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Help with A/C questions

Discussion in 'The OT' started by fluffybear, Jul 15, 2012.

  1. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    Peachtree...
    IS their any HVAC techs out there who might be able to offer me some assistance.

    Our 20+ year old Whirlpool 3 ton 12 seer A/C finally gave up last week (Home Warranty company sent 3 different companies who all confirmed it). Anyway, the Home Warranty company had a new 4 ton 16 seer Amana SSX16 & a 4-5 ton Goodman Evaporative coil installed.

    When you set the unit to 70, it would cool the entire house in the matter of a few hours even if the unit had been set to 82. This new unit does not seem to do even half as good. I do not hear the fan blowing like I use (if it is on it's quiet) and while the air coming out is cold, it takes hours just to cool to the house a few degrees (we turned on the unit at 6pm when it registered 77 and here it is now 9pm and it reads 75).

    When I have to run my A/C for hours on end just to cool the house a couple of degree's I am starting to think something is seriously wrong. The HVAC guy says it's my imagination and I'm just being picky so am I right in thinking something might be wrong or am I making a big deal out of nothing??
     
  2. trh

    trh This Space for Sale

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    I can't address what might be wrong with your new install, but if you had a 3-ton unit that was cooling your house, why did you install a 4-ton?

    In the AC world, bigger is not always better. If the 4-ton unit is too big, it will 'short-cycle' and then you end up with a moisture problem -- which could lead to a mold problem.
     
  3. Davenlr

    Davenlr Geek til I die

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    Im not a HVAC guy, but have a couple working for our company, and talk to them alot. Some things they told me when I was having problems...

    Measure the output of the register. It should be 20 degrees less than the air intake air temperature. Is it running the entire two hours (when you say it only dropped 2 degrees) or is the outside unit cycling on and off during that time? Is there any ice forming on the evaporator coils? Is their a good drip of water coming out of the drain? Just some things to check.

    Also check the inside unit, and make sure they didnt forget to tape/connect a duct, and no air is "leaking"...that the air intake filter is clean and not blocked, and the unit is not sucking air from outside, the attic, or under the house. It should only be sucking air from the living space.

    You are correct in that is not a very good drop. When it is 105 outside here, house is 82 during the day (set). At 4pm it shifts to 75, and takes about an hour. 2.5 ton, 1000 sq ft house, bad insulation.
     
  4. Stewart Vernon

    Stewart Vernon Roving Reporter Staff Member Super Moderator DBSTalk Club

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    Some of this also depends on the size of your house, and the layout... if you have all interior doors open or some shut, etc.
     
  5. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    We had an analysis done last year by GA power after we completed a new addition (adding roughly 600 sq feet to the house) and it was determined that a 3-ton unit was not sufficient for a home of our size. They recommended going with either a 4-ton unit or installing a new 2.5 ton unit to cover just the second floor.
     
  6. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    2 story home - 3200 square feet on insulated crawl space
    1st floor - 1900 square feet (6 rooms + 2 full baths)
    2nd floor - 1300 square feet (4 bedrooms & 1 full bath+master suite & bath
    Attic - insulated

    Since the kids are on vacation, most of the interior doors are open - all outside doors and windows are closed at all times unless someone is using them.
     
  7. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    I'll check those things tomorrow but yes it does seem the condensor is running the entire time the unit is on.
    I am thinking I might need give Amana call tomorrow and speak with them and see if they want to send someone out here through warranty...
     
  8. Davenlr

    Davenlr Geek til I die

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    Yea. I can pretty much tell you that if the air temp drop from intake to register is -15 degrees or more, they will say the unit is ok and to look elsewhere.

    Of course, the outside temp probably matters. Was it cooler there last year when you had the faster drop? If all else is up to snuff, you would probably save more money by keeping the temps close to the same all day, rather than stressing the system out at the hottest part of the day to cool things down from the "daytime high" setting. It takes a while to cool things down, and extract the residual heat from the floors and furniture, only to get it there and then go back to the "daytime" 82 setting.

    I also close the registers (and shut the doors) on unused rooms in the summer. I just dont see any point in cooling an empty unused room when its so hot.
     
  9. trh

    trh This Space for Sale

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    Excellent. An energy audit by a 3rd-party organization is the best way to go. I've seen way to many AC companies that try to sell larger units when they are not required.
     
  10. Getteau

    Getteau Icon

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    Is your unit stuck in low mode? My 16 seer Amana has 2 modes, low and high. When it first turns on, it runs in low for awhile to reduce the humidity and to start the cooling. After awhile, or if I turn the thermostat way down, it will kick into high mode. If you stand by the return air duct, you can barely hear it in low mode. However, when it kicks into high, you know it. If yours has it, maybe look at the humidity setting and see if it's set too low.
     
