Keeping Cool in the Desert

[Tabo]

My dad sold his house and bought a 5th wheel to live in year-round in Phoenix, AZ. My husband and I have been helping him get situated, but we are all total newbies to RV living. His 37 ft Keystone Montana has two Dometic rooftop ac units, one 15,000 BTU over the living room and one 13,500 BTU over the bedroom. He's afraid they won't keep his 5th wheel cool enough in the hot summer. He wants to add a third Dometic ac unit in place of the Fan-tastic roof vent in the kitchen. I hate to see him get rid of the vent, though. Do you think the two ac units should be enough, or does anyone know if the Dometic Brisk II Rooftop Heat Pump performs better than the regular Dometic air conditioners? And is the Fan-tastic roof vent a must-have? Any info or advice would be greatly appreciated!

 

[RKins]

I think Phoenix is in a special area of the country - I used to go there to teach some techs at the Intel fab there and it was 117 degrees at 3pm. The Air Conditioner (a/c) in my rental car didn't cool the car down at all for the 10 minute drive from hotel to Intel. A/c cools by dehumidifying the air. I think that houses there use combination a/c and swamp cooler to cool the house down depending on the time of year. So to answer your question - no. If the 5er is going to stay there I would look into swamp coolers.

When I lived in Sierra Vista, AZ we used a swamp cooler on our house and I even had one on my van. Fits over standard vent access hole.

 

[FL-JOE]

I would start figuring how many amps his present a/c units are pulling, then you will know what size of unit the 3rd one could possibly be. I'm guessing he will struggle with 2 units and a Montana fiver in that kind of summer heat. Does it have the factory "artic" package? Window insulation and/or tinting may help him just as much.

 

[Joe Hogan]

Living in a 5th wheel or any camper in the desert is going to be hot without shade. Insulation, ventilation and shade might be better than installing more A/C to cool the 5th wheel.

 

[Gronk]

I'm just south of Phoenix (Casa Grande) and I can tell you it isn't going to be cheap to try to keep cool. My trailer gets full sun and I put another A/C on so now I have two, but it still gets warm in here with temperatures over 100 degrees. As I type this my thermometer says 105* outside and 77* inside, plus two fans moving air. In the last three weeks we have used almost 600kw of electricity!! at about 18 1/2 cents a kw it gets expensive. We are leaving here and heading north on Tuesday just to get away from the weeks of over 100* weather.

 

[MapNerd]

I remember @Neal having a really good write up over on IRV2 about staying cool
In the desert. Maybe he’s copied it here but iirc, it basically came down to getting ahead of the heat with the AC and never backing off. Also, he posted about an insulating cover for the domestic freezer if you have one. I will be purchasing that for sure.

I’ve always wondered if it would be worth it, if you were going to spend a good amount of time in the sun, to purchase a 50’ long, 12’ wide, 14’ tall tent with just a sunscreen top and sides. Idk what the CGs would have the say about it but in 100-degree sun, I bet it would make a world of difference.

the other problem of course, is where do you get a 50’ long, 12’ wide, 14’ tall tent with a sunscreen top and sides?

 

[BGMAC]

I think Phoenix is in a special area of the country - I used to go there to teach some techs at the Intel fab there and it was 117 degrees at 3pm. The Air Conditioner (a/c) in my rental car didn't cool the car down at all for the 10 minute drive from hotel to Intel. A/c cools by dehumidifying the air. I think that houses there use combination a/c and swamp cooler to cool the house down depending on the time of year. So to answer your question - no. If the 5er is going to stay there I would look into swamp coolers.

When I lived in Sierra Vista, AZ we used a swamp cooler on our house and I even had one on my van. Fits over standard vent access hole.

I agree with RKins. If you can find a swamp cooler that would be the best. We lived in Utah for 3 years in a metal mobile home and the only thing that could really keep it cool was the swamp cooler. It will only cool down so far, but the humidity it puts in the air makes it feel much better. I remember when we had a heat wave it still got pretty hot. I put an oscillating sprinkler on the roof. The water bounced around like on a frying pan. Once the roof cooled we were in heaven inside. A day later almost everyone had sprinklers on their mobile home.

So that said, maybe a swamp cooler with a carport type cover over the trailer might do the trick.

 

[Kevin D Pem]

With the long running high in AZ thought I would open this conversation again.
The heat is brutal in Phoenix,Yuma, Bull Head city and many other places here.
To clarify systems I make this statement:

Swamp coolers are an open loop evaporation system. It will cool air about 20 deg, but because recirculating humid air is not an option, 20deg is about the best you get.

A/C systems on the other hand are closed loop system and humidity has little to do with the cycle. Recycling the already cooled air will allow a lower temperature in the room than what can be attained with a swamp cooler. There is more but later in the post.

One of the least costly ways to keep a house or RV cool is thru shading the dwelling, Many studies can be found to attest to that.

But shade alone has a minimum effect. Parking under a tree will lower the temp even more than just shade. We can synthesize the cooling effect of a tree, by introducing evaporation, but the same BTU of the tree will be hard to beat. The swamp cooler on the patio is one way, sprinkler on the roof another. The best way is the modern way of spray misters. This method you will find on many a restaurant patio. Another location this method is used is at the NASA visitor center at their bus stop shades. Proving they work even when the humidity is high.

The best part about misters is they don't increase the power draw on the grid, and in phoenix this time of year is important. If well installed you can leave them installed even when you move your rig.

A win win for the grid, comfort, pocket book and the opportunity to be on the porch
during more of the year.

 

[MapNerd]

I was thinking about this not too long ago while sweating my tail off at Myrtle Beach and wondered why campgrounds had never thought of installing misting systems And shade sails in some of their public areas. It’s a moot point these days as those public areas aren’t getting used much, but the idea itself stands and is a solid, lower power way to reduce heat.

 

[murphysranch]

We lived in a 5th wheel way back when while we were building a home. We ended up putting up shade cloth and camo netting to try to keep some of the sun from baking the trailer, which was like a tin can.