The biggest merger of a troubled savings and loan ever carried out by federal regulators was announced yesterday by the Federal Home Loan Bank Board.

In a precedent-setting deal that puts some of the risk on the acquirer, Glendale Federal Savings and Loan Association in Glendale, Calif., acquired First Federal Savings and Loan Association of Broward County in Fort Lauderdale, Fla.

The merged associations, with assets of $8 billion, will become the largest federally chartered savings and loan and the fourth largest of all S&Ls in the country. The three largest, all based in California with state charters, are Home Savings, Great Western Savings and American Savings.

This is the second interstate merger affected by federal regulators since the policy was changed last spring to help the ailing savings institution industry. The first was a three-way deal involving failing savings institutions in New York City and Miami, which were acquired by Citizens Savings and Loan in San Francisco, a National Steel subsidiary.

In past supervisory mergers, the Federal Savings and Loan Insurance Corp., which insures S&Ls, has pumped in funds so that acquiring institutions are assured a certain profit margin. This practice has become costly and has caused industry insurance premiums to rise.

The Glendale-Broward coupling initially will involve no expenditure of FSLIC funds as the result of an unusual agreement whereby Glendale willingly undertook some of the risk in exchange for the opportunity to establish itself in the cash-rich Florida market.

The plan works like this: Glendale and FSLIC agreed on an insurance deal based on initial interest rate index of 11.32 percent, based on the average coupon equivalent rates yesterday of 90-day, 5-month and 2-year Treasury securities. If the average combined rate for the next year goes up or down by one percentage point, no payments will be made by either Glendale or FSLIC.

If, however, the interest rate goes up by more than one percent, FSLIC will pay Glendale the amount in excess of one percent, but the payment would not exceed 2 percent of the base in any one year. If, on the contrary, the interest rate average goes down by more than one percent, Glendale will pay FSLIC on the same terms. The five-year agreement covers a diminishing fraction of Glendale's assets. In the beginning $1.2 billion will be covered; in the fifth year the covered amount decreases to $500 million and thereafter to zero.