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  1. #1
    Join Date
    Feb 2008
    Posts
    6

    Mix old coils with new unit?

    I have a 12 year old split system 5-ton Lennox AC, gas furnace in a 2000 Sq foot home that heats fine but needs a new cooler.

    I was going to replace everything until a friend of a friend who does AC work suggested I install a new Goodman 13 SEER R22 unit outside and keep the Lennox coils from my existing 10 SEER unit. He said he checked with Lennox and that the coils will work with the new unit.

    I'm new to all this but read you need to match the coils to the new system to achieve the stated SEER rating. Is this correct?

    Any thoughts would be greatly appreciated?

  2. #2
    Join Date
    Feb 2007
    Location
    18951
    Posts
    1,593
    I seriously doubt if anyone at Lennox who actually knew anything technical would tell your friend that it would be fine. Replace them both after your friend does a Manual J heat loss/gain on the house, and if you don't have a 90+ furnace, replace that too. Your "friend" is doing you no favors.

  3. #3
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,635
    Quote Originally Posted by cap2240 View Post
    He said he checked with Lennox and that the coils will work with the new unit.
    Uh huh... No Lennox dude in his right mind said that.

    Work? Sure. Work correctly? Not a chance. If the old evaporator coil has a TXV then it'll "work". Efficiency will be less than 13 SEER and capacity will be less than 5 tons. But it'll blow cold. You might even be happy with it's performance. And it might even cost a smidge less to run than the old setup. That's not an endorsement of the idea, just a reality. It's really best to get a new coil.

  4. #4
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,841
    No doubt your advisor keeps the old radiator for his pick-up when he trades it and puts it in the new pick-up, right? Or is it the engine or the rear end? Just which part DOES he keep when he trades? Why treat your HP any differently? Don't be a cheapskate just 'cuz you friend is. He doesn't live in your house and he's not paying the bill. He's just trying to inflate his own ego by throwing around some technology. Every authority in the country will advise you to replace both units so you get a new mechanical system. I'd also go so far as to say you should have a current load analysis done (Manual 'J'), duct analysis (Manual 'D') and get an ARI certificate that the new system components meet the 13-SEER standard once it's all installed. Do it right and you won't regret it. As for the manufacturer, that's open to opinion. I'd search first for the company that will do the load analysis and then get their opinion on which system you should get. But no matter what, I'd replace the whole shootin' match. Shucks, I just pulled out a perfectly operating system in my own house and replace it with a new system, 2-stage, variable speed blower. Eletric bills are already down 30%!! Eat your hear out!!!
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  5. #5
    Join Date
    Feb 2008
    Location
    Frisco , Texas
    Posts
    4
    You can replace the piston with a txv and the system will work although not as efficiently as designed, with the R22 the refrigerant lines need to be sized properly especiallly if run further than 50'

  6. #6
    Join Date
    May 2007
    Location
    somewhere between heaven and hell
    Posts
    957
    Cap do yourself a favor and avoid the headaches from later problems. Replace the coil ,line set, and the outdoor unit all the same time. It is best to match the coil with the unit to avoid further complications. You will be glad you did.

  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,619
    A moonlighter
    selling Goodman
    says mismatch the coil

    RUN!!!!

    You're asking for trouble with a moonlighter and from someone willing to mismatch the thing. Nothing wrong with Goodman other than how common it is to be in the wrong hands.

  8. #8
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,805
    Yep. Someone just interested in making a quick buck.

    Stay with your original plan and match the coil and condenser. And use a real contractor.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    Quote Originally Posted by R2Kool View Post
    You can replace the piston with a txv and the system will work although not as efficiently as designed, with the R22 the refrigerant lines need to be sized properly especiallly if run further than 50'
    Absolutely not recommended by anyone.

    If you install a new condensing unit to an existing 12 year old indoor coil, you have a 12 year old system with a big new part that no one can say what capacity or efficiency is.

    Keep this friend for things other then HVAC and get yourself a new HVAC friend who is a qualified contractor.

    As has been stated; no one at Lennox has condoned this.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  10. #10
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    If this guy is lying to his friends like this....can you imagine what he is telling his customers??? WOW!!!
    I need a new signature.....

  11. #11
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,981
    Quote Originally Posted by I_bend_metal View Post
    If this guy is lying to his friends like this....can you imagine what he is telling his customers??? WOW!!!
    The real tragedy is he probably isn't lying. Way too many technicians are convinced that using an existing coil is ok to do.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  12. #12
    Join Date
    May 2007
    Location
    somewhere between heaven and hell
    Posts
    957
    Quote Originally Posted by I_bend_metal View Post
    If this guy is lying to his friends like this....can you imagine what he is telling his customers??? WOW!!!
    Hope he lives near me so I can fix his goof ups

  13. #13
    Join Date
    Dec 2007
    Location
    Ohio
    Posts
    2,876
    Quote Originally Posted by mrlighturfire View Post
    Hope he lives near me so I can fix his goof ups

    Yeah...these guys are great for business!
    I need a new signature.....

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