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A Guide to Case Fans

written by: M.S. Smith•edited by: J. F. Amprimoz•updated: 12/24/2009

The case fan is an unsung hero. Though responsible for keeping your PC cool, most people don't spend any time thinking about what kind of fan is in their PC. Not every fan is the same, however - differences between fan size and quality will affect noise and temperature.

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    Not A Fan?

    Case fans. They're the computing equivalent of napkins. Sure, a case fan is almost always necessary, but it is rarely considered exciting. It is just there, ready to fulfill its duty quietly. Most have little or no branding. Jump around computer review websites, and you'll see exactly what I mean - finding an extensive review about any particular case fan is very nearly impossible, and should you manage to find one, good luck on a second opinion.

    But there are some important facts that you should know about case fans. Some fans are quieter than others, some fans push more air than others, and there are certain features you should consider before making a purchase.

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    Fan Size - What's The Difference?

    Case Fan Sizes From 40 to 120mm The most common fan sizes are 80mm, 92mm, and 120mm. It is difficult to tell what the difference is between these fans simply by relying on consumer reviews and marketing blurbs, making it easy to come to the conclusion that the size of mount included simply has to do with the space available in the case.

    But the size of fan you buy is important, and has a major effect on your computer. As you might expect, bigger fans are capable of pushing more air. The amount of air that a fan circulates is measured in cubic feet per minute (CFM), and larger fans nearly always move more air that smaller fans when rotating at the same RPM. The noise a fan generates - typically measured in decibels, or dB for short, it also reliant on fan size. Here, however, the opposite of intuition is is true. Small fans are not quieter. Because larger fans push more CFM than small fans, they don't have to spin as quickly to create useful airflow. This results in less noise.

    As a result, there are two ways of looking at fan size when deciding which ones to buy. You can look at fans from a cooling perspective, in which case you'll simply want to buy the largest fans possible and run them at the fastest possible speed. But you can also look at them from the noise perspective, in which case you'll want to buy the largest fans possible and run them at a very low speed. Either way, large fans win. That said, you shouldn't write off a PC case simply because it won't let you mount 120mm fans. When operated at low speeds, the majority of 80mm and 92mm fans are nearly silent. It is only when running at full tilt that the noise from these smaller fans can become a problem.

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    Get Your Bearings

    The kind of bearing used by a case fan can have an impact on its characteristics, such as maximum speed and vibration noise. The kind of bearing used by a fan can also give you an indication of the fan's life expectancy. There are currently four common types of bearings available.

    Ball Bearing: Ball bearing fans consist of metal balls which rotate against an axle. Lubricants aren't needed, making fans using a ball bearing very reliable over long periods of time. The fan's operation is not effected by heat, and most fans of this type remain relatively quiet in all conditions.

    Sleeve Bearing: Sleeve bearings used lubricated surfaces that rotate around each other. As such, they're limited to the life-span of the lubricant, and as the lubricant drys up and decomposes, the fan will become noisier. Their only advantage is a low cost of production. Sleeve bearings are the most common bearing found in case fans.

    Fluid Bearing: A fluid bearing uses a thin layer of liquid between the surfaces inside the bearing. Fans with this kind of bearing can be expected to have a long lifespan, because fluid bearings eliminate contact between rotating surface. This also means that fluid bearings are quiet. This kind of bearing isn't common,and is generally found in higher-end products.

    Magnetic Bearing: This bearing works by using magnets to keep two surfaces out of contact which each other, allowing rotation. They are very quiet and have a very long life-span. Magnetic bearings are rare, but not necessarily limited to high-end products.

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    Case fans are not glorified upgrades. Some PC enthusiasts believe a case fan is simply a fan. In some ways, they're correct - but there are important features that PC users should not do without. The ability to change case fan speed, for example, is an important feature. Budget models rarely allow the user to change fan speed, but more expensive PWM or Pulse Width Modulated PC case fans can allow the user to change fan speed from their operating system.PC Fans, Case Fan Guide, Computer Fans, PWM
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    Features To Look For

    Fans are fairly simple. Therefore, they don't come with many options. But there are some options worth looking for.

    The most important feature is the ability to select the fan's speed. This is often a standard feature, but some budget models don't offer it. It can be tempting to buy those models, since they typically cost only a few bucks, but I would advise against it. The ability to adjust the speed of fan, which usually manifests itself in a switch attached to the fan itself, gives you the ability to calibrate the fan to your personal tastes. If you prefer performance, you can turn it up, but if you prefer silence, you can turn it down.

    Taking flexibility a step further, some fans come with connectors that can be fitted into the "fan" slots on your motherboard. These connectors have three or four pins. Three pin connectors will report fan speed to the motherboard, and four-pin connectors allow the fan speed to be controlled from the mobo if the fan supports Pulse Width Modulation. Fans with four-pin connectors are generally the most expensive products, such as Arctic Cooling's PWM models. However, this grants the ability to adjust fan speeds without opening the case, either by using software provided by your motherboard manufacturer or by using a third-party program like SpeedFan . This can result in the best of both worlds - your fans will remain quite at idle, and they'll provide maximum performance under load. Plus, the price difference isn't really an issue: PWM fans are 3-4 times more than a cheap, non-adjustable fan, but that adds up to about six bucks, and the functionality is well worth it. The problem is finding them, as Newegg only stocks four models, including this unit from Scythe. For a wider selection, consider a PC cooling specialist like FrozenCPU.com.

    LED lighting isn't useful for reducing noise or increasing cooling, but it is a feature that should be remembered. Some users will prefer the eye-catching quality that a LED fan can bring to nearly any case. On the other hand, fans with LED lighting can be extremely distracting in dark rooms, and are a very poor choice for PCs meant for home theatre use.

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    The Wisdom Of Your Peers

    Pay attention to user reviews when buying fans. Since there are few fan reviews by high-quality review websites, consumer reviews will often be your best source of information. Examine what users are saying about their fans carefully. Users who say that their fan has "really good performance but is kinda loud" likely means it keeps their computer quite cool but sounds like a wild boar being sucked into a jet engine. Watch for reliability concerns, as well, because while fans are cheap, there is no reason why they should not last an extremely long time.

    Most importantly, remember that although fans are simple, and they won't directly increase the performance of your computer, it is still important to look for a product which is quality. It is entirely possible to buy large 120mm fans for only a few bucks, particularly when searching through case fans being sold on Ebay. However, having purchased those types of fans in the past, I can't recommend them. They are loud, often rattle due to cheap construction, and some even came with a sort of grease leaking from them. Cheap fans from reputable retailers can also result in poor quality products, such as this fan which appears to almost never function correctly. Paying the extra money to purchase from companies like Antec, Silverstone, or Scythe will result in a much better experience. When comparing these reputable brands, you can give some credence to the CFM and dBs ratings they report.

    Once you have chosen a fan, check out our article on installing a case fan for help with installing it properly.