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  1. #1
    Join Date
    Jul 2012
    Posts
    6

    The Right Questions?

    I have two A/C units (1 @ 24 years and 1@ 16). I want to be prepared to make a good decision about replacement units when the time comes. I don't want to make that decision when the house is 101F and my wife is upset.

    What questions should I be asking contractors now so I can review their input in the cool of my living room?

    I have 2300 SF and it is divided into two areas by a door. I heat/cool one during the day and one at night. Living area is kept at 79F and bedroom area is kept at 75F.

    Current cooling costs are about $70-80 per month during the summer in the Dallas area.

    Thanks for your inputs.

  2. #2
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,355
    Contractors very a lot in experience and what they will sacrifice to get the job. If you are so inclined, take the time to learn what you need then find the contractor that will deliver. It almost seems like there's a market for a system designer who would create the best system for you and then you could find the contractor that would install it.
    Maybe I'm a tad pessimistic.
    Tracers work both ways.

  3. #3
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,622
    yea, it's a copy & paste

    since there's no email in that profile:

    “How would your company determine the size of the (heating or cooling)
    equipment for my house?”

    Acceptable answers: “By Manual ‘J’ calculation”; “By an engineering analysis”, “By a
    room-by-room load analysis”; “By measuring and calculating the load for each room”;
    “By ACCA (Air Conditioning Contractors Association) software”; “By using a computer
    design” or similar methods that specify an actual mathematical calculation based on
    solid science.

    2. When you’ve found a company or two that will answer question #1 correctly, invite
    them into your home and enjoy the presentation. A good company will spend as much
    time as is needed to make you totally comfortable with the process of what’s happening,
    why it needs to happen and what you should expect to follow. Comfort comes in many
    guises and your emotional comfort with the process is paramount to a good company.
    Please do not be offended when they ask to have all the people involved in the decision
    present. There’s a huge amount of information to be digested, all of it representing
    added value this company will bring to the table. To expect one person to relate it all to
    another is just not going to happen. So please have everyone present who needs to be
    there. Opinions can vary, questions will arise. All of these issues need to be addressed
    to everyone’s satisfaction.

    3. Once the size of the equipment has been determined (do not expect the sales person
    to share the equipment size with you until after an agreement has been signed. They’ve
    been burned too many times by customers who get them out to determine the size of the
    equipment and then use that information to get a lower price. In the end, the client gets
    the right size but a hundred other corners were cut, leaving the homeowner once again,
    cheated) you should expect the duct system to be designed according to Manual ‘D’.
    That is the ACCA method of designing a duct system that will deliver the proper airflow
    without excessive noise. It’s important to note that the ducts can’t be sized until the
    equipment is properly sized. That once again would lead us back to the importance of
    that question you’ll be asking in item #1.



    4. Finally, after the equipment and ducts are properly sized (or in the case of ducts,
    reviewed as to current condition and sizing) it’s time to select the equipment itself. Brand
    is not normally very important and many companies can offer more than one brand. All
    manufacturers have both successes and failures of equipment most importantly based
    on the installing company. Once again, the installation company that follows the proper
    procedures will deliver the anticipated result to you. If corners are cut, you can expect
    discomfort and problems.


    or

    http://www.eere.energy.gov/consumer/.../index.cfm/myt
    opic=12340
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  4. #4
    Join Date
    Jul 2012
    Posts
    6

    The Right Questions?

    Thanks for the replies. I have talked to two contractors, neither of which have suggested I need anything different from what I currently have. They simply provided a price to replace the current systems so the comment of "How would you determine size . . ." was a very good one. I will ask that question of both of them and the others that are scheduled to come by.

    I have learned something from each but one was much more detailed than the other. Consumer Reports gives repair rates and it seems like 4 are in the "top group" and everybody else is significantly farther behind. They did say that contractor (initial installation) was more repair prone than replacement equipment suggesting the "cutting corners" you have mentioned.

    I will ask "How do you know I have the right size equipment now?" and see how they respond. Since the house was built a lot have changed in the equipment and I have added over a foot of attic insulation as well as having a lot of large trees that were not there when the house was built. Things have changed over the years and I don't know if that is being considered.

    Thanks to both responders for your help.

  5. #5
    Join Date
    Jul 2012
    Posts
    6

    A quotation

    I am thinking about using an American Standard to replace two units. I have looked the AHRI.org site and found that A/C units and air handlers must be matched and matched with a certificate related to an AHRI standard.

    Below is what one dealer is proposing however I don't know if the match is correct. I am not looking for "right price" data but just is the proposal reasonable?

    Your previous inputs have been very helpful in increasing my understanding of HVAC. Thank you.

    Currently have one 3-ton and one 2.5 ton unit that keep the house cool.

    Proposal:

    Two 3-ton units to replace the above.

    AHRI # 4176376
    Condenser: model 4a7a6036
    Furnace: AUD2c080a9v4
    Evaporator: 4TXCC044BC3

    New supply and return plenums would be installed.

