Answered: NEC ECC: Is the Contractor obliged to notify sub-subcontractors to the Project Manager for acceptance?

No, not unless there is a Z clause that specifically requires this.

The unamended ECC defines a Subcontractor as someone who has a contract with the Contractor. A Subsubcontractor in an ECS does not have a contract with the Contractor in the ECC, the subsubcontract is between the Subcontractor and the Subsubcontractor.