Resident Air Conditioning expert.....

[undy]

Originally Posted by Ronbo

All the dryer does is absorb any moisture in the system, basically nothing but an empty can with dessicant in it. If your unsure about the one your using pop it in a 250 deg oven for about an hour to re-activate the dessicant.

Make sure none of the system has any mineral oil from using R12 as R134 uses PAG oil and they will gel if mixed.

Another important item is your expansion valve, this is located between the condenser and evaporator. (opposite side of system from the pump) It's primary purpose is to regulate "flow" of refrigerant through the system. The trick of course is knowing which size to use as this is the item you "tune" to your condenser / evaporator size.

Try to use as many stock components as you can as the system components do need to be somewhat balanced to each other.

It's risky to "cook off" The dessicant. A by-product of that is the desicant pellets can break down, turning into a wide powder. It can contaminate an entire system necessitating a system flush.

There are two basic means of metering the refrigerant. The expansion valve, as you'd mentioned, and a fixed orifice (typically referred to as a "orifice tube"). The expansion does it's job by sensing the evaporator's tail coil temperature via a thermal bulb and regulating refrigerant flow via a variable orifice based on the coil's outlet temperature. The fixed orifice is "designed" for a given flow with certain assumptions and design characteristics in mind. The technical mission of the expansion valve (TXV = Thermal Expansion Valve) is to maintain evaporator superheat. (7 to 14 degrees, typically) I would suggest, with the many variables, that you use an expansion valve. The TXV (expansion valve) allows for a small amount of mis-match where the fixed orifice will not.. You should be able to find a valve to match the compressor with a little research. Some evaporator coils come with the expansion valve too.

I agree with Ronbo, ensure your oil matches the system/compressor manufacturer's recommendations. Always drain and refill oil prior to installing the compressor in the system. Get the system "sealed up" ASAP too.

I could go on, and on, and on......

Dave

[Cobrabill]

Originally Posted by undy

It's risky to "cook off" The dessicant. A by-product of that is the desicant pellets can break down, turning into a wide powder. It can contaminate an entire system necessitating a system flush.

There are two basic means of metering the refrigerant. The expansion valve, as you'd mentioned, and a fixed orifice (typically referred to as a "orifice tube"). The expansion does it's job by sensing the evaporator's tail coil temperature via a thermal bulb and regulating refrigerant flow via a variable orifice based on the coil's outlet temperature. The fixed orifice is "designed" for a given flow with certain assumptions and design characteristics in mind. The technical mission of the expansion valve (TXV = Thermal Expansion Valve) is to maintain evaporator superheat. (7 to 14 degrees, typically) I would suggest, with the many variables, that you use an expansion valve. The TXV (expansion valve) allows for a small amount of mis-match where the fixed orifice will not.. You should be able to find a valve to match the compressor with a little research. Some evaporator coils come with the expansion valve too.

I agree with Ronbo, ensure your oil matches the system/compressor manufacturer's recommendations. Always drain and refill oil prior to installing the compressor in the system. Get the system "sealed up" ASAP too.

I could go on, and on, and on......

Dave

Good info,i appreciate it.This is where i sit:

System is open right now.Engine compartment is being painted,so everything is apart.Compressor is NFG,so that is going to be new.I'll oversize the dryer and then see about sizing a condenser.There is no valve under the hood-so if there is one-it's under the dash?

[Ronbo]

Orifice tubes are typically in one of the lines (look for crimp marks on the tubing), expansion valves are mounted to the evaporator and may not be visable.

Used to maintain driers for waveguide pressurizers and re-activated lots of dessicant. Dessicant in A/C systems is contained in cloth/paper sacks inside the dryer, not loose.

[undy]

Originally Posted by Ronbo

Orifice tubes are typically in one of the lines (look for crimp marks on the tubing), expansion valves are mounted to the evaporator and may not be visable.

Used to maintain driers for waveguide pressurizers and re-activated lots of dessicant. Dessicant in A/C systems is contained in cloth/paper sacks inside the dryer, not loose.

Yep, ex-Navy Machinist Mate myself. Used to take care of the twin dessicant towers for the radar wave guides. One was filtering while the other tower was regenerating.There's several different types of dessicant, including the re-gen stuff. On the auto stuff there's just a metal screen between the drier shell and the rest of the system. The powder gets right through the screen.

If the evaporator's already in the car then the TXV's probably attached to it. The orifice tube will probably be near the condensor outlet.. but.. ya ain't got no condensor.. If already there, I'd inspect the liquid line from the condensor's outlet all the way to the evap. If there's an orifice tube there, that's where it would be.

Dave