Multiple fans connected to a single header may exceed the capabilities of your motherboard (or potentially a fan hub). This is due to a higher current draw than the maximum rating. We’ll analyze when and under what circumstances you should be cautious in this article. The threat of permanent device damage is quite real, but it’s fairly simple to safely prevent it. So, let’s take a look at it.
With a higher number of fans, not only does airflow (and thus cooling performance) increase, but so does power consumption. Its value is also decisive for fan headers. These have a recommended limit of one ampere, which a single fan usually doesn’t exceed. However, if you connect multiple fans to one header, you’re already above one ampere. This is the typical situation when one fan is daisy-chained to another (whether on liquid cooler radiators or at the front of PC cases) and ultimately a single cable leads to one header. But with three fans, there are three motors. And with faster fans, the draw can exceed 1 A.
The situation is well illustrated by the graph below (from our standard fan tests). It shows power in watts, but based on that, the current draw can be easily derived. You take this power value and divide it by 12 (volts, which is the operating voltage for fans). A draw of one ampere for a trio will be reached by fans with a result of 0.333 A and above. This certainly applies to the Phanteks PH-F120T30, Arctic S12038-4K, CPS PCCooler F9 R120, and Sudokoo Mach120. Yes, this is only at maximum speed, and when slowed to lower speeds it might not apply, but the risk is still not insignificant.
One thing is operating power draw (graph above) and another is motor power (below). You know the difference. However, it must also be emphasized that although operating power draw may stay under 1 A, it can be higher during the spin-up phase. Briefly, but still. Until the start-up time is overcome and speeds stabilize, many fans will momentarily be above the 1 A value for which standard motherboard fan headers are designed. You can identify which fans these might be using the same method described above—from a value of 4 watts and above, or from 12 watts and above if considering just one fan. And indeed, even a single, lone fan can exceed the current limit of a 1 A connector. The Phanteks T30 does so quite significantly, but this also applies, for example, to the Scythe Grand Tornado 120, CPS PCCooler F9 R120, or CPS PCCooler F7 X120.
It’s better to connect the fans listed above, at maximum power, to 3 A connectors. These are quite rare, but they do appear on some motherboards. Usually on those designed for extreme processor overclocking with liquid nitrogen (LN2). Those often have 3 A fan connectors. Precisely because they are meant to connect high-speed fans with higher consumption. Not high (fans never have high consumption), but higher. High enough to cause irreparable damage to the motherboard at this level. Fan hubs have multiple channels partly for this reason. The great thing about them is that, despite distributing fans across more connectors, they share the same PWM signal, allowing for central speed control.
So, be cautious. There are quite a few fans that, in larger numbers, can jeopardize the health of the “standard” headers used on motherboards.
And what about 140 mm fans? You’ll find out from their tests. Some nervousness is also justified with models like the NF-A14x25 G2 PWM on coolers such as the Noctua NH-D15 G2, where these fans are paired on a single header via a Y-splitter.
English translation and edit by Jozef Dudáš
Glaaad to see article-test like that. I was supriesd at some of fans power draw. One thing I’d really like to see is the ability to switch to or an additional graph in amps. After all, from the beginning, article is talking about the maximum fan header load in amps as the power consumption in watts forces me to switch my thinking to “above 12V is above 1A” or divide in my head each result to understand, for example, “how many such fans could I connect to a single header”. Either way, much needed and helpful article with the results.
Thanks for the comment. Yes, graphs showing amperage would definitely be easier to interpret. However, in our fan tests we measure power in watts, and these graphs are taken directly from those measurements. Converting everything to amps would be less efficient and more time-consuming (time we can use for other, more useful work), and the relative order of the results wouldn’t change anyway. As stated in the article, each numerical value in the charts represents the current draw in amps after dividing by twelve (volts). The power consumption shown in the graphs is, of course, calculated as voltage (U) × current (I). 🙂
Thanks for explaining, now i understand your decision clearly.