fmeili1
Solar Addict
Thanks for the details and explanations!The R4875G1 units were tested at 40°C ambient temperature and have their MTBF set at 500k hours under those conditions. This figure halves for every 10°C increase above that ambient temperature.
The units are hot-swappable, meaning they slide in and out of server racks that offer little to no additional cooling on the sides—certainly no thermal compound! (In fact, they are stacked right next to each other.) Their bottom plate also has a thick plastic insulator. In other words, the fan is all they have to stay cool.
As you observed, the fan responsible for cooling the internal components (some of which sit directly in the airstream, while others do not) operates very quietly at room temperature, even as the unit appears to get "hot." However, to effectively transfer heat via air cooling at 60°C ambient air temperature, the components need to reach around 85°C. The hotter the unit, the less air needs to be moved to achieve heat transfer.
I have conducted some limited testing of the R4875G1 at a 75A output. The units allow the "output temperature" to approach 80°C before the fan significantly increases its speed. I find that using the maximum fan setting (perhaps something to try when you're home alone) substantially reduces the output temperature, indicating that there is considerable margin built in for higher ambient temperatures. I suspect these units could reliably power a cell tower in the middle of the desert without additional cooling.
That said, many mobile operators control ambient temperature and air quality with air conditioning units and air filters to protect their radios and rectifiers from excessive dust and heat. This is why many used rectifiers appear so clean. In other words, as long as sandstorms are kept out, these units will likely last a lifetime without modifications. This is industrial-grade equipment—not the "designed-to-fail" consumer rubbish we’ve come to expect. I trust its quality.
The more I learn about these devices, the more impressed I am by them

These devices are proof that it is possible for manufacturers to build devices for moderate prices that still have high quality - this is not very often seen today...