The first gas manufacturing plants, or gas works as they often were called, were coal gas plants, utilizing bituminous coal as the fuel to produce coke with gas as a by-product. During the latter part of the nineteenth century, a more advanced, cheaper process-carbureted water gas-was introduced.

Carbureted water gas was produced through a process involving three pieces of equipment — a generator, a carburetor, and a superheater — comprising what was called a water gas set. The generator contained fuel — either coal or coke. The carburetor, and superheater were lined with firebricks arranged in a checkerboard pattern with open spaces to permit the passage of gases. Firebricks in this special arrangement were called checkerbricks.

The manufacturing process began with the production of "blue gas" — gas with relatively low heating value (approximately 300 Btus per cubic foot). Blue gas was formed in the generator of the water set when steam came in contact with the incandescent fuel.

The blue gas then flowed into the carburetor where oil was vaporized as it came into contact with the hot checkerbricks. The oil gas and the blue gas were passed down through the carburetor into a superheater. Then the two gases were permanently fixed into a gas with a higher heating value, carbureted water gas. The heat content was nearly double that of blue gas.

CL&P had gas plants at various locations — Middletown, Bristol, Meriden, Norwalk, Putnam, Winsted, Rockville and Willimantic — but its largest gas plant was Waterbury's South Gas Plant. (There was also a North Plant in Waterbury.)

The Connecticut Power Company also had several gas works at Torrington, Stamford, New London and Middletown. As many as 50 people worked at the South Gas Plant, and a total of approximately 200 production employees worked at CL&P and CP plants.

The Advent of Natural Gas

Waterbury CL&P gas distribution, 1924

The most important development in the history of NU's gas operations took place when transcontinental pipelines were extended to bring natural gas into Connecticut. Torrington was the first community in the state to receive the "new gas" — on August 29, 1952. The gas came from Texas via the Northeastern Gas Transmission company (now the Tennessee Gas Pipeline Company).

Natural gas had three major advantages over manufactured gas. It contained almost twice the heating value, it was cheaper because it eliminated the use of coal and oil, and it was cleaner. Another plus: natural gas did not contain carbon monoxide, a dangerous component of manufactured gas. For both CL&P and CP, the switch to natural gas was one of the largest projects ever undertaken. An information program for customer contact personnel and a technical training program for service personnel were created to implement it. The conversion in CL&P territory began in the late summer of 1952. Winsted was the first community in the company's service area to receive natural gas in October 1953.

Before natural gas could be used in customers' homes, the burner ports (holes) on appliances had to be enlarged. And before the natural gas began flowing, orifices (openings or holes through which natural gas flows to each burner) were changed or reduced in size and the air supply adjusted.

Telephone "brigades" answered customers' questions, while gas servicemen from the community being converted and other company districts visited homes, turning off the gas before conversion and restoring service after natural gas became available. Customers accepted the new fuel very well. Through the 1950s and first half of the 1960s, gas sendout steadily increased. As the use of natural gas spread, the gas plants were shut down, and new facilities were needed to meet the expanding use of gas throughout Connecticut. The 1955 flood of the Naugatuck River valley caused terrible damage to utility equipment. Electric service was restored much sooner than gas service. Floodwaters washed away paved streets in Winsted and Torrington. Gas mains were torn up, many meters were destroyed, and those which remained were water-logged. Gas plants were inundated; debris was piled in the yards; mud, silt and water clogged the machinery. Additional details are given in the CL&P section.

Divestiture

CL&P Norwalk Gas Works, 1928

The formation of NU in 1966 had major impact on the gas business. In approving the affiliation, the SEC reserved decision on the ultimate disposition of the gas business, pending resolution of a question about its authority by the United States Supreme Court. When the SEC's authority to order divestiture was upheld, NU agreed to sell its gas business because a registered holding company could only be involved with one form of energy. The process commenced in 1971, but an appeal of the DPUC approval by the state's consumer counsel delayed the matter for some years. Next, dramatically rising interest rates undermined the sale and in 1979 the agreement to sell the gas business was terminated by mutual agreement.

There the matter remained for nearly a decade while SEC interest in the matter was dormant. Meanwhile, NU's Gas Group conducted operations as usual, serving customers, expanding and improving service, and contributing, on average, about 10 percent to NU's annual revenues. In 1986, the SEC contacted NU to renew discussions regarding NU's separating its gas business from the electric business. After exploring several alternatives, divestiture through spin-off as an independent entity seemed the best way to proceed. Over the next two years the many necessary steps were taken to create Yankee Energy Services Inc. (YES) and its principal subsidiary, Yankee Gas Services Company.

Auxiliary propane tank trucks

Philip T. Ashton, NU's senior vice president — Gas Group, headed the effort to set up the new company. By 1989, all steps had been taken, including arranging for the purchase of assets and distribution of common shares. On July 1, the gas business was transferred to a separate corporation, YES, and became a wholly independent entity. Ashton, who resigned from NU, became its first president and nearly 600 CL&P and NUSCO employees transferred to Yankee Gas, which upon formation became Connecticut's largest gas utility.

In the 1990s, energy deregulation changed some of the rules governing energy companies, and on June 15, 1999, NU issued a press release announcing plans for a $679 million merger with Yankee Energy System Inc., with YES becoming an NU subsidiary. The merger was completed March 1, 2000.