If you want to run an RV air conditioner on propane, you should know its pros and cons.
Do RV Air Conditioners Run on Propane? An RV’s air conditioning system can be replaced with the new one working on Propane as a refrigerant. However, its use in existing refrigerant systems requires modification with special care, skills, and use the fire safety grade parts because of its explosive nature.
Refrigerant grade Propane is commercially available with Code name R-290 assigned by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. Its use as a refrigerant has a rising trend because it’s natural, non-toxic, environmental, and ozone friendly.
Do RV Air Conditioners Run on Propane?
Propane is a hydrocarbon extracted during Natural gas processing and has a variety of applications as LPG. One of its widely used applications is its use in a variety of air conditioning systems in RVs.
Some of them include industrial refrigeration, commercial air conditioning, domestic and vehicle air conditioning systems.
Because of its explosive nature, it has not gained due importance in air conditioning applications. However, with time, up-gradation, and development of safety class equipment, it has been accepted in the market.
Its usage has seen an upward trend, which is justifiable because of its natural, environmentally friendly, energy conservation, and high-efficiency properties. It is used as a replacement for other hydrochlorofluorocarbons (HFCs) like R22, R502, and R134a.
Refrigerants Used in Air conditioners of RVs
R12 was common as a refrigerant in Rvs till 1990 when the Environmental Protection Agency (EPA) banned it due to its high ozone-depleting potential.
Then R134a (a hydrofluorocarbon) was introduced as a replacement for automobiles’ air conditioning systems in the USA due to its safety and low flammability.
Although it has a low impact on the ozone layer, it is a greenhouse gas and has a high impact on global warming.
Therefore, as per the new policy approved by EPA, it has been banned for future use after 2021. The new alternative approved is R1234yf (Hydrofluoroolefin) for the USA and Europe.
Despite all the desirable properties of Propane, its high flammability hinders its use as a refrigerant in RVs.
Properties of commercially available refrigerant grade propane R290
Refrigerant grade propane, placed in safety class A3 due to high flammability, is available in standard 03-50 Kg cylinders for use in RV air conditioners.
It is purified to above 99.5% from its natural version. Other impurities like moisture below 10ppm and a mixture of hydrocarbons content are reduced to below 02% to make it suitable for use in compressors of AC Systems.
The presence of moisture, sulfur, and other hydrocarbons causes loss of vapor pressures, corrosion, and other system-level failures.
A refrigerant’s performance is measured in the Coefficient of performance (COP) of an air conditioning system. It depends on various thermophysical properties of a refrigerant, as mentioned below:
Critical Temperature: It is defined as the temperature above which the gas cannot be liquefied despite applying high pressures.
R290 has a critical temperature of 96.7℃ that is higher than R32, R407c, R410a, comparable with R22, and lower than R134a. High critical temperature means high COP and low energy consumption.
Liquid Specific Heat: The amount of heat required to raise the temperature of 1Kg of water by 1K is called Specific heat. A higher value of specific heat means good heat transfer and high efficiency of the system. R290 has a high specific heat of 2.49 kJ/kg-K compared to R22, R407c, R410a, and R134a.
Liquid Thermal Conductivity: High liquid conductivity means high heat transfer. R290 is the right choice in this sense, with a 0.106 W/m K value higher than all their counterparts.
Latent Heat: High latent heat indicates high energy absorbed per unit mass. R290 has latent heat higher than their refrigerants like R22, R407c, R410a, R134a.
Liquid Viscosity: Lower liquid viscosity of refrigerant shows high heat transfer characteristics and less pressure drop.
In this way, you will find R290 as a suitable refrigerant because it has low liquid viscosity than R22, R407c, R410a, and R134a. Vapor viscosity of R290 is also lower as compared to other refrigerants.
Molecular Weight: Heavier refrigerants have higher energy losses in compressors as compared to lighter ones. Therefore, R290 is the right choice in this scenario, having a molecular weight of 44.1g/mol that is lighter than its counterparts, including R22, R407c, R410a, and R134a.
Comparison chart for refrigerants in RVs
|Refrigerant||Group||Safety Rating||Ozone Depletion Potential||Global Warming Potential||Cost per kg||Coefficient of Performance at fixed Temperatures|
Methods to charge the AC of RV with Propane
Despite all the favorable features of Propane, you will not find its use in RVs due to passengers’ safety.
However, with advanced skills and the use of proper safety equipment, you can use R290 as a refrigerant in the air conditioning system of your RV. Moreover, the ban on R134a by the EPA has created an avid potential market waiting to embrace the adaptation of R290.
Individuals and hobbyists modify their RVs to work on Propane based air conditioning systems. These are the following three options to shift the AC of your motor vehicle on Propane.
Replace the Whole AC System: First and most straightforward solution is to replace your RV’s whole AC system with a new one that works on Propane as a refrigerant. It will be compact, economical, safe, and improves the performance of your system.
Retrofitting: Although retrofitting is not recommended for R290 due to its explosive nature. However, on an experimental basis, by hiring some skilled mechanics, you can modify your R12 or R134a based air conditioning system to work on R290.
With an R12 system, vacuum and flush the system with nitrogen, change the mineral oil in the compressor with polyester oil, and charge the compressor’s suction side with R290 up to the pressure of 50-70 PSIG.
