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  • HVAC Shot myself in the foot

    Helping a friend fix up a house to sell. Central air needs to be replaced. Saw an ad for a used 2014 2 1/2 Ton Rheem R410A complete outdoor condenser and compressor unit and also an A Coil. Cheap deal, no return. Kept wondering why it was removed. A coil looked old. Checked the model number and sure enough the A coil was an old R22 unit. Since the pressure is so much higher in a R410A unit, and probably other reasons, the old a coils can't be used. Since the system was removed, someone must have proved it. So I started shopping for a Rheem A coil. They must be made of gold because they cost about three times as much as generic.

    I had a Goodman unit installed at home and it has worked fine. Numerous HVAC installers use them because only one dealer in an area can get the big name brands and wholesalers don't care who they sell these generic units to. In that category of equipment I'm a firm believer in parts-is-parts. Same compressors, same fin tubes, Honeywell or White Rogers controls wrapped in sheet metal painted with the company's colors. I can get a Goodman 2 1/2 Ton R422A A coil for about $250 instead of Rheem's $900.

    I'm sure my installer will connect whatever I have sitting there but with what is called a Georgia Guarantee (If It breaks I get to keep both pieces). Any HVAC experts here know how picky components are to mix?

  • #2
    Originally posted by GKman View Post
    Helping a friend fix up a house to sell. Central air needs to be replaced. Saw an ad for a used 2014 2 1/2 Ton Rheem R410A complete outdoor condenser and compressor unit and also an A Coil. Cheap deal, no return. Kept wondering why it was removed. A coil looked old. Checked the model number and sure enough the A coil was an old R22 unit. Since the pressure is so much higher in a R410A unit, and probably other reasons, the old a coils can't be used. Since the system was removed, someone must have proved it. So I started shopping for a Rheem A coil. They must be made of gold because they cost about three times as much as generic.

    I had a Goodman unit installed at home and it has worked fine. Numerous HVAC installers use them because only one dealer in an area can get the big name brands and wholesalers don't care who they sell these generic units to. In that category of equipment I'm a firm believer in parts-is-parts. Same compressors, same fin tubes, Honeywell or White Rogers controls wrapped in sheet metal painted with the company's colors. I can get a Goodman 2 1/2 Ton R422A A coil for about $250 instead of Rheem's $900.

    I'm sure my installer will connect whatever I have sitting there but with what is called a Georgia Guarantee (If It breaks I get to keep both pieces). Any HVAC experts here know how picky components are to mix?

    Mixing coils with different brand condensers is done all the time although its not recommended by manufacturers. Its mostly about maintaining SEER ratings. Coils/condensers are tested to meet ashre seer standards and certified to meet that seer rating. When mixing and matching, the seer rating is not guaranteed. SEER rating is a measure of efficiency (electricity used for a given cooling output).

    Using a different brand coil will work just fine provided its the same tonnage and rated for the R410 and the same or higher SEER rating as the condenser. If you want to go the extra mile, use a TXV valve at the coil instead of a piston. TXV valve equipped coils provide better performance and efficiency than piston/orifice setups and are not expensive.

    Another point is that if the old system at your friends house is a R22 system then the lineset either has to be replaced (preferred) or flushed with special solvents before switching to a R410 system. The oils are not compatible and residual oil in the lineset has to be removed.

    Of course, there is always a risk with a used condenser like you got. You just don't know why it was removed and its condition.

    Comment


    • #3
      Calling a metering orifice a piston is ridiculous.
      I get that it is part of a check valve that allows
      the unit to function backwards in heat pump mode
      but it's primary function is to be an orifice that
      performs a metering function. Calling it a piston
      sounds extremely unintelligent to me.

      -Doozer
      DZER

      Comment


      • #4
        Sparkey_NY
        Thank you for the well explained information.

        Doozer,
        Toma-to? Tomat-o. I don't care, I just want it to work.
        Man up and delete the insulting remarks then take a break.
        Last edited by GKman; 11-14-2017, 11:22 AM.

