The AAON Rk-03 RTU has a unique circuiting configuration that includes a 1 pass sub cooler, making it an interesting condenser coil. There is and additional feed to the liquid collection header as well this allows for and independent liquid connection from the sub cooling circuit. At Nationwide Coils we have direct replacement condenser coils for the AAON RK-03 along with all other AAON models, providing our customers the perfect fit and performance every time.