The D.C. health planning director, overruling recommendations of his staff and of other health agencies, has approved construction of a $44.8 million, 240-bed rehabilitation hospital at the site of the old Children's Hospital at 13th and V streets NW.

The planned National Rehabilitation Hospital would be the first facility in the area -- and one of the largest in the country -- devoted exclusively to rehabilitating the physically disabled.

Some city health planners have sharply criticized the proposed facility as a potential "white elephant" that was not financially feasible and far larger than the expected area demand for rehabilitative care.

In an analysis prepared last month, the staff of the D.C. Health Planning and Development Agency, the agency that must rule on all health care facilities planned for the city, concluded that fewer than 100 beds would be adequate to meet the total demand for a new rehabilitation hospital in the area.

But agency Director Carl Wilson, insisting that health planning is "not an exact science," last week granted a certificate of need for a scaled-down, three-story facility, including the immediate construction of 160 beds on the first two floors and tentative facilities for 80 additional beds on the third floor. Those beds cannot be opened or licensed until there is 85 percent occupancy of the beds on the lower floors.

Wilson also attached 10 other conditions that he said address concerns raised by the staff and others about the economic feasibility of the project.

These include requirements that the new hospital's directors work closely with the local medical community to develop programs for patient care and referrals from local hospitals to the new facility.

The decision was greeted with measured praise yesterday by Jeffrey N. Cohen, a developer and recently-elected Chairman of the National Bank of Commerce here (formerly the Bank of Columbia), who is one of three owners of the site.

The others are Theodore F. Mariani, a local architect and former member of the D.C. Zoning Commission, and Samuel C. Jackson, a lawyer and Assistant Secretary of Housing and Urban Development in the Nixon administration.

"We're pleased with the decision, but we're not entirely pleased with all the conditions," said Cohen. "Some of them are somewhat unreasonable, but none are insurmountable. We'll live with them."

The proposed hospital is the centerpiece of an ambitious plan by the developers for construction of a nationally recognized health care complex in the midst of what is now one of the most economically depressed and crime ridden areas of the city.

In addition to the four-acre hospital site, abandoned when Children's Hospital moved to its new location near the MacMillan Reservoir in 1977, the three developers have also purchased about two acres of land surrounding the area.

"We hope to develop the area over time in ways related to the hospital so it would be much like the Mayo Clinic in Minnesota," Cohen said. "You'd have the hospital, and then we might have a hotel across the street for families of the patients, and then office space for doctors and professional associations."

Because of its potential for economic development -- Cohen estimates that the project will create more than 1,200 permanent jobs and annual tax revenues of $1.2 million -- the hospital project has received strong support from city officials, including the City Council and Mayor Marion Barry. Cohen was an early supporter of Barry's 1978 campaign for mayor.

Earlier this year, the city approved a $7 million Urban Development Action Grant application for the facility that was contingent upon it receiving the necessary approvals from Wilson.