On a DIY Cargo Conversion you need to put much thought and planning into your choice and type of Air Conditioner unit you eventually select.  Then just as much thought into its capacity size, its final location, and installation methods.  Other factors such as insulation will dictate unit capacities. 

There are issues you want to consider having to do with types.  The varied options of air conditioner units are listed in order of desirability based on cooling performance, installation issues, problems created by installing, and replacement issues down the road.  The top of the list being the most compatible.  There is a reason commercial builders select the RV Roof Air type over all others, unless you step down to a commercially built economy rig that lately are coming with window units adapted into a wall.

RV Roof Air
Split systems
Window Units (or other portable options)
Hacked window units to DIY a mini split

Portable Dual Hose units
Portable Single Hose units

Bear in mind there is probably a very good reason [cost, serviceability, reliability, noise issues] commercially built Travel Trailers and RVs come with RV Type roof mount units.  I have even read they are built to withstand flaky power at neglected campgrounds.  Or the varying power of portable generators.

I sourced my RV Roof Air off eBay.  New in the box shipped to my door.  Not as expensive as many prices you see.  Other sources of deals are local RV dealers.  They are often removing new units to swap out to higher capacity (for demanding customers).  Especially more prevalent in the desert southwest where the climate is much hotter and customers need upgraded capacity.

Be extremely careful you do not under rate your BTU needs. 

At the time of our latest conversion the smaller “split unit” systems were just becoming popular.  I think should I do a new conversion in the future, I would seriously consider a “split system air conditioner unit”.  But that would require gathering more data on noise, reliability, and the ability to operate on a fluctuating power source. 

Most split systems I have seen on travel trailers have moved the outdoor half of the system onto the trailer tongue.  Though pointed forward the noise is again down low, more at head level.  I would need more input to pass on info concerning a split system.

With side mount “window type” units, bear in mind your neighbors, and yourself.  Especially when positioning the unit.  You will be pointing the noise at someone, most likely right at head level and maximum hearing annoyance.  They are not conducive to sitting around your campfire.  Not tolerated well by your neighbors on the drivers side [if located there].  If installed on “their” side [neighbors site side] , expect complaints.  Or at a minimum, silent complainers that lead to other issues.  This commonly happens when in RV parks and organized campgrounds.  If you are a 100% boondocker this may be a non-issue.  But it is a very serious consideration.

Our initial thought was to build with a lower priced window unit.  Our initial priority was based on cost/money.

On the surface the window unit seems like a more economical solution.  There are plenty of aesthetically satisfying installations.  Those that are flush mounted to the exterior and built into interior cabinets to blend in.  But what looks good doesn’t necessarily function well concerning cooling, water leaks, or noise  issues.

No way would I install a window unit through the trailers front wall.  I have talked to too many DIYers that thought they could keep rain out while driving down the road.  They say “Big mistake”!

Dual Hose Portables rank about even with the performance of a window unit.  The problem becomes the space they occupy.  The space the two hoses and the unit itself consume.  Also coming up with a satisfactory intake and exhaust location and configuration which require holes that also don’t give you problems during rain, bugs, or rodents.

There are some creative installations through the floor, or through the walls using marine screw in hatch covers, and so on.

The Single Hose Portables are the least desirable and there are many complaints.  If the unit is blowing out through an exhaust port.  It creates negative pressure inside the enclosed interior space.  Outside air has to “leak” in at any place it can find.  If it can’t leak in enough outside air, the compressor overheats, shuts down, and the blower basically blows out hot air.  They do make effective heaters in the scenario!

If they do leak in enough outside air to function, and it is raining, expect water to come in too. 

Climate, and your trailers insulation, probably are the most determining factor when it comes to “How many BTU’s do I need“.  There are formula’s if you want to get technical.  If guessing, I highly recommend you go bigger than you think.  Most trailer conversions are not insulated anywhere near as much as a house.  The majority of DIY Conversions result in non-insulated windows, floor not insulated, and those with a draw bridge type rear door normally do not have that surface insulated.

We ended up installing a 13.5K Low profile RV type roof air on our insulated 8X16 Cargo conversion.  In hindsight with some years behind us now.  We are glad we went with a larger unit, the roof mount arrangement, and the added expense.   There have been a few occasions we wish we had installed a 15K unit.

We did a lot of research and questioned many on this “window unit” installation.  Here is some of the candid and honest feedback listed as bullet points.   Its difficult to get to the truth with some people that are more interested in bragging about their DIY.  They often will not be honest about negative things.  That feedback sitting around a campfire, can slant decision making, by those with no experience.  We are all simply looking for honest facts.  Good or Bad.


Positives of a RV type Roof Mount Air Conditioner

  • Used for years in the RV industry.  (usually an indicator of valid use reasons)
  • Most if not all use a standard sized roof cut out that is also the size of most crank-up roof vents.  You can start with a vent and switch over later.
  • Replacements in the future are relatively simple from unit to unit.
  • Their installation if done correctly is straight forward and they don’t leak
  • Some sources indicate some of these are built to withstand fluctuating power without damage.  Beneficial on generators, or crummy park power.
  • With the proper unit you have the option of extending thermostatic control to a wall device that also operates your furnace.
  • Noise is above the roof, above head & ear level, normally pointed to the rear, and not pointed at your neighbor on the drivers side, nor pointed toward your outdoor area typically on the passenger side. 
  • Some have optional heating strips that may provide adequate heating without a secondary source such as a furnace.

Negatives of a RV type Roof Mount Air Conditioner

  • Weight.  They are heavy, exceeding 100lbs
  • Requires additional roof support in most cargo trailers
  • More difficult to install by a lone person, on the roof, due to the weight.
  • In most cases they require their own 20amp Branch Breaker & #12 Copper wiring
  • Takes a substantial generator to start them up.  2000 watt or less, generators, often do not work, or struggle to power them. 
  • Thermostatic control is often low, medium, high.  Meaning it runs all the time.  May take an additional optional package to extend it to a wall mounted thermostat control that also can function to control your furnace.

    Positives of a “window unit” air conditioner

    • Cheaper purchase cost over the alternative RV type
    • Can be installed in wall rather than roof
    • Lower BTU, lower amp draw, smaller generator requirements

    Negatives of a “window unit” air conditioner

    • Tricky installation to avoid weather leaks
    • Installation issues to prevent condenser coil condensation water problems.  Proper draining is required.  All custom work many fail at.
    • Proper baffling is needed to isolate intake and exhaust air.  In most installations this must be custom created.  All custom work many fail at.
    • Installing anywhere in the front/nose wall is asking for weather/water problems.  Special custom covers might be needed to prevent rain blow through when driving, or rock damage from flying gravel.
    • Some type of substantial support will be required.
    • In most cases is would be wise to provide their own 20amp Branch Breaker & #12 Copper wiring
    • Thermostatic control may only be low, medium, high. 
    • A set temperature thermostat on the wall away from the unit in most cases is not possible
    • Once installed and the unit goes bad can you find the exact sized replacement to avoid trailer modifications to adapt?
    • Can these units perform without damage when operated on crummy power and fluctuating power often found in poorly maintained campgrounds, or when running off generators?
    • Either you or your neighbor on the drivers side is going to be plagued by noise when sitting outside.  People with side mounts on the driver side sometimes get complaints from neighbors.  Do you want it pointed at you while sitting at your picnic table or campfire?  A big consideration if you haven’t thought this through.