Donnelly Mechanical is a widely-regarded HVAC contractor providing both construction and maintenance/emergency services in the New York City area. Established in 1989, we have grown to become one of the largest HVAC contractors in our service area, with clients ranging from small independent businesses to large corporations. The majority of our customers are commercial tenants, building owners, health care, life sciences, institutional, and building managers in the five boroughs of New York City as well as Nassau, Suffolk and Westchester Counties.