The Under-Couch Air Conditioner Install...

Before the front couch could be built, certain things had to be done under it, basically cutting the vent holes through the floor for the condenser side (outside portion) of the air circulation. But first, a little about how air conditioners are supposed to work.

It's curious that the only portable air conditioners I see at the builder's stores is the type that only has one hose. Those who have no clue as to how an air conditioner works probably doesn't even think about how inefficient these types are. But they should.

Think about this for a second...where does all that air come from that gets exhausted outside through the hose that is attached to them? It has to come from somewhere, and the only place it can be drawn from is from the room itself! That means that for every cubic foot of air exhausted to the outside, that portable air conditioner has to suck air into the room...through vents, through cracks in trim, through poor door seals, or even through partially open windows. And that air is hot outside air that the unit then has to work harder on to get it cooled down to the cool air that you actually want!

Why would anyone in their right mind try to take 90+ degree air and try to cool it to roughly 65 degrees, when they should be taking the ambient room air that is much closer to what they want to begin with? And why bring in more of that hot air from the outside, when you are trying to stay cool?

This is why normal air conditioning systems have two separate air paths. In the case of a window unit, the front part pulls air from the room, cools it over the evaporator section and then returns it to the room. The outside part circulates outside air over the condenser section, removes the heat collected from the inside, and returns that air to the outside. The two air paths never mix!

This is why an efficient air conditioning system never sucks outside air into a room. It uses the already cooled air within the room so it doesn't have to work as hard, and also can cool the room off quicker and hold that temperature!

There ARE portable air conditioners that have two hoses...so that they suck outside air in through one and exhaust it through the other. So why don't the builder stores carry them? It's probably a matter of cost, and the fact that they can dupe the unknowing public into believing that they can spend less money, when the reality is that a single hose unit will end up costing them money in wasted electricity!

If you look on Amazon, there are all kinds of makes and models of portable air conditioners that have two hoses, but expect to pay about 10 to 20 percent more for them. However, you will recover that money within the first few months of using them...because they are much more efficient, and work the way they are supposed to!

OK, so back to my own project. I had three reasons for wanting to use a window unit, and part of that was cost. They are typically at least 1/6th the cost of a typical RV rooftop unit, and also much more readily available. Secondly, they are normally much lighter, and I also didn't want to take away roof space, knowing that I would eventually put solar panels up there. Adding extra weight to a roof that was never designed to carry it is asking for future structural problems, as well as making the trailer top heavy. The third reason (at the time) was stealth, but I really consider that reason very low on the list.

As far as location, I could have been satisfied with a wall, but which one? If it is put through the front wall, then the fins on the air conditioner are subject to damage from anything kicked up by the rear wheels of the towing vehicle, as well as rain and weather practically being forced into it. Even if a cover is put over it, the edges are still subject to getting wind-driven rain blown in and finding its way down the wall or into the interior. No matter how good you think you can seal it, the power of the wind when going down the road at highway speeds, coupled with the normal vibration of travel is going to break any seal that caulking or anything else can provide, and force water into the trailer.

Although mounting it on a side wall would be somewhat better, and it would still be within safe limits (since the wheel wells on the trailer already stick out at least that far), it still presents the opportunity for rain to enter on the leading side. Also, anywhere it could be put on the inside walls would take away from overhead cabinet space and/or future window space. Again, the front wall is the only place that wouldn't have a window or cabinets, but then it would become a head knocker for anyone sitting on the couch.

And with a ramp door, it was impossible to put it through the back wall. After seeing several of the new smaller-sized camper trailers being made with the air conditioner down low, I figured why not put it under the couch? All it needs is proper vents, and the problem is solved! Granted, cool air drops and hot air rises, which makes them much more efficient to be mounted up high, but that can easily be overcome with a little extra air circulation from a fan. Not a big deal, as we'll have one with us anyway, and the air conditioner won't be run unless we're plugged into a pedestal.

