PC Power and Cooling Myths

Probably you’ve heard people saying that the more fans there are in your PC, the cooler the components are going to be and hence, the longer their life span. Then, you came across technicians who claims that power supply units with large wattage rating will draw more power then lesser versions. Are these true??? Bits of Bytes will now debunk the two most common PC power and cooling myths!

1. The more fans there are, the cooler the PC

MAYBE.If you have lots of fans sucking air out from your chassis, you might inevitably be creating negative pressure inside your chassis. In a near vacuum state, don’t expect heatsinks to be able to dissipate heat effectively since there are less air molecules to conduct heat away.

What about all fans sucking in? You will be creating positive pressure. In this case, heat will be conducted faster due to higher air pressure. However, without proper exhaust, the heat will remain trapped inside your chassis.

Contrary to popular claims, you should keep your case closed tight at all times (unless your chassis was poorly designed and has thermal problems). An ATX casing was designed such that a power supply exhaust fan complements the front intake fan to ensure proper air circulation. With the side panel of your casing removed, proper airflow cannot be ensured and you’re motherboard chipsets will be screaming for help. Note: The metal chassis acts as a Faraday Cage that shields your PC components from electromagnetic interference and electrostatic discharge. You should not run a PC without a chassis.

Conclusion: Few strategically placed fans are better than many unplanned fans.

Case study:

Ideally, positive pressure should be created inside the chassis so that hot air will be forced out through vents of the heatsinks at the back of the motherboard and video card. A large back exhaust fan is not recommended as it might interfere with the cooling of the video card and motherboard. A power supply unit with a single large intake fan is the best way to remove excess heat produced by the processor. Two large intake fans spinning at low revolutions per minute, placed strategically in front of the chassis (to cool the hard disk) and side (to cool the video card and in case of CPU fan failure, helps to dissipate some amount of heat from its heatsink) will help cool down the system significantly without torturing your ears.

2. The larger the power rating of my PSU, the higher my electric bills will shoot up

FALSE. The power rating of a power supply unit normally represents the peak amount of power (potential difference x current, V*A) it can supply before blowing the fuse. The total of amount of current your PC will draw is calculated by summing up the power consumption of individual components, ie:

Central Processing Unit : 65W Peak
Graphics Accelerator: 70W Peak
Two Hard Disk: 24W x 2 = 48W Peak
Motherboard + Components: 50W Peak
Fans: 6W + 4W = 10W Peak
DVD Writter: 18W Peak
Total Power Needed: 261W Peak

The above calculation shows that a power supply capable of supplying 300W of power is more than enough to power up the system. Your system (excluding power supply) will draw a maximum of 261W from the supply line, not 300W, as contrary to what some people claim.

Now assuming that your power supply is 80% efficient (which is rather good), your power supply unit will draw a total of 326.25W from the supply line.


Assuming your generic PSU is only 70% efficient, then you will have to draw 46.6W more power to produce the same amount of output compared to the 80% model.

However, some dodgy power supply units might not live up to claim of its rated power output. During full load operations when the temperature inside the chassis becomes very hot (> 40C) and the power rails become fully loaded, the power supply output will fall dramatically. This will lead to system crashes and probably damage.

Conclusion:Efficiency of a PSU determines if your electrical bills are going shoot sky high, not power rating. Obtain a high quality power supply unit to protect your investment.

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