Howard A. Grayson Sr., 55, the president of H.R. Grayson & son, Inc., heating and air conditioning firm in Washington, died at Southeast Community Hospital Sunday following a heart attack.

Mr. Grayson was born in Charlotte, N.C., moved to Washington with his family as a child and graduated from Anacostia High School. During World War II, he served in the Navy. He then earned a degree in engineering from George Washington University.

His first job was with T.B. Bourne Associates, an engineering firm, in Japan. After his return to this area, he worked for Griffith Consumers, an air conditioning contractor.

About 1955, Mr. Grayson joined H. R. Grayson, the company which had been founded in 1934 by his father, Howard Roy Grayson. He remained with it for the rest of his life.

Mr. Grayson, who lived in Temple Hills, was a member of Associated Builders and Contractors, Inc., and a director of the United Bank & Trust Company of Maryland. He also was past president of Anacostia Lions Club and a member of the Anacostia Masonic Lodge.

Survivors include his wife, Marian, of Temple Hills; a son, Dr. H. Avory Jr. of Gales Ferry, Conn.; two daughters, Mary Dale and Gaye Grayson, both of Temple Hills, and a grandson.

The family suggests that expressions of sympathy be in the form of contributions to the Taylors Island Volunteer Fire Department, Taylors Island, Md., 21669.