Air Conditioner Expectations

RMHarville

Advanced Member
RV LIFE Pro
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Apr 10, 2024
Posts
34
Location
Medina TN
We have just taken our 3rd camping trip in our 2024 Keystone Cougar Fifth Wheel 29RLI. Our unit has 2 air conditioning units. The outside temperature was around 85 and humid as is the norm in west Tennessee. Our unit struggled to get the temperature below 74 in the main living area. The bedroom was fairly comfortable. At night and in the early morning every thing was ok.
The fifth wheel is new to us. We had a small bumper pull until now. My question: is that normal? Are my expectations of around 70 unrealistic? Is there any service I need done? I cleaned and washed the filter.
Thank you
 
Take a thermometer and measure the air temp at the overhead RETURN DUCT and then measure the temp at t( overhead AC ducts You are looking for a temperature differential of 18 to 22 degrees difference from return duct to outflow ducts

Repeat for other AC unit ..

Note .. run one AC at a time when making the temp measurements to get an accurate temp differential reading

The ductwork is connected together for both AC units so that is why yo7 want to make your temp measurements on each AC

If you see 18 to 22 degrees differential at each AC unit then they are doing what they can

I easily can drop temps down in my fifth wheel to 68 degrees with outside temps in the 90s
 
Read some threads on here about mods and improvements that need to be investigated. There is poor workmanship in the ductwork and installation of these AC units. Things can be done to improve air flow dramatically.
 
+1 to checking your temperature differential and checking for proper fit/installation.

You're also fighting solar gain, not just outside air temperature.

The sun hitting the huge surface area of your trailer is heating the skin to the tune of about 4000W of input power (assuming your trailer is a clean white color). This is the equivalent of about 13,600BTU/hr, so basically ONE of your A/C is neutralizing the solar gain while the other is actually cooling the interior against external ambient air temperature.

If you have awnings that can shield surfaces from the sun, that helps.

In cases like this, it's important to get started BEFORE the solar gain. Get the unit cooled down to the desired temperature BEFORE the skin is heated, and then it's easier to maintain throughout the day.
 
There are many variables that are factors to conditioning the air either up or down from the ambient. The a/c units do not have service ports so taking pressure readings isn't possible. Some visual clues to a/c units with issues is to look for water running out of the unit. The units should be condensing water out of the air when the compressor is running. If there's no condensation or the refridgerant lines and or condenser coil is frosted over or blocked with ice then that's a big problem. As previous post have suggested the first step is to record the temperature differential of each unit. If that is within limits then that "rules out" an issue with the cooling units.

Once confirming that the units are performing OK it's time to chase down the deficiency. Next step, check the air distribution and return air plenum for obstructions and air leaking to/from the roof system. Those are common issues where often times the factory either did a poor .install or the tape or insulation comes loose after use. If that all looks good then it's time to review some of the other factors that impact the efficiency.

Check for major air leaks around slide outs, plumbing transitions, windows and door fitmants etc. Trailers are terrible thermal barriers with very low R ratings when they are sealed up well. Adding to that with air leaks, thermal absorption with radiant heating via the windows, etc can make maintaining a comfortable environment exceedingly difficult.

Some simple steps in how you use the trailer can make a difference. Using window coverings can make a huge difference if you can block the direct sunlight. Waiting until the heat of the day to start the a/c puts the trailer behind the eight ball, especially in high humidity environments. Keeping the doors closed as much as possible can be challenging when young children are around. I've seen some folks stand with the door open and talk with someone outside for several minutes.

I don't know if your slide outs have awnings but in my personal experience they help reduce the temp inside. The "little" things can make a difference cumulatively and make an apreitable difference. Let us know how your investigation goes.
 
Thanks so much for the input.
I will do the temperature check y’all have recommended.
My follow up question is if the temperature variation is not there, what can be done?
Do these units use Freon or something similar?
Thanks again.
 
Expecting to see 70F in 85F outside weather isn't realistic I think. It was suggested you read threads on improving cooling in the unit. I have a 15K BTU Dometic A/C and a 14.5K BTU portable exhausting out the window. I have the windows tinted dark, I have an RV Airflow device in my A/C lower part, I have resealed the ducts with HVAC tape, I have added pool noodles to each end of the run, I have covered the skylights in the bedroom and kitchen with a square pillow shaped deal made for blocking heat from the outside, I run a pedestal fan and I am sure there are other things done I can't recall. Our temps on a normal sunny South Texas day are in the mid-70s and we are happy with that. Of course, the normal temp on this type day is triple digits of close to it. Look at how your slide out is constructed and cardboard box is an appropriate analogy.

The cardboard box with a couple inefficient air conditioners and while 28.5K BTU should be plenty in a small camper, there is no insulation to speak of so take the steps you can take to make things better and enjoy 85F outside temps (we call this winter hehe). :rolleyes:
 
Thanks so much for the input.
I will do the temperature check y’all have recommended.
My follow up question is if the temperature variation is not there, what can be done?
Do these units use Freon or something similar?
Thanks again.
The RV A/C uses coolant similar to freon but the system is closed and can not easily be added to. I doubt there is anything wrong with your air conditioners.
 
