OPEN BOX - FSP Twins Pro ATX PS2 1+1 Dual Module 500W Certified Efficiency =90% Hot-swappable Redundant Digital Power Supply with Guardian Monitor Software (Twins Pro 500), FSP500-50RAB

I've built a few point of sale systems with these running with two separate backup batteries and they work great. Tested many times just yanking one of the units out and the system keep running great. Buzzer is very conspicuous if a unit is in failed, loose, or removed mode. Highly recommend these units.

The unit works as advertised and I am able to swap modules without powering down the system. I ordered a spare 520 module and received a 720 module. The packaging was correct but the sticker label on the outside of the box was incorrect. I took that opportunity to try the 720 module in the 520 unit and it worked properly. The fan speed was higher, the watts were lower on the 720 module but I found similar differences between between two 520 modules. I wish it was "modular" so I didn't have a wad of wires stuffed into the case. It is also fairly loud when first powering on but it quickly gets significantly quieter.