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  1. #14
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    Quote Originally Posted by msglsmo View Post
    So here is the response from my HVAC contractor:

    "Concern #1 is you feel that your system is too large, so it will not dehumidify correctly. When we, or anyone for that matter sizes the cooling for a home, we always round up to the nearest 1/2 ton size. This is standard practice, and meets certifed energy star guidlines. The 3.4 ton size is the bare minimum size, and whenever the outside temperature exceeds 93 degrees, your home would lose ground and struggle to keep up. A 3.5 ton system is actually rated at 3.3 tons, and the 4 ton is rated at 3.8 tons. The energy star guidlines on your home would size your hvac between 43,000 and 49,000 BTUs for cooling. Your ac unit now specs out at 46 to 47,000 btus of cooling, and that is when it is running in a brand new, clean status."

    Thoughts?

    Mike
    Enery Star Guidelines.....Select the smallest unit possible taking 50% excess latent and applying towards sensible...Energy Star allows 5% under and 15% over capacity on single stage equipment .....You DO NOT round up 1/2 ton unless ( for example) you were using 2 stage equipment and it does not come in 1/2 ton increments ...and the previous increment would not meet the load....This IS NOT. The case in your situation.....Since they are Citing Energy Star...Google ACCA 5 that is Energy Star and it is very well documented....roumg up is not acceptable...

  2. #15
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    Measure the on/off cycle in mins, and record the temp/%RH return and supply. The rest is just commentary and constructive at this point unless you are just looking for a fight with your contractor.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #16
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    Thread Starter
    Quote Originally Posted by lkapigian View Post
    Enery Star Guidelines.....Select the smallest unit possible taking 50% excess latent and applying towards sensible...Energy Star allows 5% under and 15% over capacity on single stage equipment .....You DO NOT round up 1/2 ton unless ( for example) you were using 2 stage equipment and it does not come in 1/2 ton increments ...and the previous increment would not meet the load....This IS NOT. The case in your situation.....Since they are Citing Energy Star...Google ACCA 5 that is Energy Star and it is very well documented....roumg up is not acceptable...
    As I read ACCA5 section 3.3.1, it appears rounding up is acceptable (which is unfortunate):

    "Total equipment capacity is between:
    - 95% and 115% of total cooling requirements (for air conditioners
    and heat pumps)
    or
    - 95% and 125% of total cooling requirements (for heat pumps with heating dominated requirements)
    or
    - the next largest nominal piece of equipment, per OEM increment, that is available for either to satisfy the latent and sensible requirements."

    I agree that it doesn't make sense to round up. I've always been told that slightly undersized it better than oversized.

  4. #17
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    Thread Starter
    On additional thought. Also on the load report, it lists my house as facing the South. However, my home faces West-Southwest, 231degrees on a compass. What impact does that on the report?

  5. #18
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    Quote Originally Posted by msglsmo View Post
    As I read ACCA5 section 3.3.1, it appears rounding up is acceptable (which is unfortunate):

    "Total equipment capacity is between:
    - 95% and 115% of total cooling requirements (for air conditioners
    and heat pumps)
    or
    - 95% and 125% of total cooling requirements (for heat pumps with heating dominated requirements)
    or
    - the next largest nominal piece of equipment, per OEM increment, that is available for either to satisfy the latent and sensible requirements."

    I agree that it doesn't make sense to round up. I've always been told that slightly undersized it better than oversized.
    Which would mean the largest allowed for your house is 3.5 tons, not four tons unless its a heat pump.

    However, if Manual S was used, you would find that 3 tons would probably been more then enough.
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  6. #19
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    Quote Originally Posted by Gunslinger View Post
    Why no duct loads????? What is the location of your ducts?
    I'm not sure about this, but hopefully this helps:

    My basement is finished, so all duct work is in finished/condition spaces of the home. We have one large air return vent on each level of the home - 2nd floor, main floor and basement. Vents are in the floor for all rooms, except one bedroom which has a wall mounted vent.

    Hope that helps.

    Mike

  7. #20
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    Quote Originally Posted by teddy bear View Post
    Measure the on/off cycle in mins, and record the temp/%RH return and supply. The rest is just commentary and constructive at this point unless you are just looking for a fight with your contractor.
    Regards Teddy Bear
    I'll measure the on/off cycles. I don't have the ability to measure the return and supply temp and humidity.

    I'm not looking for a fight; rather I'm looking for my builder and HVAC contractor to ensure my system was designed/engineered correctly. Your Bear Rules of <50% RH in the summer makes complete sense to me, but I'm sitting at upper 60's/low 70's RH. Something isn't right.

  8. #21
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    Thread Starter
    Quote Originally Posted by beenthere View Post

    PS: You can go as low as 320 CFM per ton with your high indoor humidity.
    That was a type by me. He adjusted it down to 350 (I typo'd 450).

  9. #22
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    Quote Originally Posted by msglsmo View Post
    I'll measure the on/off cycles. I don't have the ability to measure the return and supply temp and humidity.

    I'm not looking for a fight; rather I'm looking for my builder and HVAC contractor to ensure my system was designed/engineered correctly. Your Bear Rules of <50% RH in the summer makes complete sense to me, but I'm sitting at upper 60's/low 70's RH. Something isn't right.
    Get a temp/%RH meter for $10 at walmart.
    https://www.walmart.com/search/?query=temperature

    What if your t-stat is not correct?
    Difficult to comment on ???? info.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  10. #23
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    Quote Originally Posted by msglsmo View Post
    As I read ACCA5 section 3.3.1, it appears rounding up is acceptable (which is unfortunate):

    "Total equipment capacity is between:
    - 95% and 115% of total cooling requirements (for air conditioners
    and heat pumps)
    or
    - 95% and 125% of total cooling requirements (for heat pumps with heating dominated requirements)
    or
    - the next largest nominal piece of equipment, per OEM increment, that is available for either to satisfy the latent and sensible requirements."

    I agree that it doesn't make sense to round up. I've always been told that slightly undersized it better than oversized.
    Rounding up IS ONLY ACCEPTABLE IF you have taken 50% excess latent AND/OR the unit does not come im1/2 Increments..(This is confirmed by Manual S not J)...you are allowed 5% undersized and the "Smaller unit will not meet the load...Your unit comes in 1/2 Ton increments....

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  11. #24
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    Quick update. The installer has now refused to hand over any further paperwork (Manual S, for example), but has decided it might be worth a look to check out the condenser unit (valve bleed down test, humidity controller and humidifier) and air return (potential system is sucking in attic air).

  12. #25
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    Quote Originally Posted by msglsmo View Post
    Quick update. The installer has now refused to hand over any further paperwork (Manual S, for example), but has decided it might be worth a look to check out the condenser unit (valve bleed down test, humidity controller and humidifier) and air return (potential system is sucking in attic air).
    Include checking for a 30^F split on the coil temperature verses return temp.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  13. #26
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    Quote Originally Posted by msglsmo View Post
    Quick update. The installer has now refused to hand over any further paperwork (Manual S, for example), but has decided it might be worth a look to check out the condenser unit (valve bleed down test, humidity controller and humidifier) and air return (potential system is sucking in attic air).
    Probably cause it was never done.
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