On a custom-built server with an Intel SC5600BRP Chassis (2 power supplies included), I originally had plugged into an APC UPS battery backup model SC1500. Sometimes (not every time) when the server rebooted, the battery backup would overload. The only solution was to unplug the server from the UPS, reset the UPS, then plug the server back in. It happened every 2 months or so.
I thought that it may have been a faulty UPS model, so we bought an APC UPS battery backup model BR1500, and experienced the same exact problem.
Both the SC1500 and BP1500 have the same maximum watt load of 865 watts
Running watt checks with the server on and the APC software loaded, the watts never seemed to go over 250W, which is well below the 865W maximum load.
The only way to get the server to not overload the UPS sometimes on reboot is to have one power supply plugged into one UPS unit, and the other power supply plugged into another UPS unit. It seems like the power required during reboot (system revving up?) overloads the UPS units, but splitting the power between the 2 units resolves the problem.
Obviously, we only want one UPS unit there, since I can’t really justify having two there for price reasons. I’ve never experienced this sort of overloading problem with other Intel servers with the same battery backup models. What is going on? Is there a BIOS setting I should change to get the wattage down to a manageable level for the UPS units? Is something else going on? It seems odd that it doesn’t occur every time the server rebooted, only sometimes.
I’ve contacted APC about the battery backup unit problem, and they don’t think there is anything wrong with the UPS battery backups. Since both models exhibited the same problem, I tend to agree with that opinion.
Personally I don't think connecting both PSUs to the same UPS is a good way - it makes the UPS a single failure point. I believe the better way is to connect one PSU to UPS and the other PSU to wall outlet directly.