT power supply and so you wont have to worry about cooking your ATX. Get the AT and use a multimeter/voltmeter to poke around on the motherboard connectors and you should be able to find two wires that make 18v and just use that. I have found some psu's that dont like to have those connected so they spas out and tend to revert to a primitive state when you connected the two wires to any kind of load so that wont work for the given reason. Also some psu's need a load to work so all you have to do is hook up a old hdd or cd-rom drive.

I bet that you could have figured out how to give them extra volts by reading bigben2k's posts ahh oh well.

08-28-2002, 03:09 AM	#1
Syncore Cooling Neophyte Join Date: Aug 2002 Location: Albuquerque, NM Posts: 5	172mm Fans Long time reader of this forum and I finally have a reason to post. I recently started watercooling and I am now hooked. I started simple with a Maze3, BIX and Via Aqua 1300 closed loop setup. but I am already yearning for bigger and better. First thing I am going to do is upgrade the BIX to a nice large heatercore which leads me to my question. I was going to use the Comair Rotron 172mm fan that caseect.com sells but when looking for a better price I ran across these for $2.95: http://www.mpja.com/product.asp?product=13243+FN For that price I gambled and bought 5 of them since there is a minimum $15 purchase there. Now since they are 24v I am wondering if they will run at 12v just by wiring and hooking them up to a molex connector. If they do run then any idea what the 205 CFM would drop too? -Syn

08-28-2002, 04:52 PM	#3
jtroutma Cooling Savant Join Date: Aug 2001 Location: SLO, CA Posts: 837	What you could try and do is use a 12V rail and a 5V rail together so you can get the fan up to 18V ......... that is if you are shotting for some realy nice CFM scores yet fairly quite operation. __________________ Athlon64 X2 4200+ @ 2.5Ghz (250FSB x 10) OCZ VX 1GB 4000 @ 250FSB (6-2-2-2 timmings) DFI LANParty nForce4 Ultra-D SCSI Raid 5 x (3) Cheetah 15K HDDs LSI Express 500 (128MB cache) OCZ PowerStream 520W PSU ATI X850XT PE (Stock) DTEK WhiteWater + DTEK Custom Radiator Eheim 1250

08-28-2002, 05:26 PM	#5
jtroutma Cooling Savant Join Date: Aug 2001 Location: SLO, CA Posts: 837	Ok ok ok My math skills are not completely up to par.. (maybe that is why I cant pass Calc.3 ) Anyways.... Ben... your saying that if he gives those fans a positive 12V line an a negative 5V line, then that would produce a 17V line????? Sorry that I dont follow you but that doesnt sound like it will work.. can you please explain... __________________ Athlon64 X2 4200+ @ 2.5Ghz (250FSB x 10) OCZ VX 1GB 4000 @ 250FSB (6-2-2-2 timmings) DFI LANParty nForce4 Ultra-D SCSI Raid 5 x (3) Cheetah 15K HDDs LSI Express 500 (128MB cache) OCZ PowerStream 520W PSU ATI X850XT PE (Stock) DTEK WhiteWater + DTEK Custom Radiator Eheim 1250

08-28-2002, 06:02 PM	#7
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Actually, it's possible to check this on-the-fly: Typical -5V line is rated for 0.5 amps, max (may vary) This fan is rated for 24V@ .75amps, which gives it roughly a resistance of 32 Ohms. If we ran that fan at 17 volts, it would draw 0.53 amps (I know it's not accurate, but rough enough!), so it would overpower the -5 line. With the +5 and -12 option, the -12 line is typically rated at 1.0 amps (may vary), so that should be OK. The -12 to +12 should work too. (If any ya'll try this, it's at your own risk, OK?) __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

08-29-2002, 03:44 AM	#11
Brad Thermophile Join Date: Oct 2001 Location: Nuu Zeeelin Posts: 3,175	but because it's using the -5v as a ground does it really matter at all what the -5v is rated at? __________________ 2x P3 1100's at 1400, Abit VP6, 2x Corsair 256mb PC150 sticks, 20gb 'cuda ATA-III, 2x 40gb 'cuda ATA-IV in raid 0. 20" Trinitron. No fans 2x 2400+ at 2288mhz (16.0 x 143), Iwill MPX2, 2x Kingmax PC-3200 256mb sticks, 4x 20gb 60gxp in Raid 5 on a Promise SX6000. Asus Ti4200 320/630. Cooled by Water

08-28-2002, 06:28 AM	#2
gmat Thermophile Join Date: Mar 2001 Location: France Posts: 1,221	First, welcome to this fun, money-hungry (and wet) experience ! For your question, usually DC fans work at half their rated voltage, though it's about the limit. The only way to know is, to try and see At this price i'd order 10 of them and build a crazy wind tunnel just for the fun of it !

