RV Air Conditioners - all you need to know when selecting your new cooling system, be it roof mounted, or under-bench, with heat-pump or heat-strip or without….
Air Conditioning system became one of crucial elements determining the comfort of life.
For most of us the “sauna” is a conscious choice for dozen of minutes, but definitely no one would like to live and sleep in hot and humid environment. And this is especially true when we are on our summer’s RV-vacations and want to enjoy the opportunity of being out.
Let’s start with basics: The cooling capacity of an Air Conditioner unit is traditionally expressed in BTUs/h (British Thermal Units per hour). Do not try to understand the meaning, just keep in mind that higher the BTU number, the AC can lower temperature and remove moisture faster. To some extent the feeling of warm-cold is relative (it’s an individual experience), so when selecting the AC just follow the guidelines for the RV you own (size and thermal insulation), the climate zone and eventually your own preferences. Obviously you need some BTU margin to make the cooling process fast but keep in mind – “bigger” is not always better and usually comes with some restrictions and obviously price. In practice the choice of cooling power is simple – the most popular units on the market are 13,500 BTU (13.5k BTU) and correspondingly 15,000 BTU (15k BTU). If you can live with less, you will find also smaller units rated at 6-to-9k BTU. If you need more than that ,you will end-up with two or three units!
Note: For those more familiar with electrical power: 13.5k BTU/h is equivalent to about 4 kWh, and 15k BTU/h correspondingly to 4.4 kWh
Now let’s continue with more or less obvious statement: AC unit designed for RV installation is not exactly a “copy” of what we have in our residence. Here is why:
1. While we can (or maybe “have to) “somehow” tolerate brutally noisy window AC units at home, it will be out of question when it comes to a Recreational Vehicle. It is because it is much smaller space (no place to “hide”) and RV’s shell will rather amplify the noise than absorb it. The preferred types of RV’s air conditions are:
Pop-up tent campers are not really designed for interior “climate control”. The main reason is lack of any thermal insulation (canvas), so the cooling and heating efficiency is very low and the effect does not last long. However, if someone really wants this luxury, then probably a PAC (Portable AC) unit will be if not the best than at least “good-enough” solution. But we will not address here in details this solution.
2. While proper BTU rating, efficiency and price are of concern when it comes to residential AC systems, the size, weight, profile, mounting place etc… are not so much. That is why for RV-ers these parameters define an “uncharted territory”.
Ford 220RB Travel Trailer with roof-mounted 13.5k BTU ducted Air Conditioner. As you can see it is barely visible thanks to its "ultra-low" profile.
Dometic Penguin 2 AC unit: 13.5k BTU Sleek, aerodynamic profile (about 10") designed for non-ducted air systems
... and even lower profile rooftop AC (just 8.25") Coleman Mach 8
Rooftop AC systems
Modern low-profile roof-mounted AC units especially designed for RVs represent superior choice. They come in two “flavors” – ducted (cold air is distributed through vent-pipes and then ceiling or floor registers) and non-ducted (air is blown directly from the AC unit through the “distribution box”.
Dometic QuiteZone air return system: It feeds cool air directly into the ductwork system. Cool air enters a port built into the rafters at the first stage of distribution. Warm air is pulled through a separate ductwork system to be vented to the outside.... It keeps noise and vibrations away from the sleeping and living space
Source: Dometic (www.forestriverinc.com)
For obvious reasons the Chalet XL 1935 A-Frame Travel Trailer is equipped with an "under-bench" AC/Heat-Pump unit (Cool-Cat). In this case it is actually located in the kitchen cabinet (under the sink) - Here visible large exterior vent
And here is how does it look: Dometic Cool-Cat AC/Heat-Pump unit
Under-Bench Air Conditioners
Under-bench AC units are popular solution for small RVs (travel trailers). It’s because small RVs are either not designed for installation of roof AC or their clearance is an important factor. Note that big rigs will be rarely stored in the garage, but small ones may and every inch of extra height will cause problems. BTW - under-bench “concept” includes also AC units installed in storage compartment (the name underlines the fact that the AC unit is placed at the floor level).
Dual use systems (AC/ Heater) may be a logical choice when you plan RV-ing over extended seasons (and/or in “colder” climate zones) when the heating may be necessary. RV industry proposes two “integrated” solutions: AC/Thermo-Pump or AC/Heater. Their main advantage of such solutions is the level of integration. It is just one unit (so takes less of the precious space).
