Quieting the Enermax & other thermistor fan PSUs

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April 6, 2002 - by Mike Chin

Some ATX power supply units (PSU) for computers are equipped with two fans, one positioned normally to blow air out of the unit (and the PC), and another fan positioned so that it draws air from within the case onto the heat sinks in the PSU. Many power supplies are equipped with thermistors that control the voltage fed to the fan so that it speeds up only when internal temperature within the PSU rises. These units are often tagged or advertised as being noise controlled or noise-reduced. Some power supply units have both dual fans and thermistor control.

The Enermax EG-365P-VE is a popular example of a thermistor-controlled, dual fan PSU. This article shows how to reduce its noise output so that it is just a whisper, barely audible from even just a couple of feet away. The basic methodology can probably be applied to any thermistor-controlled fan PSU that is too noisy.

This is not a review, so detailed observations of the performance of this PSU are not commented on here. That will come in another article, as will an analysis of the fans used in these units.

DISCLAIMER & WARNING: While the modifications described here have been successfully completed by Silent PC Review, we take no responsibility for your actions, your equipment, your property, your data and your safety. The information is provided here in good faith; what you do with this information is your responsibility. We recommend you study the article carefully and take all necessary precautions to guard against electrical shock from high voltages, data loss, equipment damage or personal injury before attempting to duplicate our results. Power supply units should always be unplugged from AC voltage before being opened. Large capacitors can hold a dangerous high voltage charge for long periods. Some technicians suggest to always ground yourself when working around electronic components. Finally, be aware that any kind of tampering, even just opening the case, usually voids the manufacturer’s warranty. Reducing airflow in a PSU may also reduce its longevity and reliability.

Dual Fans

At first glance, the push-pull orientation of the dual fan arrangement looks very sensible. For a typical tower-style ATX case, this design tends to encourage the optimal airflow from the lower front intake to the CPU / HSF area, and from there through the PSU and out the back. Outside air from the lower front rising as it increases in temperature while drawing heat away from hot components, then being ejected out the back. The accompanying case airflow diagram illustrates this process well (image borrowed from a document entitled Performance ATX Desktop System Thermal Design Suggestions v1.0 available for download at Form Factors.)

I did a lot of research to find out more about the dual-fan system, about PSUs in general, and about the Enermax specifically.

Dual Fans Summary

Here are some observations about the push-pull dual fan setup. These aspects of fan performance in an in-line configuration is well-documented by the fan manufacturers and others. Please visit their sites for confirmation. (You could start by looking through our http://www.silentpcreview.com