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  1. #1
    Join Date
    Feb 2013
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    15

    Smile Got load calcs, now which equipment

    Hello all. I am getting ready to have a complete heat pump installation done on a 1978 home that had electric baseboard heat and window A/C units. I have had load calcs done by two different companies. They came up with the following:

    Contractor 1: Equipment total load: 27,130 Btuh, required capacity of 2.6 tons, sized a 3 ton unit
    Contractor 2: Equipment total load: 21,178 Btuh, required capacity of 2.2 tons, sized a 2.5 ton unit

    Should I be concerned with the load calc differences? Is 2.6 tons close enough to go with a 2.5 ton unit? I was impressed with both contractors, but Contractor 1 has definitely provided the most information and is the most responsive to my questions. He gave four equipment options. I have narrowed it down to two. Is one better than the other and why? Thanks in advance for your responses!

    Option 1: Carrier Comfort Series 25HCC536 Heat pump condenser with a FX4 air handler. 15 SEER. One year labor, ten years parts warranties. ($ more expensive than option 2)

    Option 2: Amana ASZ140361A Heat pump condenser with an AEPF variable speed air handler. 15 SEER. One year labor, ten year parts, and lifetime compressor warranties.


    Pricing isn't allowed
    Last edited by jpsmith1cm; 02-25-2013 at 09:01 PM.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    34,184
    Depends upon the 2 ton or 2.5 ton unit. Really, 27K is 2 1/4 ton not 2.6 tons. So you'd think a 2.5 ton unit would do it but many units these days are shy on capacity so that unit could really be putting out 27K. That's cutting it close. I guess depends upon what the load really is since you have 2 figures. If it is really closer to the 21K figure #2 got, putting a 3 ton on it would be way oversized.

    If I got 27K I'd probably call for a 3 and if I got 21K I'd probably call for a 2.5 ton. So I don't disagree with the bids but wonder which is most accurate?

  3. #3
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    27kbtu=2.25 ton
    21kbtu=1.75 ton
    depending upon which air handler is matched with heat pump will dictate the btu output

    can't speak specifically to either, not my game.

    somebody check my math..........12kbtu=1ton
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  4. #4
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,967
    If you are using electric heat as backup heat, why not go with a 2 speed heat pump? This way you can size the first stage to handle the cooling, and the 2nd stage to better handle the heating.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  5. #5
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    5,520
    I'd be curious what number each used on their load calulation. I'd lean towards the lower one... and that the 2nd padded their numbers and used the wrong design temperatures or didn't factor in shading or used the wrong insulation values.


    A 3 tons 2 stage might be the best option. Its' about 2.2 Tons on 1st stage...a little lower when dehumidifying. Look at Amana's 16 SEER 2 stage unit. IT should be a fairly small increase given you total istalled price. It has really good heating effciencies too. Much higher AHRI numbers than the Carrier. I think it hits 9.5 HSPF in most matches.

  6. #6
    Join Date
    Mar 2006
    Location
    The South
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    2,197
    If going single stage HP, I would go no higher than a 2 1/2 ton HP that has an AHRi rating of full cooling BTUs in that size.

    12 KBTU=1 ton
    2 1/2 ton cooling=30 KBTUs

    IMO

  7. #7
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,989
    Quote Originally Posted by kmax1000 View Post
    Hello all. I am getting ready to have a complete heat pump installation done on a 1978 home that had electric baseboard heat and window A/C units. I have had load calcs done by two different companies. They came up with the following:

    Contractor 1: Equipment total load: 27,130 Btuh, required capacity of 2.6 tons, sized a 3 ton unit
    Contractor 2: Equipment total load: 21,178 Btuh, required capacity of 2.2 tons, sized a 2.5 ton unit

    Should I be concerned with the load calc differences? Is 2.6 tons close enough to go with a 2.5 ton unit? I was impressed with both contractors, but Contractor 1 has definitely provided the most information and is the most responsive to my questions.(..cut edited...)
    Why not try to make the home itself more energy efficient & then see what the cals show - using more reliable data?

    They are guessing at air infiltration & how efficient the duct system & airflow is.

    What counts is the quality of the installation along with addressing all the factors that determine whether the unit size will meet your comfort demands.

    Normally, the smaller unit will work more efficiently with the blower & duct system, which helps improve efficiency & reduce utility bills.
    Also, bigger does not necessarily improve comfort...other factors contribute much more to comfort levels.

  8. #8
    Join Date
    Feb 2013
    Posts
    15
    Thanks for all of the input so far!

    I was planning on taking the electric baseboard heaters out (maybe relocate 2 or 3 to the garage).

    I am planning on upgrading attic insulation. Currently it is no more than 6 inches deep of original and settled loose fill. I plan on blowing in another 3" (spray foam if I can find the cash) in the attic. The interesting thing is that I think the 2.6 ton guy figured that extra insulation in and I forgot to tell the 2.2 ton guy that.

    Let me know if there is any information from the load calc reports that would help with my question.

    Also, isn't the jump from 15 SEER single stage to 16 SEER 2-stage pretty significant? I know that the 13 SEER to 15 SEER jump will be easily recouped pretty quickly, but most of the prices for 16 SEER have been out of my budget range.

    Thanks again!

  9. #9
    Join Date
    Sep 2009
    Location
    Arnold mo
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    3,967
    Perform air sealing before adding insulation. Best to get a company that will perform a blower door test first, and then air seal with spot blower door testing to measure how effective the air sealing is.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  10. #10
    Join Date
    Feb 2013
    Posts
    15
    Quote Originally Posted by tipsrfine View Post
    Perform air sealing before adding insulation. Best to get a company that will perform a blower door test first, and then air seal with spot blower door testing to measure how effective the air sealing is.
    Thanks, I forgot to mention that I was going to do a blower door test after heat pump installation and before adding insulation. Thanks!

    Speaking of insulation, this is a retrofit obviously and I have a finished basement ceiling so the least invasive install is obviously attic ducting. Am I going to be paying out the wazoo for thermal loss with the attic ducts? Would spray foam insulation help with making the attic ducts less painful to my wallet or is there another recommendation?

    Thanks again!

  11. #11
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,967
    You can just spray foam the ductwork in the attic; not cheap, but cheaper than doing the whole roof.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  12. #12
    Join Date
    Feb 2013
    Posts
    15
    Quote Originally Posted by motoguy128 View Post
    I'd be curious what number each used on their load calulation. I'd lean towards the lower one... and that the 2nd padded their numbers and used the wrong design temperatures or didn't factor in shading or used the wrong insulation values.


    A 3 tons 2 stage might be the best option. Its' about 2.2 Tons on 1st stage...a little lower when dehumidifying. Look at Amana's 16 SEER 2 stage unit. IT should be a fairly small increase given you total istalled price. It has really good heating effciencies too. Much higher AHRI numbers than the Carrier. I think it hits 9.5 HSPF in most matches.
    Thanks! The increase to go to the 2-stage 16 SEER was quoted at about $.
    Last edited by jpsmith1cm; 02-26-2013 at 07:00 AM. Reason: pricing

  13. #13
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
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