TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMS

1- INTRODUCTION
The destruction of the ozone layer by thechlorofluorcarbons (CFC’s), among which are CFC 11,CFC 12, and CFC 13 and its vital effect on the earth's ecosystem, were the principal reasons for the signing of theMontreal Protocol in 1987, which regulates the world
production and consumption of these substances. Thequestion which must be answered is based on thealternative to be chosen concerning the future availabilityof CFC’s, mainly CFC 12.
One of these alternatives, especially in domestic
refrigeration, is the R 134a alternative refrigerant which
was chosen due to its ozone layer non damaging
characteristics, and it also has physical-chemical
properties very similar to CFC 12.
This document has been prepared as part of the services
we are providing our customers with during this period ofchange, in order to offer guidance and avoid pitfalls that
may be encountered during the introduction of R 134a in
new refrigeration systems.
It must be noted that recommendations contained in thisguide are intended to complement any measures devisedby the manufacturer and do not carry any responsibility on
our part as to their efficiency and applicability to eachindividual situation.

2- THE ALTERNATIVE REFRIGERANT R 134a
Due to its environmentally compatible characteristics, i.e.,
the absence of chlorine (an ozone depleting agent) andthe fact that it presents physical and thermodynamical
properties which are relatively similar to those of the R 12
refrigerant, the R 134a is one of the present choices forreplacing the R 12.

As demonstrated in figure 1, R 134a presents higher
pressures at high temperatures and lower pressures at low
temperatures when compared to R 12. Both refrigerants
present the same pressure at around 20oC .
The following table shows the major impacts of the use ofR 134a compared to the use of R 12.
The tests were performed with the current EM 55NP
220-240/50Hz R 12 compressor and its R 134a
replacement, the EM 60HNP 220-240V/50Hz.
COMPRESSOR
Displacement

cm³

REFRIGERANTEM 55
NPEM 55
NPEM 60
HNP

4.99

4.99

5.54

R 12R 134a

R 134aA - Evaporating Pressure (-25 C)

bar

1.237

1.068

1.068

Condensing Pressure (55 C)

bar

13.6614.92

14.92

Enthalpy (-25 C/32 C)

kJ/kg

375

431431

Enthalpy (55 C)

kJ/kg

254279279

Enthalpy Difference

kJ/kg

121152152

B - Refrigerating Capacity (C1)

W

102

88101

Mass Flow Rate

kg/h

3.07

2.08

2.39

Cylinder Outlet Gas Temperature

C133

123

C - Expansion Device Inlet Temperature

C

55

55

55

Specific Volume

dm³/kg

0.841

0.927

0.927

Volume Flow

dm³/h

2.58

1.93

2.22

D - Liquid Enthalpy (32 C)

kJ/kg

231244

Enthalpy Difference

kJ/kg

144

187

W

1211081.19

1.23

Refrigerating Capacity (C2)Capacity Ratio (C2/C1)

As demonstrated in the above table the enthalpy differenceof R 134a is significantly larger than that of R 12.
Consequently, a smaller mass flow is required for the samerefrigerating capacity.
Section B, of the same table, shows lower discharge
temperatures with R 134a, obtained in experimental
measurements.
It also demonstrates the significant drop in capacity, whichreached 14.5% in the EM 55NP model using R 134a.
The refrigerant conditions at the entrance of the expansion
device are presented in section C - table 1. The volume flowwith R 134a is about 25% lower than with R 12, when using
the same compressor model. Should a compressor with thesame refrigerating capacity be used, there would be adecrease of around 14%, indicating the need to increase
the refrigerant flow resistance in the capillary tube.

Fig. 1 - Pressure versus temperature behavior of R 134a, ascompared to R 12.

CODE 93402 - DEC/96 - REVISION No. 02

The influence of subcooling in the refrigerating capacity isshown in section D - table 1. Note that R 134a presents anincrease in the refrigerating capacity of about 23% against
19% of that of R 12 when the liquid temperature at theentrance of the expansion device is decreased from 55oC
to 32oC.

