Porsche early A/C tutorial...or NOT.

[wwest]

In my opinion the early 911 A/C system design parallels the one in my MH, or even a typical window A/C.

The only control point is the temperature of the evaporator vane surfaces or the airflow through those surfaces. So what happens if that control point fails in a manner wherein the compressor runs continuously...?

In my MH or the typical window A/C the house circuit breaker might open, or is more typical the CB inside the compressor drive motor opens due to heating of the windings. Now the CB cycles every 5-7 minutes until the refrigerant pressure declines to the point that the motor will restart without tripping the CB.

So, what happens when the control system in these early Porsche A/C fail in the same manner, how did the Porsche factory design prevent subsequence damage to the compressor due to "slugging", liquid refrigerant reaching, entering the compressor inlet. Or did they just ignore the issue..?

Is the clutch designed to begin slipping with too much refrigerant pressure? Is the compressor itself of somehow a design that limits downstream pressure? A spring loaded relief valve, Pressure CB, that ports downstream pressure back into the inlet if pressure rises too high...? Or is the factory recommended refrigerant charge intentionally low enough that the compressor running continuously will not, will NEVER result in slugging?

My advice to anyone is that BEFORE you begin upgrading your factory A/C you should either find a positive answer to one of the above questions or add a hi/lo pressure switch downstream of the compressor so the (old/ new) compressor doesn't inadvertently destroy itself.

[kuehl]

Wild West,

You started a thread over 2.5 years ago and no one responded?
Not fair at all !

Let's see if we can straighten you out , ey!

"In my opinion the early 911 A/C system design parallels the one in my MH, or even a typical window A/C."
I have no friggin clue what you are saying here, probably why no one responded, ey?

"In my MH or the typical window A/C the house circuit breaker might open, or is more typical the CB inside the compressor drive motor opens due to heating of the windings. Now the CB cycles every 5-7 minutes until the refrigerant pressure declines to the point that the motor will restart without tripping the CB."
OMG, I'm clueless again. What the frig is with the acronyms dude! MH, CB. Geez guy. Its like trying to read text messages in a kids cell phone.

"So, what happens when the control system in these early Porsche A/C fail in the same manner, how did the Porsche factory design prevent subsequence damage to the compressor due to "slugging", liquid refrigerant reaching, entering the compressor inlet. Or did they just ignore the issue..?"
If the thermostat fails either the compressor does not operate = you get toasty.
Or, the compressor continues to operate = you get nice and cold and them warm again as the evaporator coil fins turn into funky ice cube. However, the compressor seldom is slugged with liquid refrigerant. As a matter of fact very few 911 compressors fail because of slugging. Rather most of them either leak over time or simply wear out.

"Is the clutch designed to begin slipping with too much refrigerant pressure? Is the compressor itself of somehow a design that limits downstream pressure? A spring loaded relief valve, Pressure CB, that ports downstream pressure back into the inlet if pressure rises too high...? Or is the factory recommended refrigerant charge intentionally low enough that the compressor running continuously will not, will NEVER result in slugging?"
Clutches are not "designed" to slip, they can slip, but seldom do 911 compressor clutches slip; it can happen but its not the common failure.
The factory recommended charge is 'the recommended charge'. Its the charge that Porsche decided works best. But, if you know what you are doing you don't simply look at the amount of charge, rather you look at the P&T (know that is an acceptable acronym in the context of this subject).

"My advice to anyone is that BEFORE you begin upgrading your factory A/C you should either find a positive answer to one of the above questions"

OIY! there you go again, no friggin clue where that sentence is going.

"or add a hi/lo pressure switch downstream of the compressor so the (old/ new) compressor doesn't inadvertently destroy itself."
Here you got it half right, a binary switch will "help" prevent problems; "help".