Page 1 of 5 12345 LastLast
Results 1 to 13 of 59
  1. #1
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    I am replacing an 18 year old Trane heat pump in a house of the same age. I live in very humid Tampa, Florida, where heat is needed at most 10-12 days per year, while the a/c runs day and night for 6-8 months per year. The old Trane is a 2 1/2 ton, and the house was originally 1400 square feet. Since then, a 400 square foot back room has been added, bringing the total to 1800 square feet. The addition is ducted with overhead vents, but the air barely reaches the room. If not for two glass doors, there would be virtually no heating or cooling the addition. I've talked to three contractors so far, but their information seems confusing or contradictory. First, all three recommend a new 12 SEER unit. The say that anything rated higher won't save enough electricity to warrant the additional cost. But 12 SEER seems on the low side, especially considering the new government minimums. Also, they differ on size recommendations: One says stay with 2 1/2 ton. He claims that anything larger would necessitate replacing all the duct work. (However, he said this without ever examining the existing ducts.) Another contractor recommended a 3 ton, and the third said 3 1/2 ton. (These would be the sizes of the outside compressor unit, with the corresponding air handler 1/2-ton bigger in all three cases.) Finally, the three guys all want to sell me different names: Carrier, Bryant, and Payne. I wonder if you could provide some solid info to cut through the confusion. Also, any other considerations or recommendations (i.e. Puron vs. Freon) will be appreciated. By the way, I have lived in this house less than a year, so I have little extensive past history of the existing unit, comfort level, etc. But I do know that the current electric bill runs at least 50% higher than it should.
    Thanks for your consideration.
    ~rick

  2. #2
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by rickintampa
    I've talked to three contractors so far, but their information seems confusing or contradictory. First, all three recommend a new 12 SEER unit. The say that anything rated higher won't save enough electricity to warrant the additional cost. But 12 SEER seems on the low side, especially considering the new government minimums. Also, they differ on size recommendations: One says stay with 2 1/2 ton. He claims that anything larger would necessitate replacing all the duct work. (However, he said this without ever examining the existing ducts.)
    The only way to determine the correct system size (and the duct work needed to handle the air flow) is to do a heat gain / loss calculation (AKA "Manual J"). The duct work is sized by a calculation known as "Manual D". Did any of the contractors offer to perform such calculations? If not, call another contractor or two until you get one that sizes by calculation, not by 'rule of thumb'.

    It is true that at TECO's current electric rates, anything more than about 13.0 SEER (a Trane XR12 with VS air handler) won't pay for itself during it's expected lifespan. Energy costs may rise in the future, but those are today's calculations.

    The quality of the system design and the installation is more important than the brand name. If you are within 1000' of the coastline be sure to look at examples of the brands that you are considering to see if they are rusting after a few years. Basepan rustout has been a real problem on the coast and that is why Trane (and now others) have started using composite basepans.

    Either R-22 or R-410a refrigerants will be available in plentiful quantities for the expected life of your unit.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Minimum SEER 13.0 ,next year.

    2010,no more R22 systems built for sale in the USA.

    Check http://www.410a.com for information.


    Just north of you in New Port Richey and Crystal River,so I know the climate,Humid.


    I'd go with a Carrier Infinity,two stage ,heat pump,strip heat would be less and if you really only use it 6 days a year,you don't need a heat pump.

    Check out a Carrier Factory Authorized Dealer,you can find them on Carriers website,or the yellow Pages,in the column.
    100% satisfaction or your money back,garanteed by the Factory!

    Whatever you do go with ,get a variable speed air handler ,WIT a good control system to reduce humidity in the summer,Thermidistat Carrier/Bryant is almost as good as the Infinity.

    Get a load calculation,and have them test the ESP(static) of the duct system.Consider any upgrades to windows,insulation ,etc.,when doing the calculation,increasing the attic insulation,could save a 1/2 ton .Have it checked out.

    The ducts for the addition ,need to come off the trunk or plenum close to the air handler,and be the correct size.They probably "tapped" it in to the closest duct instead.
    If attic space allows,not hard to correct,make comfort in the addition part of the "deal"!


