LarryD

Here is the formula for Autofrost:

Autofrost X3 -- Known as R406a

R22 55%
R142b 41%
R600a 4%

Autofrost X4 -- Known as Chillit and R414a

R22 51%
R142b 16.5%
R124 28.5%
R600a 4%

So, you need to make your own decision relative to the flammability and using R406a so make sure you educate yourself as best you can. The R600a is Isobutane but only 4% of the blend based upon what I have found on the internet. Also, I understand from internet research that R406a is EPA approved for automotive use.

LarryD

Additionally, you can find several copies of the MSDS (Material Safety Data Sheet) for R406a online and interestingly they list it as non-flammable with R142b concentrations less than 60%. So again, do your own research before you decide for yourself.

Reid Fleming

iTrader: (2)

Flammability?

4% Isobutane in a car with 1.8 lbs of R-406a gives you 1.1 oz of isobutane. A bic lighter for comparison weighs 4.8 oz. So we're talking roughly 1/4th of a bic lighter in your car.

Achieving a fire caused by R-406a's isobutane would be rather difficult. You need air to create the fire. But air is not inside A/C systems. They're vacuumed before hand. If you didn't vacuum the system, then you wouldn't be able to install the refrigerant into the system in the first place. (Ever notice the first can of any refrigerant goes into your car quite easily after vacuuming. But the 3rd (final) can takes quite some time.)

If you did spring a leak under the ideal fire circumstance, the refrigerant exits the system faster than the flame goes into the system. And under these conditions, you'd run out of refrigerant quite fast. Being a gas state, it goes into the air quite rapidly, thus eliminating the risk of anything major happening. Gasoline on the other hand leaks out in liquid form and gives off vapor for quite some time.

The above is why when you light your BBQ, the flame simply shoots up and stays like that until you turn the BBQ off or run out of propane. The propane bottle doesn't explode. The flame doesn't go down into the tank.

Your most likely chance of a major leak being a risk to fire would be a fender bender where you puncture a hole in the condenser up front. Very hard to poke a hole in the evaporator in the firewall without damaging the condenser or the lines connecting the system before hand.

Even then, it's no more risk of fire than R-12 or R-134a. It's not the refrigerants so much as it is the oil in your A/C that causes a fire risk. When was the last time you heard of an R-12 or R-134a car catching on fire because of the air conditioning system?

fasteddi

iTrader: (2)

Anymore some blends do have some risks of flamibility but are so little that its no concern. Hotshot, is one that has propane in it also and anyone in hvac knows propane is a awsome refrigerent. But IIRC Hotshot has roughly 6% propane in it so its not enough to cause a issue if lit. Im not sure on the exact makeup of the item, just the slang term for it.

Also if you want to talk about flamibility, try brazing in hvac on some situations. I personally have had to replace a compressor on a residential system and literly almost blew my face off becuause I was a IDIOT at the time. I didnt think of the expanding Ref let alone the flammible oil in the lines and compressor. So needless to say when I was sweeting out the line set from the compressor, the suction side(crankcase line) shot off and a nice size flame ball came out along with a ton of smoke and Phosphine Gas!!

Fast355

iTrader: (2)

I've run a mixture of R290 and R600A for years in more than one vehicle. Blows ICE cold. With less than 1 lbs in your typical GM 3 lbs system, I am much more concerned about the 200 lbs of highly flammable gasoline under my butt and the 2 lbs circulating over the hot engine through the fuel rails.

I had a heater hose clamp move slightly and rub a hole through the low-side line of the 97 Express completely emptying the system onto a hot, running engine idling around town. Nothing happened, other than the a/c stopped working.

Fast355

iTrader: (2)

Propane/Butane mixture works great for a/c systems, much more efficient and environmentally friendly than anything else out there. The only reason I feel it is banned in many places is because of public fear for it. Never do people realize if they have a can of hairspray and a can of "Pam" spray cooking oil in their car they have a better chance of blowing up than from the a/c of their car. I've had alot of fun in my day lighting WD40 and Brake clean out of the can. Makes a nice fireball.

The word you are looking for my man is Phosgene gas! Deadly gases used in the trenches of WWI

http://en.wikipedia.org/wiki/Phosgene

fasteddi

iTrader: (2)

Thanks for the correction. Autocorrect is horrible on the computer let alone I know I was butchering the spelling. Thats some wicked stuff. I only had the "pleasure" to breath it in once and it will take your breath away instantly, same feeling as if you breathed in acetone or ammonia.

fcukit33

Just a safety note guys the 400 series of refrigerants operates at EXTREMELY (2-3X the cfc's and hcfc's they replaced) high pressures. It is not a drop in substitute. I only browsed the thread but the reason for special fittings ( thicker piping as well) on a 400 series system is because of the pressure compared to other high pressure systems. Just a heads up to Readers seeing numbers.

LarryD

Not sure what you mean by 400 series but my system charged with R406a has always operated at pretty much the same pressures as it did with R12. But, everyone needs to do their own research and study the problem.. There is a very detailed technical pdf article on the internet that explains pressures etc. for R406a.. It may all be a moot point since I think the supply of R406a is drying up and looks like R12 may be easier to get these days...

jermdm

I dont know a whole lot about the 406a refrigerant. I've always been happy with my 134a conversion. The only concern I would have about 406a or others that get that kind of vent temps would be iceberging the evaporator all the time. Especially when you have the blower at a lower speed.

Reid Fleming

iTrader: (2)

The reason for the special fittings is to please the EPA. You could run the stock R-12 fittings or R-134a fittings if you wanted. Technically it wouldn't be legal. But the system doesn't see anything different. It's all after the schraeder valves anyways.

