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  1. #14
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    Jan 2004
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    Lancaster PA
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    68,171
    You may have a 16 by 25 plenum. But more likely the duct is not the same size.
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  2. #15
    Join Date
    Aug 2005
    Location
    San Diego,CA
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    285
    I know you are supposed to use the right calcs. to determine your size system. BUT, There is also a rule of thumb for sizing systems. Out here in CA its 400 sq ft = 1ton . I think on another post they said out in your area its around 600 sq ft =1ton. well either way it seems your undersized. also,loads....windows,lighting,etc.
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  3. #16
    Join Date
    Jun 2008
    Location
    Perry Village, Ohio
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    164
    Quote Originally Posted by beenthere View Post
    You may have a 16 by 25 plenum. But more likely the duct is not the same size.
    Okay... I will have to measure it when I get home then. I was thinking they were the same. I assume I would want to measure it before it takes the 90 degree turn towards the furnace? To be honest though, I believe it is the same size before the bend and after which would mean it is the same as the plenum. If that is the case, is that a bad thing?

  4. #17
    Join Date
    Jun 2008
    Location
    Perry Village, Ohio
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    164
    Quote Originally Posted by yorkdude View Post
    I know you are supposed to use the right calcs. to determine your size system. BUT, There is also a rule of thumb for sizing systems. Out here in CA its 400 sq ft = 1ton . I think on another post they said out in your area its around 600 sq ft =1ton. well either way it seems your undersized. also,loads....windows,lighting,etc.
    So if that is the case what do I do with my two year old compressor? Scrap it and buy a whole new one? If so, the installer and builder may get hurt because I brought this up with them when my house was still under warranty and they insisted that it was the right size.

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by yorkdude View Post
    I know you are supposed to use the right calcs. to determine your size system. BUT, There is also a rule of thumb for sizing systems. Out here in CA its 400 sq ft = 1ton . I think on another post they said out in your area its around 600 sq ft =1ton. well either way it seems your undersized. also,loads....windows,lighting,etc.
    That rule of thumb is worthless.

    Around here they like to use 500 and 600 sq ft to the ton.
    And it over sizes most houses.

    An accurate load calc, and proper use of Manul S (if you don't have extended performance specs for your brand ) would be the right way to size.
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  6. #19
    Join Date
    Aug 2005
    Location
    San Diego,CA
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    285
    I know you are supposed to use the right calcs. to determine your size system. BUT, There is also a rule of thumb for sizing systems. Out here in CA its 400 sq ft = 1ton . I think on another post they said out in your area its around 600 sq ft =1ton. well either way it seems your undersized. also,loads....windows,lighting,etc.
    __________________
    We realize that Beenthere as stated in the thread...Just trying to make a point.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  7. #20
    Join Date
    Jun 2008
    Location
    Perry Village, Ohio
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    164
    Okay.. so maybe I am undersized and maybe I'm not. I will have to get a contractor out to find out.

    But answer this question if I may ask. Since my return vent's have 1008 square inches and my supply is about half that, shouldn't the supply vents be really producing a lot of airflow in the room (almost to the point that they may be obnoxious)?

  8. #21
    Join Date
    Aug 2005
    Location
    San Diego,CA
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    285
    No comment..
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  9. #22
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Thats just teh size of the register. The size and length of the duct thats hooked to it also has to be taken into condiferation.
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  10. #23
    Join Date
    Aug 2005
    Location
    San Diego,CA
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    285
    There are a million things that could bewrong with your set up. Best thing to do is have them run a new calc. double check the sizing. Then i would have them do a good thorough check on it from head to toe. check all ducts,s/a,r/a,fan etc.
    If everything checks out good, then ask them why your hot! You need an explanation.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Quote Originally Posted by yorkdude View Post
    .
    __________________
    We realize that Beenthere as stated in the thread...Just trying to make a point.
    Pointing out rules of thumb, doesn't really help.

    The whole problem in this case could be the duct system is undersized.
    Or maybe its a half or a whole ton undersized.
    But using your "out side of your area rule of thumb" they would be putting in 6 tons.

    A 2600 sq ft rancher may need a larger A/C then a 3200 sq ft 2 story. But your rule of thumb would over size the 2 story.
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  12. #25
    Join Date
    Aug 2005
    Location
    San Diego,CA
    Posts
    285
    Sounds Great im gonna sit back and listen.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

  13. #26
    Join Date
    Aug 2005
    Location
    San Diego,CA
    Posts
    285
    3400 sq ft house.. Lots of windows, and im sure there is more heat loads that we can type in. So 12,000 btu's = 1100 sqft? something does not sound right. correct meif i wrong.
    Sink or Swim!
    A Man has to know his limitations..
    To be old and wise, one must be young and dumb..

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