06/93 - PAGE 01 OF 06

TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMSAs observed in section B, the refrigerating capacity is,depending on the evaporating temperature, stronglyaffected by the replacement of R 12 with R 134a. This
influence may be verified using the volumic refrigerating
effect (ratio between the specific enthalpy difference in theevaporator and the specific volume of the refrigerant undersuction condition). The greater the volumic refrigerating
effect, the greater the refrigerating capacity produced by acompressor with a fixed displacement.
Figure 2 shows the behavior of this effect on R 134a andR 12, under different evaporating temperatures.

4 - LUBRICANT OIL
Apart from its lubricating characteristics, one of the mostimportant properties of a refrigeration compressor lubricant
oil is its capability to mix with the refrigerant being used.
A lubricant with this property ensures a perfect mixing withthe refrigerant, enabling a passage throughout the systemand back to the compressor without causing oil pockets
inside the evaporator and the condenser.
The mineral and synthetic oils, presently used as
refrigeration compressor lubricants, are fully miscible withR 12 in all ranges of concentration and temperature.
However, R 134a, due to its high polarity, is immiscible withthese oils. Therefore, it is necessary to use another type of
lubricant oil for this system to function properly.
To solve this immiscibility of the R 134a, high polarity esteroils have been developed.
Although ester oil is miscible with R 134a, it is not as
miscible with R 12 as the mineral oil is.
This aspect together with R 134a pressure behavior related
to temperature, elevates the system’s characteristic curve,
as shown in figure 3.

Fig. 2 - Volumic refrigerating effect versus evaporating
temperature.

As observed in fig. 2, R 134a presents larger refrigerating
capacities (high volumic refrigerating effect) at high evaporating
temperatures (HBP conditions) and smaller refrigerating
capacities at low temperatures (LBP conditions).

3 - R 134a COMPRESSOR SELECTION
Embraco’s R 134a compressors have the same
displacements as the R 12 compressors.
As previously mentioned, there is a 10-15% decrease in therefrigerating capacity under LBP conditions, depending on
the compressor displacement. Small displacement
compressors are more sensitive to the refrigerant
substitution process.
Depending on the refrigeration system design it is possible
to use an R 134a compressor with the same displacement
as used for R 12. However, to obtain the same refrigerating
capacity under LBP conditions, it is necessary to select anR 134a compressor with the next higher displacement to theone used for R 12.

CODE 93402 - DEC/96 - REVISION No. 02

Fig. 3 - System’s characteristic curve versus compressor’s
stalling curves, considering the same systems with R 12and R 134a.

06/93 - PAGE 02 OF 06

TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMSAs shown in figure 3, the R 134a systems runningpressures are higher than for R 12 systems, therefore
requiring stronger electrical motors to elevate the stalling
curve (maximum compressor loading) to a higher level.
It is expected that R 12 systems which have regularequalized pressures do not show starting problems.
Another distinct and very important characteristic of ester
oils, when compared to mineral oils is the ability to absorb
moisture (hygroscopicity), as shown in figure 4.

5 - REFRIGERATION SYSTEMS FOR R 134a
The substitution of R 12 by R 134a is not solely restricted
to the change of refrigerant in the hermetic refrigeration
systems.
The components must be suitable for use with R 134a, asdescribed below.
It must be emphasized that cleanliness in the system is
extremely important for the use of R 134a. Further details
in item 7 of this document.
5.1 - TUBINGThe R 134a is compatible with all metals, i.e., steel, copper,
brass and aluminum, presently used in refrigeration.
Elastomers such as CAF, Nylon and Neopren are also
R 134a compatible. However, natural rubber, Butyl andVitons are not recommended due to swelling and bubble
formation properties.
5.2 - HEAT EXCHANGERS
Condensers and evaporators not showing adverse
operational effects in R 12 refrigeration systems can also
be used in R 134a systems.
Should the R 134a compressor capacity be larger than thecapacity which the R 12 system was originally designed
for, it may be necessary to use a larger condenser.

Fig. 4 - Moisture absorption by ester and mineral oils versus time
(open beaker).

