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  • Question for the home A/C gurus.

    It's time for my annual A/C system crisis. We've been lucky here in my area and I've able to get by with running the attic and ceiling fans only until last weekend. My system is pretty old and the 1st start of the year is a nagging worry. When I had SWMBO switch it on with me outside standing beside the outside unit with the cover off, uttering incantations and knocking on wood, the compressor went "ugggghhh, click." Last week I went down to the HVAC place & picked up (yet another) new compressor capacitor and a kick start kit.

    We've been inundated with rain, severe thunderstorms & tornado warnings in the area and I haven't been able to safely work on it 'til today. The air has been thick as molasses and the inside of my house & shop is so moist you can cut it with a knife. I installed the kick start kit & capacitor and she started up with a bit of protest and ran smooth.

    My question is about charge level. It's only a bit above 75 deg outside but the humidity is terrible. I've had it running about an hour now and the gauges read 73/275 with sweat dripping off the low side pipe where it exits the outside unit. The house measures 72 degrees with the outlet air coming out of the farthest outlet from the inside unit at 57 degrees. This is an old R-22 unit. Do these figures seem reasonable? It seems to me to be doing well but I'm paranoid. I'm hoping to get another season out of it.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  • #2
    In a word, yes! I was told if you can get a home AC unit to drop 20 degrees from the outside temperature you are doing pretty well. More then temperature is that your unit be able to run long enough to dry out the house. Units that are too efficieant at cooling may not run long enough to dry the house out and you get the clamminess.

    Note: Take all of this with a grain of salt as you've just read my entire knowledge base about HVAC systems
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    It is true, there is nothing free about freedom, don't be so quick to give it away.

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    • #3
      Yep - I'll second the 20 deg drop across the coils.

      Any more then that and you need to change the pully and/or motor to speed up the air movement

      Comment


      • #4
        If your system is " split ", that is cooling evaporator inside and condensing unit outside and the lo-side (large copper tube ) is sweating, the charge is fine. This says the ref. gas is still below the dew point. By the way the cold line is the return to the condensing unit.
        Be sure there is plenty of air able to circulate through the condenser. Also clean filters in the indoor air circuit.

        Stay cool.
        Jim

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        • #5
          I am not sure but it seems to me that your high side pressure is a bit high at 275 PSI with 75 degree temperature. This could be caused by low airflow through the outside coil. You might want to clean and wash the outside coil as they will often get really stopped up over time. Clean coils, both inside and outside, help the unit cool better and last longer.
          Don Young

          Comment


          • #6
            Thanks all for the feedback guys. That makes me hopeful that it's functioning pretty decent. It's been cycling on and off now for hours and the house is mercifully dry inside. Good point about cleaning the condenser Don, I'm sure it needs it.
            Milton

            "Accuracy is the sum total of your compensating mistakes."

            "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

            Comment


            • #7
              Make sure air flows through the condenser coil easily. If you have any cotton wood trees in the neighborhood they your probably familiar with cleaning it. If not then a wire brush and a garden hose will work wonders! Your pressures are fine and hope it hangs in there all summer.

              Comment


              • #8
                Originally posted by jnissen
                Make sure air flows through the condenser coil easily. If you have any cotton wood trees in the neighborhood they your probably familiar with cleaning it. If not then a wire brush and a garden hose will work wonders! Your pressures are fine and hope it hangs in there all summer.
                No friggin' kidding on the cottonwood trees. The neighbors next door had their system serviced 3 times last year. You could see a felt-like build up from the street.

                A waterhose with a spray nozzle will work simple wonders. If the condenser has bad airflow, the whole thing will be uncomfortably hot to the touch, not just the fairly warm they usually are. Similarly, if the compressor sounds really angry, check airflow then pressures.

                Comment


                • #9
                  Watch the evaporator with an eye to freeze up and carryover. Carryover happens when the air velocity is high enough to blow condensate across the evaporator coils into the living space, or at least beyond the capture range of the drip pan. Freeze up is the inverse - not enough air to warm the coils and the moisture freezes which of course reduces further the air flow. Somewhere between freeze up and carryover is the ideal air speed for the current humidity.

                  I recall renting a room in Greeley, Colorado - the AC was on full blast but the room was muggy and warm. I pulled the grill off and saw it was frozen solid. As it was both a heater and cooler, I just reversed it to heat. The ice melted and fell off into the drip pan very quickly. After mopping it up and digging all the dead Miller moths out of the pan I put it on cool again and was immediately rewarded with cool dry air.

