Another dumb question

[Nilao]

With a vacuum gauge that reads in microns. But in an automotive system I wouldn't concern myself with getting a perfect vacuum. That's more for commercial HVAC that might be sealed for a decade or more. Most automotive AC systems are going to be opened every few years for some reason or another.

[Wildcard]

(06-17-2021 )tree98 Wrote:  And how do you "measure microns" ?

You need a digital vacuum gauge or micron gauge, specifically used for evacuation. It can also be converted from "s to microns for example 29" is about 23k microns and 29.91 is the industry standard of 400 microns. However if you not using digital gauges or a specific vacuum gauge your not reading this on a standard needle gauge manifold set. If you are, look at your low side gauge and tell me if you can accurately tell me the difference between 29" and 30" on that gauge.

All this can mean the difference of it cooled last summer but needs refrigerant, compressor or expansion valve next summer -OR- it lasts reliably for years to come.

It really amazes me as an Industrial HVAC tech that the auto industry has such poor craftsmanship and standards. That was not aimed at anyone in here by the way. Just trying to help better ourselves.

[Wildcard]

(06-17-2021 )Nilao Wrote:  With a vacuum gauge that reads in microns. But in an automotive system I wouldn't concern myself with getting a perfect vacuum. That's more for commercial HVAC that might be sealed for a decade or more. Most automotive AC systems are going to be opened every few years for some reason or another.

They shouldn't. And I disagree. Be it Refrigeration, home A/C, Industrial A/C, transport refrigeration or the A/C system on your KW/Pete or Volvo a refrigerant circuit is the same.

Moisture left in the system is 1- non condensible causes poor performance. 2- turns oil to sludge and acid, causes txv's, orphises and small passages to clog. 3- causes copper plating which equal poor heat transfer.

Why would you open the circuit on your truck every few years? Unless the compressor has to be unbolted there is no need.

[Nilao]

Prostar a/c systems typically get opened at least once a year for thermistors. And the typical residential or commercial fixed units are not the same. Everything on a stationary fixed system is sealed. The compressor is sealed, all connections are brazed so with the exception of the adjustable TXV and Schrader valves it's not the same. Automotive systems are sealed via bolts, seals, o-rings etc. While I agree a system should be able to last for years I have yet to see one make more than about 5 before the condenser eats a pebble at 70 then leaks or road craters crack a line/seal/condenser and require the system to be repaired. Plus any small amount of moisture that may remain between 29 and 29.91 inches of vacuum will be absorbed by the dessicate in the filter dryer.

[Kw9006nz]

I'm loving all the information, yes change the dryer if a dryer is easily attained. I have used a very extended vacuum to dry the dryer out in a pinch when it's Saturday at 6 p.m. and living 29 mi from any town while needing to run Monday morning with a predicted 100 deg day.

[Wildcard]

(06-17-2021 )Nilao Wrote:  Plus any small amount of moisture that may remain between 29 and 29.91 inches of vacuum will be absorbed by the dessicate in the filter dryer.

I rest my case. A truck comes in with a cracked line, lost charge and just drove 2 days through the rain to get to your shop. The difference between 29 and 29.9 is the difference between a component full of water and a component dry...it's that simple.

Every thing I work on has flanges, gaskets, orings, thermistors, transducers and 200-to over 1000lbs or R-134a or R123, auto or a 1000 ton million dollar Centrifugal chiller refrigeration is refrigeration. We don't say the hell with it its probably going to have a component failure in 6 months, let's just half azz this, and I put systems on a vac pump for days to dehydrate.

They receiver/dryer is not for that purpose. It's purpose is to remove trace amounts that are trapped in the oil. POE (PAG) oil is hygroscopic and will not release moisture via vacuum.

Your Prostar thermistor failures, ever think they might be getting copper plated from moisture in the system? International or component mfg ever done a root cause analysis on the failures?

[Nilao]

The thermistors always go out of range. Last time I replaced them one was reading ambient the other insisted the temperature of the suction line was 297 degrees with the system off and at ambient.

The thermistor problem was the reason they went back to simple pressure switches after the 2011 model years.

I always vacuum my system with a professional AC machine with a dual stage vacuum pump. I can get it pretty close to absolute vacuum but when you're expected to complete a service within 2 hours you can only vacuum the system for so long. I know in the commercial HVAC world you guys get the luxury of leaving your system on vacuum while you go off to another job but when you only have 1 machine and 20 trucks needing to use it your time is severely limited. You just do the best vacuum you can, ensure it holds whatever it stabilized at, charge it and send it.

[Rawze]

(06-17-2021 )Wildcard Wrote:  They shouldn't. And I disagree. Be it Refrigeration, home A/C, Industrial A/C, transport refrigeration or the A/C system on your KW/Pete or Volvo a refrigerant circuit is the same.

Moisture left in the system is 1- non condensible causes poor performance. 2- turns oil to sludge and acid, causes txv's, orphises and small passages to clog. 3- causes copper plating which equal poor heat transfer.

Why would you open the circuit on your truck every few years? Unless the compressor has to be unbolted there is no need.

- Your talk so far just like one of those OEM trained idiots!!!... get your head out your arsse ... Its a big-truck and it is inevitable that the system is torn down every couple three years or so for any of - CAC replacements, radiator leaks, bad sensors, front end work of one type or another that requires the system to come apart, compressors failing / getting weak due to constant road use and commercial environment type of use, thermistors going bad, and the rest of what constant road torture and vibration related failures. - Your theory sounds ok to me but it is just not practical to be so touchy-feely with it in such an environment. -- STOP drinking the cool-aide and get back to reality.. and spit out that corporate bullshite that has no practical purpose except to over-think things and fancy-talk yourself into circles.

- My truck has more than a million plus miles on it and my AC has been apart likely a dozen times already... NONE of which was because of any of those issues you described as a contributing factors. - I have replace my drier only once in a million miles. - And the system still works great. - COME OVER AND PULL MY SYSTEM APART, SHOW ME THE COPPER CORROSION AND OTHER GARBAGE THAT YOUR SPEWING ABOUT -- YOU WELCOME TO INSPECT AND TAKE PICS, ETC. AND EDUCATE US ALL ON YOUR SUPERIOR (BULLS#HIT CORPORATE GARBAGE-BRAINWASHED) WISDOM!

(being sarcastic, not trying to be a meanie there)..

matter of fact... i have not seen a single truck AC system over here suffer any of those type of things... and I have seen a lot of them apart.


- Like Nilao said... those are great things to consider when looking at a home unit that does not suffer the fate of torture that an 80,000-lb big-rig and the roads do to A/C systems. theory and things to consider are good things to keep in mind but what you spewing is sales-mans garbage at best when it comes to the world of trucking.


-- and BY THE WAY!!!>>>> Anyone who has to have their system apart for a week, say because they are doing an in-frame... or for several days while its raining outside, etc... can simply put their dryer-accumulator in a dehydrator (or oven) for about 4-6 hours or so and bake it at 210F and cook off all the moisture, renew the desiccant medai from within it if they do not want to buy a new one to the tune of a few hundred bucks... if the spring in it is not worn out.

Trucking is simply a different world when it comes to AC work. - too much plastic, cheap-arsse compressors, valves and sensors that fail regularly due to vibration and road use, temp extremes, etc... blend doors that get sticky + their plastic gears warping and stripping out, constant battle to keep A/C running in a modern truck these days... They are way-over designed and a money-maker for the OE stealers$its out there and they know it.

[Wildcard]

Gotcha!