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  • #16
    Was the reclaimed stuff tested for purity? We could really be chasing our tails if it had some Zeotropic (blended) refrigerant, like R 502. There are a lot of different mixes used in commercial freezers

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    • #17
      Thanks, Cornbinder

      Originally posted by Cornbinder89 View Post
      Pressures don't show a 42 deg temp drop they show a 155 deg condensing temp. Misting is a quick and easy test. Your car, your choice on what to do. I fear there is no quick and easy answer to your problem. A little corrosion on the tubes and the condenser will not shed heat and the thermocouple will not transfer the heat reading properly
      I don't see how my situation is unique, it is just using thermodynamics to optimize the system as best as I could. By removing as much heat from the refrigerant as possible, the evaporator size (capacity) becomes the limiting factor in the system. The oversized condenser has the added benefit of reducing the head (high side) pressure, reducing the load on the compressor.
      Most Tx used in automotive use are either 1, 1.5 or 2 ton valves, so there is no way the system can move 100,000 BTU. 2 ton units are mostly in trucks and vans, I don't have a listing for a Merc Tx valve, but I doubt it would be over 1.5 ton. A 2 ton condenser would eliminate the condenser as a limiting factor.
      What pressures don't show a 42 deg temp drop? What do they show? If there is a 155 deg condensing temp what does that mean? The way I understand it is that the temperature of the liquid refrigerant doesn't matter. 150 deg liquid will cool the same as 50 deg liquid. Is this true? Mercedes has a temperature switch on the receiver to start the electric condenser fan at 144 deg F.

      I am resistant to the mist thing because there is no way to know how much heat the water is removing. I never said any thing about a 100,000 BTU system. The figure is as an extreme to illustrate the inaccuracy of misting. The water could remove 100,000 BTU and everything works fine. I could use this information to justify buying a new 32,000 BTU condenser only to install it and the problem not be solved. Conversely, the water could remove 100 BTU and there is no change. This would lead to the conclusion that the condenser is fine when it may not be.

      I get your point on possible measurement errors but it is the best I can do. Any errors would be on the order of several degrees not dozens.

      Lets assume that my measurements are good, would a 42 deg temp drop be good?

      Did you read the thread at http://acsource.net/acforum/viewtopic.php?f=1&t=2545 ? It is interesting. Here is a quote: "Postby GM Tech » Thu Jul 27, 2006 4:08 am
      I've run tests with access ports in between every component- all fed into a data aquisition computer- there is no significant pressure drop across a condenser- high pressure is the same whether it is liquid or gas- the OT or TXV causes the restriction which creates the pressure,,,,,,"

      Have a good day.















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      • #18
        Originally posted by Cornbinder89 View Post
        Was the reclaimed stuff tested for purity? We could really be chasing our tails if it had some Zeotropic (blended) refrigerant, like R 502. There are a lot of different mixes used in commercial freezers
        How is that tested? The compressor in the restaurant was marked R-12. The AC in the F350 and C10 were charged from the same bottle and they work well. The C10 works particularly well because the carburetors fast idle.

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        • #19
          Testing for purity and type! Yikes - if that's unknown or for real this is going to be impossible. Machines can cost 2 grand to test types and % of moisture. One shown here........
          https://www.instrumart.com/products/...t-gas-analyzer

          Where did this stuff come from? There's just so much motivation to use or mix up on purpose it's scary. New could still be acquired with a real hunt. Can't only be my opinion now as I only suspected contamination once with a LOT of R-12 said to be recovered but only used that on some pretty late chance of a whole vehicle lasting too much longer to just boost it back up and saving brand new sealed stuff for restoration projects I'll probably never get to now and have enough Dupont, green/ clear shrink seal intact "FREON 12" the namesake of the liquid gold.

          There was so much trouble so called "up here" I don't know of anyone who deals with it anymore. Entire places will not keep servicing equipment and state will not work with it.

          Good grief - some archives at the old site on this. Propane can work, butane and other total flammables. The assorted gasses used in computer duster have been known to work.

          152a is said to be the next coming refrigerant currently sold in now for assorted uses behaves much like R-12.

          Step one if any questions on this I'll default to my friend Nacho, a listed member here and at the archived site you can click on above.

