Does a forking or splitting "Y cable" underpower the fans?

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oblongpolygon

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Imagine you have two Noctua PWM NF-A9x14 fans in your case, but both are being driven by the one fan header on the mobo, because a forked or splitting "Y-cable" has been used.

(That is, the Y-cable splits or forks one connection into two, allowing two fans to be connected.)

Would this arrangement mean that the fans are underpowered?

Or, if not exactly "underpowered", are there any other disadvantages to using a forked Y-cable?

Again, talking about two PWM fans, here.

(I guess I only ask because I'm unsure if I actually have two fan headers on this ROG Z370-i mobo, but I'd like to know the above "out of interest" anyway.)
 
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Negative, the voltage will remain constant, just the amperage draw will increase on the header that they are attached to
 
oblongpolygon said:
(That is, the Y-cable splits or forks one connection into two, allowing two fans to be connected.)

Would this arrangement mean that the fans are underpowered?
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No, that's not how it works. Think about that for a moment. If that is how it worked, then your computer and monitor would be "underpowered" every time you used a surge protector, as a surge protector is basically a fancy Y-cable with more ends.
 
GotNoRice said:
No, that's not how it works. Think about that for a moment. If that is how it worked, then your computer and monitor would be "underpowered" every time you used a surge protector, as a surge protector is basically a fancy Y-cable with more ends.
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I turn on my space heater and my PC turns off, is that because it is under powered?
 
Zepher said:
I turn on my space heater and my PC turns off, is that because it is under powered?
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A 15 amp breaker is only 1800 watts. It's not uncommon for a floor heater to use ~1500 watts all on it's own. Not sure how much power your PC uses but ~300w wouldn't even leave enough for mine to run at idle.

Zepher said:
If you pull too many amps, won't the voltage drop?
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Most fan headers have max amp draw limitations. If you are configuring your fans such that the total amp draw exceeds what the motherboard is capable of, that is mostly user error and will likely damage the motherboard. Within the current-draw limitations of the fan header, it won't matter if you have 1 fan or 10 fans connected to it.
 
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this is the rear case fan,
IMG_0864.JPG
 
I think the general rule is 1A per fan header, but your motherboard manual sometimes tells you the max rating.

That Nidec fan is crazy, I watched a youtube video of it and it was pulling 3amps and sounded like a jet engine.
 
that nidec fan out of what case? that's 3.3a and is probably on a specialty fan header. a dell or hp or other oem system? oh and nice thread jack...

OP your board will do up to 1a for sure, maybe more, look in the manual. so you can have as many fans as you want as long as they total around 1a or the max supported by the board.
 
Zepher said:
If you pull too many amps, won't the voltage drop?
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No, the power supply has voltage regulators to help prevent that from happening. I mean, it will drop a little, but it should stay within tolerance as long as you don't exceed the current capacity of the power supply.
 
pendragon1 said:
that nidec fan out of what case? that's 3.3a and is probably on a specialty fan header. a dell or hp or other oem system? oh and nice thread jack...

OP your board will do up to 1a for sure, maybe more, look in the manual. so you can have as many fans as you want as long as they total around 1a or the max supported by the board.
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lol
It was in this Intel chassis plugged into my Intel S2600COE motherboard.
IMG_0748.JPG
 
I think it does the two fans on the 240mm are on a Y "splitter" and the bios says their running a little slower can't really confirm that...I don't think it makes much a difference though. like I said I do think the Z97 block is a hair warmer, but it's pretty normal with heat on and or higher ambients overclocked, wants to idle 35-40c sometimes maybe mx-4 isn't helping too much....pretty normal. That's Further out of how good water is suppose to be though. Admittingly there is Airr Solution's that could perform about the same some of the bigger units.
 
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Zepher said:
lol
It was in this Intel chassis plugged into my Intel S2600COE motherboard.
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So a specialty fan in a specialty system? Did you have an actual point that you were trying to make or do you just get off on throwing threads as off-topic as possible?

Jayy88 said:
I think it does
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The fans that the OP mentioned (Noctua NF-A9x14) have only 0.11A current draw. That means that on most motherboards you could have up to 9 of those fans on a single fan header without seeing any significant voltage drop.
 
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GotNoRice said:
So a specialty fan in a specialty system? Did you have an actual point that you were trying to make or do you just get off on throwing threads as off-topic as possible?



The fans that the OP mentioned (Noctua NF-A9x14) have only 0.11A current draw. That means that on most motherboards you could have up to 9 of those fans on a single fan header without seeing any significant voltage drop.
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yeah so really the splitter shouldn't be affecting anything...unless there's something wrong with it obviously.
 
