Let's save the audience from suffering through your avoidance.

When the ac is turned off, engine is turned off:
High side does not rise, it drops. Low side rises. System equalizes.

You will never see a system that is turned off have a higher high side pressure
than what it is when it is running.

Why not provide data indicating that my theory is wrong?? So far all I have seen from you is confirmation of my theory, ref: R-134a conversions "tripping" of 450 PSI pressure relief valves with no system failure cause.

Our Porsche have no such pressure relief valve, what might be the reason for that other than lack of foresight..?

Oooo, nice. Let's guess the tactic:

Subject change. "But leaks around the o-rings..."

Personal experience trumps all: "But in my Lexus...."

Shift of burden of proof: "But why don't you prove me wrong by...."

Of course, he will never prove that high-side pressure climbs after shut-off. Because when he actually does the experiment, and hooks up the hoses, the video will show just the opposite of what he says, and everything will evaporate in a puff of shame.

Unless you can prove to your peers that your theory of over pressurizing of the system
is caused by engine heat, meaning you can provide real data of system pressures
A) System turned off, prior to starting engine and running AC
B) System running normally
C) System turned off, after running engine and AC
Everything you continually post on all the threads is simply your own personal
theory.

The 911/930 system equalizes rather quickly when the engine is turned off; the high side drops and the low side rises. The high side bleeds over to the low side through the TEV (no matter how cold the evaporator was before hand), its just a simple fact based on the construction of the TEV. And this is true for various other types of systems (industrial, commercial, residential), all depending upon the TEV design.

So tell us, how many 911 or 930' air conditioning systems have you worked on in the past 30 years?

http://forums.pelicanparts.com/uploa...1368986832.jpg

So, after 4 emails and a phone call with the EPA asking them, in regard to the following statement on an EPA website:
"When R-134a was first introduced, it was thought that all non-barrier/nitrile hoses would have to be replaced during an a/c retrofit. Early laboratory tests showed that the small R-134a molecules leaked through the walls of non-barrier hoses more readily than the larger R-12 molecules did. In the lab, this caused unacceptably high leakage rates. More recent testing, however, has shown that oil used in automotive a/c systems is absorbed into the hose to create a natural barrier to R-134a permeation. In most cases, the R-12 system hoses will perform well, provided they are in good condition. Cracked or damaged hoses should always be replaced with barrier hoses.

1) Whom in the EPA wrote the paragraph?
EPA Answer: We have no way of knowing.

2) Cite the studies and authors with regard to "recent testing, however, has shown that oil used in automotive a/c systems is absorbed into the hose to create a natural barrier to R-134a permeation."
EPA Answer: We have no idea, no way of knowing.

3) If the EPA feels barrier hoses are not needed then why suggest "Cracked or damaged hoses should always be replaced with barrier hoses."
EPA Answer: Yeah, that does not make sense.


And, after 2 phone calls with the primary U.S. based refrigerant hose manufacturers, with regard to the EPA statement.
1) Both hose manufacturers commented the EPA statement is stretching things; "sure, oil in the hose will help reduce permeation however not to the extent implied by the EPA, actually the oil film will do very little in terms of 'refrigerant loss'.
2) One representative laughed at the EPA statement.
3) When both hose manufacturers were told that a 911/930 has nearly 40 feet of non barrier hose and they were asked for their thoughts ... both said replace the non barrier hoses with barrier hoses.

"...When both HOSE MANFACTURERS....were asked.." Nuff said.

Cracked or damaged hoses should always be replaced with barrier hoses.

Does the EPA stand behind their statements...... do you mean statements like this?


EPA Statement - Least-Cost Aftermarket Retrofit
Many car owners may express interest in receiving a least-cost retrofit. Procedures required for a least-cost retrofit are simple and do not require major component changes. Generally, the process calls for removal of the old refrigerant, installation of new fittings and a new label, and the addition of either a polyalkylene glycol (PAG) or polyol ester (POE or ester) lubricant as well as the R-134a refrigerant. For many vehicles, this simple, least-cost retrofit should provide the vehicle owner either with a/c performance comparable to the R-12 system performance or with a/c performance that, [U]although slightly reduced,[/U] is still sufficient to satisfy the customer. A least-cost retrofit, however, may not provide a satisfactory solution for certain vehicles.