          Step two if this is seriously in question IMO dump it and start over with known product from a reliable source that can prove it.

          This can and would change everything - properties all off. You may get "hacked" product to work but all bets off for it's life, ability to carry oils, flammability or acidity that simply destroys the entire system!

          Yikes,
          Tom
          MetroWest, Boston

          Comment


          • #20
            Originally posted by I hate working on cars View Post
            Thanks, Cornbinder



            What pressures don't show a 42 deg temp drop? What do they show? If there is a 155 deg condensing temp what does that mean? The way I understand it is that the temperature of the liquid refrigerant doesn't matter. 150 deg liquid will cool the same as 50 deg liquid. Is this true? Mercedes has a temperature switch on the receiver to start the electric condenser fan at 144 deg F.

            I am resistant to the mist thing because there is no way to know how much heat the water is removing. I never said any thing about a 100,000 BTU system. The figure is as an extreme to illustrate the inaccuracy of misting. The water could remove 100,000 BTU and everything works fine. I could use this information to justify buying a new 32,000 BTU condenser only to install it and the problem not be solved. Conversely, the water could remove 100 BTU and there is no change. This would lead to the conclusion that the condenser is fine when it may not be.

            I get your point on possible measurement errors but it is the best I can do. Any errors would be on the order of several degrees not dozens.

            Lets assume that my measurements are good, would a 42 deg temp drop be good?

            Did you read the thread at http://acsource.net/acforum/viewtopic.php?f=1&t=2545 ? It is interesting. Here is a quote: "Postby GM Tech » Thu Jul 27, 2006 4:08 am
            I've run tests with access ports in between every component- all fed into a data aquisition computer- there is no significant pressure drop across a condenser- high pressure is the same whether it is liquid or gas- the OT or TXV causes the restriction which creates the pressure,,,,,,"

            Have a good day.














            The condensing temp is what tells me you don't have a 42 deg drop! The quote from GM tech is exactly what I am saying! If you had a 42 deg temp drop the condensing temp would be 113 and the PRESSURE would be Aprox 132 PSI on the high side!
            Look, the output of the compressor is hot gas, how hot depends on many things, it can be 250 or hotter (ever grab the outlet of an air compressor when it is running?) , but the pressure is determined by the restriction in the Tx or other metering device and the temp at which the refrigerant turns to liquid. So in a working condenser, the hot gas, lets say is 250 deg, enters the condenser and is cooled to 100 deg, and looses 150 degs, and leaves a liquid. once a gas goes thru a phase change to liquid, the space required to hold it is an order of magnitude less, in most cases the receiver is sized to hold all the refrigerant in liquid form that the system holds! Without the restriction there would only be flow, but no pressure, without the condenser, there would be pressure but no cooling. The high side pressure is a function of the restriction and the condensing temp! The two together, the restriction is more or less a constant, the variable is the condensing temp. If a gas is above the condensing temp, for the pressure it is at, it will remain a gas, so you could have a 250 deg gas coming out of the compressor at 120 psi, it will remain 250deg until it hits the condenser then cools to 100 deg by the time it leaves as a liquid. The pressures tell the phase change point in the system.
            Hot liquid refrigerant doesn't cool (absorb) as much as cool does! If your spraying in 155 deg liquid and expecting the same heat absorbstion as 113 deg your reasoning is false! You must get the heat out to absorb more! With no condenser and enough compression you will ALWAYS have liquid at some point!
            Misting the condenser is just a test to prove that it is the condenser that is at fault.
            Misting is a industry accepted method for testing, if you choose not to use it, that is your choice, but it doesn't change what the symptoms point too! Misting can only remove what heat is there, it can only sub-cool to slightly below ambient just like sweating does on the human body.
            I understand the condensers a PIA to change, but wishing it to be something else when the symptoms point clearly in that direction will not change that fact. Misting the condenser will remove heat from even a poorly working condenser and will drop the high side condensing temp, you should seen a corresponding drop in high side and vent temp while misting and a reversion to previous readings when you stop. Can't think of a more clear test than that! If you choose to not do the test or ignore the results, that is your prerogative, but it doesn't change the validity of the test.

