R-410A Systems Choices

MAKING the
RIGHTChoices for
R-410A Systems
New component selection choices and more rigorous servicing
techniques are required to ensure success while working with
R-410A equipment BY AL MAIER
s the industry moves closer to the 2010 phaseout of
R-22, more manufacturers
are beginning to produce
air-conditioning and refrigeration systems that
use environmentally friendly HFC
refrigerants such as R-410A. It is estimated that 15 percent to 20 percent of
new air-conditioning units introduced into service in 2006 will use the
chlorine-free, energy-efficient, nonflammable R-410A.
To accommodate its use, manufacturers have developed a new generation of components. As a result,
both engineers and service technicians face choices today that did not
previously exist.
Choosing the appropriate components during both design and service
is necessary to ensure safety and
increased R-410A system efficiency
and reliability. This article will cover
new component selection choices and
the more rigorous servicing techniques that are required to ensure
success while working with R-410A.
In the new world of HFC refrigerants, all the old rules regarding proper design and servicing of air-conditioning and refrigeration systems
still apply. But the penalty for not
using proper techniques when producing, assembling and servicing
R-410A systems is much greater.
Choosing the wrong components
A
Choosing the appropriate components during both design and service is necessary
to ensure safety and increased R-410A system efficiency and reliability.
Refrigerant differences
The first and most noticeable difference between working with R-22 and R-410A exists in the system operating
pressures. At a typical air conditioner evaporating temperature of 45° F, the saturated pressure of R-410A is 54
psi greater than that of R-22. At a typical condensing
temperature of 100° F, the saturated pressure of R-410A
is 121 psi greater than that of R-22.
Engineers and service technicians need to understand
that the higher pressures of R-410A require contractors and
technicians to use only new gauge sets that have been specially designed to handle the higher pressures. These highpressure gauge sets are typically rated for 500 psi to 800 psi
on the high side. All hoses also must be rated for 800 psi.
In addition to high-pressure gauge sets and hoses, use
high-pressure recovery machines and tanks specifically
designed for R-410A. Technicians should inspect equipment labels for the color rose, which is used to identify
equipment designed for use with R-410A. By using highpressure charging and recovery equipment, technicians
and contractors can safely work with R-410A.
The higher pressures of R-410A also require air-conditioning and refrigeration system designs to utilize only
those system components that have been approved for
higher pressures. Components and tubing designed and
approved for a maximum working pressure of at least
680 psig are recommended for R-410A systems.
One downside of the system requirements for higherpressure R-410A is that R-22 systems cannot be retrofitted for use with R-410A. If an R-22 system must be directly retrofitted to an HFC refrigerant, then R-407C is a good
option because it has operating pressures similar to R-22.
Differences in oils
The next significant difference between R-22 and R-410A
systems is refrigerant oil. For HFC systems, you must use
polyolester (POE) oils, which are typically included in HFCrated compressors. Service contractors must be aware of the
differences between POE oil and mineral oil, as improper
handling of POE oil will lead to system failure much more
quickly than the same improper handling of mineral oil.
POE oils attract moisture much more quickly than the
mineral oils historically used for CFC and some HCFC
systems. POE oil is highly reactive to moisture and forms
acids in a chemical reaction with water. It is also significantly more difficult to remove moisture from POE oil
once it has been absorbed.
The general term for oil’s ability to attract and retain moisture is hygroscopicity, and POE oils are very hygroscopic.
Some POE oils absorb up to 20 times more moisture than
ordinary mineral oils.
When assembling or repairing HFC systems with
hygroscopic POE oils, you must minimize the amount of
time the system is left open. Ideally, leave the system
open for less than 15 minutes. Always try to use a dry
nitrogen environment when any POE system is open for
assembly or service. While this also is true for servicing
mineral oil systems, the practice of using dry nitrogen
has not been rigorously followed as much as it should be.
If a POE system is open for the same amount of time
service technicians are used to having mineral oil systems open, there is a much greater chance of moisture
contamination of the oil and, consequently, downstream
system failures. These failures will cause expensive callbacks and repairs. Most important, if the failures occur
within the service warranty period, the contractor will be
responsible for the repair costs.