    [Edited by dash on 02-01-2005 at 10:36 AM]

  4. #4
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    Originally posted by travisfl
    Originally posted by rickintampa
    I've talked to three contractors so far, but their information seems confusing or contradictory. First, all three recommend a new 12 SEER unit. The say that anything rated higher won't save enough electricity to warrant the additional cost. But 12 SEER seems on the low side, especially considering the new government minimums. Also, they differ on size recommendations: One says stay with 2 1/2 ton. He claims that anything larger would necessitate replacing all the duct work. (However, he said this without ever examining the existing ducts.)
    The only way to determine the correct system size (and the duct work needed to handle the air flow) is to do a heat gain / loss calculation (AKA "Manual J"). The duct work is sized by a calculation known as "Manual D". Did any of the contractors offer to perform such calculations? If not, call another contractor or two until you get one that sizes by calculation, not by 'rule of thumb'.

    It is true that at TECO's current electric rates, anything more than about 13.0 SEER (a Trane XR12 with VS air handler) won't pay for itself during it's expected lifespan. Energy costs may rise in the future, but those are today's calculations.

    The quality of the system design and the installation is more important than the brand name. If you are within 1000' of the coastline be sure to look at examples of the brands that you are considering to see if they are rusting after a few years. Basepan rustout has been a real problem on the coast and that is why Trane (and now others) have started using composite basepans.

    Either R-22 or R-410a refrigerants will be available in plentiful quantities for the expected life of your unit.
    One of the contractors phoned just as this message came in and I read part of it to him. He said that these calculations (Manual J & D) are complex, costly, and sometimes wind up not proving much. Just his opinion, I realize. I am basically right on the coast (Tampa Bay) and I will keep in mind about rustout. Thanks for your advice. ~rick

  5. #5
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by rickintampa
    One of the contractors phoned just as this message came in and I read part of it to him. He said that these calculations (Manual J & D) are complex, costly, and sometimes wind up not proving much.
    He must not be an ACCA member, and he certainly isn't technically competent to do your job.

    http://www.acca.org/tech/manualj/
    http://www.contractingbusiness.com/n...sarticleid/616
    http://www.acca.org/tech/manualj/art...ane_letter.doc

    "Trane / American Standard and ACCA have always agreed on the need to do a load calculation on each installation and are now pleased to announce that we both agree on using ACCA’s Manual J 8th edition."

    Run, do not walk away from this contractor.

    [Edited by travisfl on 02-01-2005 at 11:35 AM]

  6. #6
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    Originally posted by dash
    Minimum SEER 13.0 ,next year.

    2010,no more R22 systems built for sale in the USA.

    Check http://www.410a.com for information.


    Just north of you in New Port Richey and Crystal River,so I know the climate,Humid.


    I'd go with a Carrier Infinity,two stage ,heat pump,strip heat would be less and if you really only use it 6 days a year,you don't need a heat pump.

    Check out a Carrier Factory Authorized Dealer,you can find them on Carriers website,or the yellow Pages,in the column.
    100% satisfaction or your money back,garanteed by the Factory!

    Whatever you do go with ,get a variable speed air handler ,WIT a good control system to reduce humidity in the summer,Thermidistat Carrier/Bryant is almost as good as the Infinity.

    Get a load calculation,and have them test the ESP(static) of the duct system.Consider any upgrades to windows,insulation ,etc.,when doing the calculation,increasing the attic insulation,could save a 1/2 ton .Have it checked out.

    The ducts for the addition ,need to come off the trunk or plenum close to the air handler,and be the correct size.They probably "tapped" it in to the closest duct instead.
    If attic space allows,not hard to correct,make comfort in the addition part of the "deal"!


    [Edited by dash on 02-01-2005 at 10:36 AM]
    You bring up additional interesting points, including the recommendation for a variable speed air handler, which none of the contractors who came by so far seemed to think I needed. You're right that the back room duct work was probably tapped in, but correcting that would probably be a huge job, considering the flat roof on the addition. I'm more concerned with the new recommendation that I'll need to install a second return someplace in the house (I currently have only one return)if I go to a 3 1/2 ton unit. Thanks for your advice. ~rick

  7. #7
    Join Date
    Dec 2004
    Location
    Derby City
    Posts
    3,973
    Well, that's one contractor you can immediately mark off your list! Anyone that chooses to ignore standards of the industry, is probably not someone you want to do business with. Makes you wonder what else he will choose to ignore during the course of the installation. This guy probably doesn't even need to see the home, just hold the phone up in the middle of the room so he can size it.

