APU-Powered Guide

There are two basic types of auxiliary air systems:

• Self-contained “package” units
• Split systems

The self-contained unit is designed to be wholly mounted inside the truck, usually under a berth or seat or inside a side storage locker.  All air conditioning components, including the compressor, condenser, evaporator, blower, and power supply, are mounted on a single low-profile chassis with an aluminum cover.  The system’s closed refrigerant loop is precharged and sealed at the factory.  Warm inside air is pulled across the evaporator coil and cooled, then blown through a flexible duct to a discharge grill and into the living area.  Hot air is discharged from the condenser through cutouts in the floorboard. 

Image Above: Self-contained unit installed under bunk.

Dometic’s patented split systems consist of two separate modules.  The outside unit contains the condenser and cooling fan.  It is bolted horizontally to the underside or vertically to the back of the sleeper.  The inside unit contains the compressor, evaporator, blower, power-logic box, and other associated components. 

The inside unit is mounted under a berth or seat or in a side storage locker.  The two units are connected by reusable precharged quick-connect refrigerant linesets.  The system is designed so that both units automatically charge to the correct refrigerant pressure as soon as the linesets are connected.  No special tools are required.

Image Above: Split-system inside unit under bunk.

Each approach offers advantages and disadvantages. A self-contained unit is simpler to install and maintain, since it does not have any external refrigerant lines.  It is also less expensive than a split system of the same BTU capacity.  On the other hand, it takes more interior space, and it requires cutting holes in the floor for air to flow to and from the condenser.  A split system, on the other hand, has more installation flexibility and uses less interior space.  It is also quieter, since the condenser fan is located outside the truck.

Image Above: Split-system external condenser.

Both types of air conditioning systems are available with a selection of built-in electrical heat modules.  The heat is blown through the same ducts and grills and controlled by the same thermostat.  They can also be used in conjunction with a diesel-fired heater if desired, under control of the same thermostat.  They can also be used in conjunction with a diesel-fired heater if desired, under control of the same thermostat.

Whichever type of system you select, it will come with ducts, grills, condensate drains, thermostat controls, and electrical wiring.

*Under normal conditions.