Motor Home Air Conditioning

[desmo]

We just purchased a new Charleston 41' with Dometic 1,400- front and 1,200- rear BTU air conditioners. We used them for serveral weeks on the East coast in 80- to 90-degree weather and they worked OK, But not quite as well as a home air conditioner.

Then we traveled to Yuma, Arizona, in August and the motorhome was uncomfortable with the outdoor temperature of 112 degrees and 10 percent humidity. We were only able to reduce the inside temperature by 20 degrees from outside temperature. The front window was covered with heat-reflecting material and the air conditioners were blowing cold air but the motorhome could not keep up with the heat. We finally had to run the dash air conditioner to bring the interior down to 80 degrees.

Questions:

Are motor homes built for desert climate?

Would larger-capacity air conditioners make a difference and are a 8000-KW generator and 50-amp shore power sufficient to power larger air units?

Are swamp coolers a better solution?

"Don't travel to the desert in the summer" is not a solution.

Any help is appreciated!

Steve

[garykd]

Hi Steve,

I also just finished the summer out where you were. My signature coach has 2 13500 btu A/C units. My coach cooled quite well. I did nothing special to cover the front windshield. One thing I did do was always reserve a site where the coach faced any direction but west. Next is how your coach was made. The roof and wall insulation along with the window tinting/construction can greatly help or hinder the HVAC capability. Also, all of my side windows have awnings. I know that helps quite a bit with A/C. On the other side of the coin, I don't think my coach holds heat (cold weather camping) as well as it should. That being said, I am from south Florida. Where you are from and what you are used to can have an impact on the coach's perceived ability to stay comfortable.

[tbutler]

Steve, Steve! Yuma, Arizona in August? That is why the motor home has wheels! lol

Seriously, there are things you can do which will help your air conditioner. As Gary mentioned, parking in a site facing east might help. In summer I prefer to face north. I have good shade on the sides of the coach from awnings and slide out covers. The front window is the worst and the engine compartment in the rear is ventilated so that makes it the side of choice to face south.

Being full timers, we have external solar screens for all our windows. If you are planning to be full time or are likely to be in hot places frequently, I would recommend doing something similar. A complete set of solar screens will cost less than a new air conditioning unit. My wife tells me she knows when I put the screens up because the temperature drops almost immediately inside. Even if you only purchase a set of solar screens for the driving windows (front and three side windows on most motor homes), you will gain greatly from them. Having reflective material inside the windows is better than nothing but you are allowing the heat of the sun inside and not all of it is reflected outside. That is why I prefer the external screens.

Your question about generators is yes and no. The larger coaches with three air conditioning units have 10 or even 12 KW generators. Our unit has a 7.5 KW generator and that easily runs two 13.5 M BTU units plus other appliances. I would imagine an 8KW would run two of the largest AC's for RV's though I don't know that for sure. Regarding electric supply, 50A electric really supplies 2 legs of electric at 50A each. I consider 50A electric to be essential any time you need to run two air conditioners. The largest motor homes use 50A electric hook ups so that should run most anything. Each AC will pull somewhere in the neighborhood of 12A (with a higher amperage needed to start each unit) so both would be 24 amps plus any other electric you are using. Most 30A supplies will not provide a full 30A without dropping in voltage and that will damage your air conditioners especially if they are running full time. I have had 30A supplies that wouldn't run one air conditioner without a damaging drop in voltage.

If you have been traveling, the engine compartment will be hot. After traveling on a hot day, I'll open the engine compartment to allow better ventilation and help it cool down faster. If we've been running the generator, I'll run the generator slide out to allow it to cool without adding heat to the motor home.

[desmo]

Thanks Gary and Tom, you have some. useful ideas.

We are from the Orange County California coastal region and are acclimated to 60 to 80 degree temperature year round, we have only been to the desert a couple of times in the summer and then it was in large hotel resorts. I think a lot of our problem was the heat gain from the side windows, skylight over the shower and roof vents. I should be able insulate the vents and I'll have to check into external solar screens. All our side windows are tinted dual pane and we do have awnings on all side windows and they helped. We also pulled in our slides to reduce air volume and that helped. The front window solar reflector also helped a lot and you are right that it would work better on the outside rather than the inside of the windshield.

The manager the RV park where we stayed warned us about the motor home air conditioning in desert conditions.

Do you know anything about swamp cookers, I understand they can help in very low humidity conditions?

[garykd]

I have no experience with swamp coolers (evaporative cooler). The concept says it should help your coach's HVAC system in a low humidity climate.

[tbutler]

My mother-in-law had a swamp cooler when she lived in Lake Havasu, AZ. I have never seen an RV application but if they do exist, they are less effective than an air conditioner but quite a bit less expensive to operate. It is true that swamp coolers work better in dry conditions than they do in humid conditions as they depend on evaporation for cooling. They do not have a condenser which is where the energy and cost savings come from. But the evaporative cooling doesn't produce the same cold coils for the warm air to pass over that the compressor will. As an add on to air conditioning, it might help cool the air before it goes into the air conditioner but I can't imagine it being practical for RV cooling as the evaporator is usually quite large.

When she got older, my mother-in-law replaced the swamp cooler with an air conditioner!

