I think Irwin’s response is on-the-money, but I also wanted to add how unlikely it is for a MEAN WELL to fail, and some single-supply options that might be simpler than failover, especially if the conditions that cause PS1 to fail are also applied to PS2.
The LRS-350 datasheet gives the minimum MTBF (Mean Time Before Failure) at 2100 K hours, IE 240 years, and that feels ridiculous. When MTBF is based on warrantee return data, it’s interesting; when it’s based on the minimum of all critical subcomponent MTBFs or even the correct statistical union of them, I’m skeptical.
That said, I worked with a seasoned art car veteran this year who told me that despite the alkaline dust, vibration, and rain, he’s never seen an uncovered LRS-350 fail in the desert. He said the fans can definitely seize up if you don’t blow them out with compressed air after every year, but he reports it’s surprisingly unlikely to have a failure.
If you’re installing something for a multiple-year outdoor installation where accessing the power supply for replacement is untenable, consider selecting something from Mean Well’s Harsh Environment series: In 12V and higher, these are HEP-, such as the HEP-320-XX. On a budget, my 12V / 300W waterproof supply from Ray Wu is still going well after 2 years outdoors in mild-yet-foggy San Francisco.
In 5V, the “High Reliability” HRP series (HRP-300-5) is a little sturdier, and remember that the ones 200W and under don’t have fans (which is good for longevity in some environments). The HSP-300-5 is also pretty nice: Conformal coated (which honestly looked more like epoxy to me), fanless, but note that you really need to bolt it to a decent piece of aluminum or copper for heat dissipation.