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  1. #1
    Join Date
    Jan 2008
    Posts
    7

    Confused Intallation of A/C in existing 2 story home

    I have a 2 story colonial 4 bedroom home(heated with baseboard, hot water), each floor approx. 900 sq. ft. There is 200 AMP service to the home. Contractors (Carrier and Trane) have looked to give me an estimate and an explanation as to how the ductwork would be placed for each floor and the size of the unit required. Contractors took the measurements of all the rooms in the house and came up with a 3 ton unit.

    Everything said to me was all new and I just listened and tried to absorb as much as I could. Now I have had some time to think, read this forum , and search the internet, I have questions. I want to be as much informed as I can before going back to the contractors to ask more questions.

    The second floor is straight forward - insulated round ductwork into rectangular registers into the ceiling of each bedroom. The return would be placed in the second floor hallway for the entire house.

    QUESTIONS: Are returns required for each of the bedrooms ?

    Is one large return sufficient in the hall ceiling for the entire house ?

    Would the thermostat be placed in a bedroom rather than the hallway ?

    One contractor wants to hang the unit from the rafters, others on the attic floor. Is one way better than another ?


    The first floor ducts (three) would come down through closets and one boxed in the corner of a bedroom because of the configuration of the three rooms on the first floor. ( We would be responsible to boxing in the exposed ductwork.)


    QUESTIONS: Is one duct about 8" in the center of a room 11ft x 21ft sufficient for cooling as proposed by all the contractors ?

    Should registers be placed near the outside walls where possible ?

    Would there be a problem if one room on the first floor didn't have a duct but had one in a hallway directed into the room ?

    GENERAL QUESTIONS:

    I believe I have selected two good brand names. Any comments regarding the brands I've selected ?

    One contractor wants to put the compressor on the south side of the house- is this proper since another stated the east which is shaded with trees ?

    Two contractors wants to use Aprilaire thermostats rather than the same brand as the air conditioner/handler unit they want to install. Why ? Are they cheaper or better than the branded A/C unit they are to install ?

    I understand I am asking a lot of questions and you don't have a plan of the home. I really appreciate the time and effort for all those who respond. Thank you.


    P.S.

    Thanks to all who responded to my boiler questions - Munchkin 140MR-2 and SS45 installed 2 weeks ago.

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,272
    Quote Originally Posted by Cenzo View Post
    ... 2 story colonial 4 bedroom home(heated with baseboard, hot water), each floor approx. 900 sq. ft.

    Contractors took the measurements of all the rooms in the house and came up with a 3 ton unit.

    I understand I am asking a lot of questions and you don't have a plan of the home. I really appreciate the time and effort for all those who respond.

    P.S. Thanks to all who responded to my boiler questions - Munchkin 140MR-2 and SS45 installed 2 weeks ago.
    SANYO, Mitsubishi Mr. Slim or other mfg small multi mini-split heat pump for each floor.

    http://www.sanyohvac.com/productList.php?cat1=2&cat2=11

    Springfield MA
    Heating Degree Days 6,300
    Cooling Degree Days 700

    It seems like You barely need any A/C

    http://www.wunderground.com/history/...q_statename=NA
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #3
    Join Date
    Jun 2006
    Location
    Southeastern Connecticut
    Posts
    841
    QUESTIONS: Are returns required for each of the bedrooms ?
    No, but you may want them in each bedroom if you keep the doors closed.
    Is one large return sufficient in the hall ceiling for the entire house ?
    If properly sized yes and the second floor cannot be closed off from the first, but drawing air from different areas of the house is better. Would the thermostat be placed in a bedroom rather than the hallway ? The thermostat should be placed near the return to get the best average temperture.
    One contractor wants to hang the unit from the rafters, others on the attic floor. Is one way better than another ? In my opinion no. The units do not vibrate very much so either way will work.

    The first floor ducts (three) would come down through closets and one boxed in the corner of a bedroom because of the configuration of the three rooms on the first floor. ( We would be responsible to boxing in the exposed ductwork.)


    QUESTIONS: Is one duct about 8" in the center of a room 11ft x 21ft sufficient for cooling as proposed by all the contractors ? Only the contractor doing a load estimate can tell you whether it is large enough.
    Should registers be placed near the outside walls where possible ? If possible but it is not necessary.
    Would there be a problem if one room on the first floor didn't have a duct but had one in a hallway directed into the room ? That should work. When running ducts from one floor to another in an existing structure you have to place ducts where you can get them. Sometimes that might not be the best location.
    GENERAL QUESTIONS:

    I believe I have selected two good brand names. Any comments regarding the brands I've selected ? The brand is not as important as the contractor installing it. All brands today have comparable models and warranties.
    One contractor wants to put the compressor on the south side of the house- is this proper since another stated the east which is shaded with trees ? I would install the unit where it provided the shortest run of refrigerant piping and ease of installation. If all things being equal then yes install it in the shade.
    Two contractors wants to use Aprilaire thermostats rather than the same brand as the air conditioner/handler unit they want to install. Why ? Are they cheaper or better than the branded A/C unit they are to install ? Most manafactures do not make their own thermostats. They just put their names on them. Does this system have 2 zones? If so, They maybe installing the Aprilaire zoning system which would explain the Aprilaire t-stats.
    I understand I am asking a lot of questions and you don't have a plan of the home. I really appreciate the time and effort for all those who respond. Thank you.

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,272
    Quote Originally Posted by Cenzo View Post
    I have a 2 story colonial 4 bedroom home(heated with baseboard, hot water), each floor approx. 900 sq. ft. There is 200 AMP service to the home.

    QUESTIONS: Are returns required for each of the bedrooms ?

    Is one large return sufficient in the hall ceiling for the entire house ?

    Would the thermostat be placed in a bedroom rather than the hallway ?

    QUESTIONS: Is one duct about 8" in the center of a room 11 ft x 21 ft sufficient for cooling as proposed by all the contractors ?
    Yes, in FL it is mandated by state building code.

    It might be, but it is certainly not recommended in general.

    NO

    An 8" diameter hard duct is suffiicient with an 6" x 12" or 8" x 10" diffuser for most 200 square foot rooms.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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