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  1. #1
    Join Date
    Sep 2012
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    Orlando, FL
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    AC Help in Florida - 5 DIfferent Recommendations

    Really need some expert advice. In the process of replacing 2 complete systems in our 2 story house. Total sq. ft is 3215, lower is 1814, upper is 1401. Current systems are 18 plus years old, Carrier 2 1/2 ton each. Both air handlers are located in a mechanical room on the 2nd floor and all duct work runs through our attics.

    Thought I was going about this the right way, read a lot on here. Had a company come out and perform an energy survey to include a Man J, blower door, duct testing, etc. Hers score of 114 with recommendations to seal ducts, add insulation and various other minor things. They also provided a couple of system recommendations. Also had 3 other companies come out and provide recommendations. All companies have excellent reputations and carry a variety of manufacturers. 3 Man J's came up with cooling load requirements of between 44,000 and 52,000.

    So here is the dilemma, each company come up with completely different recommendations. Company A: 2 1/2 ton up and down, B: 2 1/2 down 3 up, C: 2 down 2 1/2 up, D: 2 1/2 down 2 up. Company D also made a strong recommendation to do a single 5 ton zoned system using a Carrier 2 stage, variable speed unit.

    After all this I am even more confused as what to do.

    Thanks

  2. #2
    Join Date
    Oct 2010
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    Anderson, South Carolina, United States
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    The one that did a blower door test would have the actual infiltration rate of the house where others would be guessing on this rate, unless you shared it with the others, infiltration load has a significant effect on the outcome of a manual j calculation.

  3. #3
    Join Date
    Jun 2003
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    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by jtrammel View Post
    The one that did a blower door test would have the actual infiltration rate of the house where others would be guessing on this rate, unless you shared it with the others, infiltration load has a significant effect on the outcome of a manual j calculation.
    What was the real infiltration rate of the home? (Question for origiinal poster) This is a misleading number in that it is a measure of the leakage area in the home, not the variable real leakage rate the home has. The average air leakage is based on the assuming the air leaks are located equally on all surfaces. The estimate is at average winter temps and average wind. During calm winds and moderate outdoor temps, fresh air leakage is near zero. During high wind and the coldest temps, the air leakage could be double. Nothing wrong with blower doors but the info is limited when it comes to sizing and providing adequate fresh air to be healthy. Most of the summer infiltration loads are latent and when combined with the occupants latent load overwhelm the a/c's capacity during low cooling loads.
    Part of any evalution of the home should include a fresh air ventilation recommendation. This home owner is trying to get educated about updating the home as best as possible. There are no explanations about the needs for fresh air and supplemental dehumidification. Sign of the times.
    Regards TB
    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"

  4. #4
    Join Date
    Sep 2012
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    Orlando, FL
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    Quote Originally Posted by dan sw fl View Post
    You run into a MIRACLE THAT these recommendations and calculations are So Closely Aligned and yet you ascribe them to be "completely different".
    The recommendations are definitely within the science and art of equipment selections and what one should expect.
    One ought not to seek Five recommendations if one does not have a thought process to determine what will suit him most appropriately.
    With all due respect, in my profession I deal with Facts, if it calls for a number 2 widget, that's what it gets. I did not realize this was as much "Art" and some "Science". When all 4 of the companies came up with different recommendations, but alas with your help within acceptable limits, is when the confusion set in. Also I initially had 3 companies come out based on the equipment they carried, Trane, Lennox and Carrier. I didnt like the Lennox guy as he was a professional salesmen and not a tech. Then with the recommendation of many professionals on this list, I found a company in the area that would do a complete energy audit, for a fee of course, and hired them to do one. As part of their audit, they too made 2 recommendations.

    So in the end, what I have is 2 different recommendations, equipment aside. A unit for each floor, or one larger unit with zoning.

    Confused?
    IF the "equipment selection glass" is not half full, you are faced with hiring - a sixth unknown someone- to Tell you which recommendation to accept.
    So what your saying is with the recommendations being all equal and within acceptable limits, go with my equipment/contractor preference? What about the single unit zoned system from either Carrier or Amana?


    Quote Originally Posted by teddy bear View Post
    What was the real infiltration rate of the home? Part of any evalution of the home should include a fresh air ventilation recommendation. This home owner is trying to get educated about updating the home as best as possible. There are no explanations about the needs for fresh air and supplemental dehumidification. Sign of the times.
    Regards TB
    The infiltration numbers are somewhere in the attached reports. Would the "fresh air ventilation recommendation" come from all the contractors or just the guys doing the energy audit?

