HVAC REBUILD

[FellowTraveler]

You can only pull down to whatever atmospheric pressure is. I want to get a micron gauge one day to test my pumps to see what they actually do. The fastest vacuum pump I have ever seen is a snap on air one. It can pull my 4+ lb system down to 30 on my gauges in well under a minute, but it does sliw way down pulling the gauge down to 32. I've seen several electric pumps that can't pull either of my gauge sets to 32, but that little air one can. My electric one is slightly slower at 1st, but goes faster once the vacuum gets down to 30 and it kicks to the 2nd stage. A bigger pump just means it pulls a system down to atmospheric quicker, but it still takes x amount of time to boil out any moisture or remaining refrigerant(please for the love of GOD! DON'T CALL IT FREON! IT'S REFRIGERANT!) left in the system. Need to get out and pull mine down so I can put my fan pressure switch in to actuate my electric condenser fan.

I wish I had space for a condenser fan, I have so much going on up front w/2 aux trans coolers, engine oil cooler and 2 aux p/s coolers so I've been considering a roof mounted condenser box fan setup from RED DOT because I need room for my big Cummins CAC/IC.

 

[Will L.]

The red dot systems come with 24v fans. I'm thinking move the regular condensor up there and use the electric fan for a 05 escalade with a 6.0. That electric fan is only fan, and no problems keeping engine and AC cold.
Then no added heat to the stack, and more airflow through the rest of the stack because of less restrictions (condensor). Also, I have seen many times adding electric fans causing freeway overheating because the electric fans slow the flow of air at high speeds.

 

[FellowTraveler]

The red dot systems come with 24v fans. I'm thinking move the regular condensor up there and use the electric fan for a 05 escalade with a 6.0. That electric fan is only fan, and no problems keeping engine and AC cold.
Then no added heat to the stack, and more airflow through the rest of the stack because of less restrictions (condensor). Also, I have seen many times adding electric fans causing freeway overheating because the electric fans slow the flow of air at high speeds.

If I went to RED DOT I'd have to do 12v fan (s), even found an alloy tube cage that goes around and over it to protect it from impacts, branches and such....even a lower setup than the RED DOT would do imo....

 

[Will L.]

I considered the same thing. Why I didn't: need to take the other one out of the stack anyways as it's just dead weight and hurting air flow, so moving it is half way done. Going to have to build custom mount anyways.
Going to have to buy replacement fans or 12:24 volt transformers- once comparing prices and seeing air flow, the caddy wins.
If the rest of your AC system is staying the same, why not keep it the same size coil? Going to a smaller coil is not going to help anything. Then years down the road if you need to replace it which will be more accessible and affordable?

 

[FellowTraveler]

I considered the same thing. Why I didn't: need to take the other one out of the stack anyways as it's just dead weight and hurting air flow, so moving it is half way done. Going to have to build custom mount anyways.
Going to have to buy replacement fans or 12:24 volt transformers- once comparing prices and seeing air flow, the caddy wins.
If the rest of your AC system is staying the same, why not keep it the same size coil? Going to a smaller coil is not going to help anything. Then years down the road if you need to replace it which will be more accessible and affordable?

I was also considering a box for the condenser that is lower in height, smaller condenser would not be good if anything bigger.

 

[dangerousdave]

 

[THEFERMANATOR]

Figured I'd throw this one out there since you're running HC refrigerant. I know this was a perfect storm type of thing, but I think I'll stick with R-134a. I have ICE cold air with it, so no reason to change.

Skip to about the 4:00 mark and watch the test.

 

[Will L.]

People think it's a joke or exaggerated when you explain it. That was a tiny system with no combustible materials in there like papers, hair gel, or an elderly person on oxygen.
You should see waterless coolant go up when it's misting out a heater core. WAY worse.

I'm a firm believer in people should be allowed to do whatever with their own lives. But the consumers usually don't learn till it's too late.

