New HVAC installation - advice - Page 2
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  1. #14
    Rodney28334 - The house is on a slab and the downstairs registers are in the ceiling.

    energy_rater_La - Can you please expand on your comment -- "beware of companies that want to put 3 tons system upstairs and 4 tons downstairs."

    Thanks again to all for the comments.

  2. #15
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,125
    sure crude dude.
    2217 sq ft downstairs, and 1159 sq ft upstairs
    some companies size by sq ft 400-500 sq ft per ton.
    downstairs would be 3.5 to 4 tons
    upstairs would be 2-3 tons.

    this oversizing will never let units run long enough to
    remove humidity. shortcycles increase utility costs
    shorten life of unit.

    if we don't remove RH inside the house..we sweat with a/c on
    in summer in our hot humid climate

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

  3. #16
    Here is my first reasonable proposal from a local contractor to install two systems. I liked the gentleman who visited the house and he seemed knowledgeable. Apparently he ran a load calculation at his office and came up with the following. Let me know what you guys think.

    ------------------------------------------------------------------------

    Proposal for installing a 4ton complete system for the downstairs, and a 2.5ton for the upstairs, work done consists of:

    Install a Trane 4 ton XL16i 16 SEER complete system with a variable speed gas furnace (downstairs system).
    Install a Trane 2.5 ton XB14 14 SEER complete system with a standard electric furnace (upstairs system).

    • Removal and disposal of all old equipment and materials.
    • Multi positional gas furnace or electric air handler for the upstairs.
    • Double wall vent pipe through roof.
    • Code approved gas line and shut off.
    • Sheet metal furnace stands under furnace on the horizontal installation.
    • R-8 sheet metal transition and plenum.
    • Start collars with dampers for air distribution.
    • Adding a Return air for the downstairs system (separate cost).
    • Access door in transition for coil and heat exchanger access.
    • Horizontal Slab Evaporator coil.
    • Overflow pan and float switch.
    • Attaching to existing ductwork.
    • Sealing all equipment and ductwork seams with mastic to prevent air leaks.
    • Outdoor condensing unit.
    • New refrigerant lines for the upstairs.
    • Gas line modifications if gas furnace for the upstairs.
    • 40 x 40 x 3 ultralight pad under unit.
    • Code approved electrical and disconnect.
    • New UV rated insulation on copper outside.
    • City permit.
    • Any duct or drain modifications needed.
    • Digital programmable thermostats.
    • System purge and evacuation of existing refrigerant lines.
    • Liquid line filter drier.
    • R410A refrigerant.

    Warranties for these systems include: 12 year compressor and 10 year parts, lifetime heat exchanger, 1 year labor, lifetime workmanship.

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,225
    Quote Originally Posted by crudedude View Post
    Here is my first reasonable proposal from a local contractor to install two systems. I liked the gentleman who visited the house and he seemed knowledgeable. Apparently he ran a load calculation at his office and came up with the following. Let me know what you guys think.

    ------------------------------------------------------------------------

    Proposal for installing a 4ton complete system for the downstairs, and a 2.5ton for the upstairs, work done consists of:

    Install a Trane 4 ton XL16i 16 SEER complete system with a variable speed gas furnace (downstairs system).
    Install a Trane 2.5 ton XB14 14 SEER complete system with a standard electric furnace (upstairs system).

    • Removal and disposal of all old equipment and materials.
    • Multi positional gas furnace or electric air handler for the upstairs.
    • Double wall vent pipe through roof.

    Warranties for these systems include: 12 year compressor and 10 year parts, lifetime heat exchanger, 1 year labor, lifetime workmanship.
    Ditch this one.

    NEXT .!
    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

  5. #18
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,136
    Yup, ditch it. They are obviously using the outdated 500st per ton rule. I'd throw out any quote showing the downstairs with a higher cooling load than upstairs, it doesn't work that way in the real world...

  6. #19
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,512
    Quote Originally Posted by 54regcab View Post
    Yup, ditch it. They are obviously using the outdated 500st per ton rule. I'd throw out any quote showing the downstairs with a higher cooling load than upstairs, it doesn't work that way in the real world...
    While I have no idea what the house is. Its probably pretty close in tonnage being built in 1962 with single pane windows. It might be a little big, but we don't know. He said the guy ran a load calculation. He has twice the square footage downstairs, so he's going to have more tonnage downstairs. Now the house currently has 5 tons, whether it works or not remains to be seen, and the guy is proposing 6.5 tons with 2 systems. Probably a good idea to get 1 or 2 more bids and opinions.
    I like DIY'ers. They pay better to fix.

