Types of Refrigerants

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TYPES OF REFRIGERANTS

R-12

R-12 or Freon, was used in BMW air conditioning systems prior to 1992. It is a member of the class of compounds called "chlorofluorocarbons" (CFC's).

Characteristics:

- Very durable.
- Transports heat very efficiently.
- Non-explosive when mixed with air.
- Odorless; not harmful to human health when handled correctly.
- Boils at -22°F (-30°C).
- Absorbs a large amount of heat when boiling.
- Does not react with most metals (except lead).
- Reacts with many synthetics.
- Reacts with water to produce acid.
- Mixes readily with mineral-based oil.

Skin should not be exposed to liquid R-12. Since R-12 boils at -22°F (-30°C), it can cause severe frostbite or freezing damage.

R-12 should never be exposed to an open flame. When it burns in air, it produces phosgene, a poisonous gas.

R-12 should be stored at room temperature, and not exposed to extreme heat.

A serious environmental problem has been created by discharging R-12 refrigerant into the atmosphere. CFC's cause very long-term damage to the stratospheric ozone layer.







One molecule of R-12 can destroy many molecules of ozone. in the upper atmosphere, ultraviolet light breaks off a chlorine atom from an R-12 molecule.

The chlorine attacks an ozone molecule, breaking it apart. An ordinary oxygen molecule and a molecule of chlorine monoxide are formed.

A free oxygen atom breaks up the chlorine monoxide. The chlorine is then free to repeat the process.







The ozone in the stratosphere blocks most of the ultraviolet-B radiation from the sun, thus preventing it from damaging plants and animals. Without the protection of stratospheric ozone, plants and animals are exposed to damaging levels of UV-B.

R-134a

For this reason, a new refrigerant, R-134a, has been developed. It does not contain chlorine (it's a "hydrofluoro-carbon," or "HFC"). It causes much less damage to stratospheric ozone.







Despite the much lower risk of environmental damage, it's still important to handle R-134a responsibly. BMW technicians should do their part to maintain a safe environment for future generations.

Characteristics of R-134a:
- Very durable.
- Transports heat very efficiently.
- Density, pressure, boiling point similar to R-12.
- Extremely hygroscopic (absorbs water very readily).
- Non-toxic, non-flammable; slight ether-like smell.
- Contains no chlorine atoms; will not damage stratospheric ozone.
- R-134a pressures tend to rise sooner and higher as temperature increases.







IDENTIFICATION OF R-12 AND R-134a CONTAINERS







Although R-12 and R-134a are similar in some ways, the refrigerants must never be mixed or combined in any way.

BASIC SYSTEM DIFFERENCES: R-12 vs R-134a

- R-134a pressures are higher than R-2, as temperature increases.
- Compressor oils:
- R-12 systems use mineral oil.
- 134a systems use PAG oil.

- Underhood labels:
- R-12: black.
- R-134a: green.







NOTE: Charging amount should be according to the underhood label. However, refer to the S.I.B. # 64 2192 (3695) for refrigerant charge variations.







Description Changes

Compressor Clutch Higher torque capacity
Compressor New valving, no melt bolts, PRV, PAG oil RBR seals
Condensor High efficiency, no copper parts
Receiver/Dryer Zeolite desiccant, no melt bolts, PRV
Hi/Lo Pressure Switch New seal materials (RBR)
Expansion Valve Special materials for R-134a, RBR seals
Evaporator Denser tins, high efficiency, no copper
Temperature Sensor No changes
High Pressure gas, liquid Higher pressures at high temperature
Low Pressure liquid, gas Higher heat to vaporize