Laying out the front wall of the couch to accommodate the air conditioner.

The first step was coordinating how deep the couch had to be in order to allow for the pull-out section in the front, which converts it to a bed. Keep in mind, this isn't some pre-engineered layout worked out on a CAD system and CNC routing equipment. This was a "build it as you go and see how it fits" kind of project...like a prototype. Besides the couch layout, enough space had to be allowed behind the air conditioner for proper vent sizing.

Here's the important part...in ANY kind of air flow work, you always want to provide as much air flow as what the device was built for. The shape of the opening isn't as important as the square inches. In this case, I measured the rear opening of the air conditioner, where the aluminum fins are. That is the outgoing air part, and to get that air outside, you have to provide as large a hole down through the floor as that opening on the unit.

The same goes for the side vents, where outside air is sucked into the unit. You need to measure the size of those louvers, and make sure that you have an equivalent size opening in the floor on each side of the unit, so that it can "breathe" properly. If you don't, it will take away from the efficiency of the unit in cooling, and possibly even make the fan work harder and draw more electrical current, which in turn, could lead to premature failure of the fan motor.

The air conditioner fitted to the couch front.

I had originally thought I could leave the side expansion wings off and just build the unit into the couch front, but decided to leave them on at the last minute. The main reason was that if I built it in too tight, and then had to change the unit out if something went wrong with it... a different unit might be larger in size, and then I would have a problem. By leaving the expansion wings on it, It gives me an extra three inches on each side to allow for a larger unit, if it should ever come to that.

On the outside edge of the wings, is a flange. In order to get everything to fit together properly, I cut saw kerfs into the studs on both sides of the air conditioner, so that the flanges fit into the slots.

The bottom plate of the wall also had to be notched to allow the air conditioner to sit into the wall properly. Because of trying to stay to a certain height with the finished couch, I couldn't just set the air conditioner into a hole in the wall, or the couch would have been too high by the time the top trim and cushions are added. Ideally, the top of the couch cushions should be at 18-inches, or close to that. 

Another consideration is that any air conditioner has a place on it somewhere on the bottom to drain away the condensate water that it collects. You can't forget this important feature, or you will have water draining out onto your floor! In this case, I had to keep the air conditioner up off the floor about an eighth of an inch, to allow for a drain funnel to be installed in the floor under the drain opening.

For this, I used an extra plastic funnel that we had in the kitchen. It was only about 2-1/2 inches wide at the top, with a 1/4-inch opening at the bottom. I used a hole saw to create the hole, but found that the funnel set too high in the opening. I didn't want to cut the funnel as it had a nice lip at the top that would keep it from going too far down in the hole. So I used my Roto-Zip tool again, converting the 1/8-inch collet to standard 1/4-inch collet to hold a normal router bit. Then I used a ball bearing round-over bit and went around the top edge of the hole to widen it slightly. That worked perfect. The funnel now dropped into the hole with just enough at the top to fit tight to the bottom of the air conditioning unit, and centered with the drain hole.

In the photo below, you can just see the edge of the funnel sticking out from under the edge of the air conditioner about 4-5/8-inches in from the back. To fill in under the rest of the unit, to get it to set level, I inserted a piece of 1/8-inch paneling to support it.

Note the edge of the drain funnel at the edge of the unit.

The holes for the vents had to be measured to make the best use of the space on either side, as well as the back, and still allow enough square inches for proper air flow. Notice in the photos, that although the holes are longer and narrower, they are still approximately the same size as the louvers in the sides.

This air conditioner was a little strange, as it also had louvers in the top. Most air conditioners don't, simply for weather protection...to keep rain out. In figuring the size for the incoming air vents holes, I also had to account for about half the size of the top vent (times two sides). It was obviously put there for a reason, and should not be ignored.

There is about 2 inches of space between the bottom of the couch seat platform, and the top of the air conditioner, so this top set of louvers can still "breathe" in some air.