 

[WarWagon]

It does not matter what the refrigerant is that your running. To get out the moisture you hold it under the vacuum 10 min per pound.

Also getting the most out of your system is getting the widest difference between high and low gauges is key. When it says 28oz or 39oz that is a generic amount. Get to 10% of the amount and watch the gauges go to 5% over and notice the peak of the curve. Get it back to that point.
Be careful on some of the "micro" systems that use less than a pound. Only go to 2% over.

It would be interesting to see a "glass" accumulator in action as system load changed as well as simulated road speed and RPM. As far as the liquid level changes in it anyway. Overcharge, load change, and leakage reserve is stored in the accumulator.

Critical charge is explained here.
http://www.imcool.com/articles/aircondition/VOV3.htm

So is Flooded Evaporator. What is not explained is oil flow and the need for some liquid refrigerant exiting the evaporator to carry back the compressor oil.

The R4 compressor is like a 2cycle engine with no oil pump or oil sump. It depends on a steady oil mist coming in the suction port from the accumulator's liquid bleed hole. In contrast the A6 has a sump and oil pump aka a tough 4 cycle. Mess with the 2 stroke oil mix and you score and seize the engine up quick.

The R4 systems IMO blow the coldest with a low refrigerant charge. It's a matter of luck before that charge gets too low by leaks or the load changes and oil quits being returned. Then you got cold air with a noisy compressor while it dumps debris in the system. The A6 is tougher, but, eventually runs out of oil too. The oil is all left in the evaporator.

Too much refrigerant and HP draw goes up while pumping capacity goes down. It gets to the point you can wash the oil out of a compressor if you don't slug it to death. Rear air systems with TXV issues are known to do this.

Thus the number given to charge by weight on FOT systems is critical. The leakage reserve is all you can play with. Get it wrong and you clean out the system, replace lots of parts, and another compressor. As hoses and compressor shaft seals leak it's a matter of time. Shaft seals leak by design to lube themselves and hoses have a known leak rate per foot.

 

[FellowTraveler]

Interesting video shows how stupid those who are seeking a higher education really are "I wonder who in their right mind would do such a stupid and unsafe act 'aside those morons' releasing isobutane/propane mixture into the passenger area like that then lighting a match?" Kind of like a bomb maker igniting the device they made to see if it works.

Simulating a crash takes lots more effort 'real word' as in if the crash happened at say 60 mph then you also need the simulated airflow over the wreck at that speed too which more likely than not dilute the carbon release before ignition . Research ignition point of all the refrigerants they are all over the place then look into all the fluids commonly used and how they can burn, suffocate passengers too given the right combination of event's..

This flammability issue appears to mostly be an issue in the US while most of the rest of the world have accepted it...regulators as always have influence placed it their pockets by those who have everything to gain via the patents they own.....

As for me "I fear the bull excrement out the mouths of candidates is more a threat than isobutane/propane in my vehicle AC."

 

[THEFERMANATOR]

I posted it as a demonstration of what COULD happen. That was ONE can of a HC based refrigerant released into the cabin of a car, then an igntion source was lit. Lets say your evap blows out while the car is sitting(seen it happen before, so don't say it can't), and those 4 cans leak out in to the cabin. somebody with a lit cigarette comes along and opens the door to get in, BOOM!

As to crash simulations, theres a reason why teh Germans all dropped R-1234yf in such a hurry after approving it and even putting it in a few cars. This isn't even collision, but a test showing what happens when the low flamability APPROVED for DOT use HC based refrigerant gets exposed to just a hot manifold.

I SERIOUSLY considered going with a HC based refrigerant in the BURB, but after seeing some tests of what could ACTUALLY happen, I'll pass. I know they are used in Australia quite heavily, but even the European nations are now getting away from them. I know the chances of things like this happening are pretty low, but why take the chance? I'll go out and flush my system out and swap back to R-12 before I'll run a HC based refrigerant in an automotive based application.