Remember to use a connector compatible with a Propane cylinder to charge the AC unit of your RV. Also, place a combustible gas leak detector nearby as Propane is odorless.
In an R134a system, vacuum and purge the system with oxygen-free nitrogen and charge the system with R290. The charging mass required will be less than R134a.
You can use this procedure for experimental purposes only as a slight leakage of Propane will cause an explosion and enormous loss.
Use a Mixture of R290 with other HFC
Most RVs come fitted with the R134a based system. You can use a mixture of it with R290 ( in the ratio 90%/10%) to avoid the risk of fire and benefit from the high efficiency of R290.
Is there any RV in the market with Propane as coolant?
Due to the increased use of electric vehicles, efforts are being made to develop compact and low energy-consuming AC units. It will save cost and energy to preserve the battery resulting in increased driving range of the vehicle. There is a potential market for the use of R290 in the air conditioning of electric vehicles.
A prototype unit has been built and installed in Fiat 500e electric vehicle in Europe. It has shown an increased driving range up to 15-30% depending upon the outside temperature compared to R134a based system.
Pros of running RV air conditioners on Propane
A Research study has shown that a 50% market share of hydrocarbons-based refrigerants up to 2050 will reduce greenhouse gas emissions by 25%.
R290 has a global warming potential score of 03, which is well below the regulatory limit of 150. Because it is extracted from natural gas, you can release it in the atmosphere and cause no harmful environmental impacts than other CFCs like R22, R410, and R134a.
Early chlorine-based refrigerants known as ChloroFluorocarbons have harmful effects on the ozone layer, causing it to deplete. R290 is ozone friendly and has an ozone depletion potential score of 0. Therefore, it has wide adaptation in Europe in the refrigeration and air conditioning industry.
Propane is an extract from natural gas processing and oil refineries. Therefore it is a non-toxic hydrocarbon.
It is odorless and does not harm the human lungs if inhaled in small concentrations. However, its excessive inhaling causes other respiratory problems because it is heavier than air.
Approved by EPA
Due to the environmental and ozone-friendly properties of Propane, it has been approved by EPA with few limitations and safety measures. Due to the ban on refrigerants having GWP higher than 150, R290 can be widely used in the USA’s air conditioning applications in the future.
Refrigerant grade Propane has all the properties of an ideal refrigerant. It is highly efficient, has low energy consumption, and less charging mass is required to achieve the same performance as its counterparts.
No Significant Design Changes Required in AC Equipment
R22 has comparable thermophysical properties with R290. Therefore it can be used in those systems with no modifications.
At the same time, systems working on R134a and R12 require slight changes to work on Propane. However, it requires safety precautions to check all joints to avoid any leakage leading to a fire.
R290 is way cheaper than other refrigerants like R134a. Its rate is $3 while R134a costs about $15 per Kg. Because of its availability in nature, there is little cost involved in its processing to make it pure and refined.
Moreover, it is economical as it saves cost in terms of energy conservation up to 30% compared to R134a.
Lower Charging Mass
Due to its high efficiency, 50-60% less charging mass is required than other CFCs and HCFC, including R12, R407c, R410a, and R22.
Is propane dangerous for RV air conditioners?
It is a hydrocarbon, and you have used it as LPG to heat your homes. It belongs to a group of refrigerants classified as A3 (highly flammable).
Due to this class tag, it has not gained popularity in public in the USA. Moreover, its use is not very common in RVs due to safety requirements.
Limited applications range due to restrictions on its charging mass
Because of high flammability, there are regulatory restrictions on its charging mass. Its charging quantity should be below 150g in America, while its limit is 500g for the A3 group of refrigerants approved by IEC and is applicable in Europe.
Due to these restrictions, it has limited scale applications. However, these limits are well above its mass requirements in vehicles’ air conditioning systems.
Special handling requirement
It is highly flammable and needs special handling equipment while working on Propane based systems. You should be careful and use protective gear to avoid any harm.
Unavailability of certified and trained mechanics
Because of its non-acceptance in public, there is limited air conditioning equipment using R290 as a refrigerant. Moreover, working with it requires advanced skills; therefore, you will not find many trained and certified mechanics trained to work on these systems.
Availability of other natural alternates
There are other hydrocarbon refrigerants available in the market having similar properties. Two of the commonly used examples in refrigeration are R600a and R1270.
The mixture of Propane with other Refrigerants
Due to its high flammability, using its lean mixture with other refrigerants like R134a and R600a, we can benefit from its high-performance features with safe quantities.
Precautionary measures for safe use of Propane as a refrigerant in RV
● Keep DCP and CO2-type fire extinguishers nearby while working on Propane in RV.
● It is odorless; therefore, use a combustible gas leakage detector to detect any leakage.
● It is heavier than air and settles near the floor or closed spaces, and causes fire or explosion. Therefore work on it in open areas.
● Use charging equipment compatible with Propane cylinders.
● Before doing any welding work, purge the system with oxygen-free nitrogen to reduce the risk of fire.
Refrigerant grade Propane is a promising candidate for use in RV air conditioning systems in the future.
Its high efficiency and energy-saving properties enable its consumption in upcoming models of electric vehicles.
After the ban on R134, this environmentally-friendly economical solution can be the next choice for RV manufacturers to adopt it for usage on a broader scale.
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