E. C. Ernst Inc. Chairman Joseph Griffin revealed yesterday that the big electrical construction firm is discontinuing international operations and trimming back substantially on its domestic branches to concentrate on a regional business base.

Blaming most of the Washington company's recent financial woes on international contracts, which he called an "unmitigated disaster," Griffin said Ernst still expects to collect $10 million or more from overseas projects.

But such revenues will be recorded "after the disaster," he said, referring to Ernst's decision late last year to seek protection of the Bankruptcy Act in a petition for voluntary reorganization of its debts.

Because of losses on foreign contracts, Ernst suffered a net loss of $5.8 million in the year ended March 31, 1978, and an additional loss of $7 million in the subsequent six months.

Griffin, who had been with Ernst earlier as chief financial officer, was recalled last fall to head up a management rescue team at the 63-year-old firm. In an interview yesterday, Griffin said he discovered "things were in a mess" when he became acting chief executive on Oct. 18. "They had 100 people in the international division to handle business they were going to get," they hoped, Griffin recalled.

Since then, Griffin became chairman and chief executive on Dec. 1 and he has been negotiating with creditors and seeking to restore the Company's health. Among the actions he revealed yesterday:

Overhead expenses have been sliced by $11 million as Ernst moves to narrow the scope of its operations.

For the next "couple of years," sliced by $11 million as Ernst moves to narrow the scope of its operations.

For the next "couple of years," Ernst will concentrate on operations from six offices - Washington, Philadelphia, Pittsburgh, Norfolk, Atlanta and Miami. This means closing 17 branches, including the Midwest operations in Hammond, Ind., and a California business base - the latter being shut on a "favorable basis" that permits Ernst to re-enter that market in future years.

Ernst currently is conducting negotiations with Citibank about selling off L. K. Comstack Co., which merged into Renst last July 1. Citibank owns $2.1 million of Comstock preferred stock, and Comstock's former owners have started litigation seeking to sever the merger, a move Griffin said he favors.

By the end of 1979 or the completion of Ernst's fiscal year on March 31, 1980, the company hopes to have completed its Chapter XI reorganization and be in operation as a viable company.

He also emphasized that no attempt will be made to conclude the bankruptcy reorganization drive without settlement of pending lawsuits over the Comstock merger and by stockholders, who have charged that Ernst overstated earnings. The Securities and Exchange Commission has been investigating at least one foreign contract situation in Saudi Arabia but Griffin said he has "no problem" with the SEC proceedings.

Ernst, which is engaged principally in commercial and institutional electrical work, has had overseas contracts in Central America and South America, as well as the Middle East.

Griffin had sharp criticism for Washington banks, which he said turned Ernst away when the local company sought help in working out of its difficulties. The area banks are "awfully dumb . . . they have no relations with the corporate world, they don't know corporations," Griffin stated.

As a consequence, Ernst is working with banks in New York and other cities. CAPTION: Picture, JOSEPH GRIFFIN . . . "things were in a mess"