Hello dave222smith,
While I am not a refigeration engineer, my curiosity was piqued by
your question, and it has led me down a long and detailed research
path. I trust that you find the following answer satisfactory.
Please note that, because I can only lock a question for two hours at
a time, I will be posting this answer in multiple parts, with each
section as a clarification to the first answer.
So, on to your question. As I am not certain what your technical
expertise is, some of this may be a little basic, although some of my
references are quite technically advanced. Now, as you are aware, the
Montreal Protocol was signed in 1987 in an effort to curb the
production and use of ozone-depleting chemicals. Some of the biggest
offenders in this area were chlorofluorocarbons (CFCs) which were in
common use as refrigerants at that time. Examples of CFC-based
refrigerants include R-11, R-12, R-13, R-113, R-114, and R-115.
As a result of signing the Montreal Protocol industries and
governments began seeking replacement refrigerants that would be of
equivalent (or better) efficiency with less of an environmental
impact. In broad terms, there have been three major classes of
suggested replacement: hydrochlorofluorocarbons (HCFC),
hydrofluorocarbons (HFC), and hydrochemicals (HC).
The refrigerant R-22 was the most commonly used example of an HCFC.
However, one problem with HCFCs was that they still contained chlorine
in their makeup, and so were still ozone-depleting (but to a lesser
degree than CFCs). As a result, R-22 and other HCFC refrigerants were
also scheduled to be phased out with a dropdead date of 2020, although
most countries have timetables ranging from 1998 (Sweden, Finland) to
2010 (USA).
With HCFCs also being phased out, the two major refrigerant classes
remaining are HFCs and HCs, and there is a lot of effort being
expended to find the best one for a particular application. As might
be expected, each application has its own issues that leans selection
towards one refrigerant or another, so there is no one "right answer".
But with that introduction out of the way, the remaining parts of my
answer will drill down into these various refrigerant classes and
hopefully fill you in on where this industry is going. |
Clarification of Answer by
tomo-ga
on
08 Nov 2002 08:56 PST
Now, as we go into determining whether one refrigerant is "better"
than another, we need to clarify what metrics we are going to use.
You list the things that are important to you: economy, availability,
environmental friendliness, and efficiency. So let's assign some
metrics that make sense to these categories.
For economy, the metric is pretty obvious, money, but to be precise
let's use $/lb when buying in large quantities.
For availability, we can assume that most refrigerants are available
if they are in use. The big thing here is are they still, and going
to continue being, in production? And even more precisely, what is
the timeframe for which you would like availability? That last part I
cannot answer for you, but it stands to reason that using a product
that is being phased out after the lifetime of your application is not
an impediment to your using that product. So, for availability, let's
use the date at which it can no longer be used in new applications in
the US (although as I noted earlier, other countries have differing
timetables for environmentally-sensitive chemicals).
For environmental friendliness, there are three commonly used metrics
here. The first is ozone depleting potential (ODP), which is a
measure of how harmful a product is to the ozone layer. The second is
global warming potential (GWP), which is a measure of a product's
contribution to global warming, and total equivalent warming impact
(TEWI), which is like GWP but takes into account the whole system of
production, use, and disposal of a product to determine its full
impact on the environment. Since TEWI is often used in place of GWP,
let's use that if possible, in conjunction with ODP.
Finally, there is efficiency. This is tough, because it really
depends a lot on your application. You mention a ship refrigeration
system, but that is not a lot to go on. So to compare refrigerants,
let's look at the coefficient of performance (COP), a measure of how
well the refrigerant absorbs heat at a particular operating
temperature.
One other housekeeping issue: while I will be quoting certain
references during this discussion, the actual reference URLs will be
left until the end to make everything a bit more readable.
With that out of the way, let's specifically answer the first part of
your question, namely, is R-22 better than its predecessors?
The quick answer is, of course, yes because using R-11 and R-12 is
simply not an option anymore. But that is too glib. From a cost
perspective, since R-12 is no longer in production, it is very
expensive to get and costs about 20 times more than R-22. According
to a discount refrigerant supply house (http://www.r22.org/), R-22
costs $1.30/lb in bulk as compared to $24.67/lb for R-12. As for
availability, well, you know where R-12 stands there relative to R-22.
For environmental impact, the big thing is ODP. According to the
EPA, the ODP of R-12 is 1, and for R-22 is 0.055. So, R-22 is 18
times better for the ozone layer. The GWP for R-12 is around 8500, as
compared to 1700 for R-22. And, as far as efficiency goes, (according
to a Trane environmental report) the COP of R-12 versus R-22 is 10.92
to 10.85, making R-12 marginally more efficient.
