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  1. #1
    Join Date
    Oct 2005
    Location
    Alpharetta, GA
    Posts
    6
    Gentlemen/Ladies,

    I am looking for some advice. My family moved into a 2 story, 10-year old home in a north Atlanta suburb last winter. A beautiful home but the builder's special HVAC system is on it's last leg (2 systems: 2.5 ton down and 3 ton up - both at 10-11 SEER and probably running inefficiently). Coming from Florida, we like to keep the temp quite cool at 72-74 degrees 24/7 (except when we are not home) in the summer and 78-80 in the winter. The downstairs unit works fine but the upstairs unit's outside condenser motor just went. So we started the proposal process.


    Let me note that i had starting getting proposals back when we first moved in becuase I knew the units were on their last leg. AT that time we found a very knowledgable professional (who owns his own company and came to us from Home Depot) who was the only one who did the airflow testing. As a result we had our ductwork sealed (and I beleive that it did help soemwhat - airflow calculations were done before and after). However, in re-starting the proposal process he was the only one (out of 4 propsals) that recommended staying with the same size system (3 ton but increasing SEER to 16 or 19) while the other theree revommended jumping to a 3.5 ton system (at 13.5 to 14 SEER). He was the only one who sepnt time doing additional calculations for a "whole house heat/loss" calculation. He also was the only one to recommend a "dual-fuel" heat pump system that would be of great energy savings in todays rising energy cost market. The others were electric for cooling and gas for heating. All recommended variable speed.

    Also to note, one area of the upstais gets quite hot in the summer and cool in the winter...I surmise because it is at the end of the ducts away from the unit....so we need to do something soon!

    I am leaning towards his recomemndation only veasue he spent the time to back up his recoemmendations...which by the way were a Trane 3.0 ton 16 SEER split system heat pump and a 80% variable speed gas furnace OR a 4 ton 19 SEER system with the same 80% variable speed gas furnace). He was quite keen on the 4 ton unit syaing that we would never have any issues regarding colling/heating but also said that the 3 ton 16 SEER unit would be fine based on the calculations. It was also $3K less for the 16 than the 19.

    So in a nutshell....is this guy just trying to wow me with all of these calculations or are the other guys just trying to sell me on something without adequate knowledge.

    Thanks so much for your help. Let me know if you need any more information.

  2. #2
    Join Date
    Jan 2005
    Location
    Crooksville, Ohio
    Posts
    77
    A good contractor will do a heat load calculation. This will give him the adequate information that he needs to properly size the unit to your house. Since he has taken the time to do so, and the others have not, personally I would go with this guy. He has done his homework.
    All Seasons Heating & Cooling

  3. #3
    Join Date
    Jul 2005
    Posts
    435
    If he did the calcs and it shows a 3 ton system why not go with the 3 ton 19 SEER with the TWE040 VS airhandler plus furnace, this will increase the cooling capcity a little above 3 ton, provide a SEER rating of 19 (as long as the rest the system and ducting is in compliance).
    Why is he recommending a 3 ton 16 SEER but keen on taking it to a 4 ton @19 SEER? Load calcs should provide you with exactly the sizing you need!

  4. #4
    Join Date
    Mar 2004
    Posts
    1,042
    Dual fuel is a winner in the Atlanta metro, unless it's practical to switch to an all-electric heat pump. They take big electrical wiring to the indoor unit, though, and big electrical service for the house, so it's not always easy to switch when the place was built for gas heat. In that case, it's usually a lot easier to just do dual fuel with 80% furnaces (plenty efficient for how much of the work they will actually do).

    A good control system matters, too. The only system I know of that can fully control a nice system like you're looking at- a two speed heat pump and a two speed furnace- is Carrier's Thermidistat. It's not as showy as some competitors, but the features are still top of the line, and it can actually control all four stages of heating properly. Any other control system is likely to only use three of the four possible stages of heating.

    Heat load calculations are the right way to go. Just make sure that the guy ran the calculations using the temperatures YOU want. The standard assumptions are that you heat to 70 and cool to 75, and it sounds like you want a lot more than that out of the systems.

  5. #5
    Join Date
    Oct 2005
    Location
    Alpharetta, GA
    Posts
    6
    Thank you for your opinions.

