WHY NOT 134-A IN WALK-IN FREEZER
tur...@worldnetla.net
i know i'm suppose to study the chemical formation of the freon in this
application and derive that it does not work or does work. now i'm being
told that it will not work or will not do right and all that. being the
nuckel head that i am and don't listen and i put 134-A in a 3 ton walk-in
freezer. it work like a charm. of course i used ester oil in it. i know there
could be some ameba that will start growing in walk-in freezers and then kill
all the guppie in fish tanks all over the world, but i got to know.
would some one please set me start or inform me of the
draw backs of this action ?
turtle and nuckel head will not stop till they hit a brick wall.
TURTLE
-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
JimLavL
applications compared to R-22 or R-404A/R-507. That is if you are installing a
new system.
When retrofitting an existing R-12 low temperature system the same general
drawback exists - the heat exchangers and compressor are sized too small for
R-134a to do the same job at the same efficiency level. On top of that you have
the oil change to do.
That does not mean all existing R-12 systems (or all new 134a systems) won't
work at lower temperatures, it just means that there are better options
available.
New: For the same or lower cost you could put in an R-22 or R-404A unit (134a
equipment tends to be bigger for the same job = more steel = more money).
Existing: Refrigerant retrofit blends, like R-401A and R-409A, offer better
low side property match, better capacity at low temperatures, and partial
change to AB oil instead of POE flush. Drawbacks are high side pressure
increase (134a will do this also if the condenser is undersized) and
temperature glide (which only really affects control settings).
Like I said, these are general comments. All systems will respond differently,
and if you are having success with R-134a more power to you - the manufacturers
are desperate to sell the stuff.
Jim Lavelle
ftwhd
All the infomation I have read on R-134a is that it should be limited
to applications where the evaporator temperatures are above -10
degrees. Also R-134a has slighty lower capicities than R-12. When
retrofitting exsisting R-12 systems I have had good experiances with
R-409 on low, medium, and high temp applications.
Regards, Mike
John Tan
> i know i'm suppose to study the chemical formation of the freon in this
> application and derive that it does not work or does work. now i'm being
> told that it will not work or will not do right and all that. being the
> nuckel head that i am and don't listen and i put 134-A in a 3 ton walk-in
> freezer. it work like a charm. of course i used ester oil in it. i know there
> could be some ameba that will start growing in walk-in freezers and then kill
> all the guppie in fish tanks all over the world, but i got to know.
>
> would some one please set me start or inform me of the
> draw backs of this action ?
>
> turtle and nuckel head will not stop till they hit a brick wall.
I agreed on the points mentioned by Jim Lavelle.
I think in your case, using R-134a would be an alternative though R-134a
would have display temperature glide below -10 deg. F evaporating.
Main thing to take care during retrofitting is to ensure moisture free
system. POE oil should not be exposed to surrounding for too long as it
would absorb moisture easily (I think the guide is 10 mins). Where
possible, change new liquid line filters at least twice to ensure
contamination free system. Use good quality R-134a suitable drier like
Sporlan or Alco.
Also, if possible, try changing to a R-134a txv.; if not available, get
a R-12 txv with approx. 15 to 20% lower rated capacity than the
original.
Cheer ocean friend :-)
ftwhd
<tec...@Nospam.pacific.net.sg> wrote:
>tur...@worldnetla.net wrote:
>> i know i'm suppose to study the chemical formation of the freon in this
>> application and derive that it does not work or does work. now i'm being
>> told that it will not work or will not do right and all that. being the
>> nuckel head that i am and don't listen and i put 134-A in a 3 ton walk-in
>> freezer. it work like a charm. of course i used ester oil in it. i know there
>> could be some ameba that will start growing in walk-in freezers and then kill
>> all the guppie in fish tanks all over the world, but i got to know.
>>
>> would some one please set me start or inform me of the
>> draw backs of this action ?
>>
>> turtle and nuckel head will not stop till they hit a brick wall.
>
>I agreed on the points mentioned by Jim Lavelle.
>
>I think in your case, using R-134a would be an alternative though R-134a
>would have display temperature glide below -10 deg. F evaporating.
R-134a does not have a glide like the blends do. It is a pure fluid
with no other refrigerants in it to boil off at differant temperatures
like blends do. It is also not reccomeded for use on evaporator that
operate below -10 evaporator temperature. that pretty much rules out
all low temp evaps.
