Perform work in the repair, maintenance, service, modification, troubleshooting, installation and monitoring of the operation of heating, ventilating, air conditioning and refrigeration equipment and associated plumbing, electrical, mechanical, EMS (Energy Management Control System) and controls systems. Troubleshoot, diagnose, maintain, inspect, modify and repair heating (hot water, indirect and direct gas fired, and steam), ventilation, air conditioning and refrigeration systems and associated equipment and parts.