Responds promptly to after-hours calls i.e., respond to site/building, assesses problem, takes immediate steps to address any safety issues, advises supervisor, and suggests actions to remediate issue and/or restore service, and as directed, proceeds to make repairs. Performs advanced diagnostics and repairs on HVAC equipment, including but not limited to chillers, boilers, air handlers, VAV systems, pumps, cooling towers, and hydronic systems.