        Comment


        • #5
          Originally posted by Doozer View Post
          Calling a metering orifice a piston is ridiculous.
          I get that it is part of a check valve that allows
          the unit to function backwards in heat pump mode
          but it's primary function is to be an orifice that
          performs a metering function. Calling it a piston
          sounds extremely unintelligent to me.

          -Doozer
          Seems pretty harsh when the O P was good enough to share his experience and admit his error and ask advice. Will give me pause before attempting such a substitution myself. On the other hand, such a reaction will give me pause before sharing my own mistakes here.

          I will delete the above quote if the original is deleted.

          Sorry about being cranky about this. I am out of sorts, being under the influence of Chemo and Radiation at the moment.
          <edit> Oops, confused some other advise with the OP. Still my sentiments still stand.
          Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
          ~Practitioner of the Electromechanical Arts~

          Comment


          • #6
            Originally posted by Doozer View Post
            Calling a metering orifice a piston is ridiculous.
            I get that it is part of a check valve that allows
            the unit to function backwards in heat pump mode
            but it's primary function is to be an orifice that
            performs a metering function. Calling it a piston
            sounds extremely unintelligent to me.

            -Doozer
            That seems pretty abrasive even to ME. Now if BF agrees, you know you are in trouble......
            CNC machines only go through the motions

            Comment


            • #7
              Originally posted by J Tiers View Post
              That seems pretty abrasive even to ME. Now if BF agrees, you know you are in trouble......
              Abrasive, hell! I thought it was sweet as sugar! You go Doozer. Darn near a compliment actually.
              Location: The Black Forest in Germany

              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

              Comment


              • #8
                Originally posted by Doozer View Post
                Calling a metering orifice a piston is ridiculous.
                I get that it is part of a check valve that allows
                the unit to function backwards in heat pump mode
                but it's primary function is to be an orifice that
                performs a metering function. Calling it a piston
                sounds extremely unintelligent to me.

                -Doozer
                Go google "hvac coil piston" and see the huge list using that exact term, INCLUDING one by ADP, a leading manufacturer of HVAC coils. SO now who sounds extremely unintelligent?

                BTW, they are used in straight AC units also, not just heat pumps.

                Comment


                • #9
                  Not directed at anyone in particular.
                  The entire HVAC industry calls the metering orifice a piston.
                  Yes, I get that.
                  I still think it is stoooopid that so many people call it that.
                  Just because everyone has adopted a silly name for something
                  I still can stand alone in my opinion that a misnomer is continuing
                  to be used by thousands of people.

                  -Doozer
                  DZER

                  Comment


                  • #10
                    Might as well call it a dickfor.

                    -D
                    DZER

                    Comment


                    • #11
                      As long as we are arguing about air Conditioning ...

                      Looking for recommendations ....

                      After last summer working in my shop I decided I am going to install air conditioning this year. I have a little over 800 sq ft, well insulated, dual pane windows, 9ft ceilings, 1000 watts of lighting. Usually a 7 Hp RPC running, and another 5Hp lathe or mill running too. And if I have to open the garage door up to haul some thing in or out I do want it to pull the room down without having to wait too long

                      Was looking at the Mini-Split systems. Probably could get by with a 1 ton but rather go with the "More Power" option 1.5 ton system

                      Thoughts ...

                      Comment


                      • #12
                        Originally posted by Doozer View Post
                        Not directed at anyone in particular.
                        The entire HVAC industry calls the metering orifice a piston.
                        Yes, I get that.
                        I still think it is stoooopid that so many people call it that.
                        Just because everyone has adopted a silly name for something
                        I still can stand alone in my opinion that a misnomer is continuing
                        to be used by thousands of people.

                        -Doozer
                        probably comes from the thing being adjustable in ancient systems.

                        Why was a funnel for molten metal still called a "tundish" up into the last century at least, when that word dates back many centuries? Presumably all the way back to when something shaped like it was used to help in filling the size of cask/barrel known then as a "tun". Answer: tradition.