Thanks so much for the input.
I will do the temperature check y’all have recommended.
My follow up question is if the temperature variation is not there, what can be done?
Do these units use Freon or something similar?
Thanks again.

You'll likely find a poor installation issue where you're getting leaking between the intake and discharge.

This video shows an example of what can be done:

 
If an a/c unit is not cooling then it needs to be investigated as to why. If the thermostate is working and the compressor and fan is running and the coils are clean and the airflow is not restricted then it's an indication of an issue within the unit. Unfortunately, RV air-conditioned are not considered "repairable" if there's a refrigerant leak or a compressor failure. RV dealerships will replace a fan motor or some electrical components but that's about it. The a/c manufacturers don't offer compressors or replacement coils for sale. The labor costs to make major repairs is just cost prohibitive.

When you think about the RV roof top units are nothing more than a large windows a/c unit strapped to the roof bouncing down the highway.
 
RV's, especially the "Super Lite", "Ultra Lite" and "Half Ton" variety are not much more than a "mountain tent" from the 1940's. The kind of tent used for "winter mountain hunts". Every tent has a wood heater with a chimney through the roof. As long as the heater has wood, the tent is tolerable, especially if your bunk is close to the heater. When the wood burns down and the fire goes out, it only takes about 3 minutes for ice to start forming on the inside walls of that "mountain tent"... It's near the same with a "modern light weight RV"... Single pane windows, minimal insulation, lots of air leaks around the slides, inefficient air conditioners and questionable cold air ducting in the "barely insulated ceiling space" all tend to make that "RV tent" perform (or not perform) any better than those "ragged old tents with a wood heater"....

You can typically cool a room in a S&B house with a 5000-8000 BTU window unit. You'll be extremely lucky if your 15000 BTU rooftop air can keep the main cabin comfortable in 80F daytime temperatures with the sun beating down on the trailer roof and sidewalls.... It's near impossible to keep the interior below 80F when the outside temps reach 100F+ and the sun defeats any hope for comfort inside.....

Yes, you can make it cool inside, but that will mean a second AC unit (for trailers longer than about 28') and lots of "accommodations" such as slide roof covers, parking in the shade, supercooling the RV in the early morning hours (to get a head start) and blocking/shading all those single pane windows during the day (sort of like living in a cave) and forget cooking on the inside stove or using the oven and "make opening the door to enter/exit a "well thought out plan, timed specifically to meet quick and limited frequency."
 
Expecting to see 70F in 85F outside weather isn't realistic I think. It was suggested you read threads on improving cooling in the unit. I have a 15K BTU Dometic A/C and a 14.5K BTU portable exhausting out the window. I have the windows tinted dark, I have an RV Airflow device in my A/C lower part, I have resealed the ducts with HVAC tape, I have added pool noodles to each end of the run, I have covered the skylights in the bedroom and kitchen with a square pillow shaped deal made for blocking heat from the outside, I run a pedestal fan and I am sure there are other things done I can't recall. Our temps on a normal sunny South Texas day are in the mid-70s and we are happy with that. Of course, the normal temp on this type day is triple digits of close to it. Look at how your slide out is constructed and cardboard box is an appropriate analogy.

The cardboard box with a couple inefficient air conditioners and while 28.5K BTU should be plenty in a small camper, there is no insulation to speak of so take the steps you can take to make things better and enjoy 85F outside temps (we call this winter hehe). :rolleyes:

The portable unit you have exhausting out of your window, i have been thinking about doing this during the two hottest trips we make in July and August. I have the perfect place and could plug in the unit to the outlet where the washer/drying hookups are...I would assume that outlet could handle the A/C, right?
 
All great tips but I'll add just a few more

RV Airflow Systems- It works really well and we've been pleased with ours

DUCTS- Take your vent covers off, and seal off the "attic" space with foil tape. I was losing tons of air to this attic space. Between this and the RV Airflow system, its made a huge difference.

Dehumidifier- We bought a stand alone dehumidifier off Amazon and we run it non stop in the main living area and another smaller one in the bedroom. If you can cut the humidity down, it will feel drastically cooler. Also, removing moisture in the air will help prevent the coils from wanting to freeze on you.

FANS! We have a tower fan in living area, tower fan in bunk room and big fan in the from bed room. Keeping the air moving, There are a lot of spots that will hold warmer area.
 
For comparison, most automotive a/c units have about a 12K but capacity for an interior space about the volume of a typical RVs bathroom. Larger vehicles like SUVs can have units that are double or triple that capacity. Also for consideration, vehichels are nearly air tight, have windows that block UV light, can only accomondate a few bodies and there are no heat producing appliances to deal with.

