Zone current system or new?
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  1. #1
    Join Date
    Aug 2011
    Location
    Kansas City
    Posts
    78

    Zone current system or new?

    Hello everyone I have a question concerning my current HVAC system.

    It is from 1991 and is an 2.5ton American Standard 8 seer AC and 80% furance...the particulars outside of that I don't know. If you need more please let me know. It is a single stage split system. Bills in summer at 78 degrees run 75-85 bucks but the system is only on from 6pm to 5am. Heating at 68-72 degrees ran as high as $185 (and was a very warm winter). I am located in KC Missouri.

    My current problem is the main living area will get to the correct temperature as the single thermostat calls for but the upstairs is always 4-8degrees warmer/cooler. I have always used the auto setting and run ceiling fans in the rooms to help cool them off. I am the kind of person that will just lower temps in the winter or higher temps in the summer to save money, however my new finance is not, she wants to be comfortable period. Thus I am looking to improve my current HVAC system, either with a new one or a retrofit zoning system.

    I can do the zoning system myself and looks like a good deal, 3 zone retro solution for a little over $...if this will work I would like to take the cheaper option as I hope to only be in this house less than 2 years. If I have to do a system give me some ideas.

    Ok I am attaching a picture of the current ducting system, pretty simple 11"x22" main trunk line down the center of house with branches of 6" round ducts to wall vents. There are three returns, 1 at baseboard in living room, 1 in hallway of 2nd floor baseboard, and a 3rd that looks added in basement. The house is a split level 1395sqft with 300 sqft basement...nothing big. I just had an energy audit done which resulted in additional attic insulation, now R49, and air sealing so the house is tight (I can't find the report right now but was told it is to spec of what new homes require and my house in a 1959 build) The ceilings are all 8' tall, hardwood floors and tile in main living area, and carpet/tile in the bed/baths.

    Here is the HVAC ducting
    The main trunk is ran on the ceiling of the basement and 2 car garage so it is accessible. The 6" vent branches are accessible in the basement and are covered with sheetrock in the garage, so accessible but will need drywall removal. All are sheetmetal, and sealed but not insulated.

    Can I zone this system? I would like to have a downstairs (living, dining, kitchen zone) and upstairs (2 bath, 3 bedrooms) zone with the overflow zone being the basement (currently media room, bath, laundry room).

    I'm looking to do a VALUE option, if zoning isn't it then what is the better value option - investment in system compared to operating cost in conjunction with leaving in two years.

    Please let me know what you think about the zoning option first. Can it be done? If anything is confusing or you need additional information please ask.
    Last edited by beenthere; 03-29-2012 at 02:49 PM.

  2. #2
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,604
    I like the Trane 20i for zoning ,there are not cheap although they work very well .if only one zone is calling then the system runs on first stage and is about 50% capacity then if the second zone call it will go to full capacity

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,829
    I count 8 6" runs. If metal pipe, that's 2 tons worth but you have a 2.5 ton system.

    If you are leaving in 2 years, I wouldn't do anything. 3 zones will just leave you short cycling on overheat/overcool limit if there is one installed. Or cycling on furnace limit and risking freezeup if not installed.

  4. #4
    Join Date
    Aug 2011
    Location
    Kansas City
    Posts
    78
    Thanks for the reply.

    New system - before I go that way I want to see if the zoning works...also the xl20i says it is a heat pump, is that also an AC system?

    Zoning - ok, if won't work, you have any suggestion for the temperature difference between the upstairs and down stairs? Would running the system on the 'ON' setting instead of the 'Auto' setting help? Also the main level and upstairs returns don't pull much air in comparison to the basement one (could it just be how close it is to the air handler vs the further returns)? The vents blow cold but low pressure too.

    Solutions? - Would returns in the upstairs room make a difference?
    Inline duct boosters, would they help?

  5. #5
    Join Date
    Aug 2011
    Location
    Kansas City
    Posts
    78
    oh Baldloonie - I missed one run, it is a 6" at the end, if that makes any difference.

  6. #6
    Join Date
    May 2006
    Location
    Austin, Texas
    Posts
    278
    Take it from someone who has been married 20 years; let her control the thermostat. If you will only be there for 2 years, consider the payback of doing major renovations to ductwork. If it is 21 years old, it might be better to ride it out if possible.
    On the other hand, it could be an investment and make selling the house easier.

  7. #7
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
    Posts
    2,584
    I agree with B.L. If you're leaving in 2 years, I'd forget about the zoning. I would recommend a variable speed blower on the furnace (80% or 90%) and a 13.00 SEER A/C.

  8. #8
    Join Date
    Aug 2011
    Location
    Kansas City
    Posts
    78
    VS blower motor - like the evergreen unit?

    13 SEER AC...so just replace the outside condenser?

    On the control, yes she'll get control but I don't want the higher bills. I see this as an opportunity to make upgrades for the selling. If I can change the outside unit then the air handler that would be great however the three HVAC guys who have been out (all the same company) said the whole system needs to be replaced together. They say such an old system would be hard to get compatible with the new equipment, unless I want to stay single stage and lower SEER/EER.

  9. #9
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,645
    Really, this is more a classic case of improper air balance. If one area is being satisfied consistently before another area, then it likely the other area is just not getting enough of the cooling.

    If the unit itself is still functioning properly, and is keeping up with the overall heat load, then i don't really see a reason to replace it. At most, this looks like something that can be handled by increasing the duct sizing (or adding a few extra ducts -effectively the same) to the areas that are lagging behind. The idea is to get the cooling flow to match the heat introduction to a particular part of the house. As others have mentioned, you may already be a little under-ducted anyway. Even if it involved opening up few ceilings/walls, it's likely to be cheaper than a new system, and certainly cheaper than zoning a single trunk system like that - and it would probably do more for getting everything working 'right'.

  10. #10
    Join Date
    Aug 2011
    Location
    Kansas City
    Posts
    78
    crazifuzzy - it seems as though people said the system is close to the correct capacity, but if you think adding runs or more venting what do you suggest? I can pretty easily put in a couple 6" ducts with registers but unless that is going to solve/help solve the problem it won't be worth it.

    I really don't want to go into the attic with supply ducting because of the heat in summer and cold in winter but if I need to I will.

    Zoning I was considering 2 zones by shutting off the main trunkline with dampers, so basically an upstairs zone and a downstairs zone. It sounds like an easy and viable option but you Pros have said no, so now it's time of the next idea.

  11. #11
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,645
    No one on here is going to be able to give you specific advise. But, if certain areas are cooling faster than others, the fix is to cut back on those areas that are getting too much, and send more cooling the the areas that aren't getting enough. For your short time left in that house, it seems to be the cheapest way to go to get to what you want (the whole house having the same comfort level).

    In many ways, people turn to zoning so they don't have to bother adjusting the air balance properly, because it will basically do it for them, but that convenience comes with a high cost. I don't see it worth it in your situation. I'd recommend finding a local pro to come in and do a room by room heat load calc, and adjust the air balance accordingly. If this balance requires adding a couple extra registers, then have him/her do that - but you need the hard numbers first.

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