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  1. #1
    Join Date
    Jul 2006
    Posts
    151

    Manual J question

    I have a copy of a manual J done on my house. If I am reading it correctly, the heating load is 43351 and cooling is 25503. CFMs = 1234
    SQ Feet = 1933

    A 3 ton system was recommended based on these numbers. (This also happens to be the size of the current system.)

    Here is the system and it's performance numbers. The cooling numbers are close to a full 3 tons, but the heating numbers seem low. Especially if the heating load is 43351. Will this heat pump have any trouble heating my house until the temp gets low enough for the propane furnace to kick in?

    XR-13 4TWR3036A
    90% TUX1B080A9421A (74K BTU)
    4TXCB036BC3

    SEER 14.00 (35200 cooling)
    HSPF 8.50 (31000 at 47* / 19600 at17*)
    EER 11.80

    Thanks.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    They will set it up to switch at the temperature needed ,no worries,I hope.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,299
    I see some issues!

    First is the ratings. Not sure where you got yours but AHRI Directory says that HP with that coil and standard blower is 13.00 SEER and 8.20 HSPF. Heating output is low as usual with A-S/Trane.

    Now, if your heat loss is 43K, you don't need that big furnace. The appropriate furnace would be the AUX2B060. Grossly oversizing a furnace means your actual efficiency would be reduced. You could have short cycling and you could cycle on the furnace's limit if the duct system isn't rather large.

    If you like it ice cold, a 3 ton for just over a 2 ton load may be OK but the calcs if done right reflect the desired indoor temp. But the appropriate cooling (HP) unit would be 2.5 ton. Going nearly 50% oversized means short cycles and high humidity. And your 13 SEER will be effectively lowered due to constant cycling in mild weather.

    As for changeover, I set A-S systems to change to gas 5° warmer than brands with good heating figures.

    Personally I wouldn't want that system and hope our salesmen wouldn't suggest a system like that with those kind of gain/loss numbers.

  4. #4
    Join Date
    May 2008
    Location
    North Texas
    Posts
    105
    What was the sensible and what was the latent loads?

  5. #5
    Join Date
    Jul 2006
    Posts
    151
    Quote Originally Posted by sparksandfan View Post
    What was the sensible and what was the latent loads?
    It appears to me those fields are blank. There is a scan of the manual J below.

    Bald, could you give me the ARI reference number for the match you are getting? Thanks.



  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    2421 Latent?

    What area are you in again.
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