The National Association of Securities Dealers has delisted the stock of InterTechnology/Solar Corp., a Warrenton, Va., firm that designs and manufacturers solar heating systems and does research on solar and other alternative energy sources.

An NASD official said the action was taken because ITC/Solar's captital and surplus has fallen below the $250,000 minimum required for continued listing.

The action, which took effect last Friday, means quotations for ITC/Solar stock and warrants are no longer available through the NASDAQ electronic quotations system. But the stock can still be traded with prices based on what brokers call "the pink sheets."

Delisting is not a penalty imposed on a company, the NASD lawyer said, but it does mean the firm lacks the association's minimum amount of captial and surplus, or stockholder equity. He said $500,000 in capital is needed for initial and half the amount must be maintained to stay on the list.

ITC/Solar President Dr. George Szego said the NASD action "is not good, but isn't that meaningful."

Sego said his firm "used our working capital in the direction we consider important" to continued growth, and has substantially increased its backlog of orders to $1.6 million.

Szego said ITC/Solar "expects to be in the black later in the year," ending several quarters of losses.

The latest work the company has landed, he added, includes a $15,500 contract to design the world's first solar-heated bus stop for Vail, Colo., and a $47,895 contract to design a supplemental solar heating system for an elementary school in Ballston Spa, N.Y.

ITC/Solar manufactures solar collectors and related hardware, offers solar energy design and engineering services, and performs alternate energy, research. Among its projects is what the company calls "the energy plantation," a system for growing fiberous plants that can be burned for fuel.