    Man J with Blower Door.pdf1st Man J.pdf

  5. #5
    Join Date
    Jul 2007
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    Delaware
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    Quote Originally Posted by scooterfj62 View Post
    I found a company in the area that would do a complete energy audit, for a fee of course, and hired them to do one. As part of their audit, they too made 2 recommendations.
    Oh.....
    Always here

  6. #6
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    Jun 2003
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    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by scooterfj62 View Post
    With all due respect, in my profession I deal with Facts, if it calls for a number 2 widget, that's what it gets. I did not realize this was as much "Art" and some "Science". W

    The infiltration numbers are somewhere in the attached reports. Would the "fresh air ventilation recommendation" come from all the contractors or just the guys doing the energy audit?

    Man J with Blower Door.pdf1st Man J.pdf
    Florida code, ASHRAE and others suggest .2 ach when occupied. The blower door test shows .25 ACh on with an average wind and average cold weather conditions. In calm wind and moderate summer weather expect much less infiltration. Most a/c contractors say nothing. They know that the fresh air disscusion complicates the bid. If you do not care, do not expect anyone to mention it.
    I brought it up because, I sell ventilation/humidity control equipment.
    A fresh air change in 4-5 hours purges indoor pollutants and renew oxygen. The problem is that most a/c can not maintain <50%RH when the outdoor dew points are +55^F and low/no cooling loads without a whole house dehumidifier.
    That is why it is not mentioned.How good do you want your home tobe?
    Regards TB
    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"

  7. #7
    Join Date
    Jul 2008
    Location
    Rochester NY
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    4,763
    Quote Originally Posted by scooterfj62 View Post
    2518cfm50. Wow! Tight house for it's age and size! Nice!

    And some room for improvement, so if you have future comfort issues, air sealing efforts could pay off in spades.

    4 ton Greenspeed.
    With zoning, you might go 3 ton. Too bad we can't see run history on your current equipment, could parse actual load to confirm.

    Awesome, someone is using Auditor! Did they true your actual annual consumption? I can't see it in the report and that is a nice triangulation point.

    Elite. Can't see infiltration (reconcile to your actual cfm50) in the Elite report other than it looks like a big slice of your load, so it may be dead on or grossly overestimated. Also, looks like you don't have the duct to handle the 5t recommended BTU. Not terribly familiar with Elite, but I have a client in Baltimore whose Elite report has proven out to have been quite oversized in it's recommendation. I think it recommended 4 ton, he put in 2, and has been very happy. And the East Coast had a very hot summer.

    A lot of people come here looking for confirmation of bad emotionally derived decisions they've already made. Often it's to justify not spending a small incremental cost that when amortized over the life of the equipment, and reduced by the incremental energy savings and dramatic increase in comfort and control often has a $0 net added cost. When it goes bad this ends up being money that they really wish they'd spent up front.

    Yes, I see they didn't spec Greenspeed. Whose mistake is that? Did you come here looking for advice from experts? You seem to be dismissing the advice of a number of folks. You are buying surgery and have some choices. Become a surgeon, or accept that what other surgeons are saying may have merit that is beyond your depth. I don't know what you do for a living, but I certainly wouldn't expect to be qualified to understand it after a week or two, do you think you somehow have what we do all figured out? There is a very complicated critical path here with a lot of potential failure points. If you are stepping into communicating zoning, with that duct, particularly with 4 ton, I think you'll want the Greenspeed.

    We do see the results of a lot of bad decisions on this BB, fear, oversize, and short sighted focus on up front cost account for most of that pie. We have NO skin in the game of your decision, you have to live with it.

    The guys selling to you will confirm whatever they think will make you comfortable enough to sign the contract. The incremental commission on better equipment does NOT matter to them, it is VERY small. They want the SALE. Whatever you will buy, they are happy to sell you because that's how they feed their families. That's not a judgement of good or bad, right or wrong, it's simply what sales is.
    Last edited by tedkidd; 10-14-2012 at 04:10 PM.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
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    Quote Originally Posted by scooterfj62 View Post
    Really need some expert advice. In the process of replacing 2 complete systems in our 2 story house. Total sq. ft is 3215, lower is 1814, upper is 1401. Current systems are 18 plus years old, Carrier 2 1/2 ton each. Both air handlers are located in a mechanical room on the 2nd floor and all duct work runs through our attics.

    3 Man J's came up with cooling load requirements of between 44,000 and 52,000.

    So here is the dilemma, each company come up with completely different recommendations.
    Company A: 2 1/2 ton up and down, B: 2 1/2 down 3 up, C: 2 down 2 1/2 up, D: 2 1/2 down 2 up.
    Company D also made a strong recommendation to do a single 5 ton zoned system using a Carrier 2 stage, variable speed unit.

