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PC airflow guide: How to set up your case fans

May 31, 2023May 31, 2023

You'll need to set up proper airflow inside your PC case for optimal cooling. This guide will help you with that.

Your PC will run hot during intense gaming sessions, so you’ll need to optimize the airflow to avoid overheating your components. While installing new fans is one way to improve the overall temperature of your gaming rig, managing the number of intake and exhaust fans is just as important. The same is true for the overall fan layout and the type of air pressure inside your PC case. There are a ton of factors that can affect the airflow, and we'll walk you through everything you need to know to get a better cooling performance out of your PC.

When picking fans for your cabinet, you should always consider their RPM, CFM, noise levels, and size. The RPM, or rotations per minute, is a measure of the speed at which the fan blades spin. Most case fans run at 500-2000 RPM, and increasing the RPM can enhance their cooling capacity at the expense of increasing noise levels and reducing their longevity.

Noise level, as the name suggests, is the amount of noise generated by the fans in decibels (dB). Silent case fans produce barely audible noise in the 15 dB range, while performance fans can hit as high as 30-40 dB. In most fans, increasing the RPM has a considerable impact on its noise level: the faster it spins, the more noise it creates, though there are some premium fans out there that are relatively quiet even under heavy RPM.

The CFM (Cubic Feet per Minute) of your fan refers to the volume of air it can push through your cabinet. Depending on their CFM, case fans are divided into static pressure and airflow fans. Static pressure fans are built to push a large volume of air through obstructions and narrow gaps, making them the perfect choice for radiators and cases with a lack of air inlets in their front panels. In contrast, airflow fans are better at pushing air when there aren’t any obstructions in their path. If you have a mesh front panel and decent cable management that doesn't disrupt the airflow, you should go with airflow fans.

Finally, case fans come in many sizes, with 120mm and 140mm being the most common. Assuming they have the same RPM, you should always use 140mm (and larger) fans as intakes instead of smaller 120mm. The reason being two 140mm fans can push the same amount of air as three 120mm fans, albeit at much lower RPM and noise levels.

Simply put, an intake fan blows cool air into the cabinet while an exhaust fan pushes warm air out of it. All fans have intake and exhaust sides, and their orientation determines how they direct the airflow inside your case. You'll need a combination of both intake and exhaust fans to maintain the proper air pressure (more on that later) inside your PC.

Cabinet fans have one or two arrows on the side that you can use to find out their intake and exhaust sides. The first arrow points in the direction of the airflow and the second one shows the direction of rotation of the fan blades.

If your case fans don’t have these arrows, you can use the structure of the fan to determine its orientation. The exhaust side has an X-shaped spoke that holds the fans in place. This side is easy to identify as you’ll immediately notice the fan cables coming out of it.

Meanwhile, the intake side of the fan will have the fans in a convex orientation, i.e., the fans will be curving away from you and there won't be any X-shaped bars on this side.

The front panel of your cabinet has a noticeable impact on the air pressure. Cases with mesh front panels almost always have lower temperatures because the perforated mesh surface provides better airflow than glass or solid front panels. Unfortunately, this also means that mesh front panels attract more dust, but you should be fine as long as your cabinet has decent dust filters. You can even forgo all the side panels and go for an open-air case as long as you don't mind cleaning it regularly.

Speaking of, thicker dust filters can not only block dirt and grime but also create obstructions for the air blowing in from your intake fans. Of course, this doesn’t mean you should discard all dust filters, but it’s worth testing your PC without them if the system temperatures start to hit the dangerous zones even after setting up all the fans properly.

Moreover, the number of fans that you can slot into your gaming rig depends on the size of the cabinet, with some full tower cases supporting as many as ten fans. Large cabinets also include mounting areas for AIO cooler and custom liquid cooling blocks, which makes them more useful than small cases when it comes to supporting more cooling solutions. But that doesn't mean you should write off small cases altogether. Many premium mini towers and small form-factor cases are designed for airflow to ensure your system operates at better temperatures.

The next step is to decide the type of air pressure you want inside the case. Each has its pros and cons, and it's wise to test out the different air pressure configurations to find out the best one for your PC.

In a positive air pressure setup, the amount of cool air flowing in through the intake fans is greater than the hot air expelled by the exhaust fans. This type of air pressure provides decent cooling and is highly effective at lowering the amount of dust buildup inside your PC as most cases are equipped with dust filters around the intake fans. However, you should avoid excess positive air pressure because it can result in a lot of turbulence and prevent the cooler air from reaching the thermally-challenged parts of your PC.