  11. Go Beavs

    Go Beavs Hall Of Fame

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    Looking at the outdoor unit's specs, it doesn't appear to have a two stage compressor so it's either going to be "on" or "off". The evaporator may have a two speed fan motor in it though and could be set at the wrong speed. You would probably see icing in that case, either on the evaporator coil inside or the vapor line (larger pipe in the line set) indoors or at the ODU.

    Just a WAG... :)
     
  12. Rich

    Rich DBSTalk Club DBSTalk Club

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    True, but you really gotta know what you need before you buy. When I moved into my house 26 (is that OK, I've forgotten the rule already....:lol:) years ago, I knew I needed a 3.5 ton unit. I used estimating books to arrive at that figure. Must be someplace online that has tables for the cubic footage of a house.

    Rich
     
  13. harsh

    harsh Beware the Attack Basset

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    Salem, OR
    Some jurisdictions require some level of fresh air injection into the system. It can be a big help with radon and mold abatement.
     
  14. trh

    trh This Space for Sale

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    While cubic feet is used to calculate the size of the AC required, the building envelope is just as important and must also be taken into account. You must know the attic and wall insulation R-values, square footage of glass along with solar heat gain coefficient and U-factor of all the glass and the orientation of that glass (north, east, etc.), square footage of ducts and where the ducts are located, and a whole host of other data. In the AC world, you have to perform a system sizing calculation which is called a Manual-J. You might be able to get rough estimates from acca.org or just Google Manual J free software.
     
  15. Rich

    Rich DBSTalk Club DBSTalk Club

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    Any good AC contractor should be able to size a house with a computer program these days and you want to be looking at ~ 45 to 50 degrees on most of your registers. A simple cooking thermometer inserted into the register will quickly tell you the temp. The farther away from the evaporator unit, the higher the temp will be.

    In a forced air system you won't be able to see the evaporator coil if it's in the plenum of the duct work above the furnace. If you see ice on the condenser outside you've either got a problem (less gas than you should have) or the temp outside is too low to be operating an AC unit.

    I've got this dopey drunk living next door to me who runs his attic fan all summer long. With the AC on. So, he ends up sucking all the cool air up and out of the house and keeps replacing AC units, going up in size each time. Doesn't matter how big an AC unit he puts in, he'll never be able to cool his house properly. I've explained this to him several times, but the attic fan keeps running. I even told one of the contractors what he was doing with the attic fan and the guy agreed with me and told him, but the attic fan just keeps running. He's on his fourth or fifth unit since he moved in 20 years ago.

    No it's not a good temp drop, but central AC units don't cool off a hot house very quickly, just the nature of the beast.

    A properly sized, insulated unit should drop the temp inside the house to ~ 25 degrees less than the outside temp on a hot day. Ideally. Mine does.

    Rich
     
  16. Rich

    Rich DBSTalk Club DBSTalk Club

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    With central air you want the interior doors open for proper circulation. What's really important is if you have a house built for central AC or just heating. Mine wasn't built for central AC, but we close off the bottom floor registers and leave the registers upstairs open. In a house built for central air the registers will be high on the walls rather than close to the floor. We use ceiling fans to correct for air stratification.

    Rich
     
  17. Rich

    Rich DBSTalk Club DBSTalk Club

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    If you can afford it, that's the proper thing to do.

    Try this: Go outside to the condenser unit and you will see two lines going into the house. One will be insulated and one will be bare copper tubing or whatever they're using today. The insulated line should be much colder than the line that's not insulated. If they feel the same, many things could be wrong, not enough gas, blown compressor or a blown capacitor on the compressor. If you don't feel a real difference in temperature, call the contractor and show him.

    Another thing to look at is the condenser fan. Is it blowing hot air out of the condenser unit or cool air? Should be very warm.

    Rich
     
  18. fluffybear

    fluffybear Hall Of Fame DBSTalk Club

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    Everything checks out. 20+ degree temp between return and vents. Condensor seems to be doing it's thing - Hot air coming out the top and insulated line is cold. Not as cold as I was use to with the Whirlpool but that could very well be due to the different type of freon going into the system.

    I spoke with a neighbor who had a Lennox system installed last summer and they say it is not uncommon for them to run their unit at least 12 or 13 hours a day and that I should see the difference when the electric bill comes.


    I would like to have gone the dual system but the Home Warranty company arranged everything and I didn't want to risk rