How long can an incarcerated person be held for a writ from another county ?

My son is being held in the Orange County Florida jail on a "writ" from Dade County Florida on a civil matter. I paid his bond for another matter more than 72 hours ago and the jail will not release him. They told me he still has to pay that writ amount of $1,000. One of the employees o Orange County Jail told him that Dade County has 72 hours to pick him up. How long can he be held on the writ ?