According to Newegg's PC Power Supply Calculator, at least a 388 watt power supply is required... Most PC builders include a 25%-50% overhead for future expansion and headroom of the power so as not to "stress" the power supply. A 500-600 watt power supply would recommended for this application, perhaps larger if you need to incorporate other disk drives or optical drives.

That said, it should not harm anything but it will likely shutdown when power requirements are exceeded. If something went wrong though, it is possible that equipment could be harmed or the power supply could try to supply too much current which could burn out the power supply.

According to Newegg's PC Power Supply Calculator, at least a 388 watt power supply is required... Most PC builders include a 25%-50% overhead for future expansion and headroom of the power so as not to "stress" the power supply. A 500-600 watt power supply would recommended for this application, perhaps larger if you need to incorporate other disk drives or optical drives.

That said, it should not harm anything but it will likely shutdown when power requirements are exceeded. If something went wrong though, it is possible that equipment could be harmed if the power supply would try to supply too much current, which could potentially burn out the power supply. If that occurred, it is possible that other equipment like the motherboard, CPU, or GPU could be damaged from the faulty power supply.