If the bank sets an ACH credit exposure limit for an insiders account, should that limit be approved like any other insider obligation, by the board of directors, prior approved like a line etc…?

Information....

CREDIT RISK. The risk that a party cannot provide the contracted funds necessary to settle the account. Credit-risk-related losses typically arise from company failure or bankruptcy.
This type of risk falls mainly on the financial institution. Specifically, the ODFI assumes a greater credit risk in processing ACH transactions than does the RDFI, because the ODFI is exposed to credit risk for both ACH debit and credit transactions, while the RDFI is exposed to credit risk only when it handles ACH credit transactions.
Financial institutions can help control credit risk by establishing or using existing credit ratings for all of their customers. Credit ratings provide a concise, comprehensive review of the credit risk aspects of the relationship and are used extensively in credit approval and monitoring systems. Credit ratings assist the ODFI to assign credit (exposure) limits for its ACH originating customers. A dollar limit is assigned to each transaction or total file, which the ODFI monitors and represents the total exposure that the financial institution wishes to accept.