>Main thing to take care during retrofitting is to ensure moisture free
>system. POE oil should not be exposed to surrounding for too long as it
>would absorb moisture easily (I think the guide is 10 mins). Where
>possible, change new liquid line filters at least twice to ensure
>contamination free system. Use good quality R-134a suitable drier like
>Sporlan or Alco.
>
>Also, if possible, try changing to a R-134a txv.; if not available, get
>a R-12 txv with approx. 15 to 20% lower rated capacity than the
>original.
>
If you convert to R-134a and use the existing R-12 valve normally all
that has to be done is a slight adjustment to get the proper
superheat, about 6 degrees on low temp and 10 on medium temp coolers.
Providing the system was properly adjusted and sized to begin with a
lowering of the pressure control a few lbs will give the right cut-in
and cut out pressures. Usually about 34 lbs cut-in and 14 lbs cut-out.
Actual settings will vary slighty from job to job but if you sit there
and watch it cycle a few times you will be able to dial the cut-in and
out pressures to obtain the desired box temp.
Regards, Mike
John Tan
a mistake by saying that R-134a exhibits temperature glide. I apologise
for that and thanks Mike for pointing it out.
Just to clarify, blends (zeotropes) shows temp. glide which means that
the difference between the dew point and bubble point temp. This does
not apply to R-134a.
Besides the previous notes, there are certain points to take note when
considering or when retrofitting to R-134a from R-12:-
01)Where practically possible, try using R-134a only where system
evaporating temp. is -10 deg. F or higher. This is because R-134a
exhibits lower volumetric efficency than R-12 at low evaporating temp.
where high compression ratios are found. Capacity losses had been
mentioned to be as great as 33 to 39% compared with R-12.
02)The existing txv may need to be change since existing R-12 valve when
used with R-134a approx. 15 to 20% more capacity. Hence, get the same
R-134a nominal rating txv. as your R-12 txv. where possible. If not
available, use a R-12 txv. with a 15 to 20% lower rating than the old
R-12 txv.
Oversized txv. may cause hunting and floodback as you will understand.
03)Accordingly, R-134a shows higher pressures than R-12 at normal
condensing temp. However, the difference is marginal and hence
adjustments of safety controls is minimium. Where in doubts, verify with
the manufacturers.
04)Because R-134a may have a lower system pressure drop than with R-12,
controls like pressure regulators and pilot operated solenoid valves use
in the system need to be verified with the manufacturers or your parts
suppliers. These controls may need to be downsized in order to operate
properly. However, I envisage this will apply to larger systems
(guessing approx. 2 tons or higher at low temp.)
05) In R-12 system using capillary tube and is retrofitting to R-134a,
the capillary tube may need to be change to increase refrigerant flow
resistance. It has been mentioned that the volume flow with R-134a is
about 25% lower than with R-12, when using the same compressor model.
Hope this helps.
Cheers.
John Tan
Marc L O'Brien
<3651F1...@pacific.net.sg>...
: tur...@worldnetla.net wrote:
: > i know i'm suppose to study the chemical formation of the freon in
this
: > application and derive that it does not work or does work. now i'm
being
: > told that it will not work or will not do right and all that.
being the
: > nuckel head that i am and don't listen and i put 134-A in a 3 ton
walk-in
: > freezer. it work like a charm. of course i used ester oil in it. i
know there
: > could be some ameba that will start growing in walk-in freezers and
then kill
: > all the guppie in fish tanks all over the world, but i got to know.
: >
: > would some one please set me start or inform me of the
: > draw backs of this action ?
: >
: > turtle and nuckel head will not stop till they hit a brick wall.
:
: I agreed on the points mentioned by Jim Lavelle.
:
: I think in your case, using R-134a would be an alternative though
R-134a
: would have display temperature glide below -10 deg. F evaporating.
: Main thing to take care during retrofitting is to ensure moisture
free
: system. POE oil should not be exposed to surrounding for too long as
it
: would absorb moisture easily (I think the guide is 10 mins). Where
: possible, change new liquid line filters at least twice to ensure
: contamination free system. Use good quality R-134a suitable drier
like
: Sporlan or Alco.
:
: Also, if possible, try changing to a R-134a txv.; if not available,
get
: a R-12 txv with approx. 15 to 20% lower rated capacity than the
: original.
