Ralph Pritchard, president of the National Association of Realtors, is recuperating at his home in suburban Chicago after suffering a heart attack in Athens during the recent convention of the Congress of International Real Estate Federation. He is expected to resume his duties later in the summer. Vice president John Wood of Fort Lauderdale, Fla., is substituting for Pritchard.

Costain Washington, an home-building firm, has introduced a heat-circulating system in the fireplaces installed in its new homes at Southport, a subdivision in the Springfield area.

Sydney Kemper, president of Welsh Construction and Remodeling Co. in Baltimore, has been named a regional vice president of the National Home Improvement Council. Kemper formerly headed the Maryland Home Improvement Contractors Association.

Routh Robbins Real Estate Corp. has appointed these managers: Jackie Armstrong, the Arlington office; Carole Jenkins, the new Reston office opening in August; Anne Lockwood, Alexandria, and Sherry Vanskiuver, for a newly opened office in Bowie Plaza.

Seven mortgage plans are being offered at 29 subdivisions under construction by Pulte Home Corp. Roy Krag, area president, said there are three graduated payment mortgage plans and four fixed-rate plans at below-market rates.

Alan Dellefield has been named manager of the AMF Real Estate office in Highland, Md. A member of Electronic Realty Associates franchise group, AMF is owned by Ann Marie Fentress.

Coldwell Banker's commercial real estate division has named Kenneth McVearry sales manager of the Washington office.

C-I/Mitchell & Best Co. has opened Carpers Farm, its first community of detached houses in Northern Virginia. Located opposite Colvin Mill Run Mill Park, the community has traditionally styled homes priced from $160,000 to $188,000. The houses were designed by Wilfrid Worland.

The 132,000-square-foot Calvert Village Shopping Center in Prince Frederick, Md., has been sold for $4.7 million by Cedar Beach Limited Partnership to Calvert Village Associates.

The Property Management Association of Metropolitan Washington will sponsor a day-long seminar on energy conservation in existing multi-family residential buildings Aug. 26 at the Tysons Corner Ramada Inn. Information for reservations is available at 587-6543.

The National Rental Housing Council and the National Association of Condominium and Cooperative Housing, both based here, have merged to form the National Multi-Housing Council. Richard L. Fore, former president of NRHC, is the new president of the NMHC, based at 1800 M St. NW. Richard H. Francis is executive vice president of the new group, which represents owners and developers of apartments and condominiums.

The Piccard Building, on Piccard Drive in Rockville, has been sold for $3.2 million to the American Occupational Therapy Association.