Just curious, why does the service manual show the 30 lb cylinder of freon R12 upside down in there machine? If you look at a normal 12 oz can it say to hold it upright. Why one upside down and the other one right side up?
Does this same philosophy apply to R134a?
Thanks in advance...

 

R12 goes to the bottom of the can (or bottle). The 30lb bottle does not have a long tube in it, just a valve at the top. Thus, you turn a 30lb bottle upside down to let the freon get to the valve. That's all there is to it.
Also, on 1lb cans, if the top is punctured, then you turn the can upside down. If you use one of the squeeze handles that punctures the can at the botton, then it is held upright.

 

Does R134 work the same way? ie 30lbs upside down?
It makes since... I wish the book would have explained it the way you did.

 

The orientation is based upon whether you want gas or liquid from the can. As with any job, for a shop to make money, the faster they can do a job, the more they make. When filling a system that has been purged, it takes much longer to transfer enough R12 (or 134a) gas than liquid, significantly longer. The shop machines are designed to deliver liquid. The rate can be finely adjusted to keep from over filling. The individual cans can also be used upright or inverted, depending on whether you are filling a system or just topping one off. Inverted and you get liquid, emptying the can fast. Up right, you get gas and slowly fill or top off the system.
That's all there is to it.

 

I was told that if you added liquid too fast (to the low suction side), you could damage the compressor (liquid will not compress). So us "amatuer" AC techs are better off filling the slow way with gas (can upright).

Plasticman

 

Too fast will damage the compressor. Safe way is service as a gas.

 

The reason you should not add liquid to a system ( without proper knowledge ) is it will as mentioned, damage the compresor. Just like your engine that drive that A/C comp. It can not compress liquid, for that matter nothing can. Hence Hydraulics. In the event a comp. does recieve liquid "sluging" in will usaually tear up the valves. I am not as sure of automotive comp. design as industrial use refrigeration comp.

 

I maybe should explained that put refrigerant in as a gas you must keep in mind it is all the same "stuff" it is just changing from a liquid state to a gaseous state and changes back after being compressed then it becomes a high presure gas that is subcooled be the condeser and becomes a liquid again. Boring Huh!!!!!! There is more to it. But thats enough I quess..

 

As a proffesional A/C tech, I can tell you many of the previous respones are right on.

I would add that when you charge liquid into a system (can upside down), you indeed CAN damage the compressor - liquid does not compress TRUE. Altho some compressors /oil systems can take a trickle of liquid, just not big SLUGS of it.

However, you can charge the system quicker with liquid ... but you must be careful. You can 'trickle' the refrigerant in as a liquid and do it so most of it so the liquid evaporates before it hits the compressor. This takes a little practice and if not careful you can easily overcharge the system.

When charging with liquid, I like to let the system turn off and settle down a bit, then turn it back on to check pressures.

Altho I seldom work on auto air, autos offer something that is easily achieved that many residential and commercial systems do not: The ability to 'weigh in the charge' of a system....If the system holds a finite amount of freon, and you have a scale, then 'weigh in', lets say 24 ounces, that's what you put in. BOOM you are done!

Whenever you can do this, it is THE WAY to go. Remember your fan should be on HIGH in most cars when you charge them.

Also when you are charging freon as a GAS (bottle right side up) your jug will get cold as you near pressure equalization.

To make the jug warm up and get the remainder of the gas out of the jug, put the jug in hot water. This will raise that pressure and force more into your system.

The main reason I charge with liquid is SPEED. When done right, I can charge the A/C system at your house in 1/4 of the time with 'liquid', than I can with 'gas.' You also don't have to worry about the jug cooling off as much, which further slows things down.

There is also a way to charge the system almost entirely with liquid when it is off that I won't go into.