: Cheer ocean friend :-)
With existing systems having very little residual capacity we need
remember R134a's specific volume increases faster with reduced
pressures than does R12 while its latent heat remains a constant
approx. 33% greater than R12. Its specific volume starts off about 33%
greater than R12 at higher temps like about 0 deg C and then increases
quicker as the pressure drops. Perhaps with the extended run time with
reduced mass flows over the motor for cooling there could be motor
overheating problems.
--
Marc L O'Brien
Senior Service Engineer
York International
London, UK
0044 7887 634020
0044 7957 358550
Marc L O'Brien
: Just found out from Mike's post in another news server that I have
TEV Sizing: With the increased TEV pressure differential but similar
liquid viscosity's comes increased mass delivery. With increased latent
heat and specific volume comes reduced compressor mass take. So with
increased TEV mass delivery and reduced compressor mass take comes the
dreaded floodback.
John Tan
>
> John Tan <tec...@Nospam.pacific.net.sg> wrote in article
> <36534A...@pacific.net.sg>...
>
> liquid viscosity's comes increased mass delivery. With increased latent
> heat and specific volume comes reduced compressor mass take. So with
> increased TEV mass delivery and reduced compressor mass take comes the
> dreaded floodback.
> --
> Marc L O'Brien
> Senior Service Engineer
> York International
> London, UK
Howdy Mighty Marc :-)
Thanks for the details.
Great, I've copied down your phone numbers and probably going to call
you ...... wonder how you sound like :-)
I can't get through your web-page anymore, wonder if there is a change
in the URL.
Cheers.
John Tan
P. O'Callaghan
cost etc, especially for a compressor, using something like R22 or moreso
R404 for low temp makes more economic sense because the compressors will be
smaller and cheeper. This is possible because of the refrigerant properties
of the gasses. "more bang for your buck" so to speak.
Phil
John Tan <tec...@Nospam.pacific.net.sg> wrote in article
Marc L O'Brien
<01be185f$0c2d2ec0$30bc07cb@aircons>...
: wouldnt it have been easier to say that when you compare equipment
size and
: cost etc, especially for a compressor, using something like R22 or
moreso
: R404 for low temp makes more economic sense because the compressors
will be
: smaller and cheeper. This is possible because of the refrigerant
properties
: of the gasses. "more bang for your buck" so to speak.
Phil, I found, at least back in South Africa 5 years ago, that the R22
low temp compressors were more expensive. Probably because they were
capable of R22/R502 low temp application and then R12 high temp
application whereas a R12 low temp compressor would not have
sufficiently large valve ports and motor for any R22/R502 application.
--
Marc L O'Brien
Senior Service Engineer
York International
London, UK
0044 7887 634020
0044 7957 358550
I'm looking to travelling the world for the next 5 years or so. Anyone
got some temp work and have the whereabouts of some cheap lodgings?
P. O'Callaghan
It would obviously depend on the type of installation you were using it on.
I agree that in some instances r22 low temp compressors may have been
dearer, some needing liquid injection etc etc, but according to my supplier
catalogues, according to memory, 5 years ago not much stuff was on r22 low
temp (here) and was a bit experimental but now its everywhere besides, a
lot has happened in compressor design and system component design since
then.
If you look at a decent catalogue, and compare compressor X on r134a and
then see it at the same SST on r404a, I think you will find a fair amount
of difference in actual refrigeration capacity.
With that in mind, A smaller compressor running on r404a will be able to
give the same refrigerating capacity as a larger compressor running on
R134a.
You can throw around mass flows and get really technical, but at the end of
the day, when your quoting or selecting equipment, I bet that the equipment
I select will be smaller and cheeper to buy and run on r404a than r134a.
One instance I saved a client a few hundred dollars alone on repairing a
system and fitting a new compressor that run on r22 than r134a (med temp).
Phil.
Marc L O'Brien <Mlob...@btinternet.com> wrote in article
<01be18b8$acd14ec0$LocalHost@desktop>...
> P. O'Callaghan <air...@Xozemail.com.au> wrote in article
> <01be185f$0c2d2ec0$30bc07cb@aircons>...
John Tan
>
> It would obviously depend on the type of installation you were using it on.
> I agree that in some instances r22 low temp compressors may have been
> dearer, some needing liquid injection etc etc, but according to my supplier
> catalogues, according to memory, 5 years ago not much stuff was on r22 low
> temp (here) and was a bit experimental but now its everywhere besides, a
> lot has happened in compressor design and system component design since
> then.