As seen in figure 4, ester oils are more hygroscopic thanmineral oils. Despite the moisture absorption by the oiltakes longer when the oil is inside the compressor
housing, this characteristic is extremely importantbecause a high moisture concentration causes hydrolisis,
i.e., the transformation of ester oil into acid and alcohol.
The presence of such chemicals has a serious impact oncompressor components such as the electric wire
insulation, stator slot and winding insulating materials,
causing them to become fragile and ultimately rendering
the compressor inoperable.
Despite the higher hygroscopicity of the ester oils, therules applied for compressors with open connectors at theassembly line may not have great impact on the assembly
process, since the following parameters are observed:
1. No component, including compressor, must remain
open for more than 15 minutes;
2. The R 134a must be as moisture free as possible.

CODE 93402 - DEC/96 - REVISION No. 02

5.3 - CAPILLARY TUBE
Theoretical and experimental results have shown that thecapillary tube in LBP refrigeration systems must beadjusted to increase the refrigerant flow resistance inaccordance to its different operating conditions, as can beobserved in table 1.
When a compressor with the same refrigerating capacity isselected, a 10-15% reduction in the N2 flow is generally required
for a 10 bar pressure at the inlet of the capillary tube.
5.4 - FILTER DRIER
The desiccants presently used in filter driers of the R 12
refrigeration systems are not compatible with R 134a.
Desiccants similar to XH7 or XH9 (3Å) type arerecommended.
The quantity of desiccant used in R 134a filter driers
should be about 20% higher. This is due to the lower water
absorption by XH7/XH9 combined with the fact that themoisture level of R 134a refrigeration systems may behigher due to the extreme hygroscopic properties of esteroils, as previously mentioned.

06/93 - PAGE 03 OF 06

TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMS

5.5 - REFRIGERANT CHARGE
The R 134a charge should be determined in accordance
to the same procedures used for R 12.
In unchanged R 12 refrigeration systems, the R 134acharge may be about 5-10% lower.

6 - IMPACT OF REPLACEMENT OF R 12 BY
R 134a IN DOMESTIC REFRIGERATIONSYSTEM
Certain behavior trends become evident in the pressureand operation temperatures of the system when R 12 isreplaced by R 134a in a domestic refrigerator, as shown infigures 5, 6, 7 and 8.
It is interesting to observe in this example that someoriginal R 12 refrigerator components were adapted foruse with R 134a.
An R 134a compressor of the same capacity as the oneused in the original R 12 system was chosen. It used theXH7 desiccant in the filter drier and a 5% lower refrigerant
charge. There were no changes to the condenser,evaporator and capillary tube.

Fig. 5 - Condensing temperature behavior of the system with R 12and R 134a.

Fig. 6 - Condensing pressure behavior of the system with R 12and R 134a.

Figures 7 and 8 show that the refrigeration system
operating with R 134a presents an increase in theevaporating temperature while having the same
evaporating pressures. Therefore, in order to reach thesame evaporating temperature the capillary tube must be
adjusted to increase the refrigerant flow resistance.

Fig. 7 - Evaporating pressure behavior of the system with R 12
and R 134a.

As observed in figure 5, the condensing temperature was
not affected with the use of R 134a. This is due to the factthat in many domestic refrigerators, such as the one usedin this experiment, the condenser heat transfer isdominated by the air-side, which is not influenced by adifferent refrigerant.
However, as shown in figure 6, the condensing pressure ofthe system with R 134a is higher than with R 12. This wasexpected because both refrigerants presented the samecondensing temperatures (see fig. 1).

CODE 93402 - DEC/96 - REVISION No. 02

06/93 - PAGE 04 OF 06

TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMSThe knowledge acquired in the last years, supporting andfollowing the experience of the leaders of the refrigerationindustries around the world indicates that a successful
conversion operation as well as a relatively simple
manufacturing process can be achieved.
The presence of foreign substances such as chlorinated orgreasy residues and mineral oil or impurities in the R 134a
Embraco compressor would render warranty null and void.
Therefore, it must be emphasized that before filling withrefrigerant, refrigeration system cleanliness is much morecritical in the case of R 134a systems than R 12 systems.
Through its intensive research, Embraco is aware of thisproblem and the R 134a compressor production has been
designed to eliminate such residues.
Fig. 8 - Evaporating temperature behavior of the system with R 12and R 134a.

