Understanding The new 410 a refrigerant for central air conditioners in Ontario Canada 905-403-9914
Why 410A?
Refrigerant 410A was developed to replace refrigerant 22 because R-22 is being
phased out due to its ozone depletion potential. R-410A has no ozone depletion
potential but does have a higher global warming potential. However, according to
experts, the overall global warming potential with R-410A should decrease
because of its higher efficiency reducing power plant emissions.
The Essentials Of R-410A
System Pressures
Technicians with R-22 experience will need to become familiar with working with
high and low side pressures that are much higher when using R-410A. A typical
R-22 system operating normally with a head pressure of 260 psig at a 120-degree
condensing temperature and a low side pressure of 76 psig at a 45-degree
evaporator saturation temperature will find the equivalent pressures in a R-410A
system to be much higher.
A normally operating R-410A system with the same condensing temperature of 120
degrees and a 45 degree evaporator saturation temperature will have a high side
pressure of 418 psig and a low side pressure of 130 psig.
Although refrigerant 410A is a near-azeotrope and has a slight temperature
glide, there is no need to correct for refrigerant dew point and bubble point
differences. Superheat and subcooling calculations can be calculated the same
way we have always done with R-22 refrigerant. The only difference will be the
higher pressure-temperature relationship when reading the temperature-pressure
chart. The temperature glide for R-410A is only .3 degrees Fahrenheit and can be
ignored and fractionation is not a concern.
Compression Ratio & System Efficiency
At first glance, one might ask the question, with 410A operating at higher
pressures are the compression ratio higher and the efficiency less? The answer
is no, the compression ratio is about the same or slightly lower than that of
R-22 and the efficiency is higher. Compression ratio is the absolute high side
pressure divided by the absolute low side pressure. The compression ratio is
affected by the pressure differential between the high and low sides of the
system not how high both pressures are. Using the previous examples comparing
the operating pressures of an R-22 system to an R-410A system, the R-22 system
would have a compression ratio of 3.02:1, while the R-410A system would have a
compression ratio of 2.98:1. The actual efficiency gains from R-410A are due to
its superior thermodynamic values over R-22. Under identical operating
conditions the discharge temperature on a 410A system may actually be lower than
on an R-22 system.
With all else being equal, it is possible to manufacture an R-410A air
conditioning system that is physically smaller using less refrigerant and a
smaller compressor than an R-22 system of the same capacity and SEER rating.
Compressors
Compressors used on 410A air conditioners use thicker metals to
withstand the higher operating pressures. Therefore, only a compressor designed
for 410A should be used with 410A. The ideal compressor type for use with 410A
is a scroll built to withstand the higher pressures. The scroll compressor has
the advantage over the reciprocating compressor when comparing volumetric
efficiencies and internal heat transfer losses between the suction and discharge
ports. Scroll compressors compress the refrigerant in stages through the use of
up to six individual pockets in its scroll assembly while reciprocating
compressors raise the pressure from the suction pressure to the high side
pressure in a single stroke. In addition, the scroll compressor’s suction and
discharge openings are farther apart than those in a reciprocating compressor
thus decreasing heat transfer losses between the suction and discharge ports.
Dealers.
The internal pressure relief valves inside the compressor opens at a pressure
between 550 & 625 psig on compressors designed for R-410A service. Compressors
designed for R-22 service have internal pressure relief valve settings that open
between 375 & 450 psig. So only compressors rated to work with R-22 should be
used with R-22 and those rated for use with R-410A used with R-410A.
Metering Devices
The metering device used in a 410A system must be about 15% smaller in capacity
as opposed to a metering device used in a R-22 system of the same capacity. It
is imperative that only a metering device designed and properly sized for R-410A
be used on a R-410A system. In fact, no parts designed for R-22 use should be
used on a 410A system.
Refrigerant Lines
Refrigerant lines used for R-410A must be properly sized for R-410A systems. It
is possible to use existing refrigerant lines from an R-22 system in a R-410A
system installation if they are of the correct size however, they must be
cleaned of all debris and oil. The best practice is to replace the lines with
new copper liquid and suction lines to ensure they are clean and do not have any
weak areas that could be a problem at the higher operating pressures of 410A.
