I am a self employed refrigeration technician, specializing in marine refrigeration/airconditioning on sail and motor pleasure boats. These vessels have units with compressors which are AC and DC hermetic, AC and DC belt or direct drive, or engine driven by belts. The condensers are cooled by air or sea water, and the expansion takes place in thermal expansion valves or capillary tubes. Are there others in this field in this forum or is there another forum more suited for those in my field?