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  1. #1

    Receiving recommendation of 5 ton furnace for 1600 sq ft

    My contractor and I went to a local HVAC supply company. I overheard the owner on the phone telling his supplier that he is almost out of furnaces and needs to be resuppied asap. He then discussed the split system for my home with me, which will be a new system build. The home is 1600 sq ft in Pasadena CA (46 to 95 degrees avg). He recommended a 5 ton Bryant 359AAV060100 95% 100k (manufacturer page say this model is 120k) BTU single stage, gas furnace. The condenser is suggested to be a 4 ton Heil 16 SEER. He did say that this furnace will be a match for the condenser.

    The home is well insulated and single story with good attic space. I need some confirmation (or not) that this system will not cycle too much. I worry that since he is short on product, he wants to sell what he has now. There will be 8 vents and one return throughout the house.

    Jeff

  2. #2
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,537
    Some words of advice, get a load cal. Done. As a 4 ton system sounds way to big for your home!!! What size do hvac system do you have now?

    I would be curious to see what he used to size your home for (4) ton system. While I am in Louisiana and roughly we have the same design temps but unless your home is all singe pane glass, I would say you will end up with a oversized system If you go with the (4) ton system!!!

    Ask to see a load cal. If he says he didn't perform one for any reason walk away. You stated you have 8 supply's and 1 return? If so then more then lickly your duct system will not supply or return (4) tons of air flow!

    You are here asking the question because you must have some connerns about the size and you should. Make sure a load cal is done and a proper sized system is installed. Even with rule of thumb (my thumbs are big) it is still oversized!!! You need some cold hard facts why your home needs a (4) ton system...

  3. #3
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,429
    Quote Originally Posted by agogodaddyo View Post
    My contractor and I went to a local HVAC supply company. I overheard the owner on the phone telling his supplier that he is almost out of furnaces and needs to be resuppied asap. He then discussed the split system for my home with me, which will be a new system build. The home is 1600 sq ft in Pasadena CA (46 to 95 degrees avg). He recommended a 5 ton Bryant 359AAV060100 95% 100k (manufacturer page say this model is 120k) BTU single stage, gas furnace. The condenser is suggested to be a 4 ton Heil 16 SEER. He did say that this furnace will be a match for the condenser.

    The home is well insulated and single story with good attic space. I need some confirmation (or not) that this system will not cycle too much.
    Jeff
    Furnace is about THREE times too big, condenser nearly 2 times.
    Talking about someone who doesn't have a clue.
    You did mean 1,600 sq feet, not 3,600 sq feet, didn't you?

    IN OTHER WORDS, START OVER.
    Actually, I mean, START. You must ignore that first attempt at getting started.

    You need a return in each bedroom and a general area return.
    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

  4. #4
    Thx for the reply duckman. There is no system in the house at present. There was a gravity feed furnace in the tiny 8x8 basement, but that is coming out. I want a split with the A/C unit in a 2/12 pitch valley section of the roof (back center of house), and furnace & coi,l horizontal in attic. From my discussions with neighbors, it seems those with similar size and construction have 3.5 to 4 ton systems. Insullation, including windows is good. Would you also please comment on the furnace size. I do appreciate your comments on the 4 ton, but what concerns me even more is that the supplier would recommend a 5 ton 100k furnace.

    Jeff

  5. #5
    1600 sq ft single story. Hmm, seems like I was right then.

    Jeff

  6. #6
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,429
    Quote Originally Posted by agogodaddyo View Post
    1600 sq ft single story. Hmm, seems like I was right then.

    Jeff
    One could easily perform an abridged ACCA Manual J calculation given the Pasadena region design temperatures, house layout, wall & ceiling R-values, and window characteristics.
    This basis will be used to develop equipment selection and a DETAILED duct layout.

    It's a Design Process - Find It - Adhere to It.
    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

  7. #7
    Join Date
    Aug 2010
    Location
    West Monroe, LA
    Posts
    1,537
    Quote Originally Posted by agogodaddyo View Post
    Thx for the reply duckman. There is no system in the house at present. There was a gravity feed furnace in the tiny 8x8 basement, but that is coming out. I want a split with the A/C unit in a 2/12 pitch valley section of the roof (back center of house), and furnace & coi,l horizontal in attic. From my discussions with neighbors, it seems those with similar size and construction have 3.5 to 4 ton systems. Insullation, including windows is good. Would you also please comment on the furnace size. I do appreciate your comments on the 4 ton, but what concerns me even more is that the supplier would recommend a 5 ton 100k furnace.