The air conditioner with the divider wall for the storage compartment.

In the photo above, you can see the divider wall that separates the air conditioner compartment from the storage compartment to the left. Notice that I made this wall to set into guides, so that it can be lifted straight up and removed, if any work should have to be done around the air conditioner.

At this point, I still have to get in there and install screens and filters. I will probably make some little "Z-shaped" sheet metal brackets to fit around all four sides of the screens. These brackets will be screwed directly to the floor to hold the screens down. A second set of brackets with a deeper offset will be installed on top of the first set (on the side vents only) to hold the filters in place. This way, the filters can be changed without disturbing the screens.

The screens will be two parts. The bottom screen will be a heavier "hardware cloth" type of screen with heavier wire and 1/4-inch holes, for rodent protection. The top layer of screen will be a normal aluminum screen, for bugs.

I have seen rodents eat through normal window screen or tear it up to get into places, so the heavier hardware screen will prevent that. No filter will be on the rear outgoing air opening, because that air will be blowing out. 

The vent holes in the floor on the back and right side.

The vent holes through the floor had to be laid out very carefully, making sure to allow enough space around them to secure the pieces that will hold the screens and filters in place.

Cutting these holes was harder than it looks. I started out by drilling 3/8-inch holes at all four corners of each hole. I then started with a saber saw, but soon found that I couldn't get all the way into the corners of some holes. Also, I ran into steel frame parts under the floor, which was expected and unavoidable. So again, I went back to the Roto-Zip tool, with 1/8-inch "saber" blades, designed to cut clear to the bottom and sideways. By setting the depth to the thickness of the floor, I was able to cut all the way through the plywood and yet over the top of the steel frame. But then I still ran into places where I could not get into because of the base plate on the tool.

So as a fourth option, I got out the reciprocating saw (a B&D industrial grade "saws-all" type tool), which cuts straight down, and with a longer blade. This allowed me to finish the cuts in the tight corners. Still, all in all, with having to fetch different tools and get them set up properly, it took nearly two hours just to cut these three vent holes. And the air conditioner wasn't even in the way at that time!

Notice the frame and part of the trailer tongue taking up part of the outgoing air hole at the back. This was a situation that I rather would have avoided, but couldn't be helped. Yes, the parts in the middle of the opening might obstruct the air flow just a little bit, but I cut the vent hole as large as I dared to, and it shouldn't be a big problem.

Just remember, that if you do something like this, you won't be driving through any flooded streets (which you really shouldn't do anyway), or you will flood the interior of your trailer! Driving in normal rain shouldn't be a problem, as the frame parts will partially divert the road spray away from the openings. But still, check it out before you do too much of that kind of driving! I will be, and if necessary, I'll add some diverter hoods to the bottom of the trailer.

Now, here is another important part! To keep the incoming air from mixing with the outgoing air, you HAVE to create a baffle between the two. For this type of installation, it is simply a matter of making a three-sided box...with a couple of modifications.

The rear baffle with the diverter in place.

In the photo above, you will see the rear air baffle. Note the diverter inside it. That diverter helps to direct the outgoing air downward, plus it strengthens the box by keeping the sides parallel. Yes, the box will still trap the air and normal pressure would force the air out the bottom, but any airflow is made more efficient when it gets a little extra help in being "directed" where you want it to go. That's what the angled baffle plate does.

If this were made out of sheet metal, you could actually use a "sweep 90" with a natural curve in it, but it's too much hassle to bend wood in a curve, so an angled (at approximatley 45 degrees) piece works nearly as well.

No front, back or bottom is necessary on this box, because the back and bottom are the front wall of the trailer and the floor, and the front is open to go over the back of the air conditioner. The only thing that is really required is to secure the box to keep it from vibrating out of place. It wants to remain centered over the back of the air conditioner, so that it doesn't allow any openings where air can be transferred to the incoming air. That would just warm up the incoming air and make the unit less efficient!

