Starts under load makes boom sound

by sumi
(chennai)

When this unit starts, my wall shakes (wall is 24" away and brick). It makes a boom sound and then starts up. The installation was made on this unit only 3 months ago and I have had the installer come out to correct the problem twice. He has checked the refrigerant level/pressure and advised they are normal or slightly below. This unit comes with a "hard start componient". Factory representative due out in a couple days but want to find out if this is a common problem with this type of unit.