Armstrong Refrigerant

[TG Twinkie]

I Have an Armstrong air conditioner. It probably has freon for refrigerant. Are today's refrigerants compatible or do I need to have the system evacuated? Then install a modern refrigerant. Is a modern refrigerant compatible with this old system?

[mimiandrews]

Unfortunately, it usually won't work. The new refrigerants are less efficient, therefore they need equipment with larger components to compensate for the loss. Also, the new refrigerants are more prone to leak, due to being a smaller molecule.

Tried this with my old car a few years ago. Seemed OK in the springtime, but didn't cut the mustard during a Texas summer.

[Inland RV Center, In]

Originally Posted by TG Twinkie

I Have an Armstrong air conditioner. It probably has freon for refrigerant. Are today's refrigerants compatible or do I need to have the system evacuated? Then install a modern refrigerant. Is a modern refrigerant compatible with this old system?

Your AC uses R-22 freon.

It's still available.

Andy

[Jammer]

TG

Andy is correct, the older air conditioners use R-22. It is still available however it is difficult to purchase at retail. I believe you're supposed to have a license. There is no more modern replacement for R-22 that has similar thermodynamic properties (unlike R-12 which can be replaced easily with R-134a), however, as an HCFC refrigerant its impact on ozone depletion is marginal which is why the refrigerant is still available.

The refrigerant used in newer air conditioners requires much, much higher line pressures and therefore requires heavier construction for the evaporator, compressor, and condenser. It can't be used in systems designed for R-22.

[perryg114]

You need to find the leak before you put more freon in it. How do you know this is the problem? Leaks in the coils are going to be almost impossible to fix. A good home AC guy should be able to diagnose the unit and tell you if it is fixable. You are going to run into a lot of money trying to fix an old unit. My 30yr old Coleman was fixable but I decided that I would be spending half the price of a new one fixing this old piece of junk up and it will still be a piece of junk that had mice living in it.

Perry

[TG Twinkie]

I don't believe there is a leak in the system. It still produces cool air. Just thought if there was a way to determine if it is still at full charge, I would have it checked.
One concern I have is with the shroud. The PO fabricated a new shroud. It us somewhat crude but does protect the unit. The discharge side of the condenser is fully exposed and faces the rear of the trailer. When the PO fabricated the shroud he cut 3 slots on each side of it about 3/16" wide by 8" long. I don't think these slots provide enough intake area for the air to efficiently cool the condenser. I haven't measured the area on the discharge side if the condenser but I'm guessing it around 200 square inches (10"x20"). I don't know what the CFM of the fan is.
My assumption is if the intake is restricted the cooling capability of the condenser will be affected. I would like to modify the intake vents to see if it has any effect. Just don't know how big to make the openings to get a good intake flow.

[Inland RV Center, In]

Originally Posted by perryg114

You need to find the leak before you put more freon in it. How do you know this is the problem? Leaks in the coils are going to be almost impossible to fix. A good home AC guy should be able to diagnose the unit and tell you if it is fixable. You are going to run into a lot of money trying to fix an old unit. My 30yr old Coleman was fixable but I decided that I would be spending half the price of a new one fixing this old piece of junk up and it will still be a piece of junk that had mice living in it.

Perry

Sorry, but I don't understand how mice can get into an AC that's on top of the Airstream.

Most home AC guys don't want to fix anything that has some age to it. But, they are ready to sell new units, all day long.

Andy

[Inland RV Center, In]

Originally Posted by TG Twinkie

I don't believe there is a leak in the system. It still produces cool air. Just thought if there was a way to determine if it is still at full charge, I would have it checked.
One concern I have is with the shroud. The PO fabricated a new shroud. It us somewhat crude but does protect the unit. The discharge side of the condenser is fully exposed and faces the rear of the trailer. When the PO fabricated the shroud he cut 3 slots on each side of it about 3/16" wide by 8" long. I don't think these slots provide enough intake area for the air to efficiently cool the condenser. I haven't measured the area on the discharge side if the condenser but I'm guessing it around 200 square inches (10"x20"). I don't know what the CFM of the fan is.
My assumption is if the intake is restricted the cooling capability of the condenser will be affected. I would like to modify the intake vents to see if it has any effect. Just don't know how big to make the openings to get a good intake flow.

Place a thermometer at the output of the AC.

Compare it's temperature reading with the inside temperature of the trailer.

If the refrigerant level is OK, the temperature difference should be about 15 to 18 degrees.

Let the AC run for a few minutes before you make the readings, so that it has a chance to cool to the maximum.

Andy

[Jammer]

TG

Again the posters above are correct. Unlike automotive-type air conditioning where it is common for small leaks to deplete the refrigerant charge over time, rooftop A/C units typically will hold their charge for the life of the compressor. Refrigerant only needs to be added if components of the sealed system (compressor, condenser, evaporator) are replaced.

Ordinarily the refrigerant pressures would not be checked unless there was evidence of a problem with the sealed system.

The way you describe the shroud I would guess that it is not providing sufficient airflow. While checking the temperatures inside will give a good indication of overall performance, checking the outside temperature rise across the condenser will show clearly whether there is enough airflow. Anything over 30 degrees would indicate a problem.