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Have all the new refrigerant laws
left you out at sea?
The reputation, reliability and maintainability of equipment normally
improves with age, but this has not been true when it comes to boat refrigeration. the
1990 Clean Air Act amendments imposed new regulations with landmark dates that industry
was unable to meet. So stop gap solutions and lack of time to do research and development
have resulted in a lack of standards and poor information. With more than 12 new
refrigerants on the market and 4 different types of oils, it easy to get confused about
which oil to use with which refrigerant. A mismatch can not only affect the reliability of
your system but it can also destroy a system.
Although the automotive industry did agree on a
standard for the replacement refrigerant, HFC-134a, also
known as R134,, they are not in agreement on the type of oil that
should be used with it. They also agreed on use standards for labeling and service
equipment and they have adapted a new standard for service connectors that makes it
difficult to make a mistake. These standards are intended to prevent cross-contamination
of gases and oils, but these standards are not always followed through in boat
refrigeration. All boat refrigeration systems should be labeled for type of oil and
viciosity and the type of refrigerant used.
Cruising boats must be extra careful in selecting a
refrigerant as it might not be available in remote ports of call.
Below is a list of the most
commonly used oils in boat refrigeration.
Mineral
is a wax free oil used for many years as a standard for
refrigeration. When it is mixed with Freon 12 it travels throughout the
system, but it does not mix with R134a.
Alkylbenzene refrigerant oil is a synthetic aromatic hydro-carbon. It is
compatible with mineral oil and has improved oil return over mineral.It can be used with
most refrigerants but NOT 134a. Almost all NEW low
temperature AC hermetic compressors are serviced with Alkylbenzene oil.
Polyol Ester
oil must be used with R134a
refrigerant. This oil is compatible and acceptable for use with R12, R22, and 502.
Most replacement engine drive systems come with this oil. NOTE: Once a
system has been set up to run on Polyol Oil it can be switched back to Freon 12, but first
you must check with the manufacturer for approval.
PAG (Polyalkylene Glycol) is used in some new automobiles but is NOT
recommended in retrofits as it is not compatible with other lubricants.
Most commonly used refrigerants in
new and retrofit systems.
CFC 12
is no longer manufactured in the United States and is being
phased out. Freon 12 is still available but its high cost is prohibitive.
HFC 134a is a long term non-ozone depleting alternative refrigerant, but
it is not a direct replacement for R12.
Blends are a combination of two or
three refrigerants most of which contain Freon 22.
Freon 22 is also an ozone depletor and has the same restrictions and
regulations as Freon 12. Although the production ban on it has been
postponed until the year 2020, but only certified technicians can purchase any refrigerant
that contains Freon.
MP39 (401A) and MP66
(401B) are interim blends that were
developed to serve as a retrofit for CFC 12. These refrigerants require
Alkylbenzene oil.
Blends cause system high pressure to run
higher than R12. Blends also tend to separate into their components which
means that it may be necessary to remove and replace the entire charge if a leak occurs
and refrigerant is lost.
There are certain things you need
to do before adding refrigerant.
Things not to do.
Do not add 134a to any
other refrigerant. The mixture could become flammable or toxic. 134a can't
be used in a boat refrigeration system which uses either mineral or alkybenzene. These
will not mix with 134a and will cause oil starvation resulting in
compressor failure.
Don't change the oil or refrigerant in a
hermetically sealed compressor without checking with the manufacturer of the compressor.
Hermetically sealed compressor motors and their wiring are submerged in the refrigerant
and oil mixture. The synthetic compounds may strip the insulation off the wiring and
cause damage to the compressor.
About five years ago there were concerns about converting to 134a.
It was thought that the HFC 134a and oil mixture would
destroy the rubber "O" rings, the interior plastic and elastomers parts and it
was recommended that the oil should be flushed completely from the system or down to only
1%. Now the common consensus is that the Polyolester oil will mix with the mineral oil
that is left in the system and that the previous use of mineral oil would have sealed the
hoses and "O" rings thus preventing refrigerant leaks. After numerous
tests by the automotive industry and major oil companies the conversion procedures were
simplified to the following procedures.
Recover old refrigerant
Drain the oil from the compressor.
Replace the filter/dryers.
Add the correct amount of Polyol Ester oil.
Leak test the system Use a small amount of refrigerant to pressurize to
a pressure that is equal to the ambient temperature. If nitrogen is available, pressurize
to 150 PSI. Use no other gases such as oxygen for testing.
Deep Vacuum the system
Charge with 134a (80% of the R12 charge)
Do a performance check.
Install 134a service parts.
(optional)
Replace any exposed "O" rings
or seals with compatible 134a seals.
REMEMBER only 134a has met the minimum safety requirements and that if you
use other refrigerant substitutes in your system your system will then become a
test subject!
Things you should know about
retrofitting.
Hermetically sealed boat refrigeration units with all
solid tubing rarely need servicing and should be left with the original refrigerant since
R12 is still available although expensive.
The conversion of belt driven compressors or "Bolt
Together" systems with seals are a problem. These systems have a history of leaking
and should be converted whenever major overhaul of the system is required.
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