and below have one thermistor while serial numbers greater than 1341 have the two (separate one for the fan). 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. The Corsair RM850 is fully modular and optimized for silence and high efficiency. It’s built with low-noise capacitors and transformers, and Zero RPM Fan Mode ensures that the fan doesn’t even spin until the power supply is under heavy load. And with a fan that’s custom-designed for low noise operation, it’s whisper-quiet even when it’s pushed hard. Completely modular cables means you only connect the cables your system needs, and the wide range of included cables adds broad compatibility with modern graphics cards and motherboards.

Room isn't even close to 35c ambient, more like 25c. Machine is built in a quiet 330r Corsair case, low airflow. A 120mm rifle bearing fan with a specially calculated fan curve keeps fan noise down, even when operating at full load. Please consider the total power consumption of the entire system when choosing compatible power supply units. You can use only the cables you need, and leave the rest in the box for fast, easy, and great-looking builds. Reliable, continuous power deliveryIs this (apparently fan-driven) "natural aspiration" assumption still valid when many chassis are designed to isolate the PSU airflow from the remainder of the components and draw and eject their air directly from/to the outside of the case? This may (or may not) still provide sufficient aspiration (due to heat convection) where the PSU intake vent is on the top of the case, but would almost certainly provide insufficient aspiration where the intake vent is on the bottom. 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.

The Cybenetics organization measures efficiency and noise levels across the PSU’s entire operational range, using more than 1,450 different load combinations. For consistent, reliable power and superb electrical performance, each RMe Series power supply features a robust resonant LLC topology with DC-DC conversion and 105° rated industrial-grade capacitors. Looks like I have to wait for you to physically receive my PSU before you'll send me another one..or am I reading this wrong?In other words I'd be better off returning it to the store and buying an alternative so I'm not with a machine for a considerable amount of time. But also, that can't be your serial number. Can you take a pic? Reason being: The first two digits are the year (13 = 2013) and the next two are the week (52 = last week of the year), so 1355 is impossible. ;) Flat cables are really nice and the hybrid fan is super quiet change my computers noise level completely. Some direction on appropriate orientation of the PSU may be appropriate in the product documentation for this series.

Powering an i5-4570, 2x4gb Vengeance Ram, a single GTX660, Asus Xonar Soundcard, 2 hard drives, 3 fans (one on Hyper 212 CPU cooler) spinning really (400 rpm) slowly. Nothing too elaborate. The custom-designed fan has an optimized blade profile for low-turbulence airflow and near-silent operation even at full speed. 80 PLUS Gold-certified efficiency Actually, no. While some fanless units have orientation requirements, the RM Series can be mounted in any position just like any other actively cooled power supply.

The only difference between Type 3 and Type 4 cables is the pinout of the 24-pin ATX cable; all other cables (SATA, PCIe, etc) are the same. Well, an 850W is quite a lot of power for the rig you're powering, but you can try running Furmark and Prime95 together at the same time to put a load on the PSU and if the fan turns on, you're good. The problem occurs when the OTP trips the PSU off PRIOR to the fan turning on.