Cases: How to Avoid Overheating
By Gabriel Torres on May 19, 2005
In the normal way of things, very little or no attention at all is paid to the choice of a case for housing a computer. However, nowadays processors are heating up ever more, so choosing the right case is critical for avoiding computer overheating.
Nowadays, overheating is not only due to the computer’s processor: the motherboard’s chipset and video card’s video processor are also responsible for heating the air inside the case.
If your computer is having overheating trouble, you surely will be able to solve the problem through this tutorial. The typical symptom an overheating computer is when it locks (freezes up) too much and issues errors of General Protection Failure (“This program has carried out an illegal operation and will shut down”) and the infamous “blue screen of death”. If you remove the case’s cover and, with the computer open, the computer stops being troublesome, the problem is overheating. Note that these symptoms also turn up in other maintenance situations, i. e., they do not necessarily mean that the computer is overheating.
Usually the case comes with its power supply installed. Few people are aware of it, but the power supply plays a basic role in cooling the computer’s innards. To understand this, you must understand how the air circulates in a case. You must have noticed that every power supply has a fan. This fan should always be operating in the exhaust direction, that is, blowing towards the outside, expelling hot air form inside to outside the case.
Look at Figure 1 to get a better picture. As hot air has a natural trend to move upwards, the hot air produced by the computer automatically flows to the upper part of the case. The power supply’s fan then draws out this hot air, thus providing proper computer ventilation. Cool air automatically comes in through the case’s front via a suitable slot placed under the space intended for the hard disk.
The power supply must have slots on its side in order to let hot air get out of the case and prevent computer overheating. The precise location of such slots will depend on the case size, since depending on the size of the case and power supply the power supply can be located in above, in front or besides the CPU – which is the main heat source inside the PC. With a bit of common sense, it is easy to see where these slots should be located. Looking closer at the computer shown in Figure 1 (see its close up in Figure 2) we can conclude that its power supply is correctly sized for its case. Note that the slots on the power supply are in the proper path for expelling hot air produced by the computer’s processor and other internal components, i. e., the position of the power supply does not hamper exhausting hot air from the processor and the slots are practically in front of the processor in order to allow hot air to flow correctly out of the computer.
The choice of a case is more than a mere matter of aesthetics, as it must be able to dissipate the hot air generated inside it. But how can we know that a case is suitable for a given computer?
Take a look at Figures 3 and 4. They show an actual computer having trouble from overheating. To the point, with the case closed, the computer jammed. When we removed the cover, the problem disappeared. Examining carefully the placing of the processor and the size of the power supply unit, the reason for overheating became clear: in the first place, there is hardly any space between the power supply and the processor’s fan, preventing the processor’s hot air from being suitably dispelled. In the second place, we can see that the segment of the supply above the processor has no slots for dissipating the air coming from the processor. Thirdly, the bottom of the power supply has no holes for dissipating the heat generated by other computer internal components (video card, motherboard chipset, hard disk, etc). Although the power supply’s side is slotted – in front of the case’s 5 ¼” bays – these are obviously insufficient to remove the hot air from inside the computer.
There are several solutions to this problem, but the most suitable and easy way is changing the computer’s case. Upon buying a new case, examine the size of the power supply, checking that the new unit does not covers the processor’s fan, as happens in the above case (even a medium size tower case can be used to avoid covering the processor’s fan by the power supply). Other possible solutions are just changing the power supply unit or even drilling holes in the metal panel of the part of the power supply facing the processor (in the latter case, the power supply should be demounted and the holes drilled with the panel off the supply, in order to avoid bits of metal falling into the supply when drilling, as this could later cause a short circuit when the computer is switched on).
Studying better this story, we found out that the case is an old model, revamped by upgrading a cartridge-type Pentium III processor. This case may have been very good for a cartridge type processor, but it is not good for newer CPUs. Although the motherboard fits perfectly in an old case, this does not mean that the case is suitable for the heat dissipation required by newer components. Therefore, be careful when upgrading to new computers reusing older cases.
Also it is a good habit to organize the cables inside the case using cable holders whenever possible. The computer in Figure 4 is a mess, the cables are preventing the correct airflow inside this computer, helping the overheating situation.
If you think the inside of your computer is heating up too much and all is apparently OK regarding the position of the processor and, mainly, of its fan, as we have seen in previous pages, there are some ways to improve the computer’s inner cooling.
The cheapest way is to open holes in the power supply on its lower side, that is, the side facing down when the computer is stood up. You can also make openings in the plating facing the case’s 5 1/4" bays. These openings should only be made if originally there are no holes for expelling hot air on your power supply.
