The Corsair RM series power supplies are designed to run without active cooling for up to 40% load at typical room temperatures (25°C, or 77°F) and are capable of continuously outputting 100% of output capability at ambient temperatures of up to 40°C (104°F). We have found that our power supplies are typically used in environments much lower than 40°C and tend to have some natural aspiration within the chassis that allows for some air movement, such as from a nearby graphics card or chassis fan, within the PSU housing, when temperatures exceed normal room temperatures. We have found that this normal aspiration can maintain Corsair’s Zero-RPM fan-less mode even at temperatures as high as 35°C (95°F) when only at 40% load for durations of up to 15 minutes.
Thanks to recent feedback provided by an early reviewer, we have discovered a PSU fan operation issue that can be triggered with the RM750 and RM850W under highly unusual operating conditions. For the issue to occur, the PSU must be run for more than 15 minutes at:
Ambient temperature 35°C (95°F) or higher
Zero ambient airflow, i.e. no airflow provided by system fans or by fans on other components
Under these conditions, impacted PSUs may shut down before the cooling fan starts spinning. This shutdown will cause no damage to the PSU or the system. As these conditions are extraordinarily harsh, we believe most users will not be impacted. If you feel you have a unit that has been impacted, we are offering advance replacement returns for the PSU, with Corsair paying all freight costs. Please click here for instructions on how to obtain a replacement unit, or to ask any questions.
Thank you for choosing Corsair; we are committed to making sure you are completely satisfied with your purchase.
Update - November 14, 2013:
In an effort to improve our products for all of our users, we have updated the RM750 and RM850 to resolve this issue. The thermistor circuit that is used to measure the temperature for the fan controller and OTP has been changed in all RM750 and RM850 PSU’s moving forward. An additional resistor has been added that will result in the fan turning on prior to the condition that causes the PSU to shut down in the event that temperatures exceed 45°C.
