More information on boat refrigeration

Costs of maintaining a boats refrigerator are skyrocketing due to
resent changes in the refrigerant industry and the lack of knowledge
when servicing them. The ban on manufacturing R12 refrigerant has
resulted in mistakes in how to service these units costing many
boater's hundreds of dollars.

Here are some things boaters should know:

Refrigerant 101
Refrigeration is the process of removing the heat from the evaporator
in the refrigerated box and disposing of it to an area outside the
box. The compressor circulates the heat to the condenser where it is
transferred to another medium air or seawater. It does not matter what
type of a mechanical refrigerator you have this is the basic principle
of how it functions.

Refrigerant 102
Most older boat refrigeration systems used Freon R12 refrigerant
except for low temperature freezers which used R502. Both of these
refrigerants can no longer be manufactured as they affect the ozone
layer and global warming. If you determine that your unit needs R12,
it is best to stay with that refrigerant. Yes, there is plenty of R12
out there but it just costs more. R12 is currently selling for $20 per
small can on Ebay.
Remember the final authorization to use alternative refrigerants or
oil should come from the compressor manufacturer and no one else.
The most used 12/24 volt refrigerator compressor is the Danfoss. It is
used by Adler Barbour and at least twelve other companies. The older
Danfoss BD 2.5 compressors use Freon R12 refrigerant and mineral
refrigerant oil. Refrigerant 134a was not approved for these
compressors because of its inability to mix with mineral oil and to
change the oil to a compatible oil might destroy the insulation on the
motor wiring.
There is one blended refrigerant, 409a, that can be used as a
replacement for R12 in BD2.5 compressors, but only in an emergency in
cool climates. Warning, never mix refrigerants and always vacuum out
the old before inserting a substitute.

Hermetically sealed compressors that are powered by alternating
current 110 or 220 volt may be filled with Alkylbenzene oil which is
compatible with HCFC component refrigerants. Blended refrigerant 409a
is recommended as a replacement for R12 in systems where the
compressor contains alylbenzene oil.

Externally driven compressors, engine driven or those with large 12/24
volt motors are being converted from Freon R12 to 134a refrigerant.
This also includes changing to a compatible Poly Ester conversion oil.
If you have one of these systems, contact the system manufacturer for
their correct procedures for making this conversion.

Don't forget to clean the condenser coil annually on air/water cooled
refrigerators or when the system performance is in question.

Nondestructive testing to determine refrigerant quantity is important
to avoid contamination.
You don't need a mechanic to check out your boat's 12 volt
refrigerator before your cruise. Turn the refrigerator on and after 30
minutes there should be a thin layer of frost covering the evaporator.
Adler Barbour and other similar ice box conversion units supply a
three foot piece of insulated tubing to use on the lines just outside
the box. In moderate temperatures and humidity three feet of
insulation should be enough to prevent moisture on the lines outside
the box. If the evaporator is not 100% covered with frost the unit is
low on refrigerant. If frost extends outside the box on the line back
to the compressor then there is too much refrigerant in the system.

Large refrigeration systems in boats generally have holding plates
inside the refrigerated box that may take more than an hour to freeze.
A touch of a finger on different parts of the system can indecate if
the system is working OK. On the line just before the plate is an
expansion valve, by touching the outlet of this valve performance of
the system can be determined. After about ten minutes the temperature
of the outlet of the valve should be below +10 degrees F., If you
place a finger on the valve outlet at this time your finger will
almost stick to the valve indicating the system is probably OK.
Systems with expansion valves generally have a sight-glass in the
pressure liquid line after the receiver that will indicate refrigerant
quantity, but you must know what it looks like when the system has the
correct amount of refrigerant in it.

To extend the life and obtain the best performance from you boats
refrigerator:
• Use the correct refrigerant and oil.
• Only connect servicing gauges when it is proven necessary and purge
the gauge set before connecting it.
• One ounce plus or minus of refrigerant volume will effect the
performance of any small capillary expansion device system like the
Adler Barbour cold machine.
• On the new BD35 and BD50 compressor systems the actual compressor
run time or cycling is no longer a true indication of performance.


I provide a great deal of free boat refrigeration information on my
website so be sure to check out the Forum and FAQ section. It you have
one of the new efficient 12/24 volt compressors the Slide Show will be
of interest also.


From the author of books on boat refrigeration.
http://www.kollmann-marine.com