EPA Statement - Hoses
Cracked or damaged hoses should always be replaced with barrier hoses.

The EPA, obviously, has been hammered with complaints by car owners complaining about the costs they have encountered to properly upgrade and repair an AC system when converting to R134a. So, they re-wrote their webpage. Why did they do that?
Politics!

Understand, the EPA does not know that a 911/930 has 40 feet of barrier hose.
Had they know that fact, had they know that most "experienced" 911/930 owners whom had simply tried to taken short cuts and failed.... they would have stated that fact. But, can you see the EPA making a specific comment for a vehicle model or make that accounts for less than 1% of the vehicles on the road? No.

Like I said, when the hose mfg's heard that a 911/930 has 40 feet of hose the response can be summarized as this "WTF? Your kidding me! Heck, change all those hoses". If you doubt that fact then call the major hose mfg's in the U.S. (while they are still in the U.S.) and ask them yourself.

*** Kuehl, in this case you're ALLOWED an appropriate, obvious ASSUMPTION, as is the ROW.

forget about this jackass kuehl. all he does is talk out his ass with no proof to back anything up, and on multiple subjects.

WWEST --

May I offer a small suggestion. This will be so easy it will take less than 30 minutes.

You own a guage set. Right? why dont you do as 20 people have suggested in the 30 or so posts.

Hook up your guages and get some data. Yes it will be only a small data set. but if you are right then others can test. If you are not right, then we can all move on to other things.

The responsibility to prove a hypothesis is on the person making the hypothesis not on some thrid party. No science in the scientific community is done like that. When a real scientists comes up with a hypothesis, he / she spends their effort trying to prove it. Not demanding that others disprove it. LOL

Show us the data. for the 100th time. Either take the time and prove or disprove or everyone will realize you are just a Troll looking to spark a debate

http://forums.pelicanparts.com/uploa...1371133010.jpg

The real problem is that someone might actually believe his BS and waste time and money taking his advice. No only that, his vicious lies concerning Griff should be vigorously rebutted at every opportunity.

The dude is 73 years old, and has nothing better to do than p!ss on people over the internet. I have the luxury of ignoring his posts. Griff does not.

But he did stay at a Holiday Inn Express last night.

When the compressor stops, no more work is added to the system. How can the pressure go up?
When the system is off, the heat absorption stops at the evaporator and the compressor stops doing the compression work on the refrigerant, how can the pressure go up?
The system high and low side pressure can only equalize so the low side pressure rises and the high side pressure drops.
No need to hook up gauges to prove that.

Thank God! I was just getting bored with all the other posting....this is very entertaining!

So, I got a 26 yr old car with over 40; of old hose. I am converting and want to not do this experimenting over and over. So, for the cost (its not that bad) and a lot of dirty work, why not just replace all that old hose to new hose (just because its old!) to take that failure point out of the equation. Instead, we can spend hours debating all this hose crap and there is no way anyone of use know if keeping the old hose in is smart or just get it over with. Anyhow, call me a money waster, but playing with my A/C system over and over trying to make it work on the cheap, is just not a good investment....at least until I retire and have plenty of time to play and play.

I do agree = if anyone is going to bring up a theory and state government (EPA) output on some statement, they better have solid facts, proof, and who authored what and how they are qualified to author it. Its also well know to us all, that our cars have more hose length and fittings to fail over time than just about anything ever designed and sold on the planet.

Otherwise, this is just all very entertaining!

I don't need to PROVE anything, both SCIENCE and PHYSICS side with me.

Think about what will happen to the refrigerant pressure in the system should you use a simple propane torch to heat any one of the heat exchangers, long after the system pressures have equalized....?