08-28-2002, 07:57 PM	#8
aabtek Cooling Neophyte Join Date: Aug 2002 Location: aalborg.dk Posts: 19	or you could use one of the small powersupplies, you know for the discman/printer/hubs ... I am sure you could find one rated at 24 volts .... power it from the same mains/strip/relay as the waterpump, so that it turns on with the rest of the watercooling. I would be a lot less worried with that scenario than pushing a stressed powersupply where it is weakest. bo v

08-28-2002, 10:56 PM	#9
pHaestus Big Player Making Big Money Join Date: Aug 2001 Location: irc.lostgeek.com #procooling.com Posts: 4,782	Those fans work quite well at 12V (have one myself) and there should be plenty of 1A PSUs around at surplus stores that are 24V if that is your thing...

08-28-2002, 11:15 PM	#10
Syncore Cooling Neophyte Join Date: Aug 2002 Location: Albuquerque, NM Posts: 5	Thanks for all the replies. Some were out of my technical range but I am glad to know they should spin at 12v.

08-29-2002, 10:13 AM	#16
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Actually, any Rheobus can do it, as long as the chip is an LM317 (rated for 1.5 amps). The LM317A is rated for 1.0 amps. The difference would be the power connections, and making sure that nothing short circuits, since there would be no ground. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

08-29-2002, 12:22 PM	#17
shaft01 Cooling Neophyte Join Date: Aug 2002 Location: Georgia Posts: 41	I have these very same $2.95 fans in the system I am currently constructing.......They work just fine on 12v with fairly good flow and VERY quiet...... Though as others have discussed it would be nice to have the option of turning them up a notch......Many of you may be intrested in the details of the system they are going in and that and pics can be found here: BlackMax I also bought a 24v 6amp PS from the same vendor when I ordered the fans for $4.95 which I would love to be able to regulate from say 12 to 24v.......I am guessing a reostat would do the trick but am unsure of what exactly to get and where to get it....... Guess I am STANK cheese here for a while lol __________________ System: BlackMax See website: webpages.charter.net/mlhg01/ Last edited by shaft01; 08-29-2002 at 12:28 PM.

08-29-2002, 12:30 PM	#18
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	Welcome to Pro/Forums! That's a really nice project. Where did you pickup your iPanel? Like I said above, you can use the Rheobus design (easily found with Google), just make sure you use an LM317 or LM317A. It will work with 24 VDC. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

08-29-2002, 11:55 PM	#21
WebMasta33 Cooling Savant Join Date: Dec 2001 Location: Nebraska Posts: 526	Ok, you have 4 wires on the molex from the PS yellow +12v -- ground -- ground -- red +5v from the molex you have on the fan you have red +12v -- ground -- blank -- blank if you take the ground wire and move it to hook into the red+5 volt, you'll have a 7volt fan. I'm currently running two 12volt Panflows at 5 volts, which is you just move the 12v line to the 5volt. __________________ ========== --Soyo KT333 DRAGON Ultra (Platinum Edition) --AMD 1.4 @ 1.54 (11x) --768mb of PC2100 (@140FSB) --Asus v8200 GeForce3 @ 210/490 --Maxtor 40gb Quiet + 2 IBM 40gb 60GXPs (removable) + 8gb WD --Audigy --Maze 3, DD Gf3 block, 2x BIX, Eheim1250 ===========

08-30-2002, 12:12 AM	#22
toddalaska Cooling Neophyte Join Date: Jun 2002 Location: ALASKA Posts: 66	ok dangit, i was hoping to over volt the fan for more rpms i take it this is done for quietness __________________ Epox 8k5a3+ 2400+ @ 2340 (213*11.5) 512 corsair 3200 213 fsb turbo settings geforce 4 ti4200 -13619 3dmarks 2 ibm 120gxp raid 0 400 watts WINXP PRO BIG BLACK ANTEC CASE Water cooled tc4 - custom res and shroud by webmedic

08-30-2002, 12:32 AM	#23
pHaestus Big Player Making Big Money Join Date: Aug 2001 Location: irc.lostgeek.com #procooling.com Posts: 4,782	Check the ATX spec; there are -5V and -12V lines on the PSU's ATX connector. Tap into those for the ground of your fan for 17 or 24V. Make sure the PSU has the A to handle this.

08-30-2002, 12:48 AM	#24
thebigNil Cooling Neophyte Join Date: Aug 2001 Location: here Posts: 26	You could force feed the fans 17-18v I forgot how much exactly but you just need to get your hands on a old AT power supply and so you wont have to worry about cooking your ATX. Get the AT and use a multimeter/voltmeter to poke around on the motherboard connectors and you should be able to find two wires that make 18v and just use that. I have found some psu's that dont like to have those connected so they spas out and tend to revert to a primitive state when you connected the two wires to any kind of load so that wont work for the given reason. Also some psu's need a load to work so all you have to do is hook up a old hdd or cd-rom drive. I bet that you could have figured out how to give them extra volts by reading bigben2k's posts ahh oh well.

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