So, is R-22 better than R-12? I think the consensus answer would be
"yes".
|
Request for Answer Clarification by
dave222smith-ga
on
08 Nov 2002 09:40 PST
Hello tomo,
Thanks for your answer. I am waiting for the rest of it because, I
must admit, I am hoping for a more detailed research for this high
price. For example, when talking about the economics, may you supply
your answer with actual figures rather than talking in general terms.
One more thing please, would you write the URLs straight after your
statements. This is because I will need to know the references you
used in case I need to look up something mentioned in your answer.
Thank you once again.
|
Clarification of Answer by
tomo-ga
on
08 Nov 2002 13:09 PST
But having concluded that R-22 is better overall than R-12 and its CFC
cohorts, the really important question is should you use R-22 in your
application? There are certainly alternatives, as can be seen from
these excellent overview articles:
"Choosing the Right Refrigerant"
http://www.memagazine.org/backissues/october98/features/refrig/refrig.html
"Current and Future Refrigerants for the Marine Industry"
http://www.unitor.com/internet/info/features/docs/19981127.htm
"Trade-offs in Refrigerant Selections: Past, Present, and Future"
http://www.trane.com/commercial/issues/environmental/trade-offs.asp
As I noted before, R-22 and the other HCFC refrigerants are being
phased out. If your application lifetime is less than the phaseout
period, then you could continue to use R-22. But let's examine some
other choices from both the HFC and HC classes, and consider their use
in a new (not retrofit) application. For HFC refrigerants, commonly
used variants are R-134a and R-404a. For HC refrigerants, the two
common examples are propane (R-290) and iso-butane (R-600a), although
for the most part commercially-available HC refrigerants are blends of
these compounds that are intended as drop-in replacements for other
refrigerants.
From a cost perspective, here is a breakdown of the cost per pound of
each:
R-134a $2.37 http://www.r22.org/
R-404a 8.75 "
HC-12a 7.20 http://www.hydrocoolonline.com/50hc12a.htm
HC-22a 3.40 http://www.hydrocoolonline.com/50hc22a.htm
R-22 1.30 http://www.r22.org/
For the HC refrigerants, these prices are from HydroCool
(http://www.hydrocoolonline.com/), one of a number of HC refrigerant
manufacturers. While these products are drop-in substitutes for
R-134a and R-22 respectively, you should note that their
cost-per-pound is a bit misleading because the amount of refrigerant
required (due to their molecular properties) is about half that of
R-22 or R-134a. One other point to consider with respect to cost is
that HFC refrigerants require a different type of lubricant (polyol
ester, or POE) than R-22 cooling systems. I have not found a
definitive source that discusses quantitatively the relative cost of
these lubricants, but the suggestion is that they are "more".
From the standpoint of availability, R-134a and R-404a are very
readily available as they are the HFC refrigerants of choice for most
applications. Dupont, for example, markets them under the product
name Suva (http://www.dupont.com/suva/emea/products/technical/choose.html).
As for the HC-based products, there are a number of companies
offering their own mixes, for the most part as drop-in substitutes.
Examples include:
HydroCool, http://www.hydrocoolonline.com/
OZ Technology, http://www.oztechnologyinc.com/
EnviroSafe Refrigerants,
http://www.es-refrigerants.com/refrigerant.html
HyChill Refrigerants, http://www.hychill.com/
CARE Refrigerants, http://www.care-refrigerants.co.uk/
It would therefore seem that HC alternatives are equally readily
available.
Now, for the important environmental impact, both HFC and HC options
offer significant advantages over R-22 and its predecessors. First,
they all have zero ODP, due to the lack of chlorine in their makeup.
Second, in almost all cases, they have a lower GWP:
R-134a 1300 http://www.dupont.com/suva/na/usa/literature/pdf/pp2.pdf
R-404a 3260 http://www.dupont.com/suva/na/usa/literature/pdf/pp3.pdf
R-290/R-600a 3 http://cuts.org/sc98-1.htm
R-22 1700 http://www.epa.gov/ozone/ods.html
The exception is R-404a which, probably as a result of it being a
blended HFC, has a higher warming impact than R-22. The other thing
to note about R-404a is that it is used under higher pressures than,
say, R-134a which means that extra care against leakage needs to be
taken in applications that use this refrigerant. The clear message
from the table above, however, is that HC-based refrigerants are
outstanding from the perspective of GWP, making them the choice of
environmentalists (e.g., see
http://xs2.greenpeace.org/~ozone/greenfreeze/).
