RV Air Conditioners / Heat Pumps-
Types of RV Air Conditioners-There are many different brands of air conditioners for RV´s such as Coleman RVP, Dometic Duo-Therm, Carrier, Emerson and others. Some RV´s have from one to several roof top air conditioners and some have a single central or "package" unit that is mounted on the underside of the RV. Most RV´s have a ducted system to distribute the cool air throughout the RV but some older or smaller RV´s have a simple ceiling assembly that only distributes the air directly below the roof top A/C. Some have the thermostat and controls mounted onto the ceiling assembly and some have a wall thermostat that can operate one or more air conditioners from a single location. The RV air conditioner is fairly simple but the more advanced units with electronic controls and sensors can be quite complicated.
How it works-The typical RV Air Conditioner is a fairly simple device. Some folks are under the misconception that an RV air conditioner "makes cold air" but, in actuality, the air conditioner simply transfers heat from the interior to the exterior. In the simplest terms, a fan blows the warm air across a set of coils that contain a refrigerant (often called freon). As the warm air crosses the coils, the refrigerant collects some of the heat and the cooler air is blown back inside the RV. The refrigerant is then pumped to another set of coils on the outside of the RV where another fan (or the same fan with a blower wheel on each end) blows across the coils and removes the heat from the refrigerant. The refrigerant is in a continual loop and as the process continues over and over again, the interior continually gets colder until the preset temperature is reached. Some air conditioners also allow this process to be reversed, therefore removing the heat from the exterior and transferring it to interior of the RV. This type of air conditioner is referred to as a heat pump. Heat pumps are limited because they can no longer heat after the outside air gets below freezing (there is no longer enough heat in the outside air to bring in!). Many RV climate control systems are designed to sense when the temperature gets to cold and will automatically resort to the gas heater (furnace) as an alternative.
How do I keep it working?
AIR CONDITIONER MAINTENANCE TIPS- There is very little maintenance involved with an RV air conditioner but it is important that you take the steps necessary to prevent any problems.
Clean Filter- As mentioned earlier, the interior air passes through a coil to remove the heat and is then returned via the ducting. The only protection to prevent the coil becoming dirty and clogged is the interior filter so it is extremely important to keep the filter clean. Some filters are made specifically for a particular type of ceiling assembly and when they deteriorate will need to be replaced with an exact replacement. Most are made of a common filter material that can be purchased locally and cut to fit. It will be obvious when it is time to clean the filter by making a visual inspection. It´s also important to verify that the entire intake area is completely covered by the filter. If there are any gaps around the ceiling assembly or filter, the air will take the path of least resistance and your intake coil will accumulate dirt and dust and diminish the cooling capacity.
Check for Air Mixture Problems- Since the Rooftop RV air conditioner´s intake and output are all housed in the same 14" x 14" hole, it is important to make sure there is no mixing of the pre-cooled and cooled air. Most ceiling assembly´s are sectioned off properly, however, many use a foam or aluminum tape to isolate the two areas. Should the tape become dislodged a portion of the cooled air will recirculated back into the intake and create poor performance or icing of the coils. Be certain incoming and outgoing air is properly separated and sealed.
Check thermostat location- Over the years, I have seen many thermostats that were located in bad locations creating cooling problems. Normally, this will cause the interior temperature to become too hot, too cold, or cause frequent cycling of the air conditioner. If your thermostat is in the direct sun, directly below an air duct or mounted in a location that will allow warm air behind it (such as a refrigerator wall), you will need to take measures to correct the condition.
Check Installation bolts- Most Rooftop RV Air Conditioners are secured from the interior of the RV using 3 or 4 bolts that go through the interior ceiling assembly and pull down on the upper unit which "sandwich" the A/C onto the roof. The upper unit has a 1" thick foam gasket that gets compressed to about 1/2" against the RV´s roof during installation and prevents water from intruding. I´ve often seen bolts that either weren´t properly tightened by the manufacturer or have become loose from the vibration of travel. It´s a good idea to check these bolts during every filter cleaning. The bolts should be snug BUT NOT OVERTIGHTENED. If the bolts are overtightened, the gasket can become over-compressed and cause the drain holes on the bottom of the AC to rest directly on the roof of the RV. This can cause the drain pan to drain too slowly and water to overflow into the interior of the RV.
Cover the A/C- The upper unit of a rooftop air is protected by a plastic shroud that often has ventilation holes in it for proper airflow. By way of the design, there is plenty of room for insects or rodents to find there way into the upper workings of the air conditioner. Although there is generally no way for them to penetrate the interior through the upper portion, much damage can be done by wires getting chewed or nests being built. This is also a favorite hideout for mud daubers. The best defense is to put a vinyl cover over the air conditioner. They are available to fit all of the different styles of air conditioners and they are fairly inexpensive (especially if you consider the cost of potential damage!). You can find the cover to fit your air conditioner here. Keep it covered anytime you have the RV in storage and make sure you remove it prior to operation. it´s also a good idea to treat your vinyl cover with a UV inhibitor like 303 aerospace protectant.
Quick RV Air Conditioner Trouble Shooter- Here are a few common air conditioner problems and few things you can easily check prior to calling for service.
No A/C Operation- 1) Verify power to the RV by checking any wall outlet for 110v. Tip- It is a great idea to keep a voltage meter plugged into a wall to monitor your voltage from getting too high or too low. Poor voltage can cause shortened life of your air conditioner. 2) Check the AC breaker in the RV´s breaker panel. 3) Check for a blown12v fuse in your fuse panel. Although the air conditioner operates on 110 volt, the electronics that operate the thermostat and other functions operate on 12 volt and are required for operation.
AC Hums But No Cold Air is Blowing Out- There are a few good possibilities here. 1) The compressor is running and the fan is not which would indicate the fan motor is bad or 2) it may have mud daubers or insects that have gotten inside and caused problems. 3) The coils have iced up not allowing the air to pass through. As mentioned previously, the air could be mixing causing this condition or it could be that there is a refrigerant leak in the system that will give the same symptom. There is also potential thermostat or electronic control problems or the AC is undersized for the current conditions (too hot outside for the air conditioner to keep up).
AC keeps humming after it is turned off- This is an indication of a thermostat or electronic control problem that will require a technician to diagnose.
AC runs but won´t cool- There are several possibilities here. It could be that the air conditioner cannot keep up with the outside temperatures. The easiest way to verify proper cooling would be to run for 20 minutes and then test the temperature of the intake air at the filter and then test the outgoing temperature at the closest outlet to the air conditioner. There should be a temperature difference of 18-22 degrees. If there is, the air conditioner is working as hard as it can. You might try to find a shady spot to park or consider adding a second air conditioner to the RV.
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