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  1. #1

    are my expectations out of line for most regular a/c companies?

    I am currently lining up the installation of a new 2 ton split system for my central florida home. I have found what I believe is a competent independent contractor who deals with the Heil line of products and he made what I felt was a reasonable offer for installation of a complete new system, both air handler and condensor set, with new line set and electrical as needed to complete the setup. As I have become recently more aware of some optional items I believe would be helpful I may have identified a problem area for this contractor. He seemed hesitant when I asked how he tuned the system after the installation.

    Tell me if I am off base here, but isn't there a set of calculations that can be done to determine the proper amount of refrigerant needed for the system to run at optimal? I was told by a recently retired A/C person with a 40 year career that this was the case, but the guy I am dealing with now says the unit comes pre charged with R410 and thats all thats needed.

    so to recap, I have a list of things that should be reasonable requests for a qualified installer who wants to put out a quality job.

    1. Tune the system to run properly after installation is completed.
    2. install the optional 4 inch risers which are available from Heil to get the unit up off the ground and keep the base dry
    3. I am very interested in getting a HRU (hot water recovery) system installed at the same time, all from the same A/C company so that it was all done by the right people while it's all being installed new. This should be good, since they will be familiar with it, and know that nobody else has messed with their work right?
    I am interested in doing what I can here to ensure long life of the new equipment, and get the electric consumption reduced as much as I can.

    Like any other home owner, cost is obviously a concern for me, however I won't list pricing here as I believe that's against the rules. His bid for just the A/C install was not the cheapest, and seemed a price point where he should definitely be reasonably compensated for the day he will be spending getting this done.

  2. #2
    Join Date
    Nov 2006
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    If I understand your question, as posed, then no. A system, properly installed, has an optimum amount of refrigerant to be used, but that is not "tuning," per se. It is simply using measurements that determine the correct charge, based on manufacturer guidelines for the unit, the matched indoor coil, and the length of the lineset, should that length exceed a predetermined amount.

    Now, what you did not ask about.

    First, I would consider the building envelope. Is the home well insulated, and sealed?

    Has the contractor performed a heat load calculation, to determine the needed capacity of the system?

    Has he then determined the suitability of the ductwork to deliver the desired cooling to each area of the home? Are any changes to the ductwork needed?

    These three items are FAR more important than how much refrigerant is in the system, if the amount is within a reasonable tolerance of the recommended amount.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  3. #3
    In answer to your question as follows;

    The insulation status of the home is that I just had R30 fiberglass blown into the attic space, and all outside walls of the air conditioned space are concrete block as is common practice here in Central Florida, this was just injected with expanding foam to what should be around a R-17 rating.
    In regards to the load calculation, I performed one using the data I have available and came to 20,140 BTUH which coincides with 2 tons of capacity, which is what was originally installed when the house was built. I am replacing the 2 ton system with a new 2 ton system.

  4. #4
    Join Date
    Apr 2011
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    West of DFW
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    So the installing contractor took your word, based on your calculations?


    Lets go, burnin daylight.

  5. #5
    He didn't seem interesting in doing a calculation on his own. He was simply going with the whole replace existing with same size. If it means anything here, this is a planned community where all the houses are the same, and all came with the same air system. I went the extra mile on my own to run the numbers and see what I came up with.

    I know my old system is worn out and is why it has been having issues keeping the temp down in the hot summer months. The recent insulation will be a big help though. I just had the coldest nights of the year here and never had to kick any heat on when it went down to the 30s through the nights. Been staying very warm and comfortable with no heat turned on at all.

  6. #6
    Join Date
    Nov 2006
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    What you DON'T know is whether or not every house in that community is correct for capacity or ductwork, or if they are all WRONG.

    I would not take that bet, my friend.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  7. #7
    Join Date
    Nov 2006
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    Southeastern Pa
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    Quote Originally Posted by wmunn View Post
    In answer to your question as follows;

    The insulation status of the home is that I just had R30 fiberglass blown into the attic space, and all outside walls of the air conditioned space are concrete block as is common practice here in Central Florida, this was just injected with expanding foam to what should be around a R-17 rating.
    In regards to the load calculation, I performed one using the data I have available and came to 20,140 BTUH which coincides with 2 tons of capacity, which is what was originally installed when the house was built. I am replacing the 2 ton system with a new 2 ton system.

    I would talk with a GOOD Florida contractor, and not assume that "common practice" is good practice, or whether or not you have done correct load calcs with free software.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  8. #8
    Join Date
    Sep 2002
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    Northeast Ohio
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    4,842
    If, your existing system has functioned well over the years (adequate cooling and de-humidification) and if, you have recently done the weatherization of the structure that you describe (insulation) then, I would venture to say that the proposed new system will be over sized resulting in less than desireable comfort levels. Go the extra step here, have an energy audit done and determine the actual needs of the structure as it exists now. Free manual J software is fun to play with and might give you a generalized ball park figure, but I would not take it to the bank.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  9. #9
    Join Date
    Mar 2009
    Location
    Mount Holly, NC
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    OK, so your house had a 2 ton system on it, THEN you R17 FOAM FILLED your block walls, substantially lowering your heat gain to the structure, AND you had R-30 insulation blown in ON TOP of the existing insulation that was up there, FURTHER reducing the heat gain to your house...
    and nothing is being done about the size of the equipment?
    um, humidity is the #1 issue with cooling in FL... this sounds like the system will run very little, and it will cause moisture problems all through your house, and you will have mold and mildew growing on everything in your house.
    DO not pull the trigger on this system, get an energy audit done, and properly size the equipment to your house, so you don't end up with health issues, and destroyed clothing and furniture.
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  10. #10
    Join Date
    Mar 2009
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    Mount Holly, NC
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    if 2 tons handled the house before you insulated, and you've done as much as you list to the house, you may be looking at needing a pair of 9K mini splits installed to properly cool your house...
    The TRUE highest cost system is the system not installed properly...
    The three big summer hearththrobs...
    Mel Gibson
    Dwane Johnson
    The A/C repairman

  11. #11
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I agree, wither minisplits ( which dehumidify better than convention split systems), or look at a 1.5 Ton unit and a dedicated dehumidifier. It might cost slightly more than the minisplit... but with a block house, dehumidificaiton will be more improtatnt than cooling. Depending on shading, I bet the dehumidifier alone will keep you comfortabel 90% of hte time, especially in winter.

    With a block house with all that thermal mass, if anything you want to undersize a little. Load calculation do not take thermal mass into account.

  12. #12
    Join Date
    Feb 2009
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    Tallahassee, FL
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    If you are really getting a HRU than ideally you want a smaller unit that runs more anyway.

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