Need for proper service
Ultimately, it will be less expensive to properly repair the
system initially than it would be to make repeat calls
after a hasty first repair. Keeping systems free from air,
moisture and non-condensable materials always
improves system reliability and does not require any
additional time by the service technician.
All it takes is knowledge, training and discipline. Service
technicians need to be aware of these issues and properly
trained on servicing R-410A systems so they can avoid
these costs and the potential damage to their reputations.
To minimize the risk of moisture-related system failures,
R-22 and R-410A Pressures
R-410A
Pressure (psia)
for an R-410A system can make the system susceptible to
burst, which can lead to system failure and, worse yet,
serious injury. Furthermore, not using proper service
techniques will lead to repeated in-warranty system failures which are not only costly, but can cause irreparable
damage to a contractor’s reputation.
R-410A has unique performance specifications and
characteristics for oil, moisture indication, thermal
expansion valves, compressors, filter driers and refrigerant handling. By having a solid understanding of these
characteristics, engineers and contractors can save time
up front, design and build more reliable systems, and
minimize system failures and their associated costs.
Figure 1
+58%
R-22
+60%
Temperature (°F)
R-410A pressures are more than 50 percent higher than R-22.
system also must be designed specifically for the refrigerant. Compressor
manufacturers optimize motors, displacements, bearings, valves and others for the particular refrigerant and
its expected operating conditions.
Consequently, R-410A compressors
are vastly different from the R-22
models they replace, so use only
specifically rated R-410A compressors
with the higher-pressure refrigerant.
Importance of filter driers
Service technicians need to be properly trained on servicing R-410A systems to avoid
unnecessary costs to customers and damage to their reputation.
all new R-410A designs should
include a moisture indicator. Of
course, the device must be rated for
the higher pressures of R-410A, as
previously mentioned. To minimize
moisture infiltration caused by the
very device used to detect moisture,
use a hermetic device that does not
have O-rings or knife-edge seals.
For maximum protection against
moisture, a device that detects and
notifies when the moisture level
inside the system achieves 50 ppm
is recommended. This level closely
equates with most new oil specifications of less than 50 ppm moisture.
With R-22 systems, the typical
detection level is at 75 ppm to 125 ppm
moisture, the level at which acids
begin to form. This level of warning is
too high for hygroscopic POE oil.
Moisture indicators with multiple
levels of warning that coincide with
increasing moisture levels also are
recommended for POE oil. The earlier the detection and warning of moisture concerns, the better the chance
to catch and correct the moisture
problem, minimizing downtime and
service cost, while maximizing system reliability.
Thermal expansion valves are
regularly used as the expansion
device in air-conditioning systems
designed for R-410A because they
can help improve the total system
efficiency and performance and can
control the superheat. When choosing a thermal expansion device for
an R-410A system, the engineer or
service technician should make sure
to choose one that has been both
designed and tested for the higher
pressures of this refrigerant.
Valves suitable for R-410A are
marked with the higher maximum
working pressure (MWP) rating (700
psig) and have a rose-colored marking on the label. Note that due to the
different temperature-pressure characteristics, valves designed for other
refrigerants will not operate properly in R-410A systems.
The compressor used in an R-410A
No matter how carefully an air-conditioning or refrigeration system is
assembled or serviced, a small
amount of moisture contamination
is inevitable. Refrigerant liquid-line
filter driers remove moisture circulating through the refrigeration system and then hold that moisture to
prevent it from contaminating the
expansion device, evaporator, compressor or oil. However, filter driers
only hold a fixed amount of water.
Whenever a system is opened for
service, you must remove the filter
drier and replace it with a new, properly sized and rated drier. This will
prevent the unavoidable moisture
introduced during service from causing system failure. This is especially
true for R-410A systems with hygroscopic POE oil, in which oems typically use driers with up to 50 percent
more moisture capacity than in
equivalently sized R-22 systems.
In addition to being rated for the
higher pressures, liquid-line filter
driers used on R-410A systems also
should use a desiccant blend specifically designed for POE oils. As
compared to R-22-optimized driers,
R-410A-optimized filter driers use
less activated alumina and more
molecular sieve for increased water
capacity on these hygroscopic systems.
