Mounting a comp. fan under the hood

curtisk · 10/16/2006, 12:42 PM

How can I wire this computer fan under my hood to get air circulating under there? I don't want to buy an $50 power supply just for a single fan. Any suggestions?

AZDesertRat · 10/16/2006, 01:59 PM

Chances are you already have a power supply around the house. If you have an old unused cell phone or just about any other DC appliance you can use the DC power supply it used to charge the batteries. 12v will work best as it will give you full speed on the fan but even a 9v or 7.5v will work. If you don't mind spending less than $10, Harbor Freight Tools, Wal Mart and Radio Shack all sell variable voltage power supplies that will allow you to vary the fan speed by turning a little screw or potentiometer. I got mine at Harbor Freight for less than $4.
Just cut the plug off the fan and wire the red and black wires to the power supply after cutting the DC plug off of it. Works like a charm. If the fan has a yellow or white wire, ignore it you won't need it.

BrentN · 10/16/2006, 02:05 PM

I'm not an electrician, so there may be a way around this, but my two canopy-installed pc fans will only blow in one direction. swapping the wires did not reverse the direction of flow. Keep this in mind as you mount the fans as to which way you want the air to flow. hth

oh, I bought a power supply from Radio Shack with adjustable voltage so I can slow the fans down to adequately cool the tank, thus keeping the noise down. These normally run about $20. Got mine for $5 at a store going out of business.

BrentN · 10/16/2006, 02:07 PM

You could also use an old pc power supply. Bulky, but would work.

curtisk · 10/17/2006, 01:19 AM

Thanks AZDesertRat. You were right on about the power supply. And I did have one lying around from an ancient Mitsubishi cell phone. 12v. to be exact. Now I just need to mount it somewhere under the hood. Or on the side. I'll figure something out. Thanks again.

kamla · 10/17/2006, 07:45 AM

i have a power supply .. its 30 V, caon i use it on 2X 12 V fans..

Also.. How many 12 v Fans can i put on a 12 v supply..
If i put 4x12v fans on a 12 v supply, will they run @ full speed ??

Thax

AZDesertRat · 10/17/2006, 09:08 AM

Depending on how you wire them you could use the 30v power supply. You would have to daisy chain the fans and each would receive 15v. As far as how many you can put on a 12v supply depends on the milliamperage or watt rating of the power supply and fans. My supply puts out 500mV and the fans draw about 80mA so I could run 6 fans on one supply.

Rudy00 · 10/17/2006, 05:55 PM

I currently have 2 fans that are already in my fixture but they're very loud, would it be possible to replace them with a quiet set of computer fans? they're running off two wires now so i'd assume i'd have to use the red and black wires only like suggested on the computer fans but as for power to the fans, i'm unsure about

on the noisey fans they claim this: 110/120 v ac axial fan if thats any help

AZDesertRat · 10/17/2006, 06:59 PM

If you use computer fans you would have to run another pair of wires for the 12v DC to powert the fans, but DC fans are normally quieter than AC I have found.

Rudy00 · 10/17/2006, 07:02 PM

Ah i think i'll just suck it up, atleast at night it wont be running

10/16/2006, 12:42 PM	#1
curtisk Registered Member Join Date: Jun 2002 Location: Biloxi Miss. Posts: 305	Mounting a comp. fan under the hood How can I wire this computer fan under my hood to get air circulating under there? I don't want to buy an $50 power supply just for a single fan. Any suggestions? __________________ 100 gal. 75 lbs. live rock 4" DSB substrate 440 watts VHO 8-10 hrs./day 40 gal. sump hard/soft corals mixed External CPR overflow@1400 G.P.H Coral Life CSS 220 Mag 9.5 return Current Tank Info: 100 gal. reef