Negative air pressure, as the name suggests, is the exact opposite. Here, the exhaust fans pull more air than the intake fans to remove heat at a much faster rate. Assuming you keep your PC in a well-ventilated room, this can (theoretically) lead to better temperatures than positive airflow.

Unfortunately, negative air pressure causes significant dust buildup because air can flow from all the holes and gaps in your chassis, including the openings that aren't covered with dust filters.

Finally, your PC cabinet will have a neutral air pressure if the amount of air entering it via the intake fans is equal to the hot air blowing out of the exhaust fans. If you want a balanced cooling setup that balances adequate cooling and lower dust buildup, a neutral air pressure configuration is your best bet. Sadly, it's difficult to maintain perfectly neutral air pressure, so most users should aim for slightly positive air pressure.

For optimal air pressure, you should aim for more intake fans and fewer exhausts. The air blasted into the cabinet from the intakes should have a clear path to the exhaust, otherwise, you'll have a lower cooling efficiency due to air turbulence.

The front panel of the case should exclusively have intake fans that blow air towards the RAM, CPU and GPU, while the fan slot adjacent to the I/O ports at the back of the case should only have exhausts. For most mid-sized towers, you should aim for two 140mm fans around the intake, though you can go for three 120mm fans if you don't mind higher noise levels. The exhaust can be a 120mm fan, as most cases don't support larger-sized fans around the exhaust. Here are some great fan layouts for a typical mid-tower cabinet:

5-fan setup: For an ideal 5-fan configuration, you'd want to place three fans at the front panel to blast a lot of cool air into the case. Next, you'd want to attach an exhaust at the back of the case and another one in the top left corner (right above the CPU) to remove the hot air from your system. Out of all the non-liquid cooler setups, this is the one you should pick as it provides adequate cooling to every component of your PC.

4-fan setup: If you lack enough case fans for a 5-fan setup, you can go for a neutral airflow setup with two intake fans at the front panel, one exhaust fan at the rear end, and another exhaust at the top. Alternatively, you can remove the exhaust fan from the top of the case, and install it at the front panel as an intake. If you go with this layout, you'll need to reduce the RPM of the intakes or you'll end up with excess positive air pressure.

3-fan setup: I'd advise against going lower than four fans if you're using a mid-tower case, but you can go with two intakes at the front panel, with an exhaust at the back if you want. Your system won't win any awards for proper cooling, but you won't see abnormally high temperatures with this setup.

Now, you might have realized that even with the 5-fan configuration, we've left a fan slot empty at the top of the case. While you can install an exhaust here, I recommend leaving it empty because it can cause unnecessary air turbulence inside the case, and the extra space is better suited for adding a radiator instead of a fan.

If you have an AIO liquid cooler, you can either mount the radiator along the front panel, with the fans acting as intakes or install the radiator at the top and have the fans run as exhausts. If you have some extra space inside your case, you can place multiple fans on either side of the radiator to maximize the amount of air flowing from the front panel. Otherwise, mounting the radiator at the top of the cabinet is also a valid option.

Make sure the tubing side lies at the bottom if you install the radiator at the front panel. In most cabinets, mounting the radiator with the tubing side at the top causes the pump to be placed higher than the tubes, which results in the air from the radiator getting sucked into the pump. This can damage the liquid cooler in the long run. If it's not possible to have the tubes at the bottom, you should install the radiator at the top of case or, at the very least, make sure the pump lies below the top of the radiator.

A simple way to check the air pressure is to bring a thin piece of paper or tissue near small openings, like the PCIe slots, of your cabinet. If the tissue is attracted toward the case, you have negative air pressure. If it gets blown away, there's a lot of positive air pressure inside the case.

You can also use an incense stick or a smoke machine to determine the air pressure, but I suggest sticking tissues because the other two can damage the internals. As mentioned earlier, it's best to maintain slightly positive air pressure, and the simplest way to achieve this is by running your exhaust fans at full speed and carefully lowering the RPM of the intake fans so that the paper gets slightly pushed away from the case.

It's a bit tedious to configure the cabinet fans, but the better system temperatures you get at the end are worth all the hassle. There are other miscellaneous factors that can influence the airflow in your PC, including the amount of dust stuck to the fans and the cable management (or the lack thereof) inside your PC tower. So, you should experiment with different fan layouts and air pressure configurations to find what works best for your system.

Ayush Pande is a hardware, gaming, and crypto writer based in India. When he's not writing articles, you can find him tinkering with PCs or benchmarking new components.

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