The most common is the single-package rooftop system, shown in Figure 1. The most common types of unitary HVAC equipment are shown in Figure 2. These units provide conditioned air through ductwork. The indoor section usually consists of a fan, indoor cooling coil, heating section, and filter. The outdoor section houses the compressor and condenser.
Energy performance is similar to single-packaged units.
They are much smaller than rooftop units because they are designed to serve a single room. Simple controls are located on the unit. For cooling, it operates as a conventional air conditioner. For heating, it reverses the refrigeration process, removing heat from the outside air and blowing it indoors for space heating. Heating capacity drops off as the outdoor temperature gets colder, and for this reason heat pumps usually require a supplemental heat source for colder days.