The National Consumer Cooperative Bank opened its doors yesterday under cloud: Worse than the downpour that delayed the ribbon-cutting ceremony was the House budget committee's proposal to eliminate $50 million from the new institution's $176 million loan fund.

Esther Peterson, President Carter's consumer advisor, told the assembled guests that while everyone has to make sacrifices to fight inflation, "$50 million is too much." Carol Greenwald, the bank's first president, said that if $50 million is cut, "we won't be able to meet demand."

Greenwald called NCCB, which was 10 years aborning, "a quantum leap forward for the consumer movement." The bank, funded by taxpayers' dollars was authorized by Congress to lend $300 million over the next five years to nonprofit citizens' cooperatives. These in turn will enable consumers to save money on food, housing, health care and even energy. For example, a co-op making gasohol has applied to NCCB.

In the past, cooperatives have found it difficult to obtain financing from commercial banks. NCCB plans to offer three types of loans: start up, investment and technical assistance. The Self-Help Fund, with a $17 million initial budget, will provide seed money for groups that are being formed. Interest rates as low as four percentage points below market will be available only to groups whose members are defined as having low incomes.

Going co-ops with sufficient income may qualify for investment loans at market rates. This year $49 million is available to lend; next year, $116 million. Equipment or inventory serves as collateral.

The current loan ceiling is $2.5 million, although Greenwald said half of the loan volume would be in the $7,000 and under category. She has been actively seeking the participation of commercial banks in loans over $1 million. NCCB will guarantee the top 10 percent of the loan against loss. In addition, NCCB may borrow up to $3 billion from sources other than the Treasury.

The bank's headquarters is at 2001 S Street NW. Half of its staff of 221 will be in the field. By September the bank will have eight regional offices.

Information can be obtained by telephoning 376-0891 locally or (800) 424-2381. Applications for loans are now being accepted, and the first loans will be passed on April 7.