Diagnose and repair heating and air conditioning systems including chillers, boilers, controls, humidifiers, cooling towers, and heat pumps. Perform the following repairs: compressor change outs, locate and repair refrigerant leaks, valve replacements, motor change outs, and advanced electrical troubleshooting. Perform routine maintenance on commercial systems listed above. include basic system performance checks as well as standard manufacturer's recommended maintenance tasks. Perform basic commercial equipment installation duties including ductwork fabrication and refrigerant pipe installation. Work periodically in an 'on call' capacity to provide emergency service after normal working hours.