United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-98/015
February 1998
&EPA Project Summary
Effect of Lubricant
Contamination on the
Performance and Reliability of
Heat Pumps Charged with
R-407c
S. A. Fitzhenry, W. V. Payne, and D. L. O'Neal
The report gives results of the devel-
opment of new data that can be used
to determine the effect of mineral oil
contamination on the reliability of a heat
pump system operating with a new
hydrofluorocarbon (HFC) mixture and
polyol ester (POE) lubricant, to assess
any performance degradation due to
mineral oil contamination in retrofit ap-
plications, and to examine the impact
of water contamination on the retrofit
system. (NOTE: In heat pump refriger-
ant retrofit applications in the field, er-
rors can occur that can have an impact
on subsequent equipment perfor-
mance.)
As the result of the premature failure
of one of the units, the long term reli-
ability of contaminated systems was
not determined. Future investigation
should reexamine this issue. The ef-
fects on performance of various levels
of mineral oil contamination were not
significant, so further investigation at
specific conditions of interest may be
justified. The effects of water contami-
nation could be more significant. The
increase in total acid number could
have potentially led to increased
amounts of trace metals in the system
as the acid attacked the system com-
ponents. A more long term study would
be necessary to determine if there were
any long term effects of water contami-
nation that did not appear during this
15-week trial.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Chlorofluorocarbons (CFCs) and
hydrochlorofluorocarbons (HCFCs) are two
major categories of refrigerants that con-
tain chlorine. These chlorine- containing
refrigerants have been found to be strato-
spheric-ozone-depleting chemicals, and
their use must be discontinued as required
by international agreement and U.S. law.
HCFC-22, a medium pressure refrigerant
used in heating, cooling, and refrigeration
applications, is scheduled to be phased
out of production and must be replaced.
During the past several years, industry
and government researchers have begun
to develop and test new refrigerants for
replacing HCFC-22 in air conditioners, heat
pumps, and other applications. Currently,
no pure non-flammable refrigerant has
been identified as an acceptable replace-
ment for HCFC-22. However, several suit-
able zeotropic mixtures of
hydrofluorocarbons (HFCs) have been
identified. Most notably, the mixture of
HFC-32, HFC-125, and HFC-134a in the
proportions of 23/25/52 wt % (industry-
designated as refrigerant (R)-407c) is the
refrigerant most likely to replace HCFC-
22 in retrofit applications.
In retrofit applications, where HCFC-22
in a heat pump or air conditioner is re-
placed with R-407c in the field, errors can
occur which can have an impact on sub-
sequent equipment performance. When
-------
using R-407c, a polyol ester (POE) lubri-
cant must be used, requiring the removal
of both the HCFC-22 refrigerant and the
associated mineral oil lubricant from the
system. It is possible that the existing
mineral oil might not be totally cleaned
out of the system and remains as a con-
taminant in the new R-407c/POE system,
affecting performance. Another problem
could arise because the POE lubricant is
highly hygroscopic. If care is not taken
during the replacement of the lubricant,
moisture could enter the system with the
introduction of the lubricant and degrade
performance and equipment life.
The objectives of this research were to
develop new data that could be used to
determine the effect of mineral oil con-
tamination on the reliability of a heat pump
system operating with the new HFC mix-
ture and POE lubricant, to assess any
performance degradation due to mineral
oil contamination in retrofit applications,
and to examine the impact of water con-
tamination on a system charged with the
replacement fluid and synthetic POE lu-
bricant.
Results
The first set of tests examined the long
term reliability of a heat pump operating
with an alternate refrigerant when the unit
has mineral oil contaminant present. Two
identical heat pump units were compared:
one operated with HCFC-22 and mineral
oil, and the other used R-407c and POE
with 11.9% mineral oil contaminant. The
two units were first tested in an environ-
mental chamber to obtain a reference per-
formance level for each. They were then
to be operated under uncontrolled ambi-
ent conditions in semi-continuous cycle
for a year to simulate long term perfor-
mance. Unfortunately, due to the prema-
ture failure of the compressor for the
HCFC-22 unit after 3 months, only ap-
proximately 20% of the test cycles were
completed, and project time did not allow
for restarting the test with a new set of
heat pumps. The compressor from the R-
407c unit was examined and showed nor-
mal wear for the length of time that the
unit had been in operation. Operating data
are presented for both units.
In the second set of tests, performance
data were collected on two identical heat
pump units to determine the effect on
performance of mineral oil contamination.
Each unit was tested with R-407c refriger-
ant and POE lubricant. Increased levels
of mineral oil contamination, up to 25% by
weight, were introduced into the system
to characterize any performance degrada-
tion as a result of the contamination. Tests
were conducted for both heating and cool-
ing modes. Overall, the results showed
that mineral oil contamination had mini-
mal effect on the performance (capacity
and efficiency) of the heat pumps. Most of
the data for capacity and efficiency for
different contamination levels were within
the uncertainty of the measurements.
There did not appear to be a definitive
trend between performance and contami-
nation level.
The final phase of the project examined
the effects of water contamination in the
lubricant on the reliability of a unit charged
with R-407c and POE lubricant. Identical
units were charged with R-407c refriger-
ant and POE lubricant. One unit was left
as dry as possible, while the second unit
was contaminated with 1200 ppm of mois-
ture. The units were operated continu-
ously in the cooling mode for 15 weeks.
Analysis of the lubricant extracted from
the units showed little to no increase in
the three metals (iron, copper, and zinc)
tested in the study. The total acid number
in the water contaminated unit showed a
general increase. This increase in acid
number could have potentially led to in-
creased amounts of the trace metals as
the acid attacked system components.
Conclusions
As the result of the premature failure of
one of the units in the long term reliability
study, reliability of contaminated systems
was not determined. Future investigation
should reexamine the long term reliability
of a unit operating with an alternative re-
frigerant when mineral oil contaminant is
present. The potential exists for systems
to become contaminated with mineral oil
during retrofit operations. Although the ef-
fects on performance of various levels of
mineral oil contamination were not signifi-
cant, the effects varied between heating
and cooling tests at various test condi-
tions, so further investigation at specific
conditions of interest may be justified. The
effects of water contamination could be
more significant. The increase in total acid
number could have potentially led to in-
creased amounts of trace metals in the
system as the acid attacked the system
components. A longer term study would
be necessary to determine if there were
any long term effects of water contamina-
tion that did not appear during this 15-
week trial.
-------
S. Fitzhenry, V. Payne, andD. O'Neal are with the Dept. of Mechanical Engineering,
Texas A&M University, College Station, TX 77843.
Robert V. Hendriks is the EPA Project Officer (see below).
The complete report, entitled "Effects of Lubricant Contamination on the Perfor-
mance and Reliability of Heat Pumps Charged with R-407c," (Order No. PB98-
127079; Cost: $31.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
National Risk Management Research (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-98/015
------- |