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Iced over unit.

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  • Iced over unit.

    I installed a 3.5 ton Ruud package heat pump the other day. Customer called me next morning (around 8am/80 deg) and says it's not that cool. I go out and most of the evaporator is iced over including the lines on the low side. I switch it into heat mode and the valve switches over and melts the ice off. I switch it back to cool, no problem, runs fine. Been running great for 2 days now-no problem. Shows no signs of iceing up.

    Subcool is normal(TXV metering device)at 11 degrees. My delta t across the supply and return is 12 degrees also good. This is a new install and I redid the ductwork. I use manual D and J. When units ice up, I think first of poor airflow but that didn't seem to apply in this case.
    Buy cheap, buy twice.

  • #2
    Re: Iced over unit.

    How long did you babysit it after the install? What were ther pressure settings?
    Multi speed compressor?
    Check the T-stat fan setting. Make sure fan doesn't shut off when comp. stops. Should run for 1-2 mins after. It is a HP t-stat right?

    Hot and humid here today. If it wasn't working right you would know it by now.
    Last edited by plumberscrack; 06-02-2007, 06:38 PM.

    Comment


    • #3
      Re: Iced over unit.

      Originally posted by plumberscrack View Post
      How long did you babysit it after the install? 1 1/2 hour What were ther pressure settings? Can't remember. That info is written in my truck but I don't go off pressure, I go off superheat,subcool.
      Multi speed compressor? No
      Check the T-stat fan setting. Make sure fan doesn't shut off when comp. stops. Should run for 1-2 mins after. It is a HP t-stat right? Yes

      Hot and humid here today. If it wasn't working right you would know it by now. That's what irks me. It runs fine now but it iced up early on. Runs great now though. Are you the only who knows AC around here? Knock knock, anbody there?
      Thanks for the help Pcrack
      Buy cheap, buy twice.

      Comment


      • #4
        Re: Iced over unit.

        You are correct in that low airflow will cause a coil to Ice up. Also low refrigerant will Ice up in a hurry.

        I am not well versed with heat pumps, but maybe its possible a valve was stuck or something??

        You may want to have the owner take a peek at the suction line as it enters the heat pump/condensing unit for a few days and if she notices any frosting/ice, have them give you a call.

        Like I said, I dont fool with a lot of heat pumps.

        Regards,

        Comment


        • #5
          Re: Iced over unit.

          Not many A/C or Heat Pump guys on this forum for some reason. You might get a better response from a different forum. I'm really weak on heat pumps but it wouldn't be the first time a new product failed right out of the box. TXV could have been stuck and by going into heat mode may have fixed it. A service call 1 day after install doesn't make for a happy customer

          Comment


          • #6
            Re: Iced over unit.

            was it operator error,

            I don't now how many people seem to think if they turn down the thermostat it will cool faster, and in the process the AC will not cycle and clear the coil of any frost or ice build up, and then they seem to think it is the AC faulty, I have seen happen a number of times.

            Almost ever Sunday at Church, when the AC is used, I will check the thermostat on the AC some one has it down to 50 or 60 some how thinking it will cool the building faster, instead of just leaving it at 70. and letting it do it thing.
            ~~~~~~~~~~~~~~~~~~~~~~~~

            needless to say I am not a AC guy,
            but have worked on some of my own refrigeration, walk in cooler and freezers, and it all has TXV's on them and I was taught to do the pressure and then check the super cooling or heating, depending on the situations across the coils, (also everything I have has site glasses on and receivers on the units) , and it has been some time since I have needed to do any thing on them,
            and for some reason I was under the impression that on fixed orifices you more worked off the supercooling,
            and on the txv units you worked off the pressures, (and in my case the sight glass) but with the blended refrigerants they are not as reliable as they were with the good old stuff,
            the supercooling is use on a TXV to see that the tvx is properly flowing enough refrigerant across the coils. but I also know that there are diffrences between refregeration and AC,
            Last edited by BHD; 06-04-2007, 09:26 PM.
            Push sticks/blocks Save Fingers
            ~~~~~~~~~~~~~~~~~~~
            "The true measure of a man is how he treats someone who can do him absolutely no good."
            attributed to Samuel Johnson
            ~~~~~~~~~~~~~~~~~~~
            PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

            Comment


            • #7
              Re: Iced over unit.

              Originally posted by BHD View Post
              was it operator error,

              I don't now how many people seem to think if they turn down the thermostat it will cool faster, and in the process the AC will not cycle and clear the coil of any frost or ice build up, and then they seem to think it is the AC faulty, I have seen happen a number of times.

              Almost ever Sunday at Church, when the AC is used, I will check the thermostat on the AC some one has it down to 50 or 60 some how thinking it will cool the building faster, instead of just leaving it at 70. and letting it do it thing.
              ~~~~~~~~~~~~~~~~~~~~~~~~

              needless to say I am not a AC guy,
              but have worked on some of my own refrigeration, walk in cooler and freezers, and it all has TXV's on them and I was taught to do the pressure and then check the super cooling or heating, depending on the situations across the coils, (also everything I have has site glasses on and receivers on the units) , and it has been some time since I have needed to do any thing on them,
              and for some reason I was under the impression that on fixed orifices you more worked off the supercooling,
              and on the txv units you worked off the pressures, (and in my case the sight glass) but with the blended refrigerants they are not as reliable as they were with the good old stuff,
              the supercooling is use on a TXV to see that the tvx is properly flowing enough refrigerant across the coils. but I also know that there are diffrences between refregeration and AC,
              You halfway got it. Check system with txv w/ subcool. Fixed orifice, cap tube w/ superheat. Refrigeration has a more constant load so working off pressure isn't that bad. With AC does a unit operate under the same pressure w/ the ambient air at 90 deg. vs. 75 degrees. No, so how does one know what pressure it needs to be at?

