+1

...

No. Wrong. YOUR non barrier hoses leak refrigerant 24/7 and 12 months a year, whether your AC system in on or not. And, the more you use it the more you use it.

That is why barrier hose was developed. And we know you can't afford barrier hoses.

But, as you said many times, in your climate you really don't drive your old 911 that often and you seldom use your AC system.

Your wife's Lexus does not qualify in the discussion.

Correct. The TEV in the 911/930 NEVER closes all the way when the compressor is pumping because the low side would pressure would go negative.. into vacuum.

And, you are Correct, again, the TEV in the 911/930 NEVER closes all the way when compressor is not pumping (system off), that is why the high and low side equalize when you turn the system off. This is the nature of this kind of TEV. There are TEV's that do close all the way but you won't find them in MAC (mobile air conditioning) applications.

You're BACK..!!

So did you write/compose the GTI "Extreme Pressure" info and have long since forgotton. Or was it someone else at GTI with more knowledge, experience, and overall knowhow. Maybe someone that took a few A/C theory of operation classes?

The issue wwest is that these are not linear. Right? Adding 35 degrees at the point you mention does not mean pressure will go up enough to have an impact. Lets say you are right for a moment and that it is linear. What would 35 degrees do to the pressure? If 120 degrees equals 250 psi then 155 degrees = 322 psi... But it can't be linear because the tev is going to start opening within the amount of time it took for your temps to rise to that level if it took two minutes. My guess that even it it did rise it would not exceed 300 psi which would not be blowing past orings and fittings. Would it?
It is just not logical for this to be the reason you lose refrigerant. It would need to rise much higher than 155 and much faster than 2 minutes to have a real impact would be my hypothesis.

The bottom line Wwest is you are the only one that has to prove something.

And, from what you have written in the forum in the past year I'd say
you don't have the balls.

Think about my garden soaker hose...If the water supply is from our artesian well, 2-3 PSI, barely dribbles. Hook it up to the public water supply, >30 PSI, and it will soak the nearby area within an hour.

After reading the GTI "extreme pressure" article that's how I now think of the non-barrier hose, permeation rate equal to expectations unless it is exposed to excessive (350-450 PSI, NOT extreme wherein it would BURST) pressures from time to time.

If I didn't before then after reading YOUR information at GTI I need to go out and buy some "deep rise" pants.

Lol, like I said, you definitely don't have any balls.
You're such a wussy.

That depends on the reference subject matter.

"..you won't find them in MAC.."

Really, then tell us why not, please..?

It's linear, true. But the problem is that PV=nRT uses metric numbers in the calculations. 120F = 322K 155F = 342K Less than 10% increase in temp. And since the pressure is linear with temperature, according to this gas law, there will be less than a 10% increase in pressure, *IF* the volume stays the same. That is, if the TEV is all the way closed. Griff says it never fully closes. Therefore, the moment you turn off the motor, the pressure starts dropping, because the gas is moving back to the low side. Before ANY engine heat can begin warming up the condenser. Sure, the condenser might get warmer from the engine heat, but so what? pressure is dropping on the high side, and rising on the low side.

But thinking that somehow the temp going from, oh, 100F to 200F would cause a doubling of pressure (double the temp, so...) - that just ain't the case. This equation begins the temperature scale at absolute zero. Which doesn't exist anywhere in the universe, as far as we know. The temperature range we are operating in for AC is very small on a gas law scale. Very large temperature increases by human standards (98.4F, body temperature to 212F, boiling point of water) is a very small increase for pressure calculations using the gas law. And since the volume of the system is changing over time (TEV always open), it would take a very large temperature increase to provide ANY pressure increase at all.

The phantom menace of pressure spiking after shutdown is just the vivid imagination of wwest. Or post-purchase justification of his system. Which isn't adequate in sub-tropical or desert conditions anyway.

Agree with all your points. Thanks for the education...

"..The phantom menace.."

So now you're disbelieving Kuehl's "bible", hoses are intentionally "porus" to provide a "slow" leak under pressure rather than let that pressure build up to "extreme".

Well, wwest wanted to promote a theory. Really, in scientific terms, a hypothesis. Well, in science, a physical law is always the trump card. And the gas law is indeed a law, just like the law of gravity.

I figured I'd let him get about three months into his hypothesis before I whipped out a little ol' physical chemistry. Mind you, it's been a while (ahem) since p-chem, but I still have vivid nightmares. It was the hardest class I ever took. The math just about kicked my @$$ to the chemistry-major curb. Funny now, I look back on it and am surprised by how much of it I remember. I hardly ever use any of the stuff p-chem taught, but I still remember describing the behavior of a van der Waals gas in a closed system...

I was thinking earlier about the purported 800psi high side. Well, let's come out of Stupidland (800psi is a ridiculous number, obviously a troll) and enter Fantasyland. Let's say, oh, 420psi. I pick that number because wwest is high if he thinks the pressure climbs that far without the compressor running and something wrong with the system.

If the normal operating pressure is 250 psi high side, AND IF the TEV closes all the way, then what you have is 68% increase in pressure. If R12 is an ideal gas, then by PV=nRT (volume, mass of refrigerant and gas constant all being constant) and we start with a temperature of 120F (322K), then the temperature *of the system* (not just the condenser) would need to be 393F (473.7K). Nearly 400 degrees Fahrenheit. Hoses, fittings, everything. Since the hoses, fitting and everything not near the engine are going to be cooler, you'd actually need even higher temps to produce that kind of after-run pressure.

Maybe in wwest's cars, there is some sort of fault in the system, and he's getting TEV blockage at shutdown. And maybe the pressure spikes. But the idea that it's even going to 400psi from waste heat in the engine compartment is not merely ridiculous.

It's impossible.

And here's the kicker - the ideal gas law, where the gas is described as a constant, rather than as some form of equation (eg. van der Waals gas) is true for most gases at or near standard temperatures and pressures. When stuff gets freaky, like very low temps nearer to absolute zero, or very high temps near where a gas becomes plasma, or super-high pressures (1000x the air pressure at sea level), that where real gases stop behaving like ideal gases. But at the temperatures and pressures we're talking here? Even a big molecule like R12 exhibits mostly ideal gas behavior.

If wwest want to proffer any more of his wild-eyed hypotheses, just aim him at this post. Have him go ahead and argue with a scientific law that was established before he was born.

Then why do we still have 350-450 PSI BOV's in the marketplace...

Are you by chance forgetting, or intentionally over-looking, the fact that a "state change", liquid to gas, gas to liquid, is involved here.??

Don't we all know that heating a sealed container fill with water will eventually result the pressure inside the container rising and rising until the container bursts...?

he is just so simple minded. we are now boiling water in a container. he is 73. came from a much simplier time when things didnt require a high level of technical knowledge or understanding. He grew up with Swamp coolers. Combined with an education obtained on Google... i can see where he would constantly confuse himself and change his theories. which is what has happened over time. Afterall if its on the internet it must be true. Sounds like something my grandmother would say.... think its a generational thing... someone needs to just put the old dog out of his misery..

Worth reading...

Automotive Air Conditioning Bulletin Board • View topic - What is SUPERHEAT??

Why are you posting articles on residential AC on a Porsche 911 Tech site. wow. Your lack of knowledge is so apparent when you are posting unrelated material. There was another guy who did this.. oh yes. Reid...