Now take an operating evaporator core that has just arrived at the lowest temperature control point (28F..?), the TXV is mostly closed, or fully closed as has now been demonstrated(***). Obviously the compressor was "just" cycled off so the high side pressure is at the highest level that the compressor is capable of "driving" it to.

Now, shut off the engine and watch, mentally watch, the temperature of the rear lid condensor rise higher and higher as it is HEATED via the rising engine and exhaust manifold HEAT. How long, how many minutes, does it take for the engine temperature to stop rising, post shutdown, and begin to cool?

"...no need to hook up guages to prove that.." Whole-heartedly agree.

***Post # 22:

http://forums.pelicanparts.com/porsche-911-technical-forum/755318-first-project-thread-88-cab-c-retrofit-cheap-2.html

Just how long might the hoses be in order to reach the evaporator in the sleeping quarters of an over-the-road tractor. Or any of the various vans or minivans that have a second evaporator all the way at the back of the "bus". And speaking of busses....

According to wwest's hypothesis, it goes like this:

The compressor is doing work right up until the time is motor is shut off. This give the high side initial pressure. The additional work done to the closed system is due to waste radiant heat from the motor, heating the rear condenser further. Since the system volume is closed, adding temperature raises the pressure, according to the ideal gas law (which works well enough to illustrate) PV=nRT. Since the volume (V) is fixed, you can hold that constant. The actual amount of refrigerant (n) is also fixed. So you can hold that constant. R is the ideal gas constant. The variations due to different types of molecules in gas phase is quite small, so this won't change much no matter what kind of gas we're discussing. van der Waal's gas, ideal gas, they behave nearly the same at these kinds of pressures and temperatures. So that can be held constant as well. So, what you get, at the end of all that is that pressure is directly proportional to temperature (T). If the temperature of the condenser goes up, then the pressure will also rise proportionally, and linearly with temp.

Ahhh, but here is where the complication comes in. The high side pressure and the low side pressure will eventually come to equilibrium, and thus the high side pressure should NOT be the initial point from which calculations are made. It is claimed that somehow the high side stays isolated from the low side after this shut-down period, and that high side pressures continue to rise due to PV=nRT. This is the unproven and unfounded claim that wwest continues to make. He knows that he can never put gauges on and test it, because actual experimentation will show exactly what Griff claims - on shutdown, the high-side and low side slowly equalize. Why? Because they are not isolated like wwest claims. *EVERYTHING* he claims hinges on the assumption of high/low side isolation. Since the AC professionals say it doesn't happen, I'll take their professional opinion over wwest's fantasy any day.

Practical Suggestion
 

I really hate to add to this thread but it's like watching two male dogs peeing over each other at the same hydrant.

It seems to me a practical experiment is in order. I can see the argument on both sides of this issue so I'm not taking sides. I just want practical proof.

How about someone with the mysterious leaking refrigerant problem (including me) installing a trinary switch in an otherwise working system? No other changes.

If you've had a consistent pattern of leakage over roughly the same time period, we now have a basis for comparison. If the trinary switch greatly extends or eliminates the leakage maybe it's at least a partial answer.

I know this isn't a true lab experiment but maybe it will slow down this debate.

I'd do it but I just had my system recharged and don't want to pay to have the system evacuated again to install the switch.

The next experiment would be having someone just changing their non-barrier hoses to barrier hoses. No other changes.

Thoughts?

Even better.

Hook up a set of guages and test the theory. It will take 30 seconds to see it proved, or not. Video it and post it on here.

There are many of us who have asked WWEST to do this simple task the day he came up with his theory.

No harm in the theory. Why wont he do the work if he is presenting the theory. he keeps stating he doesnt have to prove anything. yet he does... its his theory.

All of these threads would immediately die with a 30 second video. would they not.

I think he is a troll who knows its bunk or a troll who doesnt own a guage set and doesnt know how to use them... otherwise he would just do it.
yet all he can say is "i dont have to prove anything" LOL

Crazy if you ask me. Think he just likes to make up ideas and present them as fact and he is so scared that he will be wrong that he doesnt have the balls to see one way or the other.