                  Comment


                  • #10
                    Good points dp. I've never had any problems with it freezing but I've always had to keep a full charge to prevent condensate water from dripping off the "A" coil higher up than usual.

                    My unit has the "A" coil at the top, drawing air up through the filter mounted in the bottom of the cabinet. If the charge gets low, The water drips onto the filter which of course turns it into a soggy cardboard noodle and it gets sucked up into the cabinet and a pain to get out...not to mention the loss of filtering.

                    A dose of "Super Seal" a couple years ago stopped the slow leak in the A-coil and it's been staying dry lately. However, it dripped yesterday though, hence my question above about pressures/charge level. I suspect it may have been caused by the extreme humidity levels inside the house. There was much dampness to be extracted from carpet, bedding, furniture....not to mention the more important cast iron stuff like lathe, mill, grinder tables, etc.
                    Milton

                    "Accuracy is the sum total of your compensating mistakes."

                    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                    Comment


                    • #11
                      Maybe its time to add a standalone dehumidifier in the shop.

                      Comment


                      • #12
                        Originally posted by DICKEYBIRD
                        It's time for my annual A/C system crisis. We've been lucky here in my area and I've able to get by with running the attic and ceiling fans only until last weekend. My system is pretty old and the 1st start of the year is a nagging worry. When I had SWMBO switch it on with me outside standing beside the outside unit with the cover off, uttering incantations and knocking on wood, the compressor went "ugggghhh, click." Last week I went down to the HVAC place & picked up (yet another) new compressor capacitor and a kick start kit.

                        We've been inundated with rain, severe thunderstorms & tornado warnings in the area and I haven't been able to safely work on it 'til today. The air has been thick as molasses and the inside of my house & shop is so moist you can cut it with a knife. I installed the kick start kit & capacitor and she started up with a bit of protest and ran smooth.

                        My question is about charge level. It's only a bit above 75 deg outside but the humidity is terrible. I've had it running about an hour now and the gauges read 73/275 with sweat dripping off the low side pipe where it exits the outside unit. The house measures 72 degrees with the outlet air coming out of the farthest outlet from the inside unit at 57 degrees. This is an old R-22 unit. Do these figures seem reasonable? It seems to me to be doing well but I'm paranoid. I'm hoping to get another season out of it.
                        If there is a charging chart go by that. If not charge to around 10 - 15 deg. liquid line (small line at outlet of outdoor unit) subcooling. If you read the pressures I assume you have gages with a temp. scale along with the press. scale. Convert pressures to temperatures 73# = about 44 deg., 275# = about 125 deg. These are saturation temperatures of R-22. With an accurate thermometer measure the liquid line leaving the condensing unit. It should read in the range of 110 to 115 deg. The difference is your subcooling. Indicates condenser is fully active and a subcooled refrigerant is leaving. On the low side the larger line sould be warmer than the 44 deg. saturation temp. by 10 to 20 deg. Check or clean coils. Compressor amps and volts should agree with unit nameplate. Air side should have about 17 - 22 deg. spread. You have 72-15=15. If charge is right slow fan down 1 speed if direct drive or open drive pulley a bit if belt drive. I give ranges only because a unit is rated at full load design conditions, usually 95 ambient. 275 disch is high for 72 ambient, either dirty condenser coil or noncondensables (air) introduced into the system by sloppy service practices.

                        Comment


                        • #13
                          Thanks deltap, I'm still trying to digest all your info. I'm going to clean the condenser this weekend as it hasn't been chemically cleaned in a long time. I do pull the fan screen and vacuum the leaves and trash off the top every year and wash it out thoroughly with a hose sprayer.

                          Your mention of a bit of air in the system may be correct as I had to charge it more than a few times when the A-coil was leaking. I was very deliberate with my technique and shouldn't have let much, if any air in, I hope.
                          Milton

                          "Accuracy is the sum total of your compensating mistakes."

                          "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

                          Comment


                          • #14
                            I didn't read the whole thread, but the biggest thing the home owner can do is keep the coils clean and combed out. For the outside unit, coil cleaner and a hose will work wonders. And a coil comb if needed. Inside, be sure the drain is working first, and then coil cleaner and easy with the hose to flush it out.

                            A good cleaning can work absolute wonders.
                            Paul A.

                            Make it fit.
                            You can't win and there is a penalty for trying!

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