Originally Posted by mainah
Seems a bit hard to have ducted AC when the AC is on the ceiling.
They actually do have a ducted AC unit in the larger Sunlines. Here are the basics of non ducted and ducted.
Up on the roof sets the upper roof unit. This is the self contained unit with the compressor, fans and evaporator and condenser. The roof unit is the same for a ducted to non ducted AC system.
The difference is in the attic of the camper. There is a 14 x 14 nominal hole framed out in the roof. Generally in the central area of the camper. Inside this framed out area of the attic is what Dometic calls the "air box".
A non ducted air box has ducting totally contained in the 14 x 14 opening to take the blowing cold air from the roof unit and blow it out inside the living space out of the ends of the ceiling shroud inside the camper. There are no auxiliary ducts with this system. The air box also has an intake duct to draw in warm air from the camper living space.
Here are some pics from my T1950 with the non ducted air box.
Nominal 14 x 14 opening in the attic to the roof
Inside the camper looking at the air box that is up in the 14 x 14 opening. This has an air intake duct, an exhaust duct and the simple controls box to run the roof unit.
Screwed to the bottom of the air box is the inside air shroud that directs the air out both ends.
The non ducted are a simple setup and they do work. The controls are not the most repeatable for maintaining a set point though.
Ducted AC systems
The ducted systems have the same roof unit, but the air box is very different. The roof unit is still mounted on the central part of the roof.
The air box inside the 14 x 14 roof opening. The air intake, the control system and two exhaust cold air ports are part of the air box up in that 14 x 14 opening.
Here you can see the two rectangular foil covered ~ 1/4 - 3/8" wall thickness foam insulation HAVC ducts leaving the air box. One heads to the front of the camper, the other to the rear.
Here is one of the ducts heading to the front of the camper. The duct passes through the rafter trusses.
Inside the camper, their is an air intake at the ceiling line of the air box. Looks like this. The square metal box is the control box that houses a PC control board. Has relays for the fan motor, compressor and has a defrost control
A white plastic grill goes on the air box inside. There is a white grate that goes over the open hole in the pic that is the air intake grate, just I do not have a pic handy of the grate installed.
Down the front and rear of the camper ceiling are ceiling registers. Three round ones are shown in the center to left area of the pic. (3 front, 3 back of the camper) They unscrew to allow more or less air per location to help even out the air flow. These round ceiling registers tie into the HVAC duct up in the attic.
The ceiling registers can then go into closed off rooms of the camper anywhere the HVAC duct runs. In this floor plan, the bedroom in the back with a sliding door on it. And it has a pass through bath with closeable doors.
That is sort of ducted versus non ducted AC systems, Sunline style. Other brands due this very similarly. Dometic makes all the air box parts etc. The ducts and ceiling registers by other RV parts places.
Hope this helps