pc fans wiring question

[greg0385]

I bought 3-120mm pc fans. The specs on the back of the fan's box states- 6/7v started voltage and rated current. 38A each.
Now i thought these fans ran on 12volts and the only power supply that i can find close to power these fans up is a 14volt 1.2A transformer wall plug.

If i wire these fans using this then would this overdrive the fans and be dangerous? Or should i keep looking for a 12volt old phone charger somewhere? And should it be rated for 1.2A(.4Amps x 3)?

 

[revhtree]

Bump!

 

[greg0385]

Thanks rev for the bump, i blew the dust off my old electrical books and decided to find a 12volt 1.5A power supply as running 14v wouldnt be a good idea. Now to find a power supply local so i dont have to wait on shipping.

 

[cdness]

Radio Shack has them, but they are usually not cheap. They are good supplies though.

 

[greg0385]

thats where i got the fans at. Not bad $10 each, 120mm 78cfm and 21db.

 

[AZDesertRat]

I have found adjustable voltage DC power supplies at WalMart in the electronics section for less than $15 that will power all 3 fans at once.
The advantage with the adjustable or variable voltage is you can vary the fan speed according to your cooling needs and how much noise you can tolerate.

I have used a couple DC variable voltage power supplies from Harbor Freight Tools for years and for $5 they have been great but the last few times I visited or checked out their catalogs they don't carry them anymore. I also find them at Frys Electronics for less than $10 or online from places like Newegg and of course Radio Shack. For fans I have used many but found Vantec Stealths to be the ebst for me. The move 53 CFM each in the 120mm size so are not loud at only 28 dBa. When you set them on 7.5 or 9v you don't even know they are running.

 

[greg0385]

Perfect! My office is right behind walmart, i just hope they have it in stock.

 

[greg0385]

Also do you wire in series or parallel

 

[AZDesertRat]

They should have something similar to this:
PowerLine 90304 1300mA Variable Voltage Universal AC Adapter - Smarthome

I wire parallel, each time you add a fan in series you cut the speed in half so it really slows them down.

 

[greg0385]

Thanks AZ, was planing on two fans in the canopy blowing in on the both sides with three holes on top with the 3rd in the sump. I do have a open back on the canopy so i wonder if this would work. The other plan would be to do a fan on each end and one fan on top either blowing in or out.

 

[AZDesertRat]

I have a fan in each end of a fully enclosed canopy, both blowing in, with equal sized holes in the roof of the canopy towards the center so the air has to travel at least half the distance across, picking up heat as it travels. The canopy is approx 10 cubic feet of volume so the two fans provide a approx 10 full air changes per minute on high. When I had 2x250w MH and 2x140w VHO, these two fans on a timer with the lights, and a Wal Mart clip on over the sump on a Ranco controller enabled me to sell my 1/4HP chiller and still maintain 78-80 degrees year round with no issues.

6 months ago I switched to AI Sol Blue LED's and now rarely use the fans at all, even in July and August.

 

[greg0385]

Stop by walmart and found that power supply that you can choose the volts($20). Thanks for your help

it has a black wire and a white wire, which is the hot wire? White?

 

[AZDesertRat]

When I am wiring the DC fans, I cut the DC plug off the power supply end then use the red and black or white on the fans, the yellow wire on the fans gets cut off or taped back since it is a feedback wire for computer fan speed contol and does not get used.

I temporarily twist the fans wires to the power supply wires and plug it in first to make sure I have the correct rotation. Some fans will run in reverse, others will not, not sure why?
Once I know rotation is correct I use a small butt splice crimp lug, or solder the wires together then cover the splice with heat shrink tube.

 

[greg0385]

so there is no harm and wiring up wrong other than running backward

 

[AZDesertRat]

No, DC can run either direction with no harm.