From an efficiency standpoint, the general statement that can be made
is that there is no significant difference between the COP values of
R-22, HFC-based refrigerants, and HC-based refrigerants (see Trane,
http://www.trane.com/commercial/issues/environmental/trade-offs06.asp):
R-134a 10.89
R-290 10.72
R-22 10.85
Similar qualititive results were found by Sub-Zero
(http://www.glacierbay.com/Subz_chart.htm) and researchers in
Australia (http://ctan.unsw.edu.au/pub/archive/HC/papers/iir96p1r.pdf).
That being said, the efficiency of *your* particular system might be
substantially different, but the expectataion is that choice of
refrigerant should not be a significant factor. A quote from a paper
presented at the Fourth Aerospace Materials, Processes, and
Environmental Technology Conference, in September, 2000
(http://www.etec-nm.com/library/ampet00b.htm) underlines this point:
"It is important to note that new refrigeration and cooling equipment
is considerably more energy efficient than older equipment because of
improvements in design and in the efficiencies of motors and
compressors, not because new refrigerants are more
energy-efficient..."
Another way of stating this is that there seems to be a tendency to
offer replacement refrigerants that are nearly equivalent to less safe
products that they are replacing. As a result, they are usually
thermodynamically similar and do not affect system efficiency to any
significant degree. I know that you want calculations here. But
without knowing more details about your system, or indeed what
calculations you would like, I am a bit at a loss to offer some up.
With that, I hope I have answered your question, although I expect you
will like some points clarified, so please don't hesitate to ask.
The following searches were performed during this research:
refrigerants montreal protocol
refrigerants r22 r11 r12
refrigerant marine
refrigeration efficiency comparison
refrigerant supply
HC refrigerant supply
ODP CFC12
refrigerant GWP ODP TEWI
refrigerant COP
greenfreeze
References:
These references give good general overviews on refrigerants:
"Choosing the Right Refrigerant", Siva Gopalnarayanan, October 1998
Mechanical Engineering Magazine Online
http://www.memagazine.org/backissues/october98/features/refrig/refrig.html
"Current and Future Refrigerants for the Marine Industry", Erik Schau
http://www.unitor.com/internet/info/features/docs/19981127.htm
"Marine Refrigeration Update: Replacements for R-22", Erik Schau
http://www.unitor.com/internet/info/features/docs/20000801.htm
"Trade-offs in Refrigerant Selections: Past, Present, and Future",
James M. Calm and David A. Didion, presented at ASHRAE/NIST
Refrigerants Conference,
National Institute of Standards and Technology, October 6-7, 1997
http://www.trane.com/commercial/issues/environmental/trade-offs.asp
"Where Refrigerants Are, and Where They're Going", Air Conditioning,
Heating, Refrigeration News Online, February 16, 2001
http://www.achrnews.com/CDA/ArticleInformation/features/BNP__Features__Item/0,1338,21029,00.html
The following are links to specificant refrigerant products, or
provide consolidated refrigerant summaries:
Dupont Suva Refrigerants, Dupont Corp.
http://www.dupont.com/suva/emea/products/technical/choose.html
"A11 Refrigerant Sources and Prices", Discount Refrigerants Inc.
http://www.r22.org/
HydroCool Inc.
http://www.hydrocoolonline.com/
OZ Technology,
http://www.oztechnologyinc.com/
EnviroSafe Refrigerants,
http://www.es-refrigerants.com/refrigerant.html
HyChill Refrigerants
http://www.hychill.com/
CARE Refrigerants
http://www.care-refrigerants.co.uk/
"Refrigerants", Aircon Services
http://www.aircon-services.co.uk/BodyRefrigerants.html
"Alternative One-compound Refrigerants", All-Chem Company
http://www.sdm.kiev.ua/eng/refregerants/alternative.html
The following deal specifically with performance and/or environmental
impact of particular refrigerants:
"Class I Ozone-Depleting Substances", U.S. EPA
http://www.epa.gov/ozone/ods.html
"Class II Ozone-Depleting Substances", U.S. EPA
http://www.epa.gov/ozone/ods2.html
"Global Warming Potentials of ODS Substitutes", U.S. EPA
http://www.epa.gov/ozone/geninfo/gwps.html
"High-Performance, Low Environmental Impact Refrigerants", EDWARD T.
