TTI FAB Stratus Above Ground & Elite In-Ground Heat Pumps Stratus Above Ground Heat Pumps for medium to smaller sized pools. Features a rotary compressor and an injection system that are calibrated to work optimally at lower temperatures. Works with any type of circulation pump and any type of water sanitization system. Available in three sizes: Up to 18 Round - 50,000 BTU's, Up to 21' Round - 65,000 BTU's, and Up to 24' Round - 80,000 BTU's. Elite In-Ground Heat Pumps for In-Ground pools up to 20' x 40'. Optimized for the highest efficiency at low outdoor temperatures! Includes a state-of-the-art compressor uses less power to run and ensure silent operation while injection systems are calibrated to work optimally at low temperatures. Includes unique fan motor that reduces electrical consumption therefore increasing overall performance. Available in two sizes: Up to 16' x 32' - 100,000 BTU's and Up to 20' x 40' - 130,000 BTU's.