10/16/2006, 02:05 PM	#3
BrentN Registered Member Join Date: Oct 2004 Location: Kelso, WA Posts: 277	I'm not an electrician, so there may be a way around this, but my two canopy-installed pc fans will only blow in one direction. swapping the wires did not reverse the direction of flow. Keep this in mind as you mount the fans as to which way you want the air to flow. hth oh, I bought a power supply from Radio Shack with adjustable voltage so I can slow the fans down to adequately cool the tank, thus keeping the noise down. These normally run about $20. Got mine for $5 at a store going out of business. __________________ -Gravity Powered, Air Cooled- Current Tank Info: 55 aga, 20 gal sump, 4x54 t-5, O.R. 3500 return, liter meter 3, msx 160

10/16/2006, 02:07 PM	#4
BrentN Registered Member Join Date: Oct 2004 Location: Kelso, WA Posts: 277	You could also use an old pc power supply. Bulky, but would work. __________________ -Gravity Powered, Air Cooled- Current Tank Info: 55 aga, 20 gal sump, 4x54 t-5, O.R. 3500 return, liter meter 3, msx 160

10/17/2006, 01:19 AM	#5
curtisk Registered Member Join Date: Jun 2002 Location: Biloxi Miss. Posts: 305	Thanks AZDesertRat. You were right on about the power supply. And I did have one lying around from an ancient Mitsubishi cell phone. 12v. to be exact. Now I just need to mount it somewhere under the hood. Or on the side. I'll figure something out. Thanks again. __________________ 100 gal. 75 lbs. live rock 4" DSB substrate 440 watts VHO 8-10 hrs./day 40 gal. sump hard/soft corals mixed External CPR overflow@1400 G.P.H Coral Life CSS 220 Mag 9.5 return Current Tank Info: 100 gal. reef

10/17/2006, 07:45 AM	#6
kamla Registered Member Join Date: Nov 2005 Location: NJ Posts: 489	i have a power supply .. its 30 V, caon i use it on 2X 12 V fans.. Also.. How many 12 v Fans can i put on a 12 v supply.. If i put 4x12v fans on a 12 v supply, will they run @ full speed ?? Thax Last edited by kamla; 10/17/2006 at 08:15 AM.

10/16/2006, 01:59 PM	#2
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	Chances are you already have a power supply around the house. If you have an old unused cell phone or just about any other DC appliance you can use the DC power supply it used to charge the batteries. 12v will work best as it will give you full speed on the fan but even a 9v or 7.5v will work. If you don't mind spending less than $10, Harbor Freight Tools, Wal Mart and Radio Shack all sell variable voltage power supplies that will allow you to vary the fan speed by turning a little screw or potentiometer. I got mine at Harbor Freight for less than $4. Just cut the plug off the fan and wire the red and black wires to the power supply after cutting the DC plug off of it. Works like a charm. If the fan has a yellow or white wire, ignore it you won't need it.

10/17/2006, 09:08 AM	#7
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	Depending on how you wire them you could use the 30v power supply. You would have to daisy chain the fans and each would receive 15v. As far as how many you can put on a 12v supply depends on the milliamperage or watt rating of the power supply and fans. My supply puts out 500mV and the fans draw about 80mA so I could run 6 fans on one supply.

10/17/2006, 05:55 PM	#8
Rudy00 Registered Member Join Date: Sep 2006 Location: Ottawa ON Posts: 66	I currently have 2 fans that are already in my fixture but they're very loud, would it be possible to replace them with a quiet set of computer fans? they're running off two wires now so i'd assume i'd have to use the red and black wires only like suggested on the computer fans but as for power to the fans, i'm unsure about on the noisey fans they claim this: 110/120 v ac axial fan if thats any help

10/17/2006, 06:59 PM	#9
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	If you use computer fans you would have to run another pair of wires for the 12v DC to powert the fans, but DC fans are normally quieter than AC I have found.

10/17/2006, 07:02 PM	#10
Rudy00 Registered Member Join Date: Sep 2006 Location: Ottawa ON Posts: 66	Ah i think i'll just suck it up, atleast at night it wont be running