              BHD this is not directed towards you at all and no one in particular; so please no one be offended. This is just an observation, take it for what it's worth.
              I meet a master plumber w/ 30 yrs experience and a master AC tech w/ 30 years experience. I contend that the plumber spent 5 years doing it wrong and the next 25 becoming a skilled tradesman. The AC tech spent 5 years learning wrong and the next 25 years continuing to do it the wrong way. An AC tech with years devoted in the trade holds no weight with me until I see his work and methods. I got into an arguement today with a "master" tech at work who tells me all I need to know is 70/200. He started off as a young idiot and matured into an old idiot. I'm still mad and just venting. I feel better now. Thanks
              Buy cheap, buy twice.

              Comment


              • #8
                Re: Iced over unit.

                In order to properly check and know if the pressures were near correct you would need to know the air temperature both inside and outside passing over the coils. You would also need a temp to pressure chart for the type of refrigerant used in the system. I would have the customer check lines and coils after a cool night for icing up. If everything is fine, then let it run. That's provided it does provide good cooling on a hot day.

                With AC running R22 you would normally aim the pressures for about 25F higher and 25F lower than both air temperatures. This is after the unit has been running non stop for 20 minutes or longer.
                Last edited by Woussko; 06-04-2007, 10:59 PM.

                Comment


                • #9
                  Re: Iced over unit.

                  Originally posted by Woussko View Post
                  In order to properly check and know if the pressures were near correct you would need to know the air temperature both inside and outside passing over the coils. You would also need a temp to pressure chart for the type of refrigerant used in the system. I would have the customer check lines and coils after a cool night for icing up. If everything is fine, then let it run. That's provided it does provide good cooling on a hot day.
                  It's been a week now and no icing up. Maybe this is one of those unexplained mysteries.
                  Buy cheap, buy twice.

                  Comment


                  • #10
                    Re: Iced over unit.

                    Gear

                    Maybe this customer and/or you have some special magic powers.

                    I think you may know something by Thursday morning as you'll have a few cool nights. That should give it a good test. Maybe the valves needed to be opened and closed a few times.

                    Comment


                    • #11
                      Re: Iced over unit.

                      Gear thank you for the correction, and the information,
                      Push sticks/blocks Save Fingers
                      ~~~~~~~~~~~~~~~~~~~
                      "The true measure of a man is how he treats someone who can do him absolutely no good."
                      attributed to Samuel Johnson
                      ~~~~~~~~~~~~~~~~~~~
                      PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

                      Comment


                      • #12
                        Re: Iced over unit.

                        OK, Ductman here, did the problem fix itself?

                        Yes, with most heat junks, I mean pumps, especially Crud, I mean Rudd, icing up coils is common at first install. I'm not sure if it's the factory install of coolant or a small peice of copper cutting that gets caught in the coil lines and clogs for a bit.

                        There are other factors I am sure you checked but did not think of at the time. Drain line cleared? If the condensation can't drain, it will ice up. Excessive dust in the ductwork? Did some fool mistake the floor registers for a dust pan?

                        Are there enough returns and in the right place? If you don't have enough return air, it will ice up. Too many outlets, it will ice up.

                        The best A/c guys or gals are the ones who started in duct work first...

                        Comment


                        • #13
                          Re: Iced over unit.

                          Grumpy, unit runs great. No problems. From your play on words, it sounds like you've worked w/ some real hacks who have ruined technology and brands in your eyes. I always do a manual j and d when I do installs. I don't give the customer the option if they want it or not. I include it in the price.
                          Do you guys do manual d in maryland?
                          Buy cheap, buy twice.

                          Comment


                          • #14
                            Re: Iced over unit.

                            Originally posted by gear junkie View Post
                            Grumpy, unit runs great. No problems. From your play on words, it sounds like you've worked w/ some real hacks who have ruined technology and brands in your eyes. I always do a manual j and d when I do installs. I don't give the customer the option if they want it or not. I include it in the price.
                            Do you guys do manual d in maryland?
                            I'm retired now, but yes, one of the companies I worked for did. He also reuqired us to sell humidifyers and electronic air filters as well. I cound't do that to people who live in a relatively clean enviroment and were not suspectable to alergies or do not like humid enviroments. Went commercial from there, best move I made..



                            I should add, if the ice happens again, make sure you put the right size unit in, no more than half a ton bigger than space required.

                            I am certain you did, I my self upped my house when the old girl went up five years ago.

                            When I first started out installing complete new systems, one of the builders I was assigned to, only used Rudd & heat pumps. Cheap, easy to install, common problems....

                            Heat pumps in MD are a big no-no in my book. In fact, anything within 100 miles of the Mason Dixon line should never have a heat pump, but that is me...

                            Comment


                            • #15
                              Re: Iced over unit.

                              I was also a tinner when I did commercial. Welcome to the forum. It's nice to be able to relate to someone and learn from each other's experience.
                              Buy cheap, buy twice.

                              Comment

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