PWM headers have enough power to run splitters?

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thismafiaguy

thismafiaguy

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Jan 9, 2011
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RIght now I've got two 92mm fans running from a single PWM header on my motherboard via a PWM splitter. I'm pretty sure that PWM header has enough power to run both fans at max speed, but at what point will it not have enough juice? In another system that I worked on, I used the NZXT 10 port fan splitter, and it was powered via a 3pin connection. I had 5 fans attached to it, and I can tell that the fans were turning slower than normal. So what is the threshold of chaining fans off of a single header? How many is too many?
 
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geofelt


The zalman is nothing but a rheostat that reduces the voltage, reducing the fan speed.
A motherboard header will supply only a limited amp load.
The psu connector should provide all the amps you need.
I think your plan should work fine. It is cheap to try.
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anbello262

anbello262

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I wouldn't add as many as 5, because once the fans are starting to get slower it's already way too much...
If the fans are getting slower, it would mean that the supplied Voltage is getting lower. Those headers have a fixed Voltage that should NOT go lower under normal conditions. If it IS going lower, it means that the current is way too high, more than the mobo can handle. I would be afraid of damaging the mobo on the long run.
Those headers are designed for 1 fan, but for quality and security reasons they are usually oversized. This would mean that it can handle 2 fans with no problem.
Maybe 3 under some circumstances, if the mobo is really high quality.

But the moment when the fan starts to spin at the begining, they draw a lot more current (and power) for a fraction of a second, and if multiple fans start at once it could cause some seriously high current spikes.

I would reccommend 2 fans/header, with a maximum of 3 fans. More than that and the risk is too much for something quite irrelevant, I believe.
 
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geofelt

geofelt

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The value of a motherboard header is that it will give you speed sensing and possibly fan speed control.
Once you use a splitter, that gets messed up. Why not just attach fans via a psu molex connector. You can stack as many as you want with them. You can adjust the fans if you want via a simple speed control like a zalman fanmate.

Better, yet, abandon 92mm fans if you can. They are noisy and not as effective as 120mm or e larger.
 
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thismafiaguy

thismafiaguy

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The configuration with 5 fans running from one header is for speed control purposes. It is actually a Zalman Fan Mate 2 that is plugged into the header, and the other end plugged into the input port on the NZXT Grid fan splitter. There are 5 fans attached to the NZXT Grid fan splitter, and that's how everything is set up. Could I use a Molex to 3 pin adapter to power the Zalman? Will the Zalman handle 5 fans?
 
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geofelt

geofelt

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Oct 9, 2006
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The zalman is nothing but a rheostat that reduces the voltage, reducing the fan speed.
A motherboard header will supply only a limited amp load.
The psu connector should provide all the amps you need.
I think your plan should work fine. It is cheap to try.
 
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