Wiring fans in series for lower volts?

[the pc builder]

parallel vs series

parallel is when you have two 12v fans and a 12v power supply with all red (+) tied together and all the blacks (-) tied together. fan #1 is 12v 1A and fan #2 is 12v 1.2A in parallel they need a 12v 2.2A power supply.
series is when you take the Red wire from fan #1 is connected to red (+) of the power supply.
Black (-) wire from fan #1 is connected to red(+) wire from fan #2.
Black(-) wire from fan #2 is connected to black (-) wire from the power supply. you would need a 24v 1.2A power supply.

in series, you have to add the volts (V) 12v 1A + 12v 1.2A =24v 1.2A min (you have to cover the highest amp rating if you want all to run) (if you had a 24v 1A power supply the 12v 1.2A fan has a high chance of not working at all.
in parallel, you have to add the amps (A). 12v 1A + 12v 1.2A =12v 2.2A min
W = watts = volts x amps
you have to size the fans in accordance with the power supply. if you have 12v power supply and you have 2x12v fans than you have to wire them in parallel. if you have 2x6v fans and a 12v supply then in series is ok.

 

[EarthDog]

Good info.... baaaad necro!

13 year old thread!

 

[the pc builder]

Good info.... baaaad necro!

13 year old thread!

i know but i had to say it because it is my life to fix and make computers. all the info in this post is too garbled that i had to make sure that anyone saw this post was going away with the right info and not lose money when they blow a psu or a set of fans.

you can not just wire 2 12v fans in series and make the fans run on 6v because the chips in the fan can blow if you keep the 6v going.

i did this once (when i was a noob) and it caught on fire. i lost a $2,000 pc because i thought i knew what i was doing.

 

[NM64]

I just got the go-ahead from Austin Matthews himself that I can register and grave-dig this thread to respond to the above uber-grave digging (grave excavating?).

The main issue is that this shows up as the 10th result on Google if you search for:

• pc fans "in series" amperage draw

...or at least it did all of a few days ago, but now it isn't? Well, I'm here now, so I might as well address the issue anyway.

i know but i had to say it because it is my life to fix and make computers. all the info in this post is too garbled that i had to make sure that anyone saw this post was going away with the right info and not lose money when they blow a psu or a set of fans.

This thread is from 2003 - back then, PWM fans were not even a thing and basically only DC fans were around from what I can remember back in my early Athlon XP / Pentium 4 PC-building days.

You can usually tell the difference simply by the fact that PWM fans use a 4-pin motherboard fan header while DC fans use a 3-pin motherboard fan header or just straight-up a traditional power supply molex connector like was used for IDE drives (or, more recently, a power supply sata power connector).


PWM fans operate via, well, PWM. It only operates at its given voltage, 12v in this case, but it then pulses that 12v on and off to make the fan operate at different speeds. So if 12v is sent for only 1ms for every 10ms, that would have the fan running much slower than if 12v were sent for 9sm for every 10ms. This is the same idea used by LED backlights (something that also wasn't a thing in 2003 ) to control screen brightness on displays that are not flicker-free.

These PWM fans are the types of fans that you're warning about in that, if you were to connect two 12v PWM fan in series, you would need to connect them to a 24v power source in order to avoid issues. This is because running PWM fans at a lower voltage is effectively undervolting the electronics in them and, just like undervolting a GPU, GPU, or RAM, undervolting by a large amount tends to guarantee you that you'll have a bad time (and going from 12v to 6v is definitely a large undervolt!).

Considering that the benefit to undervolting electronic components is to reduce heat and/or power consumption, and the job of a fan is to specifically eliminate heat (which itself can reduce power consumption some since hotter electronics draw more amperage even at a constant voltage, not to mention that hotter electronics also require more voltage to maintain the same amount of stability, hence LN2 overclocking), then there really should be no reason that anyone should ever want to undervolt a PWM fan.


By contrast, the vast (entirety?) of the 1st page of this thread was talking about DC fans which, by definition, have their fan speed controlled by the amount of voltage that flows to them even when connected to a motherboard directly.

This means that manually inputting a lower voltage by any means, whether by connecting a 12v fan to a 5v rail, or by connecting two 12v fans in series so that they each receive 6v, would be no different than if you simply had your motherboard set to output that voltage for its according fan-speed control.

That being said, I'm not 100% if motherboards even had fan speed control for any kind of fans back in 2003 - my ECS K7S5A Pro socket A motherboard certainly didn't, and I don't believe my Gateway or HP OEM-branded Northwood-era Pentium 4 motherboards had fan speed control either. But most if not all of my Asus and Gigabyte AM2 motherboards did have DC fan speed control, and I even remember being able to use SpeedFan on one of them to control the fan speed manually (I could reduce the speed to the point where the fan turns off and then it exhibits the distinctive DC fan behavior of requiring more voltage to get it to turn back on compared to how much voltage it required to just keep the fan spinning at a low speed).