I looked at a can of dust spray at Wal-Mart and it was exactly R134a.

quote Originally posted by 1fatcat: As I said earlier, there are a TON of unknowns. I've seen compressors lock so hard that they split the case open. Would that be enough oxygen?

Probably, not. You have to have your ignition source at the fuel air mixture, air won't force its way in, propane will force itself out.

Alright, how about a propane leak shooting onto an arching plug wire?

There are endless hypothetical examples, that’s why I’d like to see some real statistics. Hypothetically, any fluid used in an automobile (except R-134a) can burn under the right conditions:

VEHICLE FLUID FLAMMABILITY TESTS

quote The tested fluids included No. 2 diesel fuel, 89 octane unleaded gasoline, automatic transmission fluid, conventional and synthetic motor oils, brake fluid, power steering fluid, standard green and pink long-life ethylene glycol coolants (both full strength and 50/50), and R134a refrigerant, as well as the various compressor lubricating oils used with R134a. Fire-related properties of representative fluids are provided in the Material Safety Data Sheet.

quote Originally posted by 1fatcat: Alright, how about a propane leak shooting onto an arching plug wire?

fuel air mixture- check

ignition source- check

Not complicated stuff, I wasn't defending propane, it just amazes me how the most basic technology(fire) escapes people.

quote Originally posted by weaselbeak: I looked at a can of dust spray at Wal-Mart and it was exactly R134a.

They aren't required to list "air" as an ingredient, unless it is a specifc type of compressed gas, like R-134a. It only lists the R-134a, because it is the propellant used. What it is propelling, is air. Go check cans of brake clean or throttle body cleaner, and the like, and you'll possibly see R-134a listed as well.

Still no grasp of "Upper Explosive Limit" and "Lower Explosive Limit" in the group, I see.

You need to have

- an ignition source
- oxygen
- fuel

The air/fuel ratio for a propane-fueled explosion is very narrow - that' why they use it for a convenience fuel in grilles, etc.

quote Originally posted by olejoedad: Still no grasp of "Upper Explosive Limit" and "Lower Explosive Limit" in the group, I see. You need to have - an ignition source - oxygen - fuel The air/fuel ratio for a propane-fueled explosion is very narrow - that' why they use it for a convenience fuel in grilles, etc.

Grills also have a well ventilated area to burn in. If your grill was sealed well enough, and you let propane leak out into the grill over night, when went to light it the next morning or evening, it would probably not be so pleasant. Same thing in a car. If your AC system develops a leak that fills your car's cabin overnight, and you go out the next morning to start it up, you won't have a pleasant Sunday drive, I'm sure.

Of course, even if it doesn't explode, ignition to a point where the fire could spread, is plenty bad enough. It doesn't have to take out a city block to be a bad thing that happens. There are also a million other reasons to not use propane in a vehicle's AC system, which have nothing to do with fire or explosions.

Chemistry is fun!

quote Originally posted by jmbishop: Why is fire such a hard concept to grasp? Why doesn't a propane torch not explode when you light it? Its not magic, there is no oxygen in the tank therefore the propane in the tank can't ignite. There is no way you compressor locking up could cause the Propane to ignite unless there was a fuel air mixture in you ac lines.

...acutally no, the 'fire' does not get into the tank because the escaping propane is moving faster out than the fire can travel in (plus there is usually some sort of arrestor) - HOWEVER there are documented cases where flame has travelled back inside of a bottle and has exploded.

FOR the RECORD, just because the bottle is filled with propane does NOT mean there is no oxygen inside the bottle as well. If you were to do a chemical test of the gases that are inside a bottle you would find many other gases - it just happens that propane is the higher concentration. I work in an industry that requires 'high purity' gases and even in these cases, there is always a percentage of other gases mixed in (it is nearly impossible to remove all other contanimants, can be done, but the cost would be extremely high).

Propane that is on the consumer market is FAR from being pure.

quote Originally posted by olejoedad: Still no grasp of "Upper Explosive Limit" and "Lower Explosive Limit" in the group, I see. You need to have - an ignition source - oxygen - fuel The air/fuel ratio for a propane-fueled explosion is very narrow - that' why they use it for a convenience fuel in grilles, etc.

Fuel and O2 already exist, just need an ignition source, it may be a narrow ratio, but the fact remains is that it is higher than R132a and there is a chance that an explosion could happen.

To put it into perspective, if propane was ideal for use in refrigeration, why is everyone not using it as it would save them some cash? Probably because of safety regulations or concern for people safety. Using propane in a commercial refrideration unit is not the same as using it in a car that is WAY more prone to an accident and a cars a/c system is NOT designed to prevent a leak in such a case which COULD result in an explosion.

