Aqua hot ran perfectly on the way to Fla from Jersey. Its a 3 zone unit. 2 zones work perfectly, one zone throws cold air. There are no "fault" lights everything is green, the circulator pump for that zone operates, there are no kinks in the supply line or the return. I can only assume that the impeller in the pump for that zone is shot and I need a new pump. Has anyone had any experience with the Aqua Hot pumps. Word is that we're going down into the 30's tonight in sunny Naples.