Upon arrival we found that a circulator pump was making a chirping noise due to having low/no water to push because of a pocket of air. Added some water to the system and it knocked the air pocket loose letting the circulator push water. Hooked up the hose and bled all 3 zones of air until there was cold water coming back. Started and tested system on all 3 zones. Had hot water coming back on all 3 zones. Unit is working properly. Pressure when leaving was at 20