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  1. #1

    Feedback for new construction HVAC proposal

    Building new home in SE Michigan. Approximately 4,200 sq feet 2 story house with 2,100 sq ft unfinished basement

    Builder and HVAC subcontractor proposing following based upon Manual J results. Would appreciate feedback, suggestions concerning HVAC equipment being proposed as just received proposal and equipment list.

    Manual J information provided by builder
    Zone 1 - 1st floor and basement
    Total heat loss = 73,278 BTU
    Total heat gain = 34,705 BTU

    Zone 2 - 2nd floor
    Total heat loss = 59,754 BTU
    Total heat gain = 32,475 BTU

    Zone 1 & 2 specification
    Input heating = 80,000 BTUH
    Output heating = 78,000 BTUH
    Blower motor HP = 3/4
    Coil & condenser 3.5 ton capacity 42 MBH
    Air volume = 1,400 CFM

    HVAC equipment for both Zone 1 & 2 being proposed by builder and HVAC subcontractor
    Furnace - Luxaire LP9C080C16MP12C
    AC - Luxaire TCJF42S41S3 14.5 SEER
    UV light - Field Controls UV-16/120
    Air filter - Generalaire MAC2000
    Humidifier - Generalaire 900A
    Thermostat - Honeywell Focus Pro TH6320WF1005/U

    Questions for Pro's

    - Any concerns or feedback that I should further inquire to builder, HVAC subcontractor? I did not receive actual Manual J documents but was told HVAC engineer was consulted and that the specifications are the outputs from the Manual J. Did not inquire as to Manual D which I've been reading about now as to duct work.

    - For the Luxaire AC, should I be asking for Acclimate series AL6B 16 SEER rather than LX series TCJF 14.5 SEER? Understand additional cost with increased SEER rating, my concern is whether there are greater mechanical improvements, features with AL6B, e.g compressor, fan design, etc.

    - For UV light, I would've assumed Luxaire part being proposed rather than Field Controls. Should I have any concerns about this? Also should I ask for 2 UV lights per furnace to be installed or ask for different Field Control model? I see on the Field Control web page different UV light models being offered and not clear what the differences are.

    - Thermostat wise should I be asking for Honeywell Prestige or Vision Pro thermostat instead of Focus Pro model being proposed? Or are the Prestige, Vision Pro thermostats not quite comaptible or fully functioning with the Luxaire, Generalaire equipment being proposed? I understand from reading online that Luxaire Acclimate furnace modulates itself rather than being driven by thermostat. Hence should I ask for Luxaire Acclimate thermostat instead?

    Appreciate help and thanks in advance.

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
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    Quote Originally Posted by pds22 View Post
    Building new home in SE Michigan. Approximately 4,200 sq feet 2 story house with 2,100 sq ft unfinished basement

    Builder and HVAC subcontractor proposing following based upon Manual J results.

    Would appreciate feedback, suggestions concerning HVAC equipment being proposed as just received proposal and equipment list.

    Manual J information provided by builder
    Zone 1 - 1st floor and basement
    Total heat loss = 73,278 BTU
    Total heat gain = 34,705 BTU

    Zone 2 - 2nd floor
    Total heat loss = 59,754 BTU
    Total heat gain = 32,475 BTU

    Zone 1 & 2 specification
    Input heating = 80,000 BTUH
    Output heating = 78,000 BTUH
    Blower motor HP = 3/4
    Coil & condenser 3.5 ton capacity 42 MBH
    Air volume = 1,400 CFM

    HVAC equipment for both Zone 1 & 2 being proposed by builder and HVAC subcontractor

    Appreciate help ................ in advance.
    I would start over on the house design and Manual J.
    __________ _____
    The
    thermal envelop
    needs to be fixed if the Manual J is accurate.
    The HVAC engineer needs to be fixed, if the Manual J is inaccurate.

    I would target < 40,000 BTU heat loss for 2,100 square feet at design temperature of 5'F.

    1,400 CFM is ABSURDLY LOW for a total of 6,300 square feet.

    How does one provide only _ 78,000 BTU/HR when the total heat loss is 133,032 BTU/HR?
    ________________________ 42,000 BTU/HR when the total heat gain is 67,180 BTU/HR?
    What The Hell is actually going on here .xvtrwxx,dddfzxcvbnmas qwerty ??????
    I am not aware that use of zoning " saves 41%" of the heat loss.

    Did you agree to a 44'F indoor temperature when it is 5'F outside?

    Zone 1 - 1st floor and basement
    Zone 1 heat loss = 73,278 BTU
    Zone 2 ________ = 59,754
    Total Heat Loss _ = 133,032

    Zone 1 heat gain = 34,705 BTU
    Zone 2 - 2nd floor = 32,475
    Total heat gain __= 67,180 BTU
    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
    Jul 2006
    Posts
    1,091
    one system for each zone?

  4. #4
    Yes sorry for not clarifying and confusion.

    It is separate furnace, AC, etc. per zone. The proposal is for 2 of the same units. Both to be located in the basement. Basement is mostly below ground, has walk out french doors in rear. Basement to be controlled via dampers rather than separate electronically controlled zone.

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    That's REALLY high heat loss and gain for new construction in that climate. SOmethings not right. A moderateliy tight home that size with a finished basement (almost no heat gain and minimal heat loss) insulated to code should be more like 80k total heating for both zones and 4-5 tons of cooling. Not 7 and almost 150k BTU's. If you actually needed 150k BTU's you would expect to see a nearly $600 gas bill in Jan and Feb. I doubt you'll be over $300.

