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  1. #27
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    Nov 2019
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    Quote Originally Posted by mgenius33 View Post
    The variable speed blower motor should have constant cfm selected, NOT constant torque mode. They must be configured for 400cfm/ton.
    .
    Does the 400cfm/ton hold true for both heating and cooling modes?

    Also, in my OP I stated that one of the reasons I called my dealer was I could hear the AH running wide open and suddenly stop. After researching and learning a little more it has come to my attention that there are blower delay profiles. One of which is "run 90 seconds @ 100% air flow". I'm thinking this might be what I'm hearing. There are three other option available, one of which is "none". Can someone explain the reason a blower delay is advantageous?

  2. #28
    Join Date
    Sep 2008
    Location
    VA
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    Quote Originally Posted by dan sw fl View Post
    ZIP _ _ _ _ _ ?
    Year Residence Built _ _ _ _ ? | A.C.H. Natural = 0._ _ ?

    380 Sq Feet Glass total Area ?

    Blower Setting : 370 CFM/ Ton <--- dependent on ZIP.
    [ NOT APPLICABLE IN _ DRY _ REGIONS ]

    Schematic of duct layout & ACCA Manual D calc
    would indicate the necessary changes to reduce E.S.P.

    Max. E.S.P. Target < 0.7"
    Per Trane XV20i Service Manual page 7:

    "Important: VARIABLE SPEED OUTDOOR UNITS REQUIRE THAT THE BLOWER BE CONFIGURED FOR 400CFM/TON"
    "The only true wisdom is in knowing you know nothing" Socrates

  3. #29
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    Sep 2008
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    VA
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    Quote Originally Posted by wolfewl View Post
    Does the 400cfm/ton hold true for both heating and cooling modes?

    Also, in my OP I stated that one of the reasons I called my dealer was I could hear the AH running wide open and suddenly stop. After researching and learning a little more it has come to my attention that there are blower delay profiles. One of which is "run 90 seconds @ 100% air flow". I'm thinking this might be what I'm hearing. There are three other option available, one of which is "none". Can someone explain the reason a blower delay is advantageous?
    This requirement is set for cooling mode, as cooling mode is the only approved mode for setting/ validating refrigerant charge.

    I would suggest keeping the heat pump heating blower speed the same, but the aux heater can be changed per heater size. Temperature rise and other tests should be performed to ensure proper blower speed in heating mode.
    "The only true wisdom is in knowing you know nothing" Socrates

  4. #30
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    Nov 2019
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    Thread Starter
    What is the reason for a blower delay?

  5. #31
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    Sep 2008
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    VA
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    Quote Originally Posted by wolfewl View Post
    What is the reason for a blower delay?
    The on delay is designed to pre heat/cool the coil. The off delay is designed to soak up the last bit of heating/cooling effect you can get from the coil once the outdoor unit shuts down. Heating mode is fine, but cooling mode should not be more than 30 sec at 50%. If you use too much off delay in cooling mode the air will evaporate the condensed water on the coil left from the last cooling cycle. So, in turn it's re-humidifying the air after your AC just dehumidified the air. I typically set the cooling off delay for 0sec.
    "The only true wisdom is in knowing you know nothing" Socrates

  6. #32
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    Nov 2019
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    Thread Starter
    Quote Originally Posted by mgenius33 View Post
    Per Trane XV20i Service Manual page 7:

    "Important: VARIABLE SPEED OUTDOOR UNITS REQUIRE THAT THE BLOWER BE CONFIGURED FOR 400CFM/TON"
    Can you send me that? I want to show my dealer. I've searched and can't find the manual....

  7. #33
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    As has been noted the switch from a sweep 90 to a box is a downgrade not an upgrade. You have stated that you have a 3000 Sq Ft home. Is that 3000 main floor or 1500 main floor with a full basement. Just trying to get a handle on how far over sized it is. Of course location makes a big difference but on a strictly SWAG basis 3000 main floor with a full basement maybe 3 ton 1500 with a full basement 2 ton. Only a Man J will tell for sure but 5 is outrageous.

  8. #34
    Join Date
    Nov 2019
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    Thread Starter
    3000 sq ft, one story, N Alabama.

    I agree the 90 degree box is an issue and I will have that addressed next week. I have confidence that will resolve my static pressure issue. If not, I'll go further with duct design/replacement.

    I still don't understand why the majority opinion here is that my XV20i is oversized? This system can/will modulate down to a 2-Ton unit. Once my static pressure is resolved I should have one of the best residential systems on the market...

    Yes, I could have gone with a "conventional" 3-Ton system for much less spend. But, I lose the ability to have a system capable of adapting to different load situations.

  9. #35
    Join Date
    Aug 2009
    Location
    Beatrice, NE
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    What we are saying is you have lost the ability to adjust to different load situations because it is over sized.

    Maybe this will help. If you have a car with 500hp but it has to run at 25% throttle minimum will it be good to drive through town or would one with 150 hp be better?

  10. #36
    Join Date
    Nov 2019
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    38
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    Quote Originally Posted by BNME8EZ View Post
    What we are saying is you have lost the ability to adjust to different load situations because it is over sized.

    Maybe this will help. If you have a car with 500hp but it has to run at 25% throttle minimum will it be good to drive through town or would one with 150 hp be better?
    NOW I understand everyone's point!

  11. #37
    Join Date
    Jan 2019
    Location
    Vero Beach, Florida
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    https://www.google.com/imgres?imgurl...source=sh/x/im



    This best shows what’s happening inside your hard 90 on the left.
    What needs to happen is on the right. Tell your installer to take the hard 90 out and install a 3piece 90

  12. #38
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    Nov 2019
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    Thread Starter
    Thank you!

  13. #39
    Join Date
    Nov 2019
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    Thread Starter
    Can someone tell me the maximum TESP for a Trane TAM9? I thought it was supposed to be on a cabinet sticker but I can't find it...

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