UPDATE 1-FPL Fla. St. Lucie 1 reactor shut due to flooding

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HOUSTON, Aug 20 (Reuters) - FPL Group Inc's (FPL.N) 839-megawatt Unit 1 at the Saint Lucie nuclear power station in Florida shut Wednesday morning due to heavy rain that collected in a sump pit, an FPL spokeswoman said.

Unit 2 continued to operate at full power.

The spokeswoman said operators manually shut the unit about 6 a.m. CDT (1000 GMT) after more than 17 inches of rain from Tropical Storm Fay that fell in the area on Tuesday collected in a sump pit, affecting water quality equipment.

Earlier, the unit had been at 85 percent, according to the Nuclear Regulatory Commission daily report.

Heavy rain moved northward during the day Wednesday, the spokeswoman said, allowing operators to begin checking equipment before restarting the unit.

The 1,678 MW St. Lucie station is located on Hutchinson Island in St. Lucie County, about 120 miles north of Miami. There are two 839 MW Units 1 and 2 at the station, which entered service in 1976 and 1983.

One MW powers about 300 homes in Florida.

FPL's Florida Power & Light Co (FP&L) subsidiary, which owns all of Unit 1, operates the station for its owners.

FP&L (85.1 percent), Florida Municipal Power Agency (8.8 percent) and Orlando Utilities Commission (6.1 percent) own Unit 2.

FPL, of Juno Beach, Florida, owns and operates about 38,000 MW of generating capacity across the United States, markets energy commodities, and transmits and distributes electricity to more than 4.5 million customers in Florida. (Reporting by Eileen O'Grady; Editing by Christian Wiessner)