ACCO Engineered Systems is currently one of the 3 largest mechanical contractors in the United States and a leader in the development of the design/build approach for HVAC, plumbing, process piping, and control systems.

Established in 1934 as a distributor of General Electric refrigeration products, ACCO's growth began to accelerate after World War II when, in 1945, it became closely allied with the Carrier Corporation as the sole distributor of Carrier Air Conditioning products in the Los Angeles area.

Eventually, the distribution arm and the contracting division were separated with Carrier retaining the equipment distribution division. The independent construction group, which consisted of a strong group of Carrier factory-trained engineers, formed the nucleus of present day ACCO.

The 1950s - 1960s saw ACCO emerge as one of the premiere constructors of HVAC systems in Southern California, and with its expertise in design engineering and construction, it became a pioneer in the use of variable air volume (VAV) systems. ACCO has been among the top 10 HVAC contractors for the last 30 years. This long term success is attributed to an employee ownership program, where ACCO employees are stakeholders and are committed to our products and our customers. Company ownership and management has passed from one generation of employees to another, creating a very stable and predictable corporate environment that ACCO's customers can depend on over the long term. 

Since the 1960s, ACCO has established area offices in San Diego, San Francisco Bay Area, Orange County, Sacramento, Fresno, and Seattle, WA. ACCO has designed, fabricated, installed, commissioned and serviced projects across the country.

ACCO Engineered Systems has been eager to embrace change over the years. The strong technical foundation at ACCO has led to the integration of Plumbing, Process Piping, DDC Controls and many other areas of expertise.