McCULLOUGH et al, presented at the Fourth Aerospace Materials,
Processes, and Environmental Technology Conference, September, 2000
http://www.etec-nm.com/library/ampet00b.htm
"Ecofridge: Make the Right Choice Now", CENTRE FOR SUSTAINABLE
PRODUCTION AND CONSUMPTION
http://cuts.org/sc98-1.htm
"Comparative Performance of Hydrocarbon Refrigerants", I. L.
Maclaine-cross and E. Leonardi, School of Mechanical and Manufacturing
Engineering, The University of New South Wales
http://ctan.unsw.edu.au/pub/archive/HC/papers/iir96p1r.pdf
"An Assessment of Alternative Refrigerants for Automotive Applications
based on Environmental Impact", V. Sumantran et al,
http://www.sae.org/misc/aaf99/sumantran.pdf
-- tomo-ga
|
Request for Answer Clarification by
dave222smith-ga
on
08 Nov 2002 19:26 PST
Hello tomo,
I do appreciate your job so far.. Can you try to refer to maritime
applications as much as possible. Particularly, when talking about
efficiencies of refigeration systems with different refrigerants, I
need to see some worked calculations.and yes, please, include more
references inline rather listing them at the end. Keep up the good
work
|
Clarification of Answer by
tomo-ga
on
08 Nov 2002 19:46 PST
David,
I will try to get some more maritime examples, but could you possibly
be more specific on the scale of application you are talking about?
And, given what I have written so far, are there specific refrigerants
you would like me to focus on. As you might imagine, this is a pretty
broad topic otherwise.
-- tomo
|
Request for Answer Clarification by
dave222smith-ga
on
12 Nov 2002 10:48 PST
Hello tomo,
Could you please narrow your search to investigate the viability of
R-134A (with 0 ozone depletion)to be used on board ships (which are
essentially fitted with small refrigeration plants) from the
prespectives specified earlier..Particularly from efficiency, economy
and impact of environmental legislations points of view. Please, try
to include more references inline. Keep up the good work
|
Clarification of Answer by
tomo-ga
on
13 Nov 2002 07:21 PST
dave222smith,
It is interesting that you honed in on R-134a, because as I was
digging around trying to find various commercial marine refrigeration
units, they almost universally use R-134a. Here is a list of what
appears to be the most popular manufacturers of marine refrigeration
units:
Grunert Refrigeration
http://www.marineair.com/marineair/grunert/index.html
Glacier Bay
http://www.glacierbay.com/Marine_index.htm
Norcold
http://www.norcold.com/marine_main.cfm
Adler/Barbour
http://www.waecoadlerbarbour.com/
The following link does a practical comparison of a number of these
marine units:
http://old.cruisingworld.com/joecold/coldfact.htm
Note, however, that many larger shipping vessels don't have their own
refrigeration units, but instead rely on the refrigeration of the
"reefer" containers that they haul. These, too, seem to use R-134a
extensively, or as an alternative, R-404a which is a combination of
refrigerants including R-134a; for example:
Klinge Corporation
http://www.klingecorp.com/index.htm
Thermo King
http://www.thermoking.com/thermoking/container/default.asp
So, if your concern is "viability", then I would suggest that it is
not only viable but very common to use R-134a in marine applications.
Let's examine your criteria again. Note that I still don't have a
feel for how big a marine application you are asking about, so some
comments may be rather general.
First, and easiest, is environmental impact. R-134a is an HFC
refrigerant and, as a result, has zero ODP. Yay! Furthermore, it has
a reasonably low GWP of 1300, as compared to R-12 which was over 8500,
and indeed even R-22 which was around 1700. So there is no question
that R-134a is better than many (most) refrigerants, and meets all
current legislative initiatives. As I noted earlier, HC-based
refrigerants are still much, much better for the environment, but a
significant drawback to using HC (propane, isobutane) is that both are
highly flammable. This requires extra caution to ensure that ignition
is not going to happen, and in many cases, that caution can be
expensive. Probably not practical for a large marine application, but
maybe so for small (e.g., sailboat) uses.
But back to R-134a. From an economic standpoint, my earlier comments
showed the raw cost of R-134a relative to, say, R-22. It was almost
twice as expensive, per pound, as R-22, but about 3 times cheaper than
R-404a.