It's basic electricity.

Running in Parallel vs. Sequential.
Splitters noramlly make things run in parallel.

Some special wiring will make things run in sequential.
Sequential will split voltage between two or more objects.
Sometimes useful when you want to run two fans on 6V, but you would typically need to rewire things yourself.
 
MrDeaf said:
It's basic electricity.

Running in Parallel vs. Sequential.
Splitters noramlly make things run in parallel.

Some special wiring will make things run in sequential.
Sequential will split voltage between two or more objects.
Sometimes useful when you want to run two fans on 6V, but you would typically need to rewire things yourself.
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Would need to run the ground of one fan into the +12v of the other fan. Would require chopping off both fan's connectors, splicing aforementioned wires together, then take the remaining wires (minus one of the sense wires) and put them in the correct positions on a new connector. The end result would be a mess of wires and both fans running near +6v, if they worked at that voltage at all. Better off with a good fan controller if that's what you want.
 
Don't forget some "splitters" have resistors in them for low noise. There are some dual low noise splitters, too.

And, are the fans 3 pin or 4 pin? The fourth pin is how the m/b reads the speed, if they are three pin, it won't see a speed.
 
pek said:
Don't forget some "splitters" have resistors in them for low noise. There are some dual low noise splitters, too.

And, are the fans 3 pin or 4 pin? The fourth pin is how the m/b reads the speed, if they are three pin, it won't see a speed.
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read the op...
 
Didn't say whether the splitter was pwm or not, tho. Or if he knew the antecedents of the splitter, 'low noise' or not.
 
assume 4 pin as he states "this is for pwm". no need to add the low noise stuff as it wasn't asked about.
 
I know this is a long shot, but can diverging all of your mb fans into a Molex with a speed controller help in overclocking of the cpu since the mother board can give a few more watts to the cpu?
 
auntjemima said:
No.
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Right, and to add a slightly larger amount of text - if this is an actual constraint, your PSU is flaming garbage. It should have no trouble supplying everything your CPU needs, many times over.

There are many areas to save a dollar, but as someone who designs boards and chips for a living for a long time - please, PLEASE, never save a buck on your PSU. The amount of random bullcrap you can eliminate from a quality supply cannot be overstated. I'm not saying get the top of the line (although honestly, given how long they last, it's not a bad idea) - but get a known name brand and rating which hits a bit above your needs. All are pretty good. The no-name stuff is a horrific no-man's-land of quality.

It's not sexy, and doesn't translate into some benchmark number, but you can bet your bippy it DOES translate into the ability to eliminate one major cause of issues. And you can keep using it for 10+ years, so amortize the cost! To that end, spend up on this component which does not go obsolete, because physics. ;)
 
My psu is an corsair gold stx, so it is good quality. I just wasn't sure if there was a limit the b350 motherboard could provide. I have seen as much as 250w from the wall and I only have an apu, no gpu so that was almost all apu usage through the motherboard.
 
Nightfire said:
My psu is an corsair gold stx, so it is good quality. I just wasn't sure if there was a limit the b350 motherboard could provide. I have seen as much as 250w from the wall and I only have an apu, no gpu so that was almost all apu usage through the motherboard.
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The header is limited by amps. Don't go above 2 sustained.

I asked ASUS once and an engineer said ~2.
 
pek said:
Don't forget some "splitters" have resistors in them for low noise. There are some dual low noise splitters, too.

And, are the fans 3 pin or 4 pin? The fourth pin is how the m/b reads the speed, if they are three pin, it won't see a speed.
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Wrong, the 3rd pin is RPM reading, the 4th pin is PWM control. RPM reading has been around forever, so most common fans were with 3 pins. 4 pin (PWM control) is relatively recent and added a fourth pin to the pre-existing 3 pin connector for PWM. The original 3 pin fans were speed controlled by voltage.

Nightfire said:
My psu is an corsair gold stx, so it is good quality. I just wasn't sure if there was a limit the b350 motherboard could provide. I have seen as much as 250w from the wall and I only have an apu, no gpu so that was almost all apu usage through the motherboard.
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Most motherboards are wired up such that the 4 or 8 pin connector only supplies power to the CPU. The fans and everything else draw their power from the 24 pin.
 
I run 8 140mm noctuas on a cheap pwm hub from a "1.5A water pump opt" header on one of my boards. No problems, they all run pretty close to sync and move a ton of air quietly at low rpms.
 
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