Don’t think there is “gas” in the receiver or behind the sight glass, on high pressure side, Ray. Right? Just sayin. Gas there=bad.
Not s’posed to be….
It is not “compressing liquid”, as it is still a hot hi pressure gas being squeezed after compressor, until cooled in the condenser serpentine (where it , er, “condenses” --from a gas) , but that pressure of that hot gas at start is pushing on the downstream liquid.(what you read as ‘high side” ). Downstream, working right , the warm liquid is fully condensed, no gas, and present in the cooler end of compressor coil, in sight glass and in receiver.( where excess liquid is stored ok, does not cause “overcharge” unless excessive by a lot; whatever it needs to run , will come out by itself, till pressure is right , at that temp , not more.) . That warm liquid is what the expansion valve has to have . If it is boiling steadily in the receiver can , it will get cold there (expansion valve stuck open? )
When it gets low on charge , the end of condenser coil is not kept full of liquid, you start to see gas bubbles in the (wonderful !!) sight glass , and probably the receiver Freon storage place is also empty, just sitting there. That sight glass is a very good thing. Stream of bubbles means you are running low.
And on Don’s explanation, I think it actually flashes instantly to gas at the expansion valve, as it cannot be a liquid under the low pressure of suction side unless supercooled, to a temp where even under that low pressure it does not boil…(see refrigerant charts) the low pressure is the same everywhere on that side. ..which it might be very cold (by its own evaporation ) But if still a liquid after expansion valve ,obviously it might not be cold right there, at valve, as no expansion yet. . Take your choice. I think it flashes (expands!—at “expansion valve” ) the instant it feels low pressure , at end of capillary or tip of expansion valve . cold Vapor absorbs the heat ,and any liquid that gets by does vaporize, to Don’s correct point. May vary with temps and loads too.
I Learned way more about this than I ever really wanted to know , fighting Mitsubishi splits in two houses. One huge takeaway is you need the 150$+ Rigid brand “orbiting” bearing mounted cone flare maker to get good flares; the el cheapo straight on ones , like brake line flares often scratch the copper minutely and will leak. Slowly. So you are driven crazy .
Last, just FYI< those splits have the expansion valve at the compressor/ condenser housing , causing a massive confusion at first for this old guy. The high pressure hi side “liquid line” is NOT THERE going to evaporator! Instead a cooled vapor, after expansion , is in one line, no valves at all at indoor coil, vapor goes out and comes back at like 100’s of PSI. Not trying to confuse, but why understanding WTHell is going on became essential. They work now,..
I was constantly feeling the smaller line, wondering why it was cold, (usually warm, as above ) and coming to wild conclusions that were all wrong. Plus the leaks. And incorrect vacuum processes. An analogy, imagine expansion valve is located at radiator end of 300 condenser..and you do not know that.
Your email disputes itself.
Start with your tutorial, it's a British article, which shows why the Brits drink warm beer and there A/C's don't work.
There are many things wrong in it, but that's another subject...
I do have some of it wrong. Thank you for pointing that out. I retired 17 years ago and some things are getting fuzzy...
You say "The compressor actually turns the gas into a pressurized hot liquid" We can not pressurize liquids. That's why the brakes work. You can put pressure behind liquids to push them out. That's how the brakes work.
The compressor pressurizes the hot GAS and sends it to the condenser, where, as it flows thru, it sheds heat and returns to a liquid state.
This is the cold LOW pressure liquid, going thru the expansion valve where it starts to become a gas again. This valve mostly regulates the amount of flow which regulates temps. It actually allows passage at a given temp and stops it at a lower temp. The cold liquid starts to absorbs heat from the cabin as it expands to a gas and returns to the compressor as a HOT gas. And the cycle continues.
On Sat, Jul 9, 2016 at 4:35 PM, Keith Boonstra <kboonstra.zeegroup@xxxxxxxxx> wrote:
Hate to say it Ray, but you got most of that A/C info backwards. You might want to check out a tutorial like this one:
The compressor actually turns the gas into a pressurized hot liquid. The liquid goes through the condenser coils up by the radiator where it partially cools off. This is normally referred to as the "high side". Then it flows to the expansion valve just before the evaporator coils. The high pressure of that liquid is released at the expansion valve, turning it to a very cold gas there and becoming the "low side". This makes the coils cold and they absorb heat from the air passing through them. The low-side gas, which is still quite cold, then returns from the evaporator to the compressor to be compressed in to liquid state again.
One part you did get right is the critical importance of system evacuation before charging with freon. Because low pressure cause liquids to turn to gas, when you vacuum the system for several hours it causes the contaminating liquids, including water and oils, to boil into a gaseous state and be drawn out by the vacuum pump, and thereby cleansing the system before freon charging.
And one final tip: If you can't or don't want to buy a new receiver/drier (which is your A/C system's garbage can) it is possible to "rejuvenate" your old one. Use an old toaster oven - which you probably keep around anyway to bake paint on small parts. Take it out into the garage or outdoors and bake the receiver/drier in it at 400 degrees for a couple of hours. It may stink to the high heavens, but that process will boil out whatever garbage is in there - same as turning on your self-cleaning oven. Give it a new coat of paint, bake it again at 250 for 15 minutes, and it will look and perform like a brand new champ again.
Freezin' a can of beer in front of my '57 A/C
Ray Jones. Y'all come on down an see us. Ya hear?
Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx>
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