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  1. #1

    Missed match system

    I just replaced a new 13 seer 3tons condensing unit today to an existing evap coil and I got some weird data.
    pressure was off. low side was at 62 n high side was 250 during the 90deg out side temp. I heard other said that if u match 13seer condensor to a 10 seer evap, u get about an 8seer cooling capacity. wat are ur experience with the pre-installed mis-matched system?

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    33,900
    Sounds about right. Smaller evap looking for higher head pressures so you have to overcharge the outdoor unit to get the suction up.

    I hope you inspected the old coil for cleanliness before reusing?

  3. #3
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
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    At least use the right piston # or install a TXV.

    In florida they stopped allowing these 13seer condensors on 10seer handlers for this very reason.

  4. #4
    Join Date
    Sep 2009
    Location
    S.C.
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    1,369
    Where can a HO or DIY come to get some advice on their Hacked Mis-Matched System? Goooood 'Ol HVAC Talk!
    Yes, I know I Shouldn't But I Just Can't Help Myself...

  5. #5
    Join Date
    Dec 2009
    Location
    Fort Worth, Texas
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    Ditto. Piston/txv. for the 10000000000 time. if you want a correct anwere we need subcooling and superheat. for the 100000000000000000000000000 time. and is it txv or piston your using. your head pressure is way low.

  6. #6
    Join Date
    Feb 2009
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    Tallahassee, FL
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    Quote Originally Posted by HJ Controls View Post
    Ditto. Piston/txv. for the 10000000000 time. if you want a correct anwere we need subcooling and superheat. for the 100000000000000000000000000 time. and is it txv or piston your using. your head pressure is way low.
    Head pressure way low? No. way high.

  7. #7
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
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    7,635
    Quote Originally Posted by HJ Controls View Post
    Ditto. Piston/txv. for the 10000000000 time. if you want a correct anwere we need subcooling and superheat. for the 100000000000000000000000000 time. and is it txv or piston your using.
    whatjutryintosayWillis?

    Quote Originally Posted by SBKold View Post
    Head pressure way low? No. way high.
    did i miss what flavor frexone is running in this thing?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  8. #8
    Quote Originally Posted by Home&Marine View Post
    Where can a HO or DIY come to get some advice on their Hacked Mis-Matched System? Goooood 'Ol HVAC Talk!
    I went thru and finished training at an Hvac-r trade school. I started working for an Hvac company after school end in June. My boss did the selling, proposal and pricing. His clients want cheap, so the solution is to just replace old condensing unit with newer one. Now 13 seer is the min. so that's what we got for the installs. He didnt tell me about the loss capacitor of the mis-matched system. I over heard from other technicians. I brought it up here just to see wat kinds of info. being discuss here.


    Thanks for those who put out good discussion.

  9. #9
    Join Date
    Dec 2009
    Location
    Fort Worth, Texas
    Posts
    151
    my bad i was thinking 410a.

  10. #10
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,397
    There is a thread going in AOP Residential right now on this very topic.

    http://hvac-talk.com/vbb/showthread.php?t=926552

    Towards the end of the thread, there is some good information to present to your boss and your customers.

    You are doing them NO FAVORS by mis-matching equipment like this. In fact, you are actually costing them money rather than saving it for them.

  11. #11
    Join Date
    Sep 2009
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    Stumptown,USA
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    koolerdude, get your post count up to 15 and apply for pro membership! A lot of good training in the educational forums. Also check out www.rses.org
    Challenge yourself, take the CM test --- Certificate Member since 2004 ---Join RSES ---the HVAC/R training authority ---www.rses.org

  12. #12
    Join Date
    Jan 2006
    Location
    McQueeney, Texas
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    3,711
    Some systems can be downsized if the home is in need of updating such as insulation in the attic which is cheap, sealing infiltration or even fixing windows etc. Some homes have already had this done and the load calc may show for example a 2 ton system will work instead of the present 2.5 or 3 ton system. In this case a 13seer with a reduced tonnage can be installed on a present 10 seer coil with acceptable operation.
    This falls in the category of people who just don't have the money at the time for a complete change out. A more common occurrence now days.
    I don't favor using any R22 systems replacements unless it can be converted to R410 in the future. In fact I have turned away quite a few jobs because it was just wrong and let the other contractor do it. I have gotten calls to fix such wrong applications after I had turned them down and they had mr xx do it. I sadly say to them- they are stuck unless they allow me to redo all that been done and it is costly.

    I NEVER mix match heat pumps.

  13. #13
    Quote Originally Posted by Paul Bee View Post
    koolerdude, get your post count up to 15 and apply for pro membership! A lot of good training in the educational forums. Also check out www.rses.org
    I'll do that. Thanks.

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