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  1. #1

    matching 10 and 13 seer

    I'd like to know if there are any problems with installing a 13 seer heat pump condensing unit wit a 9 seer air handler. Other than not achieving full 13 seer. The air handler is a 20 year old comfortmaker with a piston metering device.

  2. #2
    Join Date
    Sep 2001
    Location
    kalamazoo,mich
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    2,174
    20 years old. Don't you think it's time to buy a new air handler. You can only squeeze a nickel so hard.
    Have you hugged the Earth today?
    Donny Baker rules

  3. #3
    Join Date
    Dec 2006
    Location
    s.w FL
    Posts
    19
    You should absolutley not install that condenser without replacing the air handler. Your contractor should tell you that. Why spend the money if you arent going to do it right?

  4. #4
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,371
    That sounds like pressure problems waiting to happen, let alone performance loss and possibly voided warranties. Do it right the first time - trust me.

  5. #5
    Join Date
    Aug 2005
    Location
    San Diego,CA
    Posts
    285

    Wink

    Acctually, I have done it before without any problems worked great! But some systems dont like it. Youll know for sure if its going to work as soon as you kick it in to heating mode.. Just do it once! Do it the right way. Might as well upgrade the whole system.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  6. #6
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Bristol (they make compressors) just had an article published in RSES Journal. They matched a 3 ton, 13 SEER outdoor unit to a 3 ton, 13 SEER indoor unit. Then they tested it. Surprise! They got 3 tons & 13 SEER. Then they matched the same outdoor unit to a 3 ton 10 SEER indoor unit. They got just under 2 tons and 8 SEER. If your unit is way over sized for your house, go ahead. It may still do the job. But I hope your electric rates are very low. Or you could do it right and save money in the long run.
    Remember, Air Conditioning begins with AIR.

  7. #7
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    Quote Originally Posted by yorkdude View Post
    Acctually, I have done it before without any problems worked great! But some systems dont like it. Youll know for sure if its going to work as soon as you kick it in to heating mode.. Just do it once! Do it the right way. Might as well upgrade the whole system.
    NO, it didn't work great at all. Maybe it worked and you lucked out, but there is no way that a mismatched system on a heat pump can work great when the indoor coil is not of a suitable size comparable to the heat pump coil.

    Absolutely do not mismatch heat pump components.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  8. #8
    Join Date
    Jul 2007
    Location
    Beautiful, Philadelphia, the City of Brotherly Love!
    Posts
    1,096

    If you must do this, install a smaller tonnage outside unit on the existing

    airhandler. I have done this many times, the system will work ok, if it was oversized originally. I find in my area many older installs were oversized. Actually in my area just about every install I see is oversized.

    I know I will catch hell on this site from a few folks, but sometimes the airhandler cannot be economically replaced. In the future these folks will have no choice, they will have no options. When that day comes they will have to spend the big bucks.

    I just did one of these very installs in a condo in Philly the unit is in a closet which is reached by climbing through a door a foot above the toilet tank. To replace the 4 ton air handler the ceramic tile tub enclosure will have to be removed, as the plumbing stack runs just next to the service door above the toilet.

    In the same building another blower is reached by removing a tiled door in the tub enclosure.

    The unit runs with normal pressures, I have no idea what the seer is and they do not care. I installed an expansion check valve on this unit. The condo should have a 2 ton heat pump.

  9. #9
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,057
    Chances are the refrigerant level will have to be changed twice a year. TXV won't help, it's coil size that is the killer. The small indoor coil functioning as a condenser in the winter will need charge reduced for heating, then put back in for cooling. You can get by with mismatching for cooling only with large SEER loss and capacity loss and a TXV does help. But nothing can compensate for the small indoor coil.

  10. #10
    Join Date
    Aug 2005
    Location
    San Diego,CA
    Posts
    285
    Yes, It did work Robo Man...Same Tonage,diffrent seer rating. We do work for a property mangement company at some apartment complex where its nearly impossable to replace the fan coils. My boss has me replace the condenser only (13 seer) . Do i think its the right way of doing things? No. I dont make the rules, i just do as im told. But it does work, we havent had any call backs. Pressures/temps are all text book.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  11. #11
    Join Date
    Apr 2004
    Posts
    7,680
    Quote Originally Posted by Kevin O'Neill View Post
    Bristol (they make compressors) just had an article published in RSES Journal. They matched a 3 ton, 13 SEER outdoor unit to a 3 ton, 13 SEER indoor unit. Then they tested it. Surprise! They got 3 tons & 13 SEER. Then they matched the same outdoor unit to a 3 ton 10 SEER indoor unit. They got just under 2 tons and 8 SEER.

    That was straight air, the HP didnt work.

  12. #12
    Join Date
    Nov 2007
    Location
    Austin Texas
    Posts
    54

    Unmatched equipment

    With the exception of "Have to do jobs" - The efficiency will be shot - example, if it was a 4 ton unit - it may only be as efficient with roughly a 2.5 ton capacity. Even changing the TXV will only marginally help it. There is a wonderful article on this subject exactly, however I will have to search for it. In a nutshell - It doesnt work.

    I believe the article below mentioned was it - published in RSES Journal

  13. #13
    Join Date
    Apr 2004
    Posts
    7,680
    The problem is nobody cares about effiency, that is not the problem. A heat pump is a system, not an outdoor unit (unless packaged of course). The coils must match by design in order to work properly in both heating and cooling. Yes efficiency can suffer but more importantly working period is another story. For those that "do work", there is then the issue of performance, capacity and reliability.

    Too much superheat in one mode or another... dead compressor (over time), poor defrost, poor capacity, poor latent performance etc. Too little in the other direction and dead compressor, poor defrost, noise etc. Capacity can be huge, for instance, if you now lack 3-6,000 btuhs in heating mode, you now have to make that up with electric heat when that 6,000 should be mechanical, or inability to keep the house comfortable when it's 95 degrees outside. Long, loaded run times = higher operating costs. The list goes on to include possible oil return issues.

    A mismatched HP will not be supported by any mfg or distributor. That leaves the contractor who will ultimately blame the equipment when the HO complains of high repair bills or more than usual service. Regardless, the consumer gets screwed.

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