 

[THEFERMANATOR]

It would be interesting to see a "glass" accumulator in action as system load changed as well as simulated road speed and RPM. As far as the liquid level changes in it anyway. Overcharge, load change, and leakage reserve is stored in the accumulator.

Critical charge is explained here.
http://www.imcool.com/articles/aircondition/VOV3.htm

So is Flooded Evaporator. What is not explained is oil flow and the need for some liquid refrigerant exiting the evaporator to carry back the compressor oil.

The R4 compressor is like a 2cycle engine with no oil pump or oil sump. It depends on a steady oil mist coming in the suction port from the accumulator's liquid bleed hole. In contrast the A6 has a sump and oil pump aka a tough 4 cycle. Mess with the 2 stroke oil mix and you score and seize the engine up quick.

The R4 systems IMO blow the coldest with a low refrigerant charge. It's a matter of luck before that charge gets too low by leaks or the load changes and oil quits being returned. Then you got cold air with a noisy compressor while it dumps debris in the system. The A6 is tougher, but, eventually runs out of oil too. The oil is all left in the evaporator.

Too much refrigerant and HP draw goes up while pumping capacity goes down. It gets to the point you can wash the oil out of a compressor if you don't slug it to death. Rear air systems with TXV issues are known to do this.

Thus the number given to charge by weight on FOT systems is critical. The leakage reserve is all you can play with. Get it wrong and you clean out the system, replace lots of parts, and another compressor. As hoses and compressor shaft seals leak it's a matter of time. Shaft seals leak by design to lube themselves and hoses have a known leak rate per foot.

This is an A6 compressor, Gm hasn't used them since the EARLY 80's.

The 96+ trucks use an HT6 compressor. There is no oil pump or sump in them either. ALL automotive based A/C systems use the circulating gas to move the oil. So long as the gas is moving, it can also circulate the oil. The oil DOES bind to gas, not just liquid. And the R4 systems work no different than any other system. It's just a pump, it has no bearing on charge other than it moves it. If a system works better undercharged, it will do the same exact thing with an A6, HT6, or any other type. The only thing that has bearing is the displacement of the pump to the type of system. And the rear air systems didn't liquid slug the compressor or wash the oil out. When a TXV gets cold, it closes off to restrict flow, when you shut the rear air off, the early TXV's would almost completely close off. When this happened it allowed refrgerant/oil charge to fill the line, but since the TXV was closed, no gas was returning through the low side line to return the oil to the compressor, and eventually the system ran out of oil because it all filled up the high side line going to the rear. That was the problem with the dual air BURBS. The 96-pp TXV simply had a stop in it so it couldn't completely close off, allowing the refrigerant/oil to continue to circulate back to the compressor. What you NEVER want to happen is for LIQUID refrigerant to EVER enter the compressor under ANY circumstances. This will DESTROY ANY compressor in SHORT order. This is one of the FIRST rules of A/C work. What kills compressors from low charge is the fact that eventually teh charge gets low enough, that not enough refrigerant gas will remain in the system to maintain a steady flow of returning gas to the compressor to carry the oil. Wether it be gas or liquid, once it stops circulating, the oil charge WILL fall out of suspension when it stops circulating. So when you get low on charge, the system will begin to short cycle allowing the oil charge to fall out of suspension, plus you throw in not enough refrigerant making it back to the compressor, and it starves the compressor of oil.

 

[FellowTraveler]

I posted it as a demonstration of what COULD happen. That was ONE can of a HC based refrigerant released into the cabin of a car, then an igntion source was lit. Lets say your evap blows out while the car is sitting(seen it happen before, so don't say it can't), and those 4 cans leak out in to the cabin. somebody with a lit cigarette comes along and opens the door to get in, BOOM!

As to crash simulations, theres a reason why teh Germans all dropped R-1234yf in such a hurry after approving it and even putting it in a few cars. This isn't even collision, but a test showing what happens when the low flamability APPROVED for DOT use HC based refrigerant gets exposed to just a hot manifold.