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            • #21
              Originally posted by I hate working on cars View Post

              How is that tested? The compressor in the restaurant was marked R-12. The AC in the F350 and C10 were charged from the same bottle and they work well. The C10 works particularly well because the carburetors fast idle.
              And the compressor on my Truck has a label that say R-12! It is why you change fittings when you convert to 134a, you could pump 134a thru r-12 fittings and in industrial/commercial that is exactly what they do! There is no retro-fit of fittings on commercial, and if you buy 134a for non-automotive, it comes with flare fittings on the keg!
              In commercial they hope and trust that the tech will label his work, but that doesn't mean it happens. Commercial shops a much more likely to have a refrigerant id'er than to go off the label on the machine, Mixing of various refrigerants in a recycling tank is a big no-no. It can cause the whole tank to be rejected, so they want to know what they are pulling out!

              Comment


              • #22
                Let me try to get my point across another way, you have two reading of the same condition that don't match, High side pressure, and thermocouple reading. One is direct, and reading the fluid in question (Pressure) and one is indirect and reading external of the system. For some reason you would choose to believe the indirect over the direct. I can't help with that.

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                • #23
                  Nice post Cornbinder89. Lots of physics at play. Without the costly machines the observations if correct are showing the problem is real.

                  With product known you know what to expect. Without an odd mechanical defect unseen this seems back to what is suspected, the refrigerant whatever it is, is not behaving along with known properties. We are stuck here IMO without some more testing or starting all over with the gas alone with known proper product for this,
                  Tom
                  MetroWest, Boston

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                  • #24
                    Well, lets look at a hypothetical situation where there is some other restriction (other than the metering device) down stream of the condenser, we would expect to see higher high side pressure and a cooling or frosting of the liquid line after the restriction. The high side pressure goes up because liquid backs up into the condenser reducing the area available to gaseous refrigerant to transfer its heat. So you would see higher high side. BUT and this is the BIG BUT, the low side would be low, may be even below atmospheric pressure. We would not see the low side pressure we are seeing in this case.
                    So lets now look at a partially restricted condenser, the same would happen, and the outlet tube may be cool, but the high side would still be high, That would explain all the hot side readings ( Including the thermocouple) But it still means a condenser change. Also you should be able to feel a point where the condenser goes from hot to below ambient temp. You would also expect to see a low, low side reading, which we don't have in this case. My read of the symptoms is: you have poor heat rejection from the condenser, and no restriction. Get the heat out and the head pressure down and you will have cooling that you expect from this system
                    I think it far more likely that the thermocouple reading is not reading the liquid temp than any of the above (restriction) scenarios. You could buff the line, add some heat transfer compound to try and get an accurate reading, or you could trust a pressure reading.
                    Last edited by Cornbinder89; 06-25-2017, 12:35 PM.

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                    • #25
                      Should be able to find strange temp changes where they don't belong? Condenser? There were several that if you blocked one passage you lost 3 the way they weave them such that they should be close to even for heat exchange. One only found when cut open had solder from new just a mistake the guy complained since thing was new it wasn't very good A/C then years later it's perfect and by then that much older and used so too bad couldn't be found easily and he was an A/C totally qualified tech and teacher of it!

                      So there's always room to get fooled and things show right when checked. I really don't know a perfect approach if newer and this bull used to just dump the charge and start over most suddenly behaved and will not know for sure why but I never used recovered refrigerant or a name I didn't know either when important enough,
                      Tom
                      MetroWest, Boston

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                      • #26
                        I finally was able to get the evacuation machine going. There was a leak that made no noise and passed the bubble test. What precipitated this leak is the manufacture of a check valve desire to save a few pennies on material cost. They made the valve out of 1/2" stock rather than 9/16" for a 1/8 NPT. This left just .050 wall thickness. This thing cracked on its own just sitting in the system. Then there was another leak that took forever to find.

                        Any how, when I evacuated the system there was only 0.4, yes, point four of a pound of refrigerant in the system. How it produced any pressure at all eludes me. When I removed the expansion valve it was saturated with oil. It was not working because the needle did not move from freezer temp to heat gun temp. Using clean dry air, I purged 3.5 oz of oil out of the evaporator. Don't know what is normal, but that seems like a lot to me. I am debating on doing the same to the condenser. I guessed on how much oil to add when I charged it several years ago. I need to learn how to get the right amount of oil the system. Any suggestions?