    Also, Your design temps should be between 88-90F, so manual S sizing should put the equipment at 3 Tons, not 3.5. Oversizing in a northern climate will cause a lot of humidy problems.


    I'm really having trouble understanding how far off contractors and builders can be. At my home this morning it was 38F and I was holding temperature downstairs with about 18k BTU's. 7-10mph wind, Only a couple CFL lights on, too early for solar gain, and only major appliance was a coffee maker. Its' 1700sqft, unfinished basement with attached garage and it's above average 1925 construction. I hate to keep using my house as a benchmark, but I think it's a good benchmark. I have dual fuel system with a 60k modulating furnace and 2 ton 2 stage heat pump. Upstairs is 2 ton AC and 60k 2 stage furnace... furnace is oversized for upstair ut it's the smallest furance in that model. The upstairs system held 74F indoors up to 98F last summer and only fell behind to 76F for a couple hours when it got above 100F for a few days. SE Iowa gets a lot hotter than Michigan.... it's also gets colder too.

    I don't get it. Either maunal J is too complicated for some, they are fudging numbers, or they build homes like junk now. Maybe a combination of the above. The expectation should be for small bills with new construction and comfortable homes and that means smaller equipment.

  6. #6
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    IF they are both in the basement, I would go with a single system and zoning, you'll have better results and for the same cost can install premium equipent to match what I can only assume is a luxury home based on it's size. Thsi includes a modulating furnace and 2 stage AC unit. I personally recommend Carrier Infinity systm and zoning.

    Unless there's something strange about your home cosntruction, if it's well insulated and well sealed, a 100k furnace and 5 ton AC should be PLENTY. A well built home wihth modern techniques should be closer to 80k and 4 tons. A superior spray foam home would be 60k and 3 tons.

  7. #7
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
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    2,032
    I'm not licensed in MI, but in WI if I were to submit a set of plans with that large of a heat loss per square foot I'd get them back so fast the stamps would be ripped off the envelope. I'd suspect a thought process of "bigger is better and GUARANTEED no complaints of the house not heating or cooling........ EVER!".

    I never use the load calcs from a builder when doing a new home. As the HVAC contractor of record and on the building permit it's my ultimate responsibility to ensure code compliance. And besides, once the bill is paid and the keys are turned over........ if you have a complaint the builder points the finger at me and it's my "warranty" that requires things to be fixed for free!
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  8. #8
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    Quote Originally Posted by firecontrol View Post
    I'd suspect a thought process of "bigger is better and GUARANTEED no complaints of the house not heating or cooling........ EVER!".
    !

    +1

    The should guranteed it will be comfortable. That means a mximum of 1 F max temp difference between rooms and RH 50-55%. Oversized equipment won't do that. However, more homeowners are used ot oversized equipment so that's their expectation. The expect to hit the temperature button and the place heats up and cools on 1F in 10-15 minutes even when it's 90F in summer or 10F in winter. I think sometimes peopel think they want an oversized sytem for the same reason they want an oversized engine in their car. I bet 90% of cars rarely even exceed 50% of their engines peak HP output for more than a total of 60 seconds a month. That means we're putting engines in cars that are 2X larger than nessesary because of driving habits, not good engineering and design.

    Trouble is, with cars, an oversized engine just uses more gas and costs more money and only has a relatively small impact on handling and braking. Its' doesn't make the car less comfortable.

  9. #9
    Appreciate much the replies. Much to think about now. Is there a service for which does Manual J calcs that I can send my plans, insulation information to?

  10. #10
    Join Date
    Jan 2009
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    A engineer firm can do them. Even better a building science professional, or if you have the flexibility with your general contractor, select your HVAC installer yourself and have them do to along with ductwork design.

  11. #11
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    Quote Originally Posted by motoguy128 View Post
    +1

    The should guranteed it will be comfortable. That means a mximum of 1 F max temp difference between rooms and RH 50-55%.
    3 F temp difference?

  12. #12
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    Quote Originally Posted by motoguy128 View Post

    Also, Your design temps should be between 88-90F, so manual S sizing should put the equipment at 3 Tons, not 3.5. Oversizing in a northern climate will cause a lot of humidy problems.

    I'm really having trouble understanding how far off contractors and builders can be.

    SE Iowa gets a lot hotter than Michigan.... it's also gets colder too.

    I don't get it.

    Either maunal J is too complicated for some, they are fudging numbers, or they build homes like junk now.
    Maybe a combination of the above. The expectation should be for small bills with new construction and comfortable homes and that means smaller equipment.
    THE DESIGN OR LOAD CALCS ARE ABSOLUTELY ABSURD.

    Where in SE Michigan? I am from Ann Arbor.
    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

  13. #13
    Join Date
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    Quote Originally Posted by pds22 View Post
    Appreciate much the replies. Much to think about now. Is there a service for which does Manual J calcs that I can send my plans, insulation information to?
    See my profile for e-mail address to send PDFs.


    ------------ WINDOW SPECS ---------- GUARANTEED MAX INFILTRATION ------------
    +++++++++++++++++++++++ TWO MOST IMPORTANT FACTORS -------------
    ///////////////// \\\\\\\\\\\\\\
    < 40,000 BTU/HR FOR 2,100 SQ. FEET
    _________ -----------
    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
    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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