Driers & System Accessories
The desiccants used in R-410A systems are the same as those used for most other
refrigerants. Zeolites, molecular sieve type desiccants work on the principle of
a material with small pockets or areas that adsorb moisture by the process of
capillary action. This type of desiccant seems to work well with all modern
refrigerants including R-410A. The metal shell containing the filter-drier
however, must be thicker to withstand the higher pressures of 410A. Therefore,
only use filter-driers rated for use on R-410A. R-410A filter-driers are those
rated for pressures no less than 600 psig.
When removing a filter-drier from a system it should be cut out with a tubing
cutter not a torch flame. The desiccant in a filter drier adsorbs and holds
moisture better when it is cool or cold. Therefore, if the desiccant is heated
moisture may be driven out of the desiccant and into the system creating a
moisture problem. This is of greater concern on R-410A systems because the oil
used (POE) is highly hygroscopic. Once moisture is absorbed in a POE oil it is
difficult to remove. Usually an oil change is necessary.
The practice of replacing the filter-drier every time the system is opened is
particularly important on R-410A systems because of the hygroscopic nature of
the oil used.
Pressure Control Settings
Because of the higher operating pressures of the 410a air conditioning systems ,
the high & low-pressure control settings must be higher than those encountered
on R-22 systems. The recommended high-pressure control settings are a cut-out
pressure of 610 psig and a cut-in pressure of approximately 500 psig. The
recommended low-pressure control setting is a cut-out pressure of 50 psig. Make
sure the pressure control you are using on a 410A system has the correct
pressure range allowing it to be adjusted for the correct pressures.
Oil
R-410A systems use a synthetic Poly Ester (POE) oil. This oil has superior
lubricating ability over the mineral oils commonly used in R-22 systems. Only
POE oil should be used in a 410A system. However, not all POE oils are the same.
There is a variety of POE oil types and grades therefore, it is important to
know which POE oil is in the system being serviced. Mixing some POE oils may
create a compatibility problem and lead to a system failure.
All POE oils are highly hygroscopic. That is, they absorb moisture quickly and
hold the moisture they absorb. Once absorbed, the moisture cannot be removed
through system evacuation even at vacuum pressures of 500 microns. Therefore, it
is important to prevent moisture from getting in the oil in the first place. The
general recommendations for handling POE oil is to keep it in a metal container,
transfer it with an oil pump and keep the container sealed except when
absolutely necessary. POE oils are also irritating to the skin and a real
medical concern if it comes in contact with your eyes. Gloves and safety glasses
are essential items when working with this oil.
Brazed Connections
The higher operating pressures encountered with R-410A systems requires the use
of brazing materials rated to withstand these pressures. Some technicians have
used lower temperature solders when making tubing connections on R-22 systems.
Such should not be the practice on R-410A systems. It is the author’s opinion
that only high temperature brazing materials such as Silphos type brazing rod or
one of the silver solders should be used on any R-22 system. It is even more
important to use suitable brazing materials on R-410A systems.
Moisture & Evacuation
The hygroscopic nature of the oils used in R-410A AC systems cannot be
over-emphasized. Moisture can be a significant problem to the proper operation
and life expectancy of any air conditioning system operating on the mechanical
refrigerant cycle. Therefore, it is more important than in the past to take
precautions to keep moisture out of a air system during installation and
service, to evacuate to 500 microns and replace filter-driers when a system has
been opened. Questionable workmanship that may have gotten us by when working on
R-22 systems will not be tolerated by R-410A systems.
System Conversions
System conversions are simply out of the question. After reading this far, it
should be obvious that the differences in construction of R-410A systems exceed
the practical and economic limits of converting an R-22 system to R-410A.
Tools
Gauge manifold sets, hoses, recovery cylinders and the recovery machine must be
rated for the higher pressures encountered with R-410A. An attempt to use
standard refrigerant service tools on 410A systems is very dangerous and simply
foolish. This is a safety issue of great concern to the industry and is one of
the reasons the AC&R Safety Coalition was formed and R-410A safety & handling
certification was established.
Recovery cylinders must be rated for R-410A use. These cylinders meet the
Department Of Transportation, DOT 4BA 400 or DOT 4BW 400 standards for recovery
cylinders. Be very careful here, it would be very easy and convenient to use
whatever recovery cylinder was handy rather than the correct cylinder. Such a
mistake could be the last one a technician makes.
Leak Detection
R-410A is an HFC refrigerant. Therefore, any leak detection device or method
that works for other HFC refrigerants will work for R-410A.
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