For the remainder of the economic discussion, however, let's use
efficiency and tie them together because, clearly, dramatic
differences in efficiency will translate directly to the cost of
operating a refrigeration unit. As I noted before, the efficiency of
refrigeration units is most often denoted by the coefficient of
performance, COP. Now, COP is simply the ratio of cooling effect to
work required to achieve that cooling. From basic thermodynamics, the
ultimate COP is given by what is called a Carnot refrigerator (for
example, see http://cs.smith.edu/~rsegal/work/thermo/carnotfrig.html).
For a Carnot refrigerator operating between two temperatures T1
(outside temp) and T2 (inside, or refrigeration, temp), the COP is
defined as:
COP = 1 / ((T1/T2) - 1)
where the temperatures are measured in degrees Kelvin. So, by way of
example, if you had a refrigeration unit that operated between 20 C
and -5 C, the maximum possible COP you could get would be 10.72. If
you also know what your heat load is, that is, how much heat your
refrigerator is leaking into the outside, then you could compute the
minimum power you would require to operate this refrigerator by simply
dividing the heat load by the COP. So, if you were leaking 130 Watts
(442 BTU/hr) of energy, you would need 12.1 Watts of power to run a
Carnot refrigerator.
The heat load, or leakage, is a direct function of your insulation,
how big an area you are insulating, and how much of a temperature
difference you are trying to contain:
heat load in BTU/hr = ((surface area in sq.ft.) * (temp.
difference)) / R-value
Now, a Carnot refrigerator is highly idealized. Practical issues such
as compressor efficiencies, internal heat transfer coefficients, and
other things I don't know about prevent that COP from ever being
reached. I found one example that attempted to model some of these
effects, and in particular showed how COP varied for different
refrigerants (see page 26):
Heat Transfer Solutions, Refrigerant Application Guide
http://www.htseng.com/DownloadCentre/Application%20Guides/AG31-007.pdf
The point in this example is that there is a signifant difference
between an ideal COP and a practical one. But even that model, which
shows a COP of 6.5 using R-134a, is not necessarily realistic. The
following two links show the effect of refrigerant on COP values for
real-world refrigeration units (marine refrigerators and reefer
containers):
Glacier Bay, Product Information
http://www.glacierbay.com/Subz_chart.htm
EA Technology, Road Transport Refrigeration
http://www.eatechnology.com/Data%20Sheets/Energy%20Efficiency%20Audits/transp.pdf
The Glacier Bay link is interesting because they have a refrigeration
unit that can handle multiple refrigerants. Now, if we look at that
link in particular, we note that using R-134a results in a COP of 2.83
when used in "refrigerator mode", as compared to 2.71 for R-22. This
is 4% better, meaning that it would result in a 4% energy savings
using R-134a. This is a surprising result, since the EA Technology
reference suggests a 2% decrease in COP in going from R-22 to R-134a.
Operating conditions, no doubt, have something to do with this
variance, but I cannot be sure. What I am sure about is that, if you
scan the tables in these two references, you will note that the effect
of the refrigerant on efficiency is only several percent in either
direction. While this can certainly add up over time if taken in
isolation, it can easily be made up in reducing the heat load of your
refrigeration system through better insulation. So, the net effect of
refrigerant on efficiency, and therefore, economy, is marginal at
best.
Incidentally, a number of references I saw all used a common modeling
application for showing the effects of multiple refrigerants. If you
are really interested in digging deeper into this, then you can get
the modeling app for $200 from the National Institute of Standards and
Technology (NIST):
CYCLE_D: NIST Vapor Compression Cycle Design Program
http://www.nist.gov/srd/nist49.htm
Also, the standard reference on refrigerants and their properties
appears to be ASHRAE, the American Society of Heating, Refrigerating,
and Air-Conditioning Engineers (http://www.ashrae.org/). They publish
a multivolume handbook that includes a section on marine
refrigeration. This section can be purchased separate from the entire
handbook for only $29:
ASHRAE Handbook, 2002 Refrigeration: SI Edition, Chapter 30
http://www.confex.com/store/items/ashrae/handbook/R02_30SI.htm
I hope this clarification is satisfactory, and thanks for letting me
look into this very interesting topic for you.
-- tomo-ga
|
Request for Answer Clarification by
dave222smith-ga
on
14 Nov 2002 14:49 PST
Thanks alot for the last clarification, it contained very good infor
and URLs. One last request if your don't mind please, could you
provide me with some URLs that tell you what kind of modifications to
the marine refrigeration system are required, for a system that
currently operating on refrigerant (R-22), to be able to operate on
R-134a. Does the size of piping system has to be changed? will we be
needing special type of compressors,etc?
