I needed to buy an air conditioners for two of our trailers for the summer of 2006. I was not really impressed by any of the recreational vehicle air conditioners (RVAC's) by Carrier, Coleman or Duo-Therm. I am sure they are all reliable and operate just fine however...
I was definitely not impressed by the air conditioners manufacturers brochures and advertising. Most seemed to state redundant information or claimed they were best because they had higher cooling capacity and/or indoor blower capacity. Do not accept these claims at face value because they may have been true at some time but may not be true today. Brochures were often confusing as they mention important points out of context. If a specific feature is important to you please double check that your choice has that feature and how well it works. Just because a manufacturer notes they have a three speed fan do not assume that your unit from the same manufacturer will have a three speed fan.
I prefer engineering facts like Energy Star rating and SEER and documented tests. I did not see any RVAC's that was Energy Star rated unit. I did not see any unit mentioning SEER and few mentioned the power consumption in watts under the test conditions of Air Conditioning and Refrigeration Institute (A.R.I.).
I got the impression that recreational vehicle air conditioning was considered a poor relative, designed to work two weeks a year for twenty years so efficiency was of low importance. The impression came from my research and the fact that only the Coleman Mach 3 P.S. was designed for improved energy efficiency. They claim the 3 P.S. uses 30% less energy then other 13500 BTU recreational vehicle air conditioners so there is definitely room for improved efficiency in RV air conditioners. Coleman also includes in the Mach3 PS brochure the watt draw at two test scenarios defined by the A.R.I. Standard 210 a definite move to open comparison. I got the following figures from the Coleman brochures.
The Coleman Mach 3 Plus. at 80ºF DB 67ºF WB indoor 95ºF DB outdoor at 115 volts was 1595 watts = 118 watts per 1000 btu
The Coleman Mach 3 Plus. at 95ºF DB 71ºF WB indoor 120ºF DB outdoor at 103 volts was 1924 watts = 143 watts per 1000 btu.
The Coleman Mach 3 P.S. at 80ºF DB 67ºF WB indoor 95ºF DB outdoor at 115 volts was 1147 watts = 85 watts per 1000 btu
The Coleman Mach 3 P.S. at 95ºF DB 71ºF WB indoor 120ºF DB outdoor at 103 volts was 1355 watts = 100 watts per 1000 btu.I was looking for a 15000 BTU Air Conditioner (AC) or Heat Pump (HP) complete rooftop unit offered by the big three - Carrier by TransportAir division of Carrier, Coleman by RV Product division of Airxcel and Duo-Therm by Dometic. From the reviews on the web that I found none of the big three were given any serious negative rating that was not related to features specific for that brand or model. The big three have a good reputation and the fact that their units are so similar in engineering design you could easily stop reading right here, however the devil is in the details.
The controls on most of the air conditioners and heat pumps are mechanical, manually set fan and temperature controls. Mechanical controls have been used since the 1950's and are very gradually being replaced by electronic controls for efficiency and reliability. Electronic controls may offer remote operation and energy saving when Air Conditioning, however in Heat Pump mode the right electronic controls will make a big difference in heating ability and efficiency.
If you want heat remember that all air to air heat pumps have two shortcomings. First they loose efficiency (i.e. heat output) as the temperature drops. Second the heat pump compressor usually turns off automatically at 40ºF outdoor air and turns on a built in electric heater. The electric heater has about 1/3 the heat output of the heat pump when you need heat the most. You should check if, how and at what temperature the heat pump will send a signal to start your gas furnace. Don't forget fan speed - RV units are designed to blow cold air at high volume so all units are very noisy compared to household heaters OR portable electric heaters.
While researching I looked at the literature on the web by the big three including the service and installation notes. Service and installation notes can be telling as far as the manufacturers consideration of ease of service, installation and costs you might incur later. As an example Carrier and Duo-Therm lists the parts only by manufacturers part number whereas Coleman lists commonly available repair parts by both manufacturers part number and description, like Capacitor Run 7.5MFD 370V, that a service man could use to buy a replacement in any HVAC supply store like Johnstone Supply. The bad part of on-line research is that the brochures, service notes, etc. are usually in PDF format and that they are rarely dated so it is hard to tell what is current from some manufacturers.
Since the 1950's all small air conditioners, both window and RV, have had the same basic layout that generally works well. Carrier, Coleman and Duo-Therm's Rooftop Recreational Vehicle air conditioners are all similarly basic 1950s design in the construction of their refrigeration, electrical and control systems.