  8. #8
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    Originally posted by travisfl
    Originally posted by rickintampa
    One of the contractors phoned just as this message came in and I read part of it to him. He said that these calculations (Manual J & D) are complex, costly, and sometimes wind up not proving much.
    He must not be an ACCA member, and he certainly isn't technically competent to do your job.

    http://www.acca.org/tech/manualj/
    http://www.acca.org/tech/manualj/art...ane_letter.doc
    http://www.contractingbusiness.com/n...sarticleid/616

    Run, do not walk away from this contractor.

    [Edited by travisfl on 02-01-2005 at 11:33 AM]
    I see your point; thanks! ~rick

  9. #9
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    I just did a very complex and costly Manual J last night on the computer in about 20 minutes

  10. #10
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by rickintampa
    I'm more concerned with the new recommendation that I'll need to install a second return someplace in the house (I currently have only one return)if I go to a 3 1/2 ton unit.
    You REALLY need a Manual J, but unless there is zero insulation and you have all south facing single pane windows with no roof overhang, 3.5T would likely be oversized for 1800 square feet in Tampa Bay.

    Another warning here - regardless of system size for maximum comfort you should have a return in every habitable room of the home except bathrooms. Another option is to undercut the doors or install ventilation ports in them. Regardless, Florida Mechanical Code is as follows:

    http://www.iccsafe.org/cs/codes/pdf/...Mechanical.pdf

    §M601.4 Balanced Return Air. Restricted return air occurs in buildings when returns are located in central zones and closed interior doors impede air flow to the return grill or when ceiling spaces are used as return plenums and fire walls restrict air movement from one portion of the return plenum to another. Provisions shall be made in both residential and commercial buildings to avoid unbalanced air flows and pressure differentials caused by restricted return air. Pressure differentials across closed doors where returns are centrally located shall be limited to 0.001 inch WC (2.5 pascals) or less.

    [Edited by travisfl on 02-01-2005 at 12:30 PM]

  11. #11
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    Originally posted by travisfl
    Originally posted by rickintampa
    I'm more concerned with the new recommendation that I'll need to install a second return someplace in the house (I currently have only one return)if I go to a 3 1/2 ton unit.
    Another warning here - regardless of system size for maximum comfort you should have a return in every habitable room of the home except bathrooms. Another option is to undercut the doors or install ventilation ports in them. Regardless, Florida Mechanical Code is as follows:

    http://www.iccsafe.org/cs/codes/pdf/...Mechanical.pdf

    §M601.4 Balanced Return Air. Restricted return air occurs in buildings when returns are located in central zones and closed interior doors impede air flow to the return grill or when ceiling spaces are used as return plenums and fire walls restrict air movement from one portion of the return plenum to another. Provisions shall be made in both residential and commercial buildings to avoid unbalanced air flows and pressure differentials caused by restricted return air. Pressure differentials across closed doors where returns are centrally located shall be limited to 0.001 inch WC (2.5 pascals) or less.
    I'm sure that a return in every room is good advice for maximum system efficiency, and to be within state guidelines. But can you imagine if everyone who installed a new air conditioner in an older home or condo were to put a return in every room, in cases when only one now exists in the whole house? I just got a price of $300 for installing one return...putting them throughout the house would a prohibitive expense. Let's face it: Few home owners will ever do that, regardless of the codes. ~rick

  12. #12
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by rickintampa
    Let's face it: Few home owners will ever do that, regardless of the codes
    No problem, undercutting the doors will work OK and meets the code requirements. It just isn't the best way in terms of comfort - IMHO.

  13. #13
    Join Date
    Dec 2004
    Location
    Tampa, FL
    Posts
    35
    Originally posted by travisfl
    Originally posted by rickintampa
    Let's face it: Few home owners will ever do that, regardless of the codes
    No problem, undercutting the doors will work OK and meets the code requirements. It just isn't the best way in terms of comfort - IMHO.
    Thanks for the clarification. So then I'll assume that in a home where doors aside from the bathroom are hardly ever closed, the need for multiple returns and door undercutting is greatly diminished. ~rick

Page 1 of 5 12345 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event