Package units are different than the more traditional split HVAC systems. The latter tend to be more common. There is one major difference between the two types of HVAC systems. In the package unit, everything is contained within one cabinet. That cabinet is installed outside on a pad or your roof.On the other hand, split systems have two cabinets. The outdoor cabinet holds the condenser and compressor. The indoor cabinet has an evaporator coil and an air handler. A copper tube, called a line set, connects the two cabinets. Split systems are ideal for homes that have enough indoor space for the indoor cabinet. If space is limited, then a package unit is typically recommended.