I SERIOUSLY considered going with a HC based refrigerant in the BURB, but after seeing some tests of what could ACTUALLY happen, I'll pass. I know they are used in Australia quite heavily, but even the European nations are now getting away from them. I know the chances of things like this happening are pretty low, but why take the chance? I'll go out and flush my system out and swap back to R-12 before I'll run a HC based refrigerant in an automotive based application.

I didn't even consider a leaky evap.....and yes that's possible...

 

[Will L.]

Folks, I'm grew up and lived in Vegas, Boulder City is 15 minute drive away. 95% or more of all rigs here run a/c. Then. For the last 20 years it has been the most transient city in America. About 20% of people stay and the rest move out within a year- usually during or after summer. Medium income is way lower here than the rest of the country.
Why point out this stuff? Because I have seen every single jury rig combo for keeping a/c working and engine from over heating.
I've known propane worked well in just about any system you can think of for years. I will never run it. Why, I have pulled people out of the fire during and after. I watched a 20 something Hispanic guy jump the barrier and run in front of a semi doing 70 after he saw his wife and baby daughter burned to death from an otherwise survive-able crash.

"They" told people a healthy smokers cough is good for you.
"They" told people just dust the radioactive fallout off your car because although it's not good for your paint job, it won't hurt you.
"They" are saying flammable liquids in the personal compartment is ok. You are a $ amount to "them" and nothing more. Don't do it.
If enough people go in and look at new cars then walk out sighting flammable a/c EVEN IF YOU HAVE NO INTENTION ON BUYING THAT DAY- they will see they are loosing sales and will quickly force the factory to choose otherwise. Think how often it happens over stupid things.
Don't run it aftermarket- then there is no chance of your kid's lawyer suing anyone to pay for their education and councilor costs.

 

[FellowTraveler]

If propane was banned in motor vehicles and trailers what would happen with RV's, campers, travel trailer industry with out propane fired grille refrigerators, freezers, stoves ovens, hot water heaters, gen sets, even engines that run on it or LPG, how about the aftermarket with propane injection for diesel performance etc....

Consider, while the danger of isobutain/propane refrigerant is at the forefront of this topic all the aforementioned seems irrelevant within the day to day life in America........

 

[Will L.]

No problem with it in rv, etc. when it gets in a crash it doesn't generally trap ocupannts inside for a BOBbq.
Having it in 100,000 rv type application is one thing.

Putting it into millions and millions of cars where jaws of life is an hourly occurrence is totally different.

Think about 1960-70's cars- fuel tank visible in trunk and openings in the metal that seperates back seat from trunk. Rear end crash and occupants burn. GM got sued threw the roof, but only because there was a Memo that got to the public where they determined the "cost" of a dead person from the fire was 2 or 3 dollars per car and wasn't worth fixing. If it wasn't for the mega million dollar lawsuit, it would still be in he same.

As soon as someone sues the heck out of Winnebago, they will move the charge system to the outside of the compartment and make it better. But it's a numbers game. How many rv,trailer, etc are built yearly compared to autos and trucks

 

[THEFERMANATOR]

And if you follow the letter of the law regarding propane in your RV, you're SUPPOSED to shut off your gas BEFORE you ever move the vehicle wether it be a trailer or motorized camper. It is against DOT, OSHA, AND ocal laws to run your fridge on propane while going down the road, same goes for your water heater, or furnace. They used to even put a electrically actuated solenoid at the propane tank of coaches to shut off the propane. So again, the arguement over propane in an RV is not in your favor as it is as illegal to do that as it is to put HC refrigerant into an R-12 system(I know you can do it legally if you put R-134A fittings on, but it's a loophole). Like I've said before, I have SERIOUSLY considered running ENVIROSAFE on SEVERAL occasions, but since R-1234yf has been approved and seeing some of the testing thats been done on a MUCH LESS flammable gas, and the results of said testing, I'll pass.