>
> If you look at a decent catalogue, and compare compressor X on r134a and
> then see it at the same SST on r404a, I think you will find a fair amount
> of difference in actual refrigeration capacity.
>
> With that in mind, A smaller compressor running on r404a will be able to
> give the same refrigerating capacity as a larger compressor running on
> R134a.
>
> You can throw around mass flows and get really technical, but at the end of
> the day, when your quoting or selecting equipment, I bet that the equipment
> I select will be smaller and cheeper to buy and run on r404a than r134a.
>
> One instance I saved a client a few hundred dollars alone on repairing a
> system and fitting a new compressor that run on r22 than r134a (med temp).
Pardon the interruption here, we forgot that Turtle is asking about
retrofitting works from R12 to R134a or alternatives (without changing
compressors).
If R22 is used instead with compressor change, our practice here is to
change the air-cooled condenser to larger size due to relative higher
condensing pressure/temp. and also the txv. as well (with a sacrifice on
the evaporator capacity); hence, the retrofitting works may cost
relative more.
I personally do not like using R-22 on new low temp. applications due to
frequent encounters of oil return problems and compressor over-heating.
2 years ago in our world trade centre, my competitor was displaying an
operating cold room with a 5 hp. low temp. R22 compressor (aircooled
condenser with an head cooling using fan ); the monster broke down on
the 3rd day of exhibition.
Anyone having problems with R22 on low temp. applications?
Regards,
John Tan
Marc L O'Brien
Hello there John, do you think it really matters that someone might
wish to change the subject slightly for the sake of variation? :-)
: If R22 is used instead with compressor change, our practice here is
to
: change the air-cooled condenser to larger size due to relative higher
: condensing pressure/temp. and also the txv. as well (with a sacrifice
on
: the evaporator capacity); hence, the retrofitting works may cost
: relative more.
I agree with the use of larger condensing units but I'd do that for
the sake of reducing the required TD ( temperature differential)
between saturated condensing and ambient air-on temp. This might be to
reduce the TD from say 15 K to 10 K providing for lower discharge
superheats.
: I personally do not like using R-22 on new low temp. applications due
to
: frequent encounters of oil return problems and compressor
over-heating.
Yes, it can be difficult, as I have said before here a few years ago,
I have many times designed, installed and commissioned R22 low temp
(-32 deg C sat evap) systems without incident. Henry Valve Helical oil
separators at 99.9% efficiency are a big help along with very low
suction superheats.
: 2 years ago in our world trade centre, my competitor was displaying
an
: operating cold room with a 5 hp. low temp. R22 compressor (aircooled
: condenser with an head cooling using fan ); the monster broke down on
: the 3rd day of exhibition.
I'm sure whatever the problem was I could have avoided it.
: Anyone having problems with R22 on low temp. applications?
Nope!
--
Marc L O'Brien
Senior Service Engineer
York International
London, UK
johntan
>
>
> Hello there John, do you think it really matters that someone might
> wish to change the subject slightly for the sake of variation? :-)
>
>
> I agree with the use of larger condensing units but I'd do that for
> the sake of reducing the required TD ( temperature differential)
> between saturated condensing and ambient air-on temp. This might be to
> reduce the TD from say 15 K to 10 K providing for lower discharge
> superheats.
>
> Yes, it can be difficult, as I have said before here a few years ago,
> I have many times designed, installed and commissioned R22 low temp
> (-32 deg C sat evap) systems without incident. Henry Valve Helical oil
> separators at 99.9% efficiency are a big help along with very low
> suction superheats.
Honorable Marc :-)
Thanks for the details.
I'm impress with your ability to diagnose and troubleshoot refrigeration
systems with a chemical/mechanical scientist-like knowledge.
Here's my appraisal of you http://members.xoom.com/aircon/wow.wav
Do you want to hear about your negative side :-)
Just joking here.
John Tan
Marc L O'Brien
Hey, you pick my nose, I pick yours :-)
http://members.xoom.com/aircon
That's and okay site that is :-)
: Do you want to hear about your negative side :-)
Nope, ignorance is bliss :-)
: Just joking here.
What a relief :-)
: John Tan
--
Marc L O'Brien
07957 358550
0044 7957 358550