  7. #20
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    I love how they are giving you " lifetime workmanship warranty" that there is a load of bs

  8. #21
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,250
    Before having more insulation blown in look into a home energy audit to see where you will most benefit for the money spent check out these sites www.comfortinstitute.org and www.bpi.org or google home energy audit or blower door testing for more info. Having the blown insulation sucked out and the roof deck spray foamed could be more bang for your buck bc not only will it better insulate but will seal the envelope so hot/cold air can't get into the home which in turn will reduce the size of the heat/ac needed and reduce upfront costs and operating costs. There are many other things the audit will uncover that the auditor will give you a priority based list of upgrades you can do from most bang for your buck to least and most increased comfort to least.

  9. #22
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,136
    Quote Originally Posted by bmathews View Post
    While I have no idea what the house is. Its probably pretty close in tonnage being built in 1962 with single pane windows. It might be a little big, but we don't know. He said the guy ran a load calculation. He has twice the square footage downstairs, so he's going to have more tonnage downstairs. Now the house currently has 5 tons, whether it works or not remains to be seen, and the guy is proposing 6.5 tons with 2 systems. Probably a good idea to get 1 or 2 more bids and opinions.
    The downstairs is mostly covered by the upstairs, therefore very low heat gain for the downstairs. Cold air floating down the stirs and no heat coming from the ceiling GREATLY reduces heat load. The load calculation could be a farce, fudge the inputs to get the result you want sort of thing. If it was a REAL heat load calculation the upstairs would require MUCH more cooling per sqft than downstairs. After all, isn't that the whole point of having 2 systems?

  10. #23
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,512
    Quote Originally Posted by 54regcab View Post
    The downstairs is mostly covered by the upstairs, therefore very low heat gain for the downstairs. Cold air floating down the stirs and no heat coming from the ceiling GREATLY reduces heat load. The load calculation could be a farce, fudge the inputs to get the result you want sort of thing. If it was a REAL heat load calculation the upstairs would require MUCH more cooling per sqft than downstairs. After all, isn't that the whole point of having 2 systems?
    Like I said I have no idea what is needed. Haven't seen nor will ever see the job. But the upstairs is half the downstairs by sq. ft. Which means half the downstairs isn't covered by the upstairs. If it were equal up and down or slightly bigger down, then yes, you would be correct. But the downstairs is twice the size of the upstairs per the OP. Minus fairly significant energy upgrades I will imagine depending on many factors in Houston. He will need a 3-4 tons downstairs and 1.5-2.5 tons upstairs from my experience being 3 hrs west of him.
    I like DIY'ers. They pay better to fix.

  11. #24
    Join Date
    Jan 2005
    Location
    Littleton, CO
    Posts
    263
    I would pay a contractor to come out and perform a Manuel J Load Calc on your house. Since you would be paying him you should receive a detailed report of the room load and the size recommendations of the heating and cooling. You can then see what the load is, and if the bidding contractors are performing a load calc or basing it off the old dated RULE.
    Become a friend or fan on Facebook

  12. #25
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,136
    Quote Originally Posted by bmathews View Post
    Like I said I have no idea what is needed. Haven't seen nor will ever see the job. But the upstairs is half the downstairs by sq. ft. Which means half the downstairs isn't covered by the upstairs. If it were equal up and down or slightly bigger down, then yes, you would be correct. But the downstairs is twice the size of the upstairs per the OP. Minus fairly significant energy upgrades I will imagine depending on many factors in Houston. He will need a 3-4 tons downstairs and 1.5-2.5 tons upstairs from my experience being 3 hrs west of him.
    So you don't change your 500 sq ft per ton rule based on upstairs or downstairs? I find it hard to belive the upstairs and down have roughly the dame heat gain per sq ft.

  13. #26
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,125
    post #15
    2217 sq ft downstairs, and 1159 sq ft upstairs
    some companies size by sq ft 400-500 sq ft per ton.
    downstairs would be 3.5 to 4 tons
    upstairs would be 2-3 tons.

    this oversizing will never let units run long enough to
    remove humidity. shortcycles increase utility costs
    shorten life of unit.

    if we don't remove RH inside the house..we sweat with a/c on
    in summer in our hot humid climate
    ________________________________________________
    sizing hvac contractor came back with:
    Proposal for installing a 4ton complete system for the downstairs, and a 2.5ton for the upstairs
    __________________________________________________ __________________________

    he/she may have run a load calc, but you can bet the entries were fudged to
    come up with these sized units.

    so have you decided to modify ductwork & add return?
    going from one unit to two adds cost to the install.

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

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