[This message has been edited by Mickey_Moose (edited 07-15-2011).]

I'll add some fuel to the fire (obviously this fire is fueled by a hydrocarbon composed of a 3-carbon long chain in the presence of excess oxygen.)


We're not talking about liquid propane like that in the cylinder hooked up to your grill, we're talking about vapor. Given the small internal volume of an a/c system, the total amount of propane is relatively small. The idea of a leak filling the cabin or engine compartment of a car and turning it into a giant bomb on wheels is wrong. A substantial leak in the system like that would result in an empty system very quickly. In a situation like that propane would quickly dissipate and not pose a big threat, even if there was a massive leak and the system dumped all the propane in the cabin you would know it immediately.

Propane (R290) is often used in the place of R134, and in such a case the amount of charge is considerably smaller than an equivalent 134 charge. The compressor does not work as hard with R290 and the system is actually more efficient.

You should be much more worried about gasoline and gasoline vapors than the small amount of propane used in an a/c system.

/\ /\ /\ Thank you /\ /\ /\

I am in no way a proponent of propane as a refrigerant.

I have posted simply to debunk the idea that your car could blow up by using it.

Thank you for doing the math.

The way refrigerant systems work is to liquify a gas under pressure so that it changes to a liquid, cooling that liquid to release heat, then evaporating the liquid to absorb heat. It's the phase change from gas to liquid and back that does all the heavy lifting. So any properly charged phase-change AC system will have liquid in it, or else it's not functioning.

The amount could be around 2-4 lbs depending on several factors. Let's say 3 pounds is used in a Fiero. That's three 1-lb cans of propane, mostly liquid inside with a head of gas at pressure. If there's a wreck that damages the integrity of the AC lines that liquid will boil off into a gas from the leak and accumulate in the area. If the wind's blowing, etc, then the accumulation poses a low risk. However, if it accumulates inside an enclosed space such as the passenger compartment or under the hood or decklid and the mixture of available oxygen is sufficient then the risk of a significant explosion goes up really fast. Look up how fuel-air bombs work, and gas pipeline explosions.

Now of course I make no claim that an explosion and/or fire in an automotive context would be as destructive as the two examples I listed, but I'd be willing to bet that two or three pounds of propane in an explosion will still wreck your day. Is it worth the risk? Not for me it's not, especially when reasonably priced and better-suited refrigerants are commonly available right now.

http://www.aa1car.com/libra...ble_refrigerants.htm

quote Originally posted by mikejhjr: We're not talking about liquid propane like that in the cylinder hooked up to your grill, we're talking about vapor. Given the small internal volume of an a/c system, the total amount of propane is relatively small. The idea of a leak filling the cabin or engine compartment of a car and turning it into a giant bomb on wheels is wrong. A substantial leak in the system like that would result in an empty system very quickly. In a situation like that propane would quickly dissipate and not pose a big threat, even if there was a massive leak and the system dumped all the propane in the cabin you would know it immediately.

If the leak occurs in the evaporator core, where is all that gas going to empty to "quickly"? Could it not make its way inside the car? How is the flammable gas going to dissipate or vent out of the cabin when the windows are closed? Does the ignition switch not create a spark (might be small) when you turn on the key? How about your door pin switches? Are these not potential ignition points? Sure, there is a fire/explosion hazard in the gasoline tank of all cars. But why ADD another one to the car by putting something highly flammable in your A/C system as well?

Did you not watch the video I posted on the first page? It only took 1 can (12-16oz) of the HC-based refrigerant they were using to cause that explosion! And that was in a car that had a bigger passenger cabin (volume) than what the Fiero has.

I guess video proof isn't enough to convince some people something is a bad idea...

quote Originally posted by olejoedad: I am in no way a proponent of propane as a refrigerant. I have posted simply to debunk the idea that your car could blow up by using it.

Does it mean it will happen? No, but the FACT remains is that the risk is higher (that is could happen) than what they are using - the point is to REDUCE the risk. (see below as well)

quote Originally posted by JazzMan: The way refrigerant systems work is to liquify a gas under pressure so that it changes to a liquid, cooling that liquid to release heat, then evaporating the liquid to absorb heat. It's the phase change from gas to liquid and back that does all the heavy lifting. So any properly charged phase-change AC system will have liquid in it, or else it's not functioning. The amount could be around 2-4 lbs depending on several factors. Let's say 3 pounds is used in a Fiero. That's three 1-lb cans of propane, mostly liquid inside with a head of gas at pressure. If there's a wreck that damages the integrity of the AC lines that liquid will boil off into a gas from the leak and accumulate in the area. If the wind's blowing, etc, then the accumulation poses a low risk. However, if it accumulates inside an enclosed space such as the passenger compartment or under the hood or decklid and the mixture of available oxygen is sufficient then the risk of a significant explosion goes up really fast. Look up how fuel-air bombs work, and gas pipeline explosions.

