Introduction; Compressor; Refrigeration Systems; Sealed System Repair - Frigidaire FFBN1721TV0 Technical & Service Manual

Service Manual - Four-door Refrigerator ( FFBN1721TV0 )
Sealed System

Introduction

This section is intended as a guide for introducing the service
technician to R-134a refrigerant, and the equipment needed to
service R-134a systems.
The replacement of R-12 refrigerant involves changes in mate-
rials, choice of lubricant, and processing procedures, with an
overall requirement of continuous high-quality system perfor-
mance and reliability. The following information provides a good
practical foundation for service needed to maintain long product
life.

Compressor

In a refrigerating system designed for R-134a refrigerant, only
R-134a refrigerant is to be used. The current design of hermetic
compressors lead to the situation that some oil (a small
percentage) will follow with the refrigerant through the whole
system. R-134a compressors require a new lubricant. At this
time, only synthetic ester oil is to be used. The R-12 compressors
used mineral oil. Mineral oil is not compatible with R-134a and is
not to be used in R-134a systems. Ester oil must not be mixed
nor replaced with any other lubricant. Compressors used with
R-134a systems charged with oil, cannot have any tube fittings
exposed to ambient air for more than 15 minutes. Ester oil is
more hygroscopic (it will absorb water at a much faster rate) than
the mineral oil used with R-12 systems.
ESTER OIL CAN BE AN IRRITANT TO
EYES AND SKIN. REFER TO MANUFAC-
TURE SAFETY DATA SHEETS FROM
LUBRICANT SUPPLIER FOR HANDLING
SPECIFICATIONS.
CURRENT REFRIGERANTS, YOU MUST
HAVE AN ADEQUATELY VENTILATED
CAUTION
WORK AREA AT ALL TIMES FOR SEALED
SYSTEM SERVICE AND REPAIRS.

Refrigeration Systems

The sealed refrigeration system will consist of the same basic
components being utilized in the R-12 systems. There is a 10%
to 15% discharge pressure increase using R-134a, with a 5% to
10% decrease in suction pressure when compared to the same
product with an R-12 system operating at 90°F (32°C) ambient
temperature conditions. Lower suction pressures result from the
lower density of R-134a refrigerant which effects refrigerant flow
rate. R-134a systems commonly operate in a 1"-2" vacuum on
the suction side.
Products using R-134a refrigerant will have a different heat
exchanger than a R-12 product. The difference is in the capillary
tube, it will be longer to maintain a similar flow rate. On some
models, a larger condenser will be used to reduce the discharge
pressures and lower start-up sound transmission. A different
filter-drier will be used on refrigerating systems with R-134a. The
molecules of R-134a are smaller than those of R-12, therefore, a
dryer with smaller pores is necessary.
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AS WITH ALL
Otherwise, R-134a could be trapped inside the filter-drier along
with the water. On some products you will see some changes to
the evaporator and suction line.
Ester oil and R-134a mix satisfactorily within the compressor.
Lower gas speed increases the risk of oil accumulation in the
evaporator. Some changes will be required to ensure good oil
return-ability.

Sealed System Repair

To prevent any form of cross contamination of R-134a, and R-12
refrigerant, or a cross contamination of ester oil and mineral oil,
you must have dedicated equipment.
The equipment consists of one set of gauges, manifold, hoses,
vacuum pump, charging cylinder, and reprocessing or transfer
pump. This means you must have one complete set for CFC,
(R-11, R-12) and HCFC, (R-22) systems, and one complete set
for HFC, (R-134a) systems. You can not share the use of any of
the same equipment on both systems.
Since the R-134a molecule is smaller than the R-12 molecule,
R-134a could pass more minor leaks than R-12 and the flow
through a certain leak would be larger for R-134a than for R-12.
As a consequence, it is critical to maintain very good brazing
processes and leak tests.
You must make sure you do not mix refrigeration oil or refrigerant
in your bulk storage area. Because moisture infiltration is much
higher in ester oil, you must keep it stored in sealed containers
and only allow exposure to room air for a very short period of
time when changing or adding oil to a system. You must not mix
refrigerant in your storage containers for used refrigerant
removed from products for service. You must have dedicated
cylinders for each refrigerant R-12, R-22, and R-134a.

Definitions

Recovery:

To remove refrigerant in any condition from a system and store it
in an external container without necessarily testing or processing
it in any way.

Recycling:

To clean refrigerant for reuse by oil separation and single or
multiple passes through devices, such as replaceable core filter-
driers, which reduce moisture, acidity and particulate matter. This
term usually applies to procedures implemented at the field job
site or at a local service shop.

Reclaim:

To reprocess refrigerant to new product specifications by means
which may include distillation, will require chemical analysis of
the refrigerant to determine that appropriate product specifica-
tions are met. This term usually implies the use of processes or
procedures available only at a reprocessing or manufacturing
facility.