There is "partial" truth to 400 series being higher pressure. The reason 55% R-22 was chosen for R-406a was because once you start going past 65% R-22, you'd end up blowing a hole in the evaporator. Even if you didn't use the A/C, the heat soak from the engine would make the pressure rise in there after you parked and left......So why use 55% instead of 65%? Well, actually there was an ultra high performance version with 65%. Even has EPA approval. It was called GHG-HP (high performance). But it was never marketed. All that would be needed is to come up with some unique fittings for it. But aside from the few of us on the internet, there just wasn't a market for it. It had trouble with variable displacement compressors (icing up the evap). Not as much of an issue with cycling compressors.

R-406a runs fine with either variable displacement or cycling compressors. And it satisfied the job of colder than R-12. The HP version must have been crazy.

Of course, if you ran 100% R-22, the hoses would blow, compressor would probably seize. Evaporator would bust......But 100% R-22 wouldn't be a "400" series refrigerant. 400 series are blends that have multiple phase change areas (which is one of the reasons why R-406a works so darn well.) R-22 by itself is a single refrigerant with one phase change temp.

Getting away from the technical side and looking at the real world, R-406a on the high pressure side does run higher than R-12 and roughly the same as R-134a, albeit with much colder temperatures.


On a humid day during the early morning (sun not up yet), and with lowest fan speed and NORM A/C (fresh "humid" air) selected in order to keep you from being too cold inside the car, you can get the evap coil pretty saturated with water. But even then, running it in low fan speed mode makes it cycle more often than high speed fan mode. It cycles off about once a minute. No problems with ice. I can always see a trail of water following me to the parking spot and then dripping gobs of water as soon as I get out of the car.

The other factor is that during spring/fall and some parts of winter in the south, you don't need to run the A/C for that long before you get cold yourself. In the summertime when it runs and runs, ice just hasn't been an issue for me. The airflow never slows down. The system drips immediately, rather than waiting 10 minutes to get water to com out after parking (as it would if it were iced up)

LarryD is right though. The supply of R-406a looks to be done for. Too bad, as it makes for one heck of a nice drive during the never ending summers of Texas.


Ah, here it is. A chart I made a few years back. You can see the high pressures between R-12, R-134a, and R-406a here. I adjusted the low side numbers to show what duct temperature corresponded to what low side pressure. The high side numbers are untouched.



GHG-HP did run the high side pressures higher than normal. Although nothing too crazy. I find it interesting that the low side temperature mirrors the pressure all the way down. So while R-12 is just about maxed out at 28 psi giving 40° air, GHG-HP was barely idling at the same temp at 40 psi. The HP stuff would cause issues with variable displacement compressors because they'd be stuck at 25 psi forever. And 25°F with no cycling = big ball of ice. You'd need to switch to VENT to clear it. So between that and people complaining that it was too cold, you can see why it never came to market.

I've run R-406a at 24°F as mentioned before. And it wasn't comfortable. We're talking painful numbing cold. Give you the shakes. That's why I adjusted it back to the "stock" 31° cycle off temp.

b4ccamaro

Ok so how much r406a do I want to use? Do I charge the full R12 amount which IIRC is 2.8 ish pounds and 8 oz of mineral oil if the sys is flushed and clean?

LarryD

Here is an earlier quote on the quantity to use in 82 to 92 Camaro's and Birds..

It comes in 9.6 oz cans and you're supposed to use 80% of the R12 amount. 80% of 2.25 lbs works out to 1.8 lbs which is exactly 3 cans.

Here is a link to the Autofrost Technical Discussions article..

http://www.autofrost.com/autodisc.pdf

Tells you way more than you probably wanted to know.. Biggest issue is to make sure you use the right type O-Rings... I ordered a kit from The O-Ring Store...

http://www.theoringstore.com/

b4ccamaro

You're not kidding. Thats a lot of info.

Did that kit have all the o rings our systems need?

So if im doing 80/20 autofrost to R12 what service port fittings did you use? Is there a can tap that will do both autofrost and R12?

LarryD

The kit I bought was a box of many sizes and then just went through it until I found the right size orings...

Technically/legally you are supposed to change the service port fittings to special ones for R406a so that it can't accidentally be connected/mixed with R12 service equipment.. But I don't think they are available any more.. I bought mine years ago so changed to the correct ones when I changed my system over... I have heard some people have just left the R12 fittings there but you have to decide about the compliance issue... You are also supposed to mark the system with info showing that R406a is used.. Normal R12 fittings and tools work, that is, the cans are the same for R12 and R406a.. Pay attention to the vertical orientation of the can during filling.. It is written on the can...

PTS

iTrader: (3)

Anyone have 1 extra can of autofrost they would want to sell!!

loneroad

iTrader: (3)

a quick little feeler to see if i should post up in classifieds, i might be letting go of 2 kits.

each kit would include:

a new dryer
a new single post fan motor with cage
a qt of mineral oil
3 cans of autofrost
a new can tap.
the new fitting
label

what do you say guys, think there would be interest

PTS

iTrader: (3)

How much for just the autofrost?

STREETDEMON

what kind of $$? i'll be redoing my system next spring for some cool summer fun.

loneroad

iTrader: (3)

Im looking to sell it all as a kit. but i'll keep you in mind.

loneroad

iTrader: (3)

ill sit down tom and figure up a price and post some pics. I will be shipping ups, and a tracking number will be supplied.

rusty vango

thank you, mr reid fleming. I had heard about this ,but I wanted to hear of someone actually using it before I ordered it. again thanks.

loneroad

iTrader: (3)

ok posted to the classifieds.

heres the link

https://www.thirdgen.org/forums/engi...ml#post5801669