What he said...also to consider is that the vapor pressure of propane is more than what 'air' would be and as such it would tend to 'pool' into low areas - it does not simply 'evaporate' and dissapate 'quickly' (in relative terms), but can easily linger in a pocket in the engine bay or passenger compartment (especially in a car that has a recessed floor pan like the Fiero).

quote Originally posted by Darth Fiero: If the leak occurs in the evaporator core, where is all that gas going to empty to "quickly"? Could it not make its way inside the car? How is the flammable gas going to dissipate or vent out of the cabin when the windows are closed? Does the ignition switch not create a spark (might be small) when you turn on the key? How about your door pin switches? Are these not potential ignition points? Sure, there is a fire/explosion hazard in the gasoline tank of all cars. But why ADD another one to the car by putting something highly flammable in your A/C system as well? Did you not watch the video I posted on the first page? It only took 1 can (12-16oz) of the HC-based refrigerant they were using to cause that explosion! And that was in a car that had a bigger passenger cabin (volume) than what the Fiero has. I guess video proof isn't enough to convince some people something is a bad idea...

You smell propane when you light your grill right? Most people would smell anything dangerous in the cab before opening the car. You smell propane long before it gets to dangerous levels.

I wouldn't use propane because I don't think its been tested enough but I know there are many cars on the road that are running propane in the A/C system. Its common in Mexico and being in Texas I know there have to be allot of cars on this side of the border running around with propane.

The ultimate safe A/C system would use CO2, the problem with it is the high pressures it would have to run I'd guess the system would have to be able to handle 3000 psi and have burst disks. How nice would it be to fill your a/c system for $3 and in the event of a fire your ac system might put it out?

quote Originally posted by jmbishop: The ultimate safe A/C system would use CO2, the problem with it is the high pressures it would have to run I'd guess the system would have to be able to handle 3000 psi and have burst disks. How nice would it be to fill your a/c system for $3 and in the event of a fire your ac system might put it out?

Eh, the ultimate A/C system wouldn't use compressed gasses at all. It would be [mostly] solid state, and not require running all those hoses and fitting large components in appropriate places for the A/C system.

That's true, we are closer to CO2 systems in cars than I thought.

http://www.autonews.com/app...01/70905003/1116/ANE
"CO2-based systems will be up to 25 percent more energy-efficient than the best of today’s R134a systems, said Nurdal Kuecuekkaya, vice president of climate systems at Visteon."

[This message has been edited by jmbishop (edited 07-15-2011).]

quote Originally posted by jmbishop: You smell propane when you light your grill right? Most people would smell anything dangerous in the cab before opening the car.

I don't wait to smell propane before my grill gets lit. I hold down the ignitor button and then turn the gas knob on - it lights instantly. No raw propane smell. Don't think I would want to wait to smell the propane BEFORE I tried lighting it...

If the windows are closed on your car and the gas is trapped inside, how is anyone going to smell the propane before opening the door? And what if it is really windy outside and you are upwind of the car when you open the door? Doubt you would ever smell anything even if some was able to leak outside from the passenger cabin because the wind would blow it away. But the fact still remains there would be a concentration built up inside the car along with plenty of oxygen - enough for a spark to ignite. So why risk it?

quote Originally posted by Justinbart: Use LP gas and be done with it.

win!

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

Why do you all argue/debate such stupid ideas?
If it is not what someone says, it is how they say it.

Is LP a good refrigerant? yes.
Is it a good idea to use it. no.

But since I said not to, I know some of you will. I guess that is just natures way of weeding out the stupid.

It may have worked for some in the past,
but remember, "nature always sides with the hidden flaw."

quote Originally posted by Darth Fiero: I don't wait to smell propane before my grill gets lit. I hold down the ignitor button and then turn the gas knob on - it lights instantly. No raw propane smell. Don't think I would want to wait to smell the propane BEFORE I tried lighting it... If the windows are closed on your car and the gas is trapped inside, how is anyone going to smell the propane before opening the door? And what if it is really windy outside and you are upwind of the car when you open the door? Doubt you would ever smell anything even if some was able to leak outside from the passenger cabin because the wind would blow it away. But the fact still remains there would be a concentration built up inside the car along with plenty of oxygen - enough for a spark to ignite. So why risk it?