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                        • #27
                          OIl: No dipstick so have to put in correct amount from known empty. That means blowing it out, flushing as needed, dump out compressor, blow out a tube and fin condenser if new may not work you throw it out again and again (know what it is and how it changes capacities) then receivers just toss for new and any mufflers if used. You can drill holes in old ones and warm them out to count what comes out.

                          Add to compressor but be sure it can spin. Some downstream and more upstream (low side) so oil get to compressor early not travelling the whole loop to get back.
                          Last general look up found by me showed 7.75oz to 8.5oz mineral. Chart I used only went back to 89 - sorry so verify that on your own. General again is up or down a couple oz shouldn't be the world but keep track and write it under the hood for later info.

                          Vacuum? Machine? What did you use? As long as you achieve full vacuum before the charge up really doesn't matter how you got there.

                          Note: Whatever you measure of .4 equates to ounces if more than a couple would show static pressures. Gases like refrigerant or "condensable" make a huge volume from liquid to gaseous state. Think of a can of spray paint for example it's mostly the paint pushing out product in that case. It too doesn't want to be cold for use or risky when too hot the pressures of all sorts varies wildly but predictably with temp if contained.

                          Leaks. Harder ones I still like all methods but find some elusive ones better if right conditions with a sniffer you can change sensitivity to. Unaware if you can rent those as they are subject to wrecking them if you use it wrong too easily,

                          Tom
                          MetroWest, Boston

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                          • #28
                            Hi Tom

                            Thanks for your response. I know that is the right way and is what the manuals say but it is so much work. Especially on this Mercedes. Removing the compressor is an hours long, very frustrating job.

                            It is a Welch vacuum pump. A laboratory grade pump that is know as a "micro torr" pump which pulls a very high vacuum. On all my gauges it goes past 30. But what is a few air molecules among friends.

                            I am using R-12.

                            Now, as when I charged it several years ago, it held vacuum and 100 PSI over night. But that is 1/3 of operating pressure. It could be leaking molecularity through an o-ring or hose as far as I know. I can't remember if I used a double lip shaft seal.

                            I keep thinking how nicely R-290 worked in the last Mercedes. Bypassing the evaporator temp switch, I was able to get 13 deg F vent temperature with less head pressure. This cooled the car quickly.
                            Last edited by I hate working on cars; 08-18-2017, 11:31 AM.

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                            • #29
                              Quoting post #28 "On all my gauges it goes past 30."
                              ? You are speaking Hg as in inches of mercury? You can't get below 29.92Hg unless below sea level - just trust me. Said full vacuum means there's NOTHING for vapor in a system no matter how you achieve that.

                              Have to work such that you don't get virtually anything but the refrigerant inside. Air we breathe doesn't condense which is a must meaning under pressure at a known temp it will be a liquid. That's all. Air would condense but it's something insane like 5-6,000 PSI not practical at all. If you have small % of air mixed in throws the show all off.

                              Reason for staying with known refrigerants is you know what to expect when/if all things are known.

                              Side note on time to remove a part - compressor in this case. An hour mean nothing. If you vacuum out any refrigerant and nothing broke in doing that, that's nothing but depends on tools and knowing what's in the way of each. The point I'm making is it's not a race rather do thing right so you don't waste mega hours with something broken or damaged by beating the clock not worth it,
                              Tom
                              MetroWest, Boston

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                              • #30
                                Originally posted by I hate working on cars View Post
                                Hi Tom



                                I keep thinking how nicely R-290 worked in the last Mercedes. Bypassing the evaporator temp switch, I was able to get 13 deg F vent temperature with less head pressure. This cooled the car quickly.
                                R290 is propane, so readily available, but I could not recommend it, in a bad crash, a flammable gas in the cabin can kill in a very painful way.
                                I'm not sure about your lab pump, but "normal" A/C vac pumps will not get all the water out of a "wet" system, and sweep charges are recommended to clear a wet system. Somewhere, I can't find it now, I have a chart that shows how hot the system needs to be in anything less then a "perfect " (total) vacuum to boil liquid water to vapor.
                                Last edited by Cornbinder89; 08-18-2017, 08:13 PM.

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