Please provide me with as much information as possible. your efforts
will be rewarded with a considerable tip.
|
Clarification of Answer by
tomo-ga
on
14 Nov 2002 18:03 PST
Hello again, dave222smith:
First, I am glad that you are finding this information useful.
Hopefully this last bit will be equally so.
I think I have a bunch of good references for you, but to start with I
need to provide some clarification. In the previous post I discussed
the merits of using R-134a in marine applications. Since you had
until now not specifically asked for an R-22 conversion (and indeed I
thought you were contemplating using R-22 unless there were something
better available, based on your original question), I have not talked
too much about that. But clearly you have an existing R-22
installation that you want to upgrade. In that case, R-134a may not
be the best choice.
As I noted earlier, a lot of effort has gone into finding refrigerants
that make it "relatively" easy to move from environmentally disastrous
chemicals to safer ones. While R-134a was one of the first HFC
refrigerants to be devised, it was done so as an R-12 replacement, not
R-22. So, while I have a number of references that discuss the
conversion process to 134a, they specifically do so for R-12
installations. But, all is not lost, because at the same time there
were many R-22 installations (like yours) that also needed to be
brought forward, and there are replacement refrigerants such as R-407c
and R-410a that fit that bill.
So, on with the conversions.
As noted in this reference on marine refrigerants, which I gave you
earlier, the single biggest issue with going from CFC/HCFC
refrigerants to HFC ones is that the lubricant needs to change from
simple mineral oils to polyol ester (POE) lubricants:
"Current and Future Refrigerants for the Marine Industry", Erik Schau
http://www.unitor.com/internet/info/features/docs/19981127.htm
This requires a very, very thorough flushing of the system before
introducing the POE and refrigerant. Another good birds-eye view of
the conversion from R-22 is this reference:
"A Food Industry Guide to CFC and HCFC Refrigerant Phase-Out, Part 1",
Agriculture and Agri-Food Canada
http://www.agr.gc.ca/food/environment/cfc/cfci.html
"A Food Industry Guide to CFC and HCFC Refrigerant Phase-Out, Part 2",
Agriculture and Agri-Food Canada
http://www.agr.gc.ca/food/environment/cfc/cfcii.html
Note that this reference, too, advocates using R-407c as a substitute
for R-22. It also provides a nice table of expected performance
impact, with a reduction in COP of 0.5.
But that is all very general. Since a major manufacturer of
refrigerants is Dupont, they understandably have a lot of material
that discusses using their products. The following references discuss
in detail the conversion process to go from R-12 to R-134a, and from
R-22 to R-407c:
"Retrofit Guidelines for Suva HFC Refrigerants: Suva 134a for R-12
Retrofit", E.I. Dupont
http://www.dupont.com/suva/na/usa/literature/pdf/h75326.pdf
"Selection Guide for Retrofitting R-22 Equipment", E.I. Dupont
http://www.dupont.com/suva/na/usa/products/pdf/h96125.pdf
"Retrofit Guidelines for Suva 407c", E.I. Dupont
http://www.dupont.com/suva/na/usa/literature/pdf/h70004.pdf
A reference source I used before, EA Technology, offers this
conversion note:
"Capitalizing on CFC/HCFC Phase-Out", EA Technology
http://www.eatechnology.com/Data%20Sheets/Energy%20Efficiency%20Audits/indust.pdf
The interesting bit here is that they do mention R-134a as a possible
substitute for R-22, but that it "will result in significantly reduced
chilling capacities."
There is a LOT of info in the references above, and it doesnt' make
sense to reproduce it here. But in terms of the general impact that
you were asking about, it would seem that there is not a huge capital
cost involved in retrofitting an existing R-22 system to use R-407c.
In particular, while the compressor operating conditions are somewhat
different, I did not come across any discussion of having to
completely replace the compressor. The same is true of the piping.
As I said at the outset, the goal is to make the migration to safer
refrigerants as simple as it can be. But these are very general
statements and a lot depends on exactly what you have. Needless to
say, hooking up with a refrigeration engineer (http://www.ashrae.org/)
would be an excellent idea before going too far down the conversion
path.
I genuinely hope this has been useful to you, and thanks, again, for
giving me the opportunity to research this topic.
Search strategy:
r22 retrofit
r134a conversion
-- tomo-ga
"Don't think you are. Know you are." - Morpheus
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