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Thread: HVAC Shot myself in the foot

  1. #1
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    Default 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. #2
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    Anderson SC
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    Quote 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.

  3. #3
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    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

  4. #4
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    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 at 12:22 PM.

  5. #5
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    Jun 2002
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    Grand Blanc Michigan
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    Quote 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~

  6. #6
    Join Date
    Jan 2004
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    Missouri
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    Quote 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......
    1601

    Keep eye on ball.
    Hashim Khan

  7. #7
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    Quote 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.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  8. #8
    Join Date
    Jun 2007
    Location
    Anderson SC
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    Default

    Quote 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.

  9. #9
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    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

  10. #10
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    Default

    Might as well call it a dickfor.

    -D

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