    Since the heat loss/gain calculation indicated a Total BTU gain of 33,931, his feeling was that the larger 4 ton, split two stage unit would run most of the time on Stage 1 and would still be adequate to cool and heat (he commented on its dehumidifying powers and that would make it extremely comfortable in the summer). Only on really hot or cold days would Stage 2 kick in. With the 16 SEER, two stage unit Stage 2 would kick in more frequently but it woudl still cool and heat to our liking (although I have asked him to rerun the calculation with some different temps - he used 70 in winter and 74 in summer. We wanted 74 in winter and 72 in summer)

    Also, his price was $11.1K for the 19 SEER and $7.9K for the 16 SEER unit (bothy before some rebates). A big enough price differential for me to justify the smaller unit. With the difference I was going to redo or supplement my attic insulation (it's currently blown fiberglass that has probably settled over the years).

    We were also going to add a Aprilair 400 humidifier in the downstairs unit to provide for some lost humidity in the winter.

    Any other details I can provide? Thanks again guys!

  6. #6
    Join Date
    Oct 2005
    Location
    North Carolina
    Posts
    3
    I'm surprised that your contractor did not recommend replacing the outdoor fan motor first. How are you to know if the system as a whole is operating properly. With labor, a outdoor fan motor is $300-$400 to replace. When that is fixed, check all pressures and temperatures for proper operation. It seems odd that the unit is being replaced after only 10 years.

    If it determined that the system, as a whole, has failed, I would go with the guy who provides the load calculation. Question: What is the Sq. footage upstairs? Your contractor should have also provided you with CFM (cubic feet per minute) of air calculations for each room. It is very important for the contractor to properly balance to air to avoid the hot/cold spots in your home. Each duct branch off your main duct should have been installed with balancing damper. Most contractors don't spend the time to balance the air.

    In my opinion, the 3 ton unit will be fine at ARI (Air-Conditioning and Refrigeration Institute) conditions for Atlanta, GA. The 3 ton unit will have a longer run time than the 4 ton unit. Remember that the longer the system runs, the more efficient it will be and it will have better humidity control. Remember your thermostat only reads sensible heat (heat that you can feel), but not latent heat (heat from humidity). If you oversize the unit, the unit will quickly cool the space and then shuts off after reaching the cooling setpoint. When it shuts down, you can no longer cool or dehumidify.

    Good Luck.

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,923
    Originally posted by ei, llc



    I'm surprised that your contractor did not recommend replacing the outdoor fan motor first. How are you to know if the system as a whole is operating properly. With labor, a outdoor fan motor is $300-$400 to replace. When that is fixed, check all pressures and temperatures for proper operation. It seems odd that the unit is being replaced after only 10 years.

    He may have found other things when he was there and sealed the duct work..

    If it determined that the system, as a whole, has failed, I would go with the guy who provides the load calculation. Question: What is the Sq. footage upstairs? Your contractor should have also provided you with CFM (cubic feet per minute) of air calculations for each room. It is very important for the contractor to properly balance to air to avoid the hot/cold spots in your home. Each duct branch off your main duct should have been installed with balancing damper. Most contractors don't spend the time to balance the air.

    Why provide this info before the contract is signed, unless youor being paid for it. So low ballers know what to put in.


    In my opinion, the 3 ton unit will be fine at ARI (Air-Conditioning and Refrigeration Institute) conditions for Atlanta, GA. The 3 ton unit will have a longer run time than the 4 ton unit. Remember that the longer the system runs, the more efficient it will be and it will have better humidity control. Remember your thermostat only reads sensible heat (heat that you can feel), but not latent heat (heat from humidity). If you oversize the unit, the unit will quickly cool the space and then shuts off after reaching the cooling setpoint. When it shuts down, you can no longer cool or dehumidify.


    He intends to run it well below ARI rating conditions, so 3 ton may not be able to reach 72 at outdoor design temp. Which is a good reason to use a 2 stage unit.

    Good Luck.
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  8. #8
    Join Date
    Oct 2005
    Location
    N Metro Atlanta GA
    Posts
    70
    Judster,
    I also live in a north Atlanta suburb.
    Was the contractor company sent by Home Depot named Universal?
    That is the company they said they use in my area. Just wondering if they use more than one contractor in north metro Atlanta.
    Hope you get the comfort that you want.

  9. #9
    Join Date
    Oct 2005
    Location
    Alpharetta, GA
    Posts
    6
    Not Universal. They shall remain nameless until I select a contractor and the job is done.

  10. #10
    Join Date
    Sep 2004
    Location
    Memphis
    Posts
    2,502
    I have a few things to add to all this. I can understand not wanting to spend 300 to 400 on a fan motor if you've already been considering upgrading. When you say builders special, i'm assuming you have a standard 80 percent furnace. I would take it as a opportunity to upgrade to a 90 plus furnace with a higher seer a/c. Especially if you plan on being in the house for a while & the upstairs hasnt really cooled right since you've lived there.