To these holes you must first unplug the computer from the power outlet, remove the power supply from the case and open it, making the holes with the plating separated from the power circuits, to prevent metal falling into the circuits, thus causing a short circuit when the computer is switched on. These holes will let hot air out easier from inside the case, following its natural path, the power supply.
You can also install auxiliary fans inside the case. Such fans are easily found in computer shops (ask for 80 mm auxiliary fan), but you can also save money by using a fan removed from an old power supply (for instance, belonging to a scrapped computer). If you intend to cannibalise a fan, be careful. Older power supplies, used in desktop type cases (from the XT and 286 age) use 110/220 V fans that cannot be reused. You must use 12 V fans, utilized in the majority of power supplies applied in mini tower type cases.
The auxiliary fan can be installed in two places in the case. The most usual place is under the hard disk drives bays (see Figures 5 e 6), where the system intakes cool air. Be very careful when seating the fan in this place, as its position in the ventilation flow must be drawing cool air from outside to inside the computer. Every fan bears, on one of its sides, an arrow showing the airflow direction. This arrow should, therefore, point towards the inside of the computer.
The second position is not found in all cases: it lies in the space between the power supply and peripheral cards, on the back of the case. In this case, the fan should be installed in the exhaust direction, i. e., blowing hot air from inside to outside the computer. The fan’s arrow must therefore point out the computer.
You must get the direction of the fans’ air flow right, as if you get it wrong the computer may heat up more, definitely not the intended outcome. The rule is very simple: fans at the computer’s rear should be fitted in the exhaust direction (inside to outside), while fans in the computer’s front should be fitted in the cooling direction (outside to inside).
Newer fans sold at outlets have three wires and a plug for connecting to the motherboard via a connector called "Chassis Fan", "Aux Fan" or something like this. On the other hand, older fans have two wires and should be connected directly to the power supply via one of the plugs for 5 1/4" units. If you intend to use a cannibalised fan, note that its black wire should be connected to the supply’s black wire, but its red wire should be connected to the supply’s yellow wire, its 12 V output, and not to its red wire, as could be assumed (the red wire is its 5 V lead). The extra wire on newer fans is intended to measure the rotating speed and, according, inform the motherboard whether the fan is working properly or not.
If you while reading our tutorial wanted to install an auxiliary fan in your case but didn't find any place for its installation, that shouldn’t be a problem. If the heating inside your case is really high, you can simply adapt any place for the installation of an auxiliary fan.
But where exactly can we install an auxiliary fan? That will greatly depend on which area inside the case is overheating. From our experience, we have seen that the upper part of the case tends to heat more for several reasons. First, and obviously, it is because hot air goes up. Second, it is in that area that we have, in ATX cases, the processor and its fan. And third, in that area we also have the 5 1/4" bays and those who have CD recorder or DVD unit will discover great heating of that area, since recorders produce a lot of heat while working.
Some cases have ventilation holes on their sides. Those holes are a perfect place for the installation of an auxiliary fan, especially at the upper part, where the PC heats more. As there aren’t enough holes, nor holes for the fixation of the fan, you should make them with a drill (obviously after removing the metal cover of case from your PC). In such case, the fan should be installed following the direction of the exhaustion. You should be careful to install the fan in a place where there is enough space for it, because it will “hang” inside the case and should not “hit” any internal component. That is, it should stay between the power supply and the 5 1/4" bays.
Another place that can be used for the installation of an auxiliary fan is the top 5 1/4" bay. Since mini-tower cases have 3 bays, and we usually only use one, we may easily make an adaptation and install a fan in that place, exhausting the hot air from the computer. That adaptation involves cutting and drilling hole on the plastic covers of the 5 1/4" bays. Indeed, some manufacturers are already selling fans ready to be fit into those bays.
Figure 9: Exhaustion system for the 5 1/4" bay.
In other words, you can install an auxiliary fan where you think the computer is heating too much, making the necessary adaptations in your case. Just one more thing to what we have been talking about the direction of the air: the auxiliary fans installed in the upper part of the case should be installed following the direction of the exhaustion (air flowing from inside the computer to outside), while auxiliary fans installed in the lower part of the case should follow the direction of the ventilation (air flowing from outside to inside). That will make the air flow inside the case follow its proper path.
Another detail that we have not mentioned is that there are smaller fans and some cases have space for the installation of that fan type, as it can be seen in Figure 10, where the case has space for the installation of a 50-mm auxiliary fan (the standard size of the auxiliary fans we have been talking about until now is 80 mm). Many times those places go unnoticed, due to their reduced size. As the space is located at the back of the case, the fan should be installed following the exhaustion direction, forcing the hot air inside the case to leave it.