You can say the same thing over and over again, maybe throw in a few more details but I won't argue with you forever. I think you might be confused, I'm not saying anyone should risk it if its not a approved safety tested automotive refrigerant but I am saying your predictions on what would happen if someone did are a little far fetched and the only way it could happen is if someone had no sense of smell.

quote Originally posted by jmbishop: I am saying your predictions on what would happen if someone did are a little far fetched and the only way it could happen is if someone had no sense of smell.

Taken from Wikipedia on propane

"One particular demonstration was conducted by a professor at the University of New South Wales that intentionally tested the result of all the hydrocarbon refrigerant leaking from the air conditioning system into the passenger compartment of a vehicle and then provided with a source of ignition. The professor had stated that no fire or other dangerous event would occur. However, an explosion did in fact result. All four of the car's doors were bent outward, interior materials were burned and melted, and the professor and several observers in and near the car sustained burns to their face, ears, and hands, as well as lacerations from flying shards of broken window glass."

Source from http://dl.dropbox.com/u/340...3/maclaine-cross.pdf

[This message has been edited by sardonyx247 (edited 07-15-2011).]

So you guys know where I stand, I'm not a fan of propane as a refrigerant and I honestly don't mean to come across as a jerk. However, we haven't answered the really important questions yet. So let's work on those... Skip the boring stuff and get to the questions if you want.


Propane is typically charged at 1/3 the rate of 134. So if we say the system in the Fiero would take a 3lb charge of 134 we can assume it would be charged with 1lb of propane.

Propane is combustible in concentrations ranging from 2-10%. Given propane's specific volume of 8.84 ft^3/lb and specific gravity of 1.013, we can say that a leaky evaporator would dump our one pound of into the cabin of the Fiero and that one pound of gaseous propane would accumulate and occupy the lower 8.84 ft^3 of the cabin (this is related to density and not vapor pressure, the cabin is not air-tight so VP is not a factor here) while the excess air above the propane is forced out of the cabin due to a pressure gradient. The heat of combustion of propane (at 1 atm) is 2450 Btu/ft^3. Given our 1lb charge accumulated in the Fiero cabin we will have a total of 21558 Btu released instantaneously after ignition.


Now we know the facts, on to the serious questions

Will the lack of frame around the side windows in the Fiero allow enough flexibility at the top to relieve pressure and keep them from breaking?

Given the amount of heat released, will the warped trim pieces be warm enough to become workable and allow someone to quickly jump in the car to re-glue and pin them down into their original shape?

Will the sunroof still be latched?

EDIT: Bad news, according to the Top Gear episode where they filled the Fiero with water, it took on 500 gallons. That is 66.8 ft^3. With our 1lb of propane refrigerant in the cabin occupying 8.84 ft^3 we're at 13.1%...not flammable at that concentration.

[This message has been edited by mikejhjr (edited 07-15-2011).]

quote Originally posted by sardonyx247: Taken from Wikipedia on propane "One particular demonstration was conducted by a professor at the University of New South Wales that intentionally tested the result of all the hydrocarbon refrigerant leaking from the air conditioning system into the passenger compartment of a vehicle and then provided with a source of ignition. The professor had stated that no fire or other dangerous event would occur. However, an explosion did in fact result. All four of the car's doors were bent outward, interior materials were burned and melted, and the professor and several observers in and near the car sustained burns to their face, ears, and hands, as well as lacerations from flying shards of broken window glass." Source from http://dl.dropbox.com/u/340...3/maclaine-cross.pdf

And I bet they could smell it outside of the car.

quote Originally posted by jmbishop: And I bet they could smell it outside of the car.

I bet they could, and the hair and skin burning too

quote Originally posted by jmbishop: Given the amount of heat released, will the warped trim pieces be warm enough to become workable and allow someone to quickly jump in the car to re-glue and pin them down into their original shape?

LMFAO

[This message has been edited by sardonyx247 (edited 07-15-2011).]

Saw some computer duster at Fry's last night, the propellant used was difluoroethane (R-152a). The cans also contained a bittering agent to prevent "huffing" the contents as some are want to do.

R-152a was considered as a replacement for R-12 but was judged to be too flammable. Now it's the most common propellent used in computer dusters. Just don't use it on your car computer.

[This message has been edited by spark1 (edited 07-18-2011).]

Just watched the myth busters episode S09E02. They had a tough time getting an apartment to explode from a gas leak. They touched on a few things discussed in this thread. I found it interesting.

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

quote Originally posted by Justinbart: Just watched the myth busters episode S09E02. They had a tough time getting an apartment to explode from a gas leak. They touched on a few things discussed in this thread. I found it interestin

I hate you for posting that, I just wasted 2 hours.