This is just some "food for thought" when considering the challenges faced when cooling down a trailer with the available BTU units provided.🤔
 
The portable unit you have exhausting out of your window, i have been thinking about doing this during the two hottest trips we make in July and August. I have the perfect place and could plug in the unit to the outlet where the washer/drying hookups are...I would assume that outlet could handle the A/C, right?
I have a 30A service going into my trailer so plug the 14.5K BTU portable into a pedestal outlet rather than into an outlet in the trailer. The outlet you might use (washer/dryer) might just work. Our window opens about 5-6" and I have cut out a wood piece that fits the hole (not square) and has a port for the exhaust. Some folks say that a portable with two hoses works better; dunno as I have never used one. Ours is pretty effective and the only negative is that the airflow out points upwards so we keep a pedestal fan in front of it to direct cool air.


portableAC.jpg
portAC2.jpg
 
Great input!
I texted my mobile mechanic guy.
He is going to come and check the unit out.
I like the idea of the fans and/or the portable air unit thing. Also the dehumidifier. As "they" say it's not the heat but the humidity.
Thanks Again!
 
I have a 30A service going into my trailer so plug the 14.5K BTU portable into a pedestal outlet rather than into an outlet in the trailer. The outlet you might use (washer/dryer) might just work. Our window opens about 5-6" and I have cut out a wood piece that fits the hole (not square) and has a port for the exhaust. Some folks say that a portable with two hoses works better; dunno as I have never used one. Ours is pretty effective and the only negative is that the airflow out points upwards so we keep a pedestal fan in front of it to direct cool air.


View attachment 1303435View attachment 1303436

The dual duct units are indeed more effective. This single duct style draws in interior air and passes it through the condenser discharging it outside. These creates a low pressure in the interior, and it's forced to draw in outside air through any gaps thus reducing the efficiency of the unit. Yes. It is absolutely better than no unit at all.

I have a Midea DUO unit where the exterior duct has both intake AND exit passages, i.e., it uses exclusively outside air to cool the condenser and has the two loops completely isolated with no tendency to build pressure/vacuum in the interior. It also has the benefit of an inverter compressor, i.e., no surge of any kind. This is not to be confused with a soft start. Soft starters reduce the surge. This unit has NO surge. It can also be programmed for different temperatures/times and can be controlled remotely via an app. My only regret is that I didn't get the heat pump version... I thought I did, but I clicked the wrong one.

It's currently the only functional A/C unit in a 34' Newmar Mountainaire. It can't keep up with Phoenix heat during daytime, but it keeps it cool at night.
 
Great input!
I texted my mobile mechanic guy.
He is going to come and check the unit out.
I like the idea of the fans and/or the portable air unit thing. Also the dehumidifier. As "they" say it's not the heat but the humidity.
Thanks Again!
The humidifier is an excellent choice if you camp anywhere there is humidity. We live in an area where humidity is usually almost non existent but love to travel to areas with water, oceans, lakes, rivers etc. The high humidity in those areas is not only uncomfortable to us but also causes all kinds of other problems.

We spend (or used to until we were sidelined for the last winter) the winters in FL right on the coast. It can get very humid. We use a dehumidifier continuously there and it improves cooling a LOT. The only kind to get IMO is one with a compressor, the others just don't do the job. For about 6 years we used a 35 pt. Hisense I bought at Lowes. Worked great but it was big, heavy and put out a lot of heat. About 4 years ago I bought an Ivation 12 pt.(?) unit that was smaller but has worked like a charm. A lot more placement options, far less heat generation and it does the job admirably (you do have to empty the little tank a bit more often because it's smaller). I would not get a smaller unit for your 29RLI.
 
Adding a portable AC can greatly increase the cool in your RV. When considering the addition of a portable AC, try to find a brand that has spare parts available and can be repaired. I bought a "Cool Living" AC at Boscovs [Chinese made] and it ran great for about four years until it stopped cooling altogether. Came to find out that parts were not available for them and no AC shops could work on them.

Some portable AC brands can be repaired. Talk to any local AC repair shop and ask them. That way you know who to go to if you need service.

As Wiredgeorge said, the nice thing about portables is that you can plug them into a separate 20 amp pedestal outlet and not tax your 30 amp system but still have a second AC.

It's also important to get that AC fired up in the morning while it's cooler outside, as JHTJH suggests, to get the RV interior cool ahead of time. Once it's hot outside, it will be difficult to cool the interior down.

Mylar Another trick I use is 4 x 8 sheets of mylar, the very thin foil "space blanket" material. They can be bought for cheap on Ebay or Amazon. I use painters tape to tape a 4' x 8'sheet or two on the outside wall facing the heat of the mid-afternoon sun. The mylar completely reflects all the sun's heat and keeps your sun-facing wall cool. It's akin to moving your RV to a shadier spot.

I only do this if we're staying somewhere for 3-4 days or more because of the additional labor to get out the ladder and the painter's tape. They are so sheer that you can cover a window with the mylar and still see outside through the mylar. Sort of like those one-way mirrors.

As was said earlier, if the sun heats up the outside skin of your RV, you'll feel that heat transferred to inside walls. Then one AC is working just to neutralize that "skin heat."
 
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To the OP; what brand of AC’s do you have? If they are the Coleman Mach, poor cooling performance of the brand is unusual, but the Blade ceiling vents are a factor in poor results. If you have the Furrion units, there is a design flaw to contend with, but it can be corrected fairly simply. Combine the Blade vents with a Furrion AC and you are double-damned.
 

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