I don't think anyone is going to be able to help you pin down anything more precise. An ACH automated electronic transfer is a scheduled process; it is not like a wire transfer, which is immediate. So when the IRS says "sent", I don't know how quickly that mean funds are actually flowing; i.e, I don't know if that means they released it to a queue/batch to enter the ACH system or if the funds have physically left the IRS, or what.
