Swinging Load on AC Line When Power Supplies Are Redundant

Hi,

I have a Dell PowerEdge R710. It has two power supplies, each rated at 870 Watts. 

The problem is that when the two power supplies are plugged, the server is constantly swinging its load from one PSU to the other. This results in frequent current surges making at lot of noise on the AC line. You can actually see the lights in the room flicker.

When I plug only one of the PSUs (any of the two), everything becomes normal and quiet. 

I would prefer to keep the server redundant but this setup might harm my other electronic equipments and the server itself. Any idea of what the problem might be? Any measurements I can do to further investigate?

Thanks!