Results of a Field Test Using R-407C in Split System Heat
Alan Boyd Principal Engineer
This paper discusses the results ofa Jield
test to determine implications ofan R-407C
replacement of R-22.
A change ofrepigerants precipitates other
changes in materials, component selection, and
processing. In addition, thermodynamic properties
are diflerent. Consequently, the eflects on
durability, thermal per-once, humidity control,
servicing, and manufacturability were questioned.
The jield test addressed many of these
questions. Anticipated changes in manufacturing
processes were implemented on the production line.
Contractors were educated on the diflerences in the
refrigerant. Data were obtained by repigerant,
lubricant, and component tear down analysis.
Experiential information was derivedpom feed back
of contractors and home owners, as well as multiple
Generally, the$eld test has demonstrated
that by following afew basic rules, the industry can
anticipate use ofR-407C with satisfactory results.
However, the surprising appearance ofa
contaminate precipitant indicates the needfir more
investigation into long term eflects.
Unitary HVAC equipment has relied on the
HCFCR-22 for many years. With phase out
eminent, the HVAC industry seeksviable alternative
refrigerants. Of those being considered, R407C has
risen to the forefront as a potential drop-in
replacement for R-22.
While laboratory tests with this blend have
been canied out by various organizations, field
testing has been limited. A need to gainexperience
with manufacturing, installation, servicing, and field
Lennox Industries, Inc. Carrollton, TX
operation was recognized and resulted in a joint
effort by Lennox Industries, Inc., Copeland Corp.,
and Du Pont Fluoroproducts. In 1993 a field test
was initiated to gain some experience with R-407C
and POE lubricants. This paper reviews that testing
and the results.
FIELD TEST DESCRIPTION
The mainobjectives of the field test were
the following: 1) validate R407C refrigerant and
POE lubricant processing procedures for both the
factory and the field, 2) monitor the installed units to
assess compatibility of the refrigerant and lubricant
with the system, 3) obtain input from the field on
issues or problems associated with installation,
servicing, operation, sound levels, etc., 4) return and
analyze components after su£ficient test time to
determine any long term effects of the refrigerant or
R-407C closely matches system
performance ofR-22. It has zero ozone potential,
low global warming potential, and is non-flammable.
It operates at a slightly higher pressure, is zeotropic
(different composition ratios in liquid and vapor
phases), and has the evaporating and condensing
"&den characteristic. The original composition of
this ternary blend consisted of 30% R-32,10% R-
125, and 60% R-134a by weight. During the course
of the field test this refrigerant was replaced with Du
Pont's current blend ratio.
The compressor used for the field testing
was a scroll manufactured for usewith R-407C
refrigerant. Due to the immiscibility of HFC's and
mineral oil, Copeland selected the Mobil EAL Arctic
22 lubricant which is a polyol ester (POE) oil. Also,
each compressor had a special oil drain fitting
installed on the side of the canin a position which
allowed limited oil withdrawal.
Lennox manufactured 3 ton split heat pump
systems for the field test. These were supplied with
Alco Glter-driers specified for use with this HFCand
the POE oil. Also, Alco thennal expansion valves
(TXV's), with a setting based on laboratory testing
of R-dOX, were provided. A new indoor coil and
new line sets were installed with each heat pump.
POE oil has an fity for moisture and
will begin to break down if too much moisture is
abso-. This was a concern during manufacture,
installation, and servicing of the systems.
Compressors were not opened to the atmosphere
until justbefore brazing into the system.
Another area of concern centered around
the charging techniques with this ternary refrigerant
blend. Since it is a zeotrope, the composition varies
between the liquid and vapor phases. In order to
maintain the proper composition, the units had to be
liquid charged in the factory and in the field (if
necessary). Also, the "&den characteristic required
determining superheat from the "Dew Point" and
subcooling hm the "Bubble Point" of the
refrigerant. This required some education of the
The field test consisted of ten systems
installed at residential sites. Eight were installed in
the Dallas, Texas area, one in Phoenix, Arizona, and
one in Fargo, North Dakota. Data collection
included oil and refrigerant samples, and
observations and feedback from the partxipants
(homeowners) as well as the dealer. The units were
retunred to standard R-22 configuration at the end of
the field test, and compressors, driers, expansion
valves, and line sets from the test were analyzed for
long term effects.
The systems were installed in the spring of
1993 by approved dealers. All of the installations
Oil samples were taken approximately 24
hours after each system was installed. Most of these
showed moisture levels higher than the
recommended 50 PPM; thus, the need for stringent
processes (and very good drier action) with this
lubricant were made apparent. Other than thaf the
samples indicated no problems.
Based on comments from the participants,
the systems provided the cooling and heating
performance required. No problems occurred that
were associated with the alternate refrigerant and
As the field test progressed, DuPont had
reformulated the refrigerant blend for ~~~~~9000:
23% R-32,25% R-125,52% R-134a by weight.
Also, Copeland had a reformulated lubricant with
improved wear characteristics. Because of these
developments, the compressors, oil, and refrigerant
were replaced in November of 1993. No driers were
changed. Although this is not good service practice,
we wanted to push the test closer to the edge in the
area of moisture.
After the units had been running 24 hours,
an oil sample was taken. Moisture levels were
better, although a few were still higher than the
desired 50 PPM. This sample established a baseline
All units operated well through the winter
months (%eating mode), and no performance
problems were reported.
Oilsamples were taken again in April of
1994. Analysis of these second samples looked very
promising; the moisture levels were reduced from
the initial oil samples (samples taken after
compressor change out). The moisture *******
measured in the two analyses are compared in Figure
1 for the Dallas area sites. The lower levels showed
that the filter drier wasperforming as it should.
(3allas Field Test Stes
Nov. 93Sanple .Ap. 94 Sample
FIgure 1 Oil Sample Analysis -kistute
The total acid number wasalso measuredfrom the
samples and the results are shown in Figure 2.
These levels also looked good. This is a further sign
that moisture levels are being controlled and no
significant oil breakdown is occurring.
Dallas Field Test Sites
Flgure 2 Oil Sample Analysis- Acid
The metals ******* for both sets of samples
was very low and thus indicated no signs of
premature compressor wear.
Refrigerant samples were also taken in
April of 1994. Some of the refrigerant samples
revealed very unexpected compositions; we suspected
the sampling technique was to blame. A subcooled
liquid refiigerant sample mustbe obtained into a
container which closely matches the required sample
volume to insure accurate composition results. A
second, careful sampling from the field sites in
question produced favorable results. The
composition of each constituent generally measured
+I- 2% from the original blend composition. These
slight changes in composition were attributed to
error inherent in the sampling and measurement of
the refrigerant. Basedon the measurements, no
significant composition changes had occurred in the
Operation throughout 1994 and 1995
continued to be very successful. The participants
remained satisfied with the performance of the
systems. However, there were occasional reports of
mild weather high pressure switch trips.
There was an attempt to take another oil
sample in early 1995 for comparative analysis. Due
to the oil level being below the oil sampling port on
some compressors, we were able to get oil from only
half of the compressors. Ofthe samples which we
were able to get, the volume of oil was insufficient to
measure the acid and moisture ******* was not
significantly different from earlier measurements.
In mid 1995, the lintof the field test units
was converted back to R-22 wl mineral oil. It was at
this time that we noticed the presence of an unusual
contaminate. By the end of 1995, all except three
sites were converted back to R-22. These threesites
willremain operating on R407C for the foreseeable
The sourceand implications of the
contaminate are still under investigation. It seems to
be associated with high discharge temperatures. A
thorough understanding of this phenomena is a
prerequisite for confidence in a product's long term
performance and reliability.
Without exception, the participants were
very satisfied with the thermal performance of the
Several points of interest are worth noting
from the field test:
Moisture levels are a concern with the
POE oil but appear to be controllable
with the proper Glter-drier and
manufacturing, installation, and service
Service personnel seemed to adapt easily
to the "glide" characteristics.
Care must be taken when extracting
refrigerant samples for analysis.
Internal volume of the sample containers
should be close to the required volume of
the sample and samples must be
There were reports of high pressure
switch trips. Threeof those reporting
sites were tracedbackto poor air
volumes across the indoor coil. One
other site remains mysterious and
possible causes are still being
investigated. It should be noted that t
pressure switch was set for R-22
operation and R407C operates ata
slightly (approx. 20 -30 PSI)higher
pressure than R-22.
Deposition of a mysterious contamina
inside the system is still under