Home AC

My friend checked my home AC system and says it's 2 lbs low on F22. I got the gas and the gages, but he's busy. Anybody here that can tell me what readings should be when the system is fully charged? I"m OK on automotive units but clueless on 22.

65 lbs.Low side

Only way he could tell if it was 2 lbs. low would be to recover the freon and weigh it. Modern AC and heatpumps cannot be charged by a "rule of thumb" presure chart anymore. Should be a charging chart with the unit that tells how to charge it. Now most are weighed in or charged by liquid line temperature. Must have correct airflow across the evaporator coil and a clean condenser coil to start with. DH

40 years ago rule of thumb was. Outdoor temp plus 35 degrees converted to r-22 pressure was high side pressures plus or minus 10 lbs. Indoor temp plus or minus 5 lbs. equals low side pressures. This won't work on todays units.

Google F22 freon pressue readings. There are several companies that provide the pressure charts. It's completely different than R12 or 134, don't go by those pressure readings, you may be paying for more repairs!

Fixed orifice metering device uses superheat for charging. TXV systems use subcooling. How does he know it's 2 lbs low. There is no way to know that until you charge it. If you know how to read your gauges and can measure the temp of suction line near compressor, you should be able to get it close! Shoot for 10 - 15 degrees of superheat if fixed orifice.

If you have gauges, there should be a temperature scale on the suction gauge. You want it to be just above 32 degrees on cool morning, 55-60.

I think that transulates to around 65 psi for R-22. If you have a newer system you need to look on pressure gauge.

Call for someone that knows their stuff.

This industry is running over with pseudo-experts. I work with several idiots that actually think they can look at gauges and tell how how much gas a particular system "needs".

And none of them can even diagnose or correct a dirty condenser.

Since you stated AC I'm assuming that's what you have. I'm also assuming you have the correct guages and they are zeroed. You have the gas and guages so your gonna charge it reguardless.

Clean the condensor and evaporator coils before you start. Fantastic will work if you don't have coil cleaner. New filter too.

Hook up the guages and charge to 40 degrees or 68.5 psi on the low side and stop. High side temp on the guage should read 20 to 30 degrees above ambient. If it doesn't you have a problem.

A professonal could dial it in to be more effeicent but that's about a close as any HO is gonna get and it will work for you on any AC unit. Good luck and watch out for frostbite when hooking up the high side.

Thanks to all for the replies. Just as info. I didn't ask the question or go into this repair half cocked. The system had seemed to be running excessively trying to maintain a comfortable room temp. First thing I did was clean the filters. There are 2 in my unit which is built into the corner of a hallway, with filter grilles on both walls. Next I cleaned the A coils,bottom and top, with a vacuum cleaner, followed by Cal-spray evap foam no rinse cleaner. Next came cleaning the condenser coils, with pink coil cleaner. The label is gone from the jug, and I don't remember the brand. All of this produced a little improvement, but 40 years of working on automotive systems told me the unit was not up to par. Rather than taking a chance on overcharging the system, I called my expert friend whom, I may have mentioned is in the HVAC business. I may need to mention that as my monicer implies, my location is Mississippi, and we have been hovering around triple digit temps for a month. HVAC systems are working hard, and some are failing, which is why Phil has been so busy. He stopped over on his way home from work after 9M, looked at my gages and made the 2 lb. diagnosis. He would have added the freon, but had used all that he had on his truck that day. As most of you may know, 22 is getting hard to come by now that it has been replaced in the new systems. I knew that I had some 15 year old 15oz, cans on hand, but waited for daylight to find them. 2 cans brought the temps in line.
Thanks again for everyone's help.