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  1. #1
    Join Date
    Jan 2008
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    91

    TXV on Carrier CD5A Condenser series?

    I just had a Trane xv95 installed; it replaced "half" of my Carrier Weathermaker system. The outdoor AC unit and coils are still good, so they remained. Coils are from the CD5A series.

    From reading this site, I understand that the AC unit has to have a TXV if you are going to slow the blower speed, to dehumidify for example. I'd like to take advantage of the Trane comfort-r capability. I checked the control board and the installer did not install the jumper between Y and O, and has the #5 and #6 dip switches set for no comfort-r. Does my existing AC have a TXV installed (I've looked and don't see anything resembling it)? If not (and I'm thinking not, based on my amateur set of eyes and the installer's setup), would this be an easy mod?

    Thanks.

  2. #2
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    Lancaster PA
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    Its relatively easy. But its more then just a 15 minute job.

    Did they also install a 2 stage thermostat, or just have you running off the furnace timer.
    2 stage furnace, should use a 2 stage stat.`
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  3. #3
    Join Date
    Jan 2008
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    Quote Originally Posted by beenthere View Post
    Its relatively easy. But its more then just a 15 minute job.

    Did they also install a 2 stage thermostat, or just have you running off the furnace timer.
    2 stage furnace, should use a 2 stage stat.`
    Have a TCONT803 as the stat, wired as 2 stage heat. Big improvement over the single stage; I'm really happy with it. Second stage only comes on as part of recovery in the morning, otherwise it is on first stage, even when we're in the teens or single digits outside.

  4. #4
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    Lancaster PA
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    What area are you in.
    Do you know what your winter design temp is?
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  5. #5
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    Jan 2008
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    Southern Ohio. Not sure about the house's winter design temp. If we're in the high 20's to low 30s, the thermostat reading will drop about a degree per hour with no heat turned on. The thermostat is located on an interior wall in the entryway.

    The house itself is a really old 2-story home (1890s), about 2000 sf. It has relatively new windows (double pane) and an unfinished attic with about a foot of fiberglass insulation rolled across floor. We did a lot of that ourselves when we moved in, sealed up cracks and that kind of thing.

  6. #6
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    Don't recall any area of Ohio that has a design of less then 0* OD temp.
    If your not going to second stage in teh single digits, it sounds like you are oversized.

    Not to bust on your contractor. But if you are oversized, your not getting the comfort you paid for.

    I'm guessing he put in the same size that was there, or close to it.
    Too late now.
    Most of the comfort you are getting is from the VS blower delivering better air flow.
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  7. #7
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    Jan 2008
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    Quote Originally Posted by beenthere View Post
    Don't recall any area of Ohio that has a design of less then 0* OD temp.
    If your not going to second stage in teh single digits, it sounds like you are oversized.

    Not to bust on your contractor. But if you are oversized, your not getting the comfort you paid for.

    I'm guessing he put in the same size that was there, or close to it.
    Too late now.
    Most of the comfort you are getting is from the VS blower delivering better air flow.
    That's exactly what he did, same size as the old. Like I said, we improved the insulation when we moved in -- is it likely that this lowered the house's design temp enough to downsize the furnace?

    Just curious, what should be happening differently with a correctly sized unit? (second stage, duh, just read your post again ).

    I will say this -- after reading this message board there are several things I will do differently when we get the AC replaced.

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Most 2 stage furnaces are 65% capacity in first stage.
    So when your OD temp is closer then 65% of OD design, it should run in first stage for awhile,( varies iwth how cold it is ) and then the stat should kick it into second stage when it senses first stage is not able to maintain temp.

    What has now happen. Is your old furnace was say 80% efficient, now with your new furnace at 95%, its oversided 15% more then the old one was.

    Or in other words, if your old furnace was oversized by 40,000BTU's output, your new one is 55,000BTU's output oversized.
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  9. #9
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    Jan 2008
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    Old furnace was a 90%.

    I can't say for sure if the new one has *never* kicked into second stage during an extended run time. I can almost say for sure it did not when the outdoor temp was in the high teens.

    And, my comment about single digits is maybe not an apple to apple comparison. Our single digits were generally overnight and early morning, when the stat was either set back (not running) or recovering (second stage). Once it did recover, it seemed to stay in first stage, but this was only until we all left the house for work/ school. Then it is set back again until mid afternoon. Even during the coldest spells, by that time the temp was generally at least 20* outside. So I have not really seen an extended run time in the single digits.

    Oh well. Too late now, like you said.

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