The rear outgoing air baffle set in place.

In the photo above, you can see the rear outgoing air baffle mounted in place. The top was cut to the rounded contour of the front of the trailer. Two little 3/4-inch square cleats down each side and screwed to the front of the trailer wall are all that is needed to hold this baffle in place. You want to be able to pull it straight up to occasionally check the screens and clean or repair them if necessary, as well as to check for any water damage. 

This baffle also serves another purpose, and that is strength. If the trailer is ever involved in a front collision, this baffle will keep the heavy air conditioner from ripping through the front wall of the couch. In the case of a rear-end collision, it could still move out through the front of the couch, but to prevent that from happening, we will attach some eye screws down through the floor on either side of the air conditioner, and use a ratchet strap to secure it. Using perforated pipe strap and screws to secure it is not enough strength for a moving vehicle and a component weighing this much. A collision would rip those out in a heartbeat!

Just for anyone curious, this floor is made of 7-layer 3/4-inch outdoor grade plywood, topped with 1/4-inch luan and then 1/8-inch thick commercial tile, making the entire floor 1-1/8-inches thick.

The air conditioner covered with the couch seat.

In the photo above, you can see the completed (or nearly so) couch seat covering the air conditioner. The only thing not finished here is the blonde paneling that will cover the front of the couch. In order to maintain at least 13 inches of space (for my big feet) between the couch and the kitchen cabinet, I had to add the heavier plywood backing for the paneling within the studs of the couch front, rather than over the top of the studs. When the paneling is applied it will cover the expansion wings on the air conditioner and fit right up to the box itself.

In the next post, I'll show more about how this couch actually works, to pull out into a 33-inch wide bed. Then the post following that one will show the rear bed, and the wall that divides that from the rear storage compartment.

Other than stubbing the pipes through the floor for the fresh water and drain pipes, and then anchoring the kitchen unit in place, this completes all the larger pieces for the trailer. I still have to make two pull-out pantries and all the drawers and cabinet doors, but those will be much smaller projects and smaller pieces of wood used. If I don't get any of the trim done before we leave, I can also do that small stuff later, even on the road during our travels if necessary.

Also, the air conditioner is now functional, and most of this work (except for the actual sawing) can be done in relative comfort, even if the heat and humidity sticks around. We have had temperatures in the mid-nineties and high humidity, making it very uncomfortable to get anything done in the afternoons. The sun hits the back of the trailer directly between noon and about 5 PM, so I am glad that part is now done. Being able to work in air conditioning will be wonderful!

I now have the last three drawer slides, the faucet and sink basket for the bar sink, and the plug strips for power distribution. So as soon as the slides are installed, and the kitchen unit is anchored down, the bar sink can be cut in. Then I can also get the new double door refrigerator out of the garage, change the door swing on it, and get it installed on the countertop. The wiring and plumbing still has to be done yet, too, as well as the dividers between the porta-potty and batteries in the bottom of the closet, but barring any other obstacles, we should have this cargo trailer camper conversion ready to move into by early July.

We want a little time to actually experience living in it in the back yard, before we leave here, to get a feel for what else we need to put in it and how to pack things before leaving here...hopefully by the 28th of July. It isn't critical if we miss that deadline by a few days, but that's what we're shooting for. That's only 46 days away, and we still have a lot to do in the house yet, as far as sorting through and getting rid of excess" stuff".

And by the way, you have already seen that the couch is mostly done, but also, the back wall behind the rear bed is finished, too, so you will get the next two posts within the next couple of days. Then it might be a few days again before I have the kitchen unit ready to photograph and post.

I know at least one person who saw our YouTube video "Ed and the Aberts" who was interested in how this air conditioner would work below the couch, so I hope this was helpful to him and anyone else planning their own cargo trailer camper conversion. If you have any thoughts or questions, please let me know in the comments, and I will be glad to answer any questions.

Thank you for following along with us on this project, and the travel adventures coming up soon.