Air Conditioning a Foam Camper Without a Proper Return

[NeilYoung]

ive got a tusca and trying to rig up air conditioning. so far ive come up with this. after 30 minutes the internal temp of the camper is 63f when the ac is set on 65. i know it’s not sucking the humidity out. are there any issues with leaving the ac like this with no “return” air. i know it will just run continuously. will it freeze up?

 

[Pmullen503]

Running a unit like that with the main unit outside is incredibly inefficient. As you noted, the humidity will never be reduced.

I've seen a window unit with intake and cooled air ducted in through a window. With that at least the inside humidity is quickly reduced as well as the temperature.

I suggest you try it at home. Just let it run for a few hours outside and see if it freezes up.

 

[NeilYoung]

i tried putting the unit inside but it it took up so much space. the box is 5x8. im going to get a few pieces of ac ducting and make a return for it

 

[Tom&Shelly]

We always run our AC with air from outside. When we tried taking air from the cabin it freezed up in about 15 minutes. Taking outside air works fine for us, even in humid areas.

Tom

 

[Camping Cur]

Interesting discussion! I have a single hose portable A/C that I converted to dual hose by attaching a duct and hose to the back main air intake. The hose sucks outside air in to the back of the A/C unit inside my 6X12 cargo trailer through 6" boat hull hatches. (Had to do this because it was creating a vacuum inside the trailer!) The hot exhaust air exits through another one on the opposite floor side at the front of the trailer. I have been wondering if I could do as the OP asked? Only, I would make a duct that would fit my little side windows that are 14X21 with the bottom portion opening about 12" wide and 10" high. It would save big time on floor space. We pay a daily rate at the campground for the electric so I am not too concerned about efficiency. Especially when I see 40' Class A busses with dual roof air units all sealed up and chillin' inside LOL. Tom, how have you been attaching the unit to your trailer? PS: If I did this I figure I would have to protect the A/C unit from rain by slipping a cover over the top. Now, If I could just find my remote control!

 

[Camping Cur]

PS: There is another small intake vent on my A/C unit down on the side. I keep that uncovered to pull in some of the air inside the trailer. If the unit were running while outside it would also pull warm outside air in through that vent as well. So, NO humid trailer air would be pulled out, only cool air would be blown in through the window. Perhaps not the best situation?? Back to the drawing board? A LONG air duct from the floor hatch to the back of the unit might do the trick, but YIKES that would be quite a job! However, if it pulled OUT hot, humid air it might be worth it!?? I don't want the expense of a roof mounted unit (1000-1500) and my windows are too teeny to attach a side mounted A/C to.

 

[DJ Davis]

After digging around on various forums that had A/C topics, I found that the answer is "mixed air." Remember, most of these units are 5K BTU or greater designed to cool +/-300 cu ft. Our campers are anywhere from 10 to 20% of that number. That means you have to trick the A/C unit into working longer to dehumidify the interior air. I turn on my A/C on low cool with the thermostat set at about 2/3 to 3/4 cool. I put my roof vent on positive flow (pushing outside air in from the top) on the next to the lowest setting and crank the cover open about an inch. I gap my side windows open an inch, as well, to allow the excess air to escape. That brings in about the right amount of warm outside air and pushes it down to mix with the cooled inside air to keep the compressor running longer. The result is cool, dry air inside where you want it! Yes, depending on your camper's interior space, outside ambient temperature, and how humid the outside air is, you might have to play with fan settings and gaps of the vent/windows. In hot arid climes (with low relative humidity) you don't have to worry about the damp air, but you will want to shade the A/C unit to protect the condenser coils from the sun's radiant heat. That helps the heat exchange of the coils of the A/C work better. I did Palo Duro Canyon State Park in June of 2025. The daytime temps were in the 100s. When the wife went inside for a nap after lunch, I noticed the air "coulda been cooler" in the camper. I grabbed a spray bottle with water and spritzed the coils periodically. The evaporative effect of the water cooled the coils and improved the efficiency of the A/C. By nightfall, the temps were in the 60s, so we didn't need the A/C.

So...you can get an A/C to provide cool, dry air as long as you can balance the inside and outside air to fool the compressor into running a longer cycle.

 

[Tom&Shelly]

Tom, how have you been attaching the unit to your trailer? PS: If I did this I figure I would have to protect the A/C unit from rain by slipping a cover over the top. Now, If I could just find my remote control!

It's just inside the right cargo door at the front of the tear, as seen in the thumbnail. We have a "utility room" for the AC and cargo that extends to about where the front begins to curve into the roof. In the thumbnail, you can just see the front cargo door. We open that whenever we run the AC.

(When we use it in heater mode, we found it best to leave that shut, and we vent air back from the cabin into the utility room.) We have that vent and the AC output vent in our headboard between us.

So our AC unit is well protected from the elements.

Tom

 

[NeilYoung]

im sitting at keystone state park outside tulsa right now. a front just blew in and its raining and 60ish out. very humid but im just gonna run my craftsman 20v fan tonight. i brought the ac just in case.

 

[NeilYoung]

last night i tried sleeping with ac blowing in the window. outside temp was 70 and i like it cooler than that. i had to keep turning it off and on with the remote. id wake up freezing and the temp was 58 inside. so i turn it off. go back to sleep and wake up two hours later hot. by 2am it was 65 so i opened the windows and pointed the fan on me. today i will stop by lowes and try to cobble together a return line. low tonight is 72.

 

[Camping Cur]

Thanks for info! That is a sweet setup for your A/C, Tom. Gives me some food for thought!

Neil, us SW Florida people are reaching for the heater controls at 65 LOL! We are heading out in the morning to a nice State Park North of Lakeland, Florida. The campground is in the middle of 5,000 acres and it is "supposed" to be like 59 in the morning and 85 in the afternoon under full sun. I might let the the A/C run in the afternoon in case a nap should come on. Then, by the evening open the windows and run our oscillating fan and the power roof vent. The 1" foam insulation and having the roof painted white really helps in this weather. Such good ideas all over this forum and us DIY camper people do appreciate the tips and tricks. Our next adventure in May will be our last one for the season since it gets so hot at most camping destinations in Florida that many are "sealed up" inside their rigs. I can do that at home LOL. Maybe by next season (beginning in October for us) we will have worked out the best, most economical solution to the A/C dilemma. I'm digging the idea of a separate storage area for a unit but would have to figure out where it would go. I do not want any more tongue weight, and I don't have a back bumper on the camper to mount anything to. So, for now I guess it will take up floor space up front and the hoses will exit through the floor hatches. Thanks folks for the replies!! And, Neil...if you do "cobble up" a return line, let us see your "Franken-Ductwork"LOL!!

 

[NeilYoung]

here is what i came up with. a quick trip in to town for some dryer duct. if the compressor cycles through the night and maintains temp, i will create a more permanent solution.

 

[NeilYoung]

not sure if its a success or failure. when the camper got to temperature, the thermostat turned off the compressor. while the compressor was running and cooling the camper, the humidity was in the 50’s percent. when the compressor shut off, the humidity would jump up in the 90 percents.

friend of mine thats an ac tech says my return line it too small and it’s pressurizing the camper. when it shuts off the pressure sucks the outside air and humidity in thru all the cracks and vents. so the franken ductwork experiment continues.

im watching marketplace for an ecoflow ac or a small rooftop ac.

 

[Tom&Shelly]

We crack our skylight when we run ours. The excess air (warmer because it's near the ceiling) runs out.

Sorry, I should have mentioned that above!

Tom