    Again, I am not asking for any price data or suggestion. I am just asking if this (proposed) combination of equipment will do the job and I will not be creating a "bottle neck" somewhere I can avoid by doing something different.

    Most of this stuff is Greek to me so any input would be appreciated.

    GH

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,998

  7. #7
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,674
    You need a contractor that will do a load calculation of the home. Most "contractors" don't they just assume that if what you have now works then the size is correct. Ac units now are more sophisticated now than they were 22 or 16 years ago and need to be sized properly so that they last 22+ years. Proper duct sizing and sealing is very important as well. I do duct leakage tests and most duct systems, even ones that are 1 year old have between 20-50% leakage. That is a big deal as far as efficiency goes. It's like going to the gas pump and filling up your tank at $4 a gallon and having a hole in your gas tank!

  8. #8
    Join Date
    Jul 2012
    Posts
    6

    Getting the right equipment

    Quote Originally Posted by jtrammel View Post
    You need a contractor that will do a load calculation of the home. Most "contractors" don't they just assume that if what you have now works then the size is correct. Ac units now are more sophisticated now than they were 22 or 16 years ago and need to be sized properly so that they last 22+ years. Proper duct sizing and sealing is very important as well. I do duct leakage tests and most duct systems, even ones that are 1 year old have between 20-50% leakage. That is a big deal as far as efficiency goes. It's like going to the gas pump and filling up your tank at $4 a gallon and having a hole in your gas tank!
    When I had the house built I went to each air duct connection (where they split) and filled all the holes I could find with expanding foam. I removed the registers in the house and filled the area around them with foam (I had to cut off the excess that expanded). I recently had an IR scan of the home under negative pressure done and it did how a lot of hot air coming from the vents. The A/C was turned off at the time so that is what one would expect. The guy who did it did not seem alarmed by the return on his infra-red camera but that may only support what you have said - there is a lot of leakage.

    I am trying to learn about A/C before I have to buy and need all the help I can get.

    At this point the contractors say they will do a load test but each has (so far) done just what you said. They looked at what I had and asked "Have you been comfortable?" and proposed just replacing the present equipment with similar equipment.

    I don't know enough about load testing but how would I know they did not come up with results that merely support their original conclusion that two 3-ton units are what I need?

    The dealer I am dealing with (I asked for quotations from 4) was the only one to talk about modifying the incoming and return air. They also did more checking of the exact model numbers of the equipment I have (most just looked at the outside and said -Oh that's a 2-Ton (it turns out to be a 2.5 ton).

    I appreciate your input since, as I said before, this is Greek to me but it is a lot of money ($15K or so) and I want to feel good I did my homework before I sign on the dotted line.

    Again, thanks for your help.

    GH

  9. #9
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,674
    If there was a lot of hot air coming from vents with a neg pressure home test then that means there is a lot of duct leakage. With a neg press home test no air should come out of vents when ac is off bc it should be the same neg pressure as the home. When there are leaks in duct is when you see air movement. You can buy the most efficient piece of equipment on the market and put it on a poor duct system and see no savings on utilities. Ductwork and installation are extremely crucial to having a comfortable, efficient and long lasting piece of equipment.

  10. #10
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,674
    Lots of contractors are in buisiness to sell boxes(equipment) the contractor you want should sell you comfort. They should be able to look outside of the box and see the whole house as a system.

  11. #11
    Join Date
    Jul 2012
    Posts
    6

    The right equipment

    Quote Originally Posted by jtrammel View Post
    Lots of contractors are in buisiness to sell boxes(equipment) the contractor you want should sell you comfort. They should be able to look outside of the box and see the whole house as a system.
    Good point on the negative pressure should be the same in the ducts as in the house because it is supposed to be a closed system.

    I added about 12 inches (more in some locations) of insulation and covered most of the ducting in the attic. In hindsight I should have made an attempt to ferret out the leaks before hand.

    Is there a way to identify where they are without tromping through up to two feet of fiberglass insulation? My guess is it isn't.

    On the other hand our electric bill for A/C is about $118 per month (175-57) in summer with the non cooling months being closer to $57/ month. From what I understand this number is low by standards in the North Texas area so, although the system leaks it might not be leaking too badly (whatever that means).

    Possibly the best advice has been to find somebody who will be more worried about my comfort than the unit that is put in. None of them seem to have that high on their list of concerns but the American Standard guy seems a little more concerned than the rest. His price, by the way, is 20% higher than the others. Even so, I am beginning to think he might be the best bet for a 20-25 year investment.

    GH

  12. #12
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,674
    Price is an issue, you get what you pay for! Sure someone that takes the time and has the know how to do the job right will probably cost a little more upfront but in the long run it will cost you less in frustration, disappointment, utilities and equipment life.

  13. #13
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    5,674
    Usually it's easiest to replace the duct system entirely but it can be sealed by trodding in insulation and peeling back duct insulation and sealing it. They need to test it before and after to prove its better

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