When camping in high-temperature locations, few RV components may be as important as your air condition system, so it’s important to know its workings. In case of failure, this information may be invaluable in diagnosing the issue, but if you’re a Good Sam Roadside Assistance Platinum or Platinum+ member, you can consult directly with a certified RV technician over the phone.
To begin to understand your RV’s air conditioning, you must understand the differences between the dash air conditioning and the coach air conditioning. The dash A/C is just like the one used in your car; the compressor is driven by the engine drive belt, the condenser is located in front of the vehicle’s radiator and the evaporator is located in the dash. The dash air conditioning is designed to cool the passenger area of the vehicle and is not intended to cool the entire RV.
Unlike the dash A/C, the coach’s air conditioning assembly, including the condenser and evaporator, is located in one compact unit. RV air conditioning systems can be further separated into two categories: roof and central units.
The roof A/C mounts on top of the vehicle where air may be directed into the coach from a diffuser assembly mounted on the ceiling. This assembly is connected directly to the air conditioning unit by a short connecting stack that passes through a hole in the roof. On some models, air distribution may be routed from the roof unit through ducts in the roof and disbursed through vents in the ceiling. Roof mounted systems can be controlled by rotary knobs or electronic switches located on the ceiling mounted A/C unit, or by a wall-mounted thermostat depending on the application.
A central A/C unit contains two refrigeration circuits each with its own compressor, and those two circuits share a common condenser and evaporator. The unit is located below the floor line and the cooled air passes through a plenum chamber, which feeds it to a distribution system ducted in the vehicle’s roof that is controlled by a wall-mounted thermostat.
Generally, maintenance on any of these A/C systems is minimal because the key to proper operation is keeping the system clean. All coach A/C systems will have air filters, which keeps foreign material from entering the cooling unit and restricting the airflow across the evaporator. A clogged filter will restrict airflow and will reduce the efficiency of the unit. A dirty filter could also lead to a freeze-up condition in which the evaporator becomes coated with ice drastically reducing cooling.
Filter location varies between systems, so consult your vehicle owner’s manual for specific filter’s location. It’s recommended that the filters be changed or cleaned a minimum of every two weeks or anytime cleanliness is in doubt. While all coach RV A/C systems have filters, the dash A/C does not. For the dash A/C, the only maintenance required is to periodically inspect the condenser (located in front of the radiator) for dirt, bugs and other debris. The condenser may be cleaned by a gentle flow of water from a garden hose. Remember to not use high pressure water sources that are commonly found at local car and truck washes because they can cause condenser damage!
For optimum interior cooling, many RV’s are equipped with two roof mounted A/C units. However, because of the amperage draw of each unit, it’s necessary to supply 50 amps of usable service if both units are to run at the same time. If the vehicle is hooked up to a 30-amp shoreline service, only one A/C unit may be ran at any given time. In this case, some models contain a dual A/C switch, which allows you to select the A/C unit to power up.
Generators of 5,000 watts and higher have both a 30-amp and a 20-amp circuit. The 30-amp circuit supplies power to the front roof A/C and the remainder of the RV 110-volt A/C systems, and the 20-amp circuit is dedicated to the second roof air. This allows both roof airs to be operational when generator power is available. RV’s equipped with 50-amp shoreline service can power both roof A/C units provided 50 amps are available from the campground circuit.
Now that you have a better understanding how your A/C systems function, how they interact with a power supply, how to most effectively manage power supply and perform proper maintenance, you can increase the systems’ longevity and enjoy a nice, cool reprieve from summer heat.
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Photo: David Stovall