    After all this I am even more confused as what to do.

    Thanks
    You run into a MIRACLE THAT these recommendations and calculations are So Closely Aligned and yet you ascribe them to be "completely different".
    The recommendations are definitely within the science and art of equipment selections and what one should expect.
    One ought not to seek Five recommendations if one does not have a thought process to determine what will suit him most appropriately.

    5 +/- 0.5 Tons ... +/- 10% is remarkably close. In fact, in comparison you won't find an air balancer in nearly any industry to provide a set-up to anything less than 10%.
    One would be rethinking ANY Bid where a building is specified to be balanced to < 10%. Saved

    _____________ 44,000 to 52,000 BTU/Hr ..
    also known as 48,000 +/- 4,000 BTU/HR ... within +/-8% is definitely within accuracy expectations of this art and science.

    The glass is MORE THAN half FULL, not half empty.

    Confused?
    IF the "equipment selection glass" is not half full, you are faced with hiring - a sixth unknown someone- to Tell you which recommendation to accept.

    I guess that 6th someone may be the ~123 responses to this thread to be posted over the next 5 weeks
    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

  9. #9
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    Jul 2007
    Location
    Delaware
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    Are you going with the company that gave you the FREE energy report?
    Always here

  10. #10
    Join Date
    Sep 2012
    Location
    Orlando, FL
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    37
    Quote Originally Posted by energy star View Post
    Are you going with the company that gave you the FREE energy report?
    There was nothing "FREE" about the energy report. I paid for it.

  11. #11
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,429

    Thumbs up It's ALL About Windows

    Quote Originally Posted by scooterfj62 View Post
    There was nothing "FREE" about the energy report. I paid for it.
    Describe your windows and I'll tell you which one knows something about Manual J calc.

    One of them totally lost..!
    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

  12. #12
    Join Date
    Sep 2012
    Location
    Orlando, FL
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    37
    Quote Originally Posted by motoguy128 View Post
    IF you did zoning with a single system, I'd go with a 4 ton unless it was an inverter drive like a Carrier Greenspeed.
    The systems they quoted were not the Greenspeed. They quoted 25HNB660A003,FV4CNB006T00,CE0501N05 from Carrier and ASZC160601B, MBVC2000AA-1A, HKT-5, TX5N4 from Amana. The 5 ton Greenspeed is crazy expensive and when you add up the cost for the zoning equipment and changing some of the duct work, you lose the cost benefit of a single system vs. 2 systems. (initial purchase) So unless it is just the cats meow and significantly more efficient and effective, I am not sure its the way to go.

    Quote Originally Posted by teddy bear View Post
    Florida code, ASHRAE and others suggest .2 ach when occupied. The blower door test shows .25 ACh on with an average wind and average cold weather conditions. I brought it up because, I sell ventilation/humidity control equipment. That is why it is not mentioned. How good do you want your home tobe? Regards TB
    Not sure what all that means, but we want the house to be good, not necessarily perfect - if there is such a thing. But we also have a budget to consider and 1st priority is repairing/sealing the ducts, sealing the holes found between the ceiling and the attic and adding additional insulation. 2nd priority is obviously replacing the current systems.

    Quote Originally Posted by dan sw fl View Post
    Describe your windows and I'll tell you which one knows something about Manual J calc.

    One of them totally lost..!
    95% of the windows are double pain but not low e. We also have 6 doors that have 19 1/2 x 64" glass cut outs in them that are not double pain. Surprisingly we only have 2 windows on the south side of the house, that either are not under at least a 12" overhang, porch, etc. or shaded by trees.

  13. #13
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,642
    Quote Originally Posted by scooterfj62 View Post
    The

    Not sure what all that means, but we want the house to be good, not necessarily perfect - if there is such a thing. But we also have a budget to consider and 1st priority is repairing/sealing the ducts, sealing the holes found between the ceiling and the attic and adding additional insulation. 2nd priority is obviously replacing the current systems.

    .
    The blower door info says your home will not get enough fresh air unless the wind is blowing. Homes tend to leak less than blower door test indicate.
    Putting a single small whole house ventilating dehumidifier in your home gets you minimal fresh filtered air during calm weather and near perfect humidity control. If you have occupants with any sensitivity to indoor air quality issues, it's important. If you want to have excellent comfort concerning humidity issues, it's important.

    WHVDEH will not cost as much as a VS speed a/c which will not get you fresh air during calm weather or <50%RH during high outdoor dew points and low/no cooling loads.
    To your credit, you are a concern home owner. Keep us posted on how this all works out.
    Regards TB
    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"

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