All three use quieter, more efficient rotary compressors that replaced piston compressors in the 1980's. They all use a "run" capacitor for efficiency and a "start" capacitor or solid state thermistor PTC/PTCR to help the compressor start under load. The compressor motor is protected by black plastic overload a little larger then a plastic soda bottle cap firmly attached to the compressor that is sensitive to heat and electrical overload. When the compressor does not start the overload opens in 3 to 5 seconds and automatically resets when it cools in 3 to 5 minutes. It also may open if the voltage is too low or too high. If the overload is used too often either it or the compressor burns out so avoid low voltage electric service and look/listen for compressor short cycling at new campgrounds.
Most compressors had accumulators.The accumulator is the black tubular object roughly the size of a cola can attached to one side of the RV AC compressor that catches liquid oil and refrigerant. The accumulator is a very good feature in any (home, business, RV) air conditioner or refrigeration system and, though not new, they were very rare on small cooling units. The compressor manufacturers started building them into the rotary compressors to stop high failure rates from sucking liquid refrigerant and oil rather then vapor. Older AC units usually will not have an accumulator. All heat pumps should/must have an accumulator or similar device.
A single blower motor usually runs both the indoor air blower wheel and the outdoor air fan. The Carrier low profile air conditioners/heat pumps have separate fan and blower motors. Most Coleman units uses a run capacitor to boost the blower motor efficiency and lower electric consumption. Carrier and Duo-Therm do not use a blower motor run capacitor. Most blower motors are usually two speed although some Duo-Therm and Carrier Ducted rooftop recreational vehicle air conditioning units may have a three speeds. Do not choose your Air Conditioner by high Cubic Feet per Minute (CFM) blower ratings - better fan design for quiet operation is much more important. Because the blower is essentially in the same room as you are so a three or more speed indoor air blower might be the difference between a quiet nights sleep or life in a wind tunnel.
What would I like to see improved?
1. The lack of real data in sales literature about energy consumption efficiency at specific operating conditions as defined by the ARI.
2. Noise, both inside and outside at various fan speeds, is important to consumers so ratings should be included in brochures.
3. Electronic controls for efficiency, ease of use, and to protect your investment.
4. Manufacturers brochures... I was confused by manufacturers brochures that blend descriptions of similar units. I had to reread the brochure a few times to begin to understand the important differences between Carrier AIR V / AIRV heat pumps and Carrier AIR V / AIRV ducted heat pumps.
5. Fan and blower motors with oil cups to keep them running many years longer. A few drops of 20w motor oil every few years can triple the motors life. Some motors have oil cups but most do not.Some manufacturers use higher efficiency parts made to their specifications and this can greatly improve efficiency at the cost of serviceability. More and more it becomes better to replace rather then repair with low efficiency parts. Let's review some of the 15000 BTU RV units brochure specifications.
Carrier - http://www.transportaircon.carrier.com & http://www.airv.com
Most units have easily changed air filters. 1/2 year warranty.
15k BTU AC #68RV15102A: - 98 watts per 1000btu
15k BTU HP #68RV11112A: - 99 watts per 1000btu
15k BTU AC #68RV14103A: - 105 watts per 1000btuDometic Duo-Therm - http://www.dometicusa.com/climate.php?id=ac
3 year parts & 2 year labor warranty.
Briskair 15k BTU calculated 1460 = 97 watts per 1000btuAirxcel http://www.airxcel.com & RV Products http://www.rvcomfort.com Coleman
2 year parts & labor warranty
Mach 15k BTU 8335 ARIstd 1748max - 116 watts/1000btuCarrier literature mentions that the 15000 BTU "free flow" air conditioner draws 14 amps when cooling while the 15000 BTU "free flow" heat pump draws 12.7 amps in cool mode. I e-mailed Carrier at the AirV and Transcold web sites about this but got no answer. I checked the repair literature for both units and found they use different compressors, however both compressors use the same overload so the Amp draw must be close.
I decided on the Carrier 15000 BTU AC unit because of various reasons including the fact that the watts were lowest. Almost as low as the Coleman Mach 3 P.S.! (Dometic was slightly lower but the watts were not listed as ARI) I searched online and found Ebay and Amazon had the best deals. Delivery was prompt and uneventful.
Amazon 15k BTU complete free flow unit delivered - AC $559 - AC with electric heat $599 - Heat Pump NA
EBay 15k BTU complete free flow unit delivered - AC $554 - AC with electric heat $593 - Heat Pump $689
List price 15k BTU complete free flow unit - AC $766 - AC with electric heat $810 - Heat Pump $890Lowest selling price of complete units delivered ranged between 72 to 77% of list so beware of prices that are for only the upper unit or are without delivery.
I used my research and collected data to guide my purchase and I thought I should put it to good use and share it.
Last revised September, 2006.
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