Help Your Air Conditioner Keep You Cool!

[tbutler]

Several years ago I wrote an article for the Forum, detailing how to control excessive moisture in your motor home. When I wrote the article it was primarily directed at wintertime concerns but did mention also that moisture in your motor home does affect air conditioner efficiency. I would encourage you to go to the link above and read through that article as it describes how heat energy is stored in water when it changes from ice to water and then from water to water vapor. As the article points out, water vapor contains a huge amount of heat energy. Any time water changes state from vapor to liquid or from liquid to ice, huge amounts of heat energy are released into the air or any surface on which it condenses or freezes.

During the summer, you won't see your windows fog up or notice moisture on the walls of your motor home. Your air conditioner will remove most water vapor from the air but it comes at a price. Because water vapor contains huge amounts of heat energy, the air conditioner must run longer to cool your motor home. If you are paying for the electricity directly, this adds to your utility bill. Even if you are in a campground, you are paying for electric in higher rates for campground fees if the campground owner has to pay high electric bills. Some campgrounds charge a surcharge for using air conditioners, others charge extra for 50 amps service needed to run several air conditioners at once. If your air conditioner is only marginally effective in cooling your motor home, then the price you pay is in comfort as the air conditioner struggles to maintain a comfortable temperature through the heat of the day.

Showering, cooking and wet clothes are primary sources of water vapor in your motor home. To help your air conditioner cool you, reduce the water vapor that you put into the air in your motor home. I'll suggest several ways to reduce the water vapor from each of these sources, please add your suggestions to this discussion.

The best way to reduce water vapor in the motor home from showers is to take your showers at the campground shower house. If you prefer showering in your motor home as I generally do, read the following. Showers are a huge source of water vapor as warm water is sprayed through the air. This alone contributes large amounts of water vapor to the air. Most RV'ers take "Navy" showers, turning the water off after getting wet then turning it on again briefly to rinse. This action reduces the amount of water we use, extends the "life" of our gray water tank load when boondocking and also cuts down on the water vapor in the motor home. Pressure regulators or reducers that we all use plus low flow shower heads also reduce the amount of spray and thus the amount of water vapor. Once your shower is finished, the walls and floor of the shower have a large amount of water remaining on them. I think that a squeegee is the best tool for reducing water vapor from the shower. With a squeegee you wipe 95% of the water off the walls and floor of the shower and send it right down the drain. Water down the drain won't enter the air and won't tax your air conditioner. If you simply step out of the shower and dry off leaving the shower walls and floor wet, that water will evaporate into the air in your motor home and will be removed by your air conditioner. After you dry off you have a wet towel which if you hang on a towel rack will release its water to the air in your motor home. If you hang the towel outdoors, the water vapor is released to the outdoor air and will not require additional run time by your air conditioner to remove that water vapor. The same can be said for any wet clothes, swim suits, rain soaked clothing, etc. If you hang wet clothing outdoors to dry it will reduce the load on your air conditioner.

Cooking done outdoors will not heat the air of the motor home and will not contribute any water vapor to the indoor air. If you are cooking indoors, water vapor is released in large quantities especially from cooking pots containing water. Water doesn't have to boil to release water vapor. Steam is visible water vapor but even when you can't see steam, water vapor is coming off a pot of hot water at a very high rate. If you cook food in a pot of water for 20 or 30 minutes, you release huge amounts of water vapor into the air in the motor home. Ventilation can help. You will draw some warm air into the motor home when you use vent fans to remove water vapor from cooking but you end up removing more heat energy when you get rid of as much water vapor as possible. You are exchanging hot air near 100% humidity for warm air at perhaps 75 or 80% humidity. The exchange helps your air conditioner keep up with the heat load it must remove from the motor home.

A secondary benefit of controlling the water vapor in your motor home is to reduce the need to defrost your refrigerator. A freezer in a moist environment will frost up much faster than one in a dry environment. Since most RV refrigerators are not self defrosting, we must periodically manually defrost the refrigerator. You will do this less if you make a conscious effort to keep the air in your motor home as dry as possible.

I hope that this information keeps you more comfortable this summer. Again, I encourage any questions and solicit your additional ideas and suggestions for reducing the water vapor in motor homes.