[aztortuga]

We both were raised in Arizona so are accustomed to the heat, or so we thought. We have lived in Oregon for the last few years but had to go to Arizona for medical reasons this summer. In Phoenix with temps of 110 to 115 both of our AC units were going full blast and the air temp inside of our travel supreme was in the low 80's. They were simply not able to keep the temp down into the 70's. I bought foil insulation and placed it on the interior of the west facing windows as well as the windshield and it helped. What finally did the trick was getting out of Phoenix and heading North. Soooo, to your question, I think that most RVs will have a hard time with temp control when it gets that hot. I saw other units in the park that were obviously full time in the park, and they had added window ac unit to augment the roof mounted ones.

[Smoker]

I have a Berkshire and it's hard to cool also. Been my pet preve since new. I blame is on Forest River and the air ducts on ceiling not insulated to starve off the roof heat. I called Forest River and they checked it and told me it's working as it should yet I sweat in mine.

[desmo]

Hi smoker

I solved my problem, just bought a beaver marquis with 3 a/c units so far so good.

best of luck

DESMO

[Guest Wayne77590]

Steve,

in my very younger days I was stationed at 29 Stumps. They gave us housing which consisted of a trailer (about 21 feet) and it had a swamp cooler. I never took the temperature inside but after being out in the 110 degree heat and walking in it sure felt cool. At night, when the desert temperature really drops, we would have to turn it off to take the chill out. It's not a really efficient way to try and cool as far as I'm concerned, and I think "cool" is a mater of interpretation with a swamp cooler.

We do as most others do. Put up the outside screens on the front and side windows (I have Magne Shade screens). Recently we were in 100 degree temps and I was a little uncomfortable so I went out and bought a roll of "astro-foil" at the hardware store. I cut it to fit the inside windows and it is a real tight fit. It helped considerably.

As for the skylight in the bathroom, you can put your hand up in there on a hot day and feel the heat being sucked in. I had one of those foam skylight plugs that I picked up at Camping World. I had been carrying it around for a year, using it as a cushion for my Carry Out Antenna. I plugged the skylight and it also made a difference.

There is a lot that one can do. I even heard on another forum that one RV'er had two basement AC's and installed a rooftop AC where his kitchen skylight was. Three has to be better than two, right?

Oh! I also agree with Tom. August, in the desert!!!

[rosszie@me.com]

Your A/C Units should keep you kool... You might want to check out the deg's your are getting...I have only two Roof A/C's and I just came back from a months trip.. Redmond OR was in the high 80tys to the mid 90tys... and later that month it was in the low 100's went to Grants Pass... our AC's were keeping us very cool.. I set the thermostat's at 74deg's around 11 O'clock and leave them on all day.. I do pull my shades down and cover my from windshield... I have a Older C/C Magna... and I have always been kool or warm what ever I need with my generator or shore power... 30amp's will run you A/C's Anyway have your units checked out.... Good Luck'

[j.barnum]

Hi All,

I have a 95' Dynasty and we traveled the USA (through the south and east during the summer. Hot , anyway.) While driving we added a shear curtain on a spring loaded rod just behind the front seats. Using this setup, the dash air usually kept the front liveable...

Hey we are from Oregon and we do not tan just rust. I added heat resistant aluminum car front windshield covers for our side windows. In fact I just leave the bedroom shades pulled down and placed these shields between the valance and the shades. This way we keep the bedroom either cool or warmer depending on the season.

Now why could we ( RV'ers ) not just add a cheap window 110 volt AC unit to one of the windows when parked? I thought this would be a good idea and not always use the roof RV air conditioner/s? Then pull it out while driving and of course and make a window adapter to make it safe, secure, and not allow for someone to break in.

J.barnum

95' Dynasty

Gladstone, OR

[shields]

We have a 97 Dynasty and also have trouble keeping it cool in the desert summer heat. We drive through Las Vegas on our annual houseboat trip to Lake Powell, and daytime temperatures are often over 110. With both rooftop a/c units (13,500 and 13,500 btu) as well as the dash air running, we can't get the coach comfortably cool. I've made plans to add a third rooftop a/c unit before the next major trip.

As for heat issues while parked, the suggestions shown look great. We'll be implementing some of them promptly. Thanks for the ideas.

Tim

[jonrjen]

Our 2008 Pacifica has the basement A/C, which doesn't cool well in very hot conditions. We just had a 15K roof unit installed in place of the fantastic fan. The wiring was run down to the basement so that if we are in a park where it is extremely hot we can simply plug the 20amp plug into the parks power and run the roof air in addition to the basement units.

As a side note, 15K roof a/c units used to be run off of a 15amp plug, they now require a 20amp service and plug due to code and refinements in the operation of the electronics at start up.

[mjs4417]

Hey All!

So glad to finally find this specific forum about cooling motorhomes in the hot - hot summer places.

For the last 8-10 years as we've suffered thru hot box temperatures and the only responses we'd seemed to muster from those camping around us and the RV service people was that all the mechanicals were working just fine and the neighboring campers would clearly imply that they actually had icles hanging from their curtains and making ice cubes in their water glasses at the diner table.

Nice to hear some reality and then practical solutions!!!!!

YYYikes!!!

mjs4417