Installing an Air Conditioner in Our Aliner

April, 2006

From the beginning, Sandy and I knew we wanted to have air conditioning in our camper. Because Aliners have sloped roofs the usual roof-top RV type AC units can’t be used. AC is available as a factory option. It consists of a standard window unit installed through a hole in the sidewall, which is fine. The factory installs their unit in the side of the trailer just aft of the entrance door. This is an easy location and makes sense for many of the available Aliner floor plans. However, in our floor plan this location precludes the use of one of the settee benches, especially when the unit is on. In our Aliner floor plan there is open wall space at the end of the galley in the front of the unit. This a good location for an air conditioner because it is out of the way and provides an excellent air circulation pattern.

Front Wall of Aliner with Propane Tanks to be Moved

There are difficulties, however. For one, the propane tanks on the trailer tongue must be moved forward to clear the portion of the AC unit that protrudes from the front of the trailer. The unit cannot protrude more than about five inches inside the unit so that the door to the fridge can be opened all the way. It has to be carefully protected from water intrusion while driving since it’s on the front of the trailer. And, finally, the front of the trailer is not flat which complicates mounting the AC unit.

I purchased a 5,000 BTU, Kenmore model 580.75050, room air conditioner. It is a low end unit with manual controls, etc., but it meets the dimension requirements, is quiet and is light in weight.

First, I needed a flat structural mounting flange on the air conditioner that could be sealed against the outside aluminum camper skin. I removed hardware for window mounting from the unit. I then framed it with 1″x1″x1/8″ aluminum angle fastening it to the air conditioner case using the screw holes for the window mounting hardware. The frame was angled slightly to provide drainage as recommended by the manufacturer.

Air Conditioner with Mounting Flange Installed

I hate cutting holes in boats and campers because it’s tough to hide your mistakes. The old adage of, “Measure twice, cut once”, applies in spades! I made carefully measured sketches of the installation long before I did any cutting but you never know when you’ll hit a gotcha! In this instance I was lucky. I decided I’d mount the unit so that the top edge of the AC unit would be at the upper seam in the interior paneling, where the wall tilts inward 30 degrees from vertical. I removed the small storage compartment/wire concealment from lower part of the wall and marked the outside of the camper for cutting, allowing 1/8 inch margin around the AC unit. Cutting the hole was easy if nerve wracking. I used my saber saw with a fine blade and it went through the camper like the proverbial hot knife through butter. It was a tad tricky trimming the inside paneling so that the hole was level on the bottom.

Hole Cut into Front End of Campe

I was lucky to miss the electrical supply wire to the ceiling light. It is buried in the wall, routed through the fold in the wall before bending upward toward the fixture.

Ceiling Light Wire, Narrowly Missed

I sealed the raw edge of the cut using two layers of 2″ wide, metallic aluminum tape. The tape provides a secondary water intrusion seal but is not really necessary. The real moisture seal will be the caulking between the mounting flange and the aluminum skin of the camper.

Hole Sealed with Aluminum Tape

Next came the tricky business of designing and building an inside clamp frame that could be bolted, through the camper wall, to the aluminum angle frame on the AC unit. I say tricky because the inside wall is not flat so the clamp frame would have to conform to the angles of the inside wall. I chose to make it of oak to match the paneling of the camper. Fortunately, I have a cabinet-maker friend who lends his considerable expertise and allows me the use of his extensive wood shop. It was a fun afternoon, learning how to make mortises on both flat and angled joints … and it all worked! The finished clamp conformed perfectly to the inside wall of the camper and fit closely to the outside dimensions of the AC unit.

Finished Clamp Frame

I carefully dry-fit the components to make sure everything would work. After sanding and finishing with a couple of coats of tung oil. I used a drill press to drill and countersink holes in the clamp frame for 1/4″ mounting bolts and drilled matching holes in the aluminum flange on the air conditioner. I then did final installation of the flange on the AC unit, sealing it with silicone. With Sandy’s help, we dry-fit the components through the camper wall, and drilled through the camper wall and fit the 1/4″ stainless steel screws. Finally we unassembled the components, applied sealant and bolted it all together. Looks good … whew!

Finished Installation – Exterior
Finshed installation – Interior

I’ll reroute the exposed wires and trim out the installation after I complete a couple of other projects. The factory duplex receptacle forward of the refrigerator will be used to power the AC unit. I’ll run a new supply wire directly back to a new, dedicated breaker in the power panel.