    Another thing I believe in doing heat load calculations, but if you have a 3 ton a/c & its never done the job like you wanted it to in the past & your confident it was operating properly through the years, I would not go back with the same size. Heat load calcs are a good way to size but you can also use logic too. If the old 3 ton didnt satisfy you, the new one probably wont either. Being a higher seer doesnt mean its gonna cool better, it just means it'll cool cheaper. I bought the Residenial Calc that this site sells & in the manual they say that you can fudge on the sizes a little. I believe the manual says you can add 15% to 25% to what the load says & still be ok. You dont have to go to a 4 ton, they do make a 3 1/2 ton a/c.

    1 last thing to consider. You said it was hotter in certain parts of the upstairs. Replacing the system by itself is not going to change the way the air is distributed through the ductwork. Those areas will continue to be a problem unless you change the way the air is distributed through the ductwork. This is done by installing dampers to the ducts that are blowing too strong to allow that excess air to go to the other areas.

    Good Luck with all of this, Hope it is all a success for you.
    Life is like a jar of jalapenos. What you do today might burn your ass tomorrow.

  11. #11
    Join Date
    Oct 2005
    Location
    North Carolina
    Posts
    3
    1) The point that I'm making is to make sure to check EVERYTHING before you replace a whole system.

    2) I always do my best to look out for the best interest of the owner. I say find out the real problem and fix it. If the owner insists of changing out the system, then you've done your due diligence. Everyone is happy.

    3) If you go with a two stage unit, what are the capacities of each stage? Do you think on a 4 ton staged unit, the first stage of a 4 ton unit will satisfy a 33,000+ Btuh load? Let the contractor show you the calculations.

    In my opinion, if you have a total heat gain of 33,000+ btuh, and a 3 ton unit is not satisfying the space, you either have a miscalculation or you have bigger issues on your home, such as leakage, poor insulation, etc. Did you provide your contractor with R value information on your walls, ceiling or roof? Did your contractor take note of where is the North facing wall? How many people will occupy the space? What is the condition or your insulation or weather stripping?

    Make sure you've done your homework and the contractor has done their due diligence.




  12. #12
    Join Date
    Feb 2004
    Location
    Tucson AZ
    Posts
    55

    Lets see?

    Let’s see,
    Was the thirty three thousand + BTU’s that his load calculation based on total BTU’s or is that the figure that his program used to determine based on some percentage of the actual BTU’s required. I live in the desert in southern Arizona and we don’t have to worry about latent heat v/s sensible heat removal. Forgive me if I am incorrect but in Atlanta I believe you need to worry about humidity control. I believe you would be best suited with the smallest system that would adequately cool the home. This will typically do a better job of humidity removal. I have a hard time understanding how it is beneficial to consumers to purchase 2-stage systems that are grossly oversized. If your unit only ever operates on the low stage what benefit did you receive? You only pay more for a system that operates on the first stage? Why don’t you purchase a properly sizes system for less money and get the benefit of higher efficiency from longer cycles as well as better humidity control and a quieter system for less of an initial investment? All the sales classes I have been to thru TRANE have dealt with out leaving money on the table. This would make sense for the dealer to push for the more expensive unit sale even if it was not the correct size for your home. I think if he did a load calculation he was a step above the competition but is pressured into “Selling UP”
    Just my opinion.

  13. #13
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,274

    Thumbs up Great Service

    Originally posted by thejudster
    Gentlemen/Ladies,

    He was the only one who sepnt time doing additional calculations for a "whole house heat/loss" calculation. He also was the only one to recommend a "dual-fuel" heat pump system that would be of great energy savings in todays rising energy cost market. The others were electric for cooling and gas for heating. All recommended variable speed.

    I am leaning towards his recommendation only because he spent the time to back up his recommendations...which by the way were a Trane 3.0 ton 16 SEER split system heat pump and a 80% variable speed gas furnace OR a 4 ton 19 SEER system with the same 80% variable speed gas furnace). He was quite keen on the 4 ton unit saying that we would never have any issues regarding colling/heating but also said that the 3 ton 16 SEER unit would be fine based on the calculations.
    Stay away from any1 recommending GAS heat only
    for ATL GA.

    The mech contractor that
    you are dealing with is GREAT!
    GREAT System at Very Reasonable Price.

    Did you request 10-Year Parts & Labor Warranty which is a low adder (few- several hundred $) for XL16i?
    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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