The Manchester Steam Plant

The Manchester Steam Plant-now the site of PSNH Energy Park-was built in 1909 to provide steam and electricity to power the Northern Division Mills of the Amoskeag Manufacturing Company. Prior to that, the weaving looms of the Manchester Millyard were powered by upper and lower power canals fed by the Amoskeag Falls.

The original facility included the boiler house, which contained 64 Manning vertical boilers, and the turbine hall, which contained two Curtis horizontal turbines rated at 3,500 kilowatts each. At the time, using many Manning boilers was superior to using a large single boiler because individual boilers could be operated based on power needs. They could also be shut down and serviced without disrupting steam to the turbine.

Running on coal until 1921, the boilers required a complex gantry system for coal delivery as well as 50 men to constantly stoke fires and perform other work. In 1921, two 500,000 gallon oil tanks were placed on the island next to the Steam Plant on the Merrimack River and the boilers were converted to oil, allowing the plant to be operated by only 30 men.

A complicated system of coal gantries fed a constant supply of fuel to the Manning boilers from 1909 to 1921. The plant ran on oil thereafter, except during World War II when it was switched back to coal.

In March, 1936 a huge flood swept down the Merrimack River, tearing the oil tanks from their anchors and washing them down the river. The flood also ruined the north end of the boiler house and destroyed the Manning Boilers.

After PSNH purchased the Manchester Steam Plant in 1937, it was converted into New Hampshire's first closed-cycle power plant, wherein steam is condensed after passing through the boilers and then reheated again. During conversion, the original boiler house was shortened by half to remove the portion damaged in the flood and to allow room for a 640,000 gallon underground oil tank to be installed. Two new Babcock & Wilcox boilers were also installed in a brand new boiler house at the northeast end of the original turbine hall. They fed steam to a new GE turbine generator that produced 21-megawatts of electricity. At the same time, a new three-story control room was added to house electrical equipment.

Once connected to the company's transmission lines, the plant began providing power to New Hampshire residents and businesses outside the millyard in 1939. It continued operating until 1981 when it was taken out of service.