A 20-year-old Northwest Washington man, charged with stealing more than $11,000 worth of jewelry from Montgomery County merchants last year, has been sentenced to eight years in prison for shoplifting.

Zachary Wages, of 224 Florida Ave. NW, who had pleaded guilty to three of seven theft charges and to one charge that he gave police a false statement, was sentenced by Montgomery County Circuit Court Judge James S. McAuliffe. "I took into consideration the number of offenses, the careful planning . . . and the specially designed tool he used to get into expensive jewelry cases," Judge McAuliffe said yesterday.

The tool was a coat hanger Wages used to reach through locked display cases at Bloomingdale's, Woodward & Lothrop and Montgomery Ward.

According to court records, Wages stole more than $11,000 worth of jewelry before he was arrested in March 1981, seconds after he pulled $1,600 worth of gold necklaces from a display case at Montgomery Ward in Gaithersburg.

After the arrest, Wages told police he was a juvenile and urged them to call his grandmother to verify his age. Police talked by telephone to a woman who said she was Wages' grandmother, but police said they discovered she was his younger sister.

Two weeks before the 1981 arrest, Wages was arrested at the same store and charged with stealing $2,700 worth of jewelry. He was convicted on that charge in May of this year and sentenced to one year in jail. The sentence was completed this month, allowing time served in detention after his second arrest.