    Jeff
    While where do I start? 100btu furnace if 80% single stage will be right around 80,000 btu talk about big! If your design temp is 46 or for that matter 30 degrees you will see the furnace short cycle during heat and cooling.

    Without a load cal. We would all be guessing as I belive your current contractor is. I am just going by expersinse with a home your size both heating and cooling sound to be oversized. Again you need a load cal. Done for a proper sized heating and cooling system. Such things as windows (type and how many panes), insulation in the walls and ceiling etc... Play a big roll in the sizing of hvac system.

    You can ask the question 100 different ways but I would still say you need a load cal ran to determine the size of the equipment (manual j) and a duct cal ran using (manual d). If your installer/contractor is not welling to do one or can't simple walk away.

    You can have let's say (5) homes that are all 1600 square foot that might require different sized equipment due the above listed things. There is no one size fits all for hvac equipment. Example my home is a little over 1700 square foot and I heat and cool it with (2.5) ton heat pump with no problems.

  8. #8
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
    Posts
    3,522
    your house sounds similar to mine.
    the old gravity ducts are huge, and they are poorly located for HVAC forced air.
    I'd have a floor guy fill them in, and get proper ductwork quoted. likely all the ducts are asbestos sealed though...
    1600 sqft single story house needs 2 returns minimum. for your design temps, I'd bet 2.5 ton would work well, and a 60Kbtuh 90% furnace.
    it all depends on your home's size, location, solar gain, insulation, ductwork layout, ductwork location, and how leaky the building is. without all this information, any size is simply a guess.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  9. #9
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,326
    5 tons on 1600 sq ft
    it will work like this...in winter you'll get hot hot hot air
    for short time, then cool til next blast of hot air
    summer you'll have short cycles of a/c. no removal of RH
    so sticky cool.

    all houses are different, even same floor plan, built by same builder.

    the sizing he is using is 320 sq ft per ton. he is selling more than you need
    or require.

    with a well sealed duct/return system in moderately tight house
    will easily get double that sq ft per ton.

    here in the hot humid south we see a lot of 400 sq ft per ton.
    short cycling, high RH..high utility, short life of unit.
    no comfort.

    stay away from rule of thumb sizing, it is the wrong way to size
    hvac. load calcs are there to figure out exactly what your specific home
    requires.

    call another contractor. I'd think 2- 2.5 tons would do you fine.

    make sure that all ducts, plenums & returns are mastic sealed.
    not duct tape, or foil tape. mastic & mastic tape.

    I think in Ca. they do duct testing to verify duct leakage.
    this is a VERY good thing. your total duct loss should be in 5-10%
    range as per requirements in your state.
    (wish that duct testing was code here!)

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  10. #10
    Join Date
    Jun 2006
    Location
    Richmond, VA
    Posts
    2,990
    Do you really have a pro installer????....and I mean professional that would size the unit properly and design the duct properly and look at the thermal envelope properly....or you got some bubba to take you to the distributor to pay for the wrong equipment cause he can't come up with the cash?

  11. #11
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,505
    40K or whatever the smallest furnace you can buy for the brand your installer carries. If your house really needs more than 40k to keep warm with 46F outdoor temps, some SERIOUS insulating needs to be done. If your house needs more than 3 tons of cooling, serious insulating needs to be done. My own house has a TWO ton unit for 1600ft and keeps 75 inside on 100 degree days.

  12. #12
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,855
    You will never be happy with a system the size you listed. Pay someone to do the Manual J and D before you agree to anything. As for calling a furnace a 5 ton or whatever ton, it only refers to the furnaces max blower capacity. In your location, heating is almost an after thought and you are likely to find lower btu rated furnaces with larger cfm rated blowers for the AC side of the system. I am in northeast Ohio, my house is a 1400sf two story century home with updated windows and average insulation. I have a 60k 95% furnace and 2.5 ton AC and they are both slightly over sized even at max design temps. Summer temps were unusual this year mid 90s for an extended period with 65%+ humidity and it still cycled on and off at mid day.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  13. #13
    Join Date
    Jan 2012
    Location
    Sanata Ana, CA
    Posts
    29
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Additional infractions may result in loss of posting privileges.
    Last edited by jpsmith1cm; 12-19-2012 at 08:11 PM. Reason: non AOP member

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