                        IIRC, the refrigerator folks call that orifice a "capillary", which is a bit closer to what it looks like, anyhow.
                        CNC machines only go through the motions

                        Comment


                        • #13
                          Its no longer necessary to completely remove the old mineral oil from an r22 system before converting to r-410a, and perhaps it never was. the two oils do dissolve into each other, and the pao iirc (or is it poe?) which is carried through by the r-410 will carry the mineral oil along with it. i suppose they might separate out if they were mixed 50/50, but if there is a few percent of mineral oil, that is not a problem.

                          however, most of the time people replace an R22 system because the old one burned out; in this case, yes you need special chemicals to pull the acid from the destroyed compressor windings out of the line set!

                          The reason people said it needs to be done, is they say the oils react.. well, they do! if there is water in the system! which is going to kill your compressor anyways.

                          Pull it down to 300 microns at least and verify that the vacuum isn't increasing when you close the valve on the vacuum pump.. and install a new filter dryer.

                          There are even people now saying you shouldn't pull it down to "too low of a vacuum" because doing so will chemically change the oil. i have no idea who came up with this nonsense, but i saw it on reddit the other day.

                          regarding the coils:

                          I brazed a custom heat pump together some time ago, i used the coils from an indoor Mitsubishi air handler for the evaporator.. and i discovered the 6mm diameter copper tubes have a thinner sidewall than the 1/4" copper coils from some old R-22 dehumidifiers (15 years old at least) that i rescued from the dumpster in a former life.

                          so this idea that the R-410A coils are thicker, does not match my observations from both Mitsubishi and Dakine air handlers. i would say they are thinner than old R-22 coils. might be a different alloy of copper though.


                          i would definitely consider using an old r-22 coil for r-410a service if it was possible to guarantee that its not about to leak any ways due to formicary corrosion, or other problems.
                          Last edited by johansen; 11-14-2017, 11:25 PM.

                          Comment


                          • #14
                            Originally posted by JoeFin View Post
                            As long as we are arguing about air Conditioning ...

                            Looking for recommendations ....

                            After last summer working in my shop I decided I am going to install air conditioning this year. I have a little over 800 sq ft, well insulated, dual pane windows, 9ft ceilings, 1000 watts of lighting. Usually a 7 Hp RPC running, and another 5Hp lathe or mill running too. And if I have to open the garage door up to haul some thing in or out I do want it to pull the room down without having to wait too long

                            Was looking at the Mini-Split systems. Probably could get by with a 1 ton but rather go with the "More Power" option 1.5 ton system

                            Thoughts ...
                            "More power" will cool the area down quicker but will not remove as much moisture. It can leave the space feeling cold and clammy.
                            North Central Arkansas

                            Comment


                            • #15
                              Originally posted by JoeFin View Post
                              As long as we are arguing about air Conditioning ...

                              Looking for recommendations ....

                              After last summer working in my shop I decided I am going to install air conditioning this year. I have a little over 800 sq ft, well insulated, dual pane windows, 9ft ceilings, 1000 watts of lighting. Usually a 7 Hp RPC running, and another 5Hp lathe or mill running too. And if I have to open the garage door up to haul some thing in or out I do want it to pull the room down without having to wait too long

                              Was looking at the Mini-Split systems. Probably could get by with a 1 ton but rather go with the "More Power" option 1.5 ton system

                              Thoughts ...
                              1000 watts of lighting - wow! I'd think about reducing that heat input so I didn't have to remove it with A/C. LED is getting affordable. I have a hunch that your big motors are just idling most of the time, a clamp on ammeter would be a good tool to see how much they are actually drawing then there is a split between the heat produced and machining work done.. My home shop has similar specs although 625 square feet. I think it's about as hot and humid here as in your location. I use a 5,000 BTU window unit and it does a great job for my needs. I have a Kmart box fan hanging near it that helps the circulation. I can't over stress how important that $18.00 investment is. During the hottest weather it will maintain a 20 degree F temperature difference from outdoors. Eighty degrees indoors when it's a hundred outside would get complaints in an execs office but it works great for me. I've seen thru-wall motel units used in shops with good results also.

                              Doozer, you've added nothing. I would be suspicious of anything you tried to add given your preference for "Look how smart I am" over "Look how smart this is".

                              If you have something to say start your own thread, stay off this one.

                              Comment

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