2 refrigeration circuit 1 5/8 ODM refrigeration connection size FOB factory in Osceola Iowa. Customer may pick up at factory Free-Heater Model D A Model D Free-Heater consists of a heavy-duty, glass-lined storage tank surrounded by our stainless steel Temp-Plate® heat transfer surface for maximum heating efficiency. Two-inch foam surrounds the Temp-Plate surface, keeping heat within the tank. A rust-resistant, stainless steel outer jacket houses the entire assembly for protection and appearance. Model D recovers up to 60 percent of your system's wasted heat energy.