8 - ASSEMBLY OF NEW R 134a REFRIGERATIONSYSTEMS
7 - R 134a REFRIGERATION SYSTEM
CLEANLINESS
Since the beginning of the utilization of CFCs in hermetic
refrigeration systems, special care has been taken
regarding the cleanliness of the inner surfaces of thesystem before filling. The reason for this is to avoid greasy
and oily residues coming from the manufacturing processof components.

Due to the sensitivity of the R 134a ester oil systems weshould like to make the following recommendations, which
would also apply to any existing refrigerant:
8.1 -One system only to be connected to each vacuum
pump.

8.2 -

Form vacuum on both sides of appliance, withvacuum level below 0.6 mbar.

The solubility with the refrigerant or the lubricant oil allows
these residues to move around the system possibly
causing a blockage of the refrigerant flow, specially in thecapillary tube.

8.3 -Vacuum pumps must be installed on the same level
as the compressor or lower.

8.4 -Use short hoses wherever possible.

One of the main reasons is the low solubility of R 134a andester oils with waxes, such as the paraffin found in theelectrical motor wires of compressors, with the protective
oils used in compressor components and greases used in
the manufacture of tubings, evaporators and condensers.

8.5 -Vacuum level to be measured on the appliance andnot on the pump.

8.6 -Perform final vacuum through charging board.

8.7 -Perform rough leak detection through charging
board. In case of leak, there should be no filling.

8.8 -Limit content of non-condensable gases to 1%.

8.9 -Use R 134a as flushing agent to clean systems.

Strongly alkaline substances, such as the protective
agents used in the manufacture of compressor
components can also be responsible for capillary tube
blockage. These substances react with ester oil producing
salts which may deposit in the capillary tube.
Other impurities, such as chlorinated residues from thecomponent cleaning process must be avoided.
The reaction of this type of residue with ester oil can resultin harmful acids (HF, HCl), causing metal corrosion anddeterioration of the desiccant and lubricant. Mineral-oil
residues must also be avoided as they result in thedecrease of R 134a and ester oil miscibility causing oil
return problems.
It is essential that all other components of the refrigerating
system be completely free of these types of residues.

CODE 93402 - DEC/96 - REVISION No. 02

8.10 - Gas charging and evacuating equipment must bereserved exclusively for R 134a to avoid chlorinatedresidue contamination.
8.11 - The halogen leak detectors presently used in R 12
systems are not efficient with R 134a. This type ofleak detector reacts with chlorine, a halogen, which
is absent in R 134a. Therefore, equipment that uses
helium as a tracer gas in combination with helium
detectors, is recommended for the assembly linesof R 134a systems.
There are compact electronic leak detectors on themarket which are compatible with the R 134a refrigerant.

06/93 - PAGE 05 OF 06

TECHNICAL INFORMATIONUSE OF R 134a IN NEW LBP REFRIGERATION SYSTEMS

8.12 - To prevent excessive moisture from entering thecompressor the connector should be kept sealed at
all times. Plugs should be removed immediately
before brazing connectors to system tubes(maximum time allowed is 15 minutes).

Based on Embraco’s experience to date, we intend toprovide our customers with some recommended pratices
to handle systems utilizing HFC 134a and ester lubricants.
The scope of this document was neither to approve nor
reject any of current procedures, nor to give final solutions
to nonconformities. Rather, Embraco’s intention is toprovide assistance and guidance in order to achieve
maximum performance and customer satisfaction.

Should you require any further assistance in the development of your refrigeration system to R 134a, please contact oursales staff at the following telephone and fax numbers indicated below.

Rua (Street) Rui Barbosa, 1020 - Cx. Postal (P.O. Box) 9189219-901 Joinville - SC - Brazil
Phone: +55 47 441-2430
Fax: +55 47 441-2870
Embraco North America, Inc.
2232 Northmont Parkway
Duluth, Georgia - USA 30096
Phone: +1 770 814-8004+1 800 549-9498
Fax: +1 770 622-4620+1 800 462-1038

CODE 93402 - DEC/96 - REVISION No. 02

Embraco Europe S.r.l.
Via Buttigliera 610020 - Riva Presso Chieri (Torino) - Italy
P.O. BOX 151 - 10023 - Chieri (TO)Phone: +390 11 943-7111
Fax: +390 11 946-8377 / +390 11 946-9950

06/93 - PAGE 06 OF 06