Example of Heat-Strip (here Dometic's model)
It’s true that the roof-mounted AC/Heat-Pump systems (including ducted ones if registers are in the ceiling) are not optimally placed for heating. In the cooling mode, the heavier cold air drifts down and warmer one raises up (convection) so the interior air is constantly “mixing” on its own. As the result the interior temperature is pretty much uniform across the camper. The opposite happens when the warm air is being distributed from the ceiling. Since warm air is “lighter”, the vertical temperature gradient in the RV will be higher than in the case of cooling. In other words the temperature at the floor level will be lower than that close to the ceiling (unless the registers of the ducted system are located in the floor). However, it should not be a big concern because:
Quality of AC’s installation matters so even a good AC unit may cause headaches. Note that the camper’s shell may act as the “Resonance Box” amplifying compressor’s and/or fan’s vibrations (so familiar effect to owners of windows units).
So far all practical AC systems ran on an electric energy. And let’s face it – unless you can be connected to the grid or you have a generator with right power rating, using your AC to bring the comfort-in will be a dream. The required amount of electrical power cannot be delivered from auxiliary batteries (they will be depleted in a matter of minutes). It also cannot be provided by solar power (unless you haul behind your RV the Solar Farm). There are plenty of generators on the market (most runs on gasoline, some on LPG), but once again, they are quite noisy. If they do not “kill” you, they may prompt neighbor(s) to take an action you may not like!
Heating systems do not have these limitations as traditionally they operate on propane gas. In other words having the gas furnace you can be much more energy independent (almost all petrol stations sell LPG) and enjoy RV-ing over the whole year (provided you have 4-season RV). But they need an extra space, add the weight (so limit the cargo capacity) and are not free!
Typically the maintenance of AC units is limited to cleaning the air filters. This should be done periodically and it is not only mater of accumulated dust, but also of germs, bacteria etc. It is also advised to check the exterior coil vents for debris, leaves, and any damage that may obstruct the air flow (especially important for roof-mounted ACs).
The circulation system of refrigerant is sealed and should not need any recharging during its lifetime (unless is damaged or simply speaking you have “bad luck”).
Similarly the electrical motors are sealed and do not need lubrication.
Summarizing: Armed with this knowledge we hope you can make the educated choice when selecting the AC unit for your RV. After all, the fresh, cool air from the AC system you can’t even hear is a key to fantastic RV-ing experience.
Major manufacturers of AC units:
Dometic is a manufacturer of roof, split and under-bench air-conditioners.
Blizzard NXT series: Low-noise ducted and no-ducted rooftop AC units rated 13.5k BTU and 15k BTU (latter w/heat pump)
Brisk II series: The next generation of rooftop heat pump climate control units that acts as both cooling air conditioner and as heater, stronger, lighter, smaller and more environmentally friendly than its predecessors. The series includes models rated 13.5k BTU and 15k BTU, some only ACs, some with Heat-Strip and some with Heat-pumps. Brisk II models are designed for ducted and non-ducted systems.
Pinguin II series: Low profile air conditioners, for both duct and non-duct applications (air distribution box available separately). With an ultra-low profile, the streamlined rooftop unit is aerodynamically designed to reduce drag when on the move. They come rated at 13.5k BTU and 15kBTU (heat-pump versions are available).
Cool Cat – Small footprint AC/Heat pump units for under-bench or storage mounting with rating of 10.5k BTU.
Mach 1 (with rating 12.7k BTU it is very efficient running at 9.3Amps),
Mach 3 ( 13.5k BTU w/optional Heat-Strip),
Mach 8 (rooftop unit, designed for ducted systems, lightest low-profile unit on the market, rated 9.2k BTU, 13.5k BTU w/optional 6k BTU Heat-Strip, can operate in temperatures up to 125 degF) and
Mach 15 (15k BTU w/ optional Heat-Strip)
Rooftop models AC135 and AC150 (rated correspondingly at 16k BTU and 18k BTU. According to manufacturer these are light, very efficient and quietest on the market units. The 18k BTU one comes with the Heat-Pump. Unfortunately the profile is not the lowest one!
Manufacturer of split Air Conditioners.