Ok, be gracious with me. I am an SE on this site but have an HVAC question. I built a new house (one story ranch on a crawlspace) and the HVAC contractor installed a 15 SEER American Standard unit. As it was a perfectly straight shot from the outdoor unit thru the crawlspace to the air handler in the mechanical closet, the contractor used ½”ø rigid copper for one of the lines. Seemed like a good idea. However, when the unit runs I hear a vibration in the house and outside. It is kind of a beating vibration like “wah, wah, wah” I can’t imagine a unit leaving the factory with a vibration. I am figuring that the rigid line is causing this. They have been back a few times to add isolators etc. and it remains. I had this same unit at my old house and it was pretty damn quiet. Does anyone have any further insight about this?

Thanks