 

[Will L.]

What's your best choice Ferm? I was plan on a couple tanks of 134a in the shop on a shelf.

 

[THEFERMANATOR]

I've still got a case of R-12 stashed away, but I always keep a cylinder of R-134 around. If SAM's has it cheap again this summer, I'll probably pick up another one. Got my last 30lb cylinder for under $70 from them.

 

[WarWagon]

This is an A6 compressor, Gm hasn't used them since the EARLY 80's.

The 96+ trucks use an HT6 compressor. There is no oil pump or sump in them either. ALL automotive based A/C systems use the circulating gas to move the oil. So long as the gas is moving, it can also circulate the oil. The oil DOES bind to gas, not just liquid. And the R4 systems work no different than any other system. It's just a pump, it has no bearing on charge other than it moves it. If a system works better undercharged, it will do the same exact thing with an A6, HT6, or any other type. The only thing that has bearing is the displacement of the pump to the type of system. And the rear air systems didn't liquid slug the compressor or wash the oil out. When a TXV gets cold, it closes off to restrict flow, when you shut the rear air off, the early TXV's would almost completely close off. When this happened it allowed refrgerant/oil charge to fill the line, but since the TXV was closed, no gas was returning through the low side line to return the oil to the compressor, and eventually the system ran out of oil because it all filled up the high side line going to the rear. That was the problem with the dual air BURBS. The 96-pp TXV simply had a stop in it so it couldn't completely close off, allowing the refrigerant/oil to continue to circulate back to the compressor. What you NEVER want to happen is for LIQUID refrigerant to EVER enter the compressor under ANY circumstances. This will DESTROY ANY compressor in SHORT order. This is one of the FIRST rules of A/C work. What kills compressors from low charge is the fact that eventually teh charge gets low enough, that not enough refrigerant gas will remain in the system to maintain a steady flow of returning gas to the compressor to carry the oil. Wether it be gas or liquid, once it stops circulating, the oil charge WILL fall out of suspension when it stops circulating. So when you get low on charge, the system will begin to short cycle allowing the oil charge to fall out of suspension, plus you throw in not enough refrigerant making it back to the compressor, and it starves the compressor of oil.

My 'Early Eighties' 1988 6.2 Diesel Suburban had the HT6. Mounted high on the engine. It does indeed have an oil sump and pump. Again my point is 'slightly' low charge but working kills the R4 where the A6 survives because the R4 depends on oil return via the suction line for lube where the A6 doesn't. A lower charge like you describe kills them both. The link I provided above contains information from one of the folks that spearheaded the design of the FOT systems and explains some of the functions of the mystery suction accumulator.

Gas doesn't return oil as well as liquid. It may return some, but, not the point I am making.

Around 53 seconds you see the oil pump in the rear. Parts diagrams also name it.

Sure I would love it if OEM's did a better job of keeping liquid out of compressors...
The low mounted compressors on 5.3L V8 engines are known to liquid slug on startup as refrigerant likes to pool in low spots after shutdown. It tears the tensioner off the engine of blows the compressor clean in half now and then so 4 Seasons came out with the deslugger.

http://www.4s.com/en/marketing/-psp-solutions/the-deslugger/

That thump you hear sometimes starting low mount on the engine AC systems is liquid slugging.

"Compressors on many modern A/C systems are mounted low in the engine. This location leaves the compressor prone to liquid slugging. When the vehicle sits, oil and liquid refrigerant collect in the compressor body. The result can be hydraulic lock with catastrophic compressor damage. The Deslugger solves this liquid slugging problem by pulsing the compressor clutch multiple times during initial engagement. By gradually engaging the compressor, trapped liquid is gently moved out, preventing catastrophic hydraulic damage. Once the brief deslugging function is complete, the compressor reverts to normal cycling operation until the system has been off again for more than 30 minutes."