Inside the liquid-line filter drier, the
filter separates particles from the
refrigerant flow, preventing clogging of
the expansion device. The molecular
sieve removes moisture from the
refrigerant, preventing it from interacting with the POE oil and forming
organic acids. Finally, the activated
alumina removes harmful acids that
formed by the chemical reaction
between the refrigerant and residual
moisture in the system.
Compressor manufacturers have
studied and tested the various materials used in filter driers to assure
compatibility with the materials and
oils used in R-410A systems. For
example, one leading compressor
manufactuer recommends a desiccant blended with a maximum of 25
percent activated alumina for HFCoptimized liquid-line filter driers.
Like the compressor, the filter
drier should not be left open to the
atmosphere except for the brief time
it takes to braze it in place. Leaving
the compressor or filter drier open for
more than 15 minutes during installation could allow damaging moisture
infiltration to occur, contaminating
the compressor’s POE oil and the
drier’s desiccant, ultimately leading to
system failure. To minimize moisture
infiltration during service, installation of the new drier should be the
last action the service technician
takes during the repair process.
nants in refrigeration systems. This procedure is especially useful if the system
is known to have had contamination,
such as from a compressor burn-out,
prior to the service. As with all service
procedures, follow the equipment manufacturer’s recommendations.
Unlike R-22 charging, which you
can do in either a liquid or a gas
state, you must charge a system with
R-410A in a liquid state. R-410A is a
near-azeotrope, which is a blend of
two refrigerants that does not form a
third unique fluid.
The properties of the two HFC
components (R-32 and R-125) that
make up R-410A have boiling tem-
After assembly
peratures that are close to one
another. The result is that R-410A
has nearly no temperature glide at
saturation and can be “topped off” in
the field, providing it is done in a liquid state. All other refrigerant charging procedures remain the same for
R-410A as they are for R-22.
Many air-conditioner manufacturers discovered that R-410A features
superior heat-carrying characteristics
compared to R-22 and that systems
designed with R-410A can achieve 5
percent to 10 percent higher EER and
After safely and properly reassembling the system with R-410A components, you should perform a thorough
and deep evacuation. A typical target
for evacuation is 500 microns. Deeper
vacuums are recommended to maximize dryness in R-410A systems.
After evacuation, perform a a vacuum-degradation check to ensure there
are no system leaks prior to refrigerant
charging. Triple evacuations with nitrogen breaks are another proven method
for removing moisture and contami-
Air-conditioning systems
designed and built
to achieve 13 SEER will
be more expensive than
the 10 SEER units
currently available
SEER ratings. R-410A systems can be
designed to pump a lower volume of
denser refrigerant, increasing the
overall heat transfer in both the evaporator and the condenser.
The low-pressure drop and lowtemperature glide of R-410A also
contribute to reduced system power
consumption and improved system
efficiency. This is particularly important as the United States shifts production to only 13 SEER or higher airconditioning units and heat pumps
beginning in January 2006.
One of the main disadvantages to
R-410A that cannot be overlooked is cost.
In some cases, R-410A is three times
higher than R-22. The cost of R-410A
components can be up to 20 percent
more than R-22 components as well.
Air-conditioning systems designed
and built to achieve 13 SEER will be
more expensive than the 10 SEER
units currently available. Failure to
use properly designed components
in new units or in repairs is unsafe
and significantly increases the likelihood of system failures.
Because R-410A is developing into
the refrigerant of choice for air-conditioning manufacturers, engineers and
service technicians need to understand and be properly trained on the
inherent differences between this
refrigerant and R-22. They also must
be knowledgeable regarding new
component choices and must be cognizant that service practices historically used are no longer sufficient.N
Al Maier is vice president of application engineering at Emerson Climate
Technologies Flow Controls.
Emerson Climate Technologies
Flow Controls Division
11911 Adie Rd.,
St. Louis, MO 63043
314.569.4500; fax: 314.569.4593
www.emersonclimate.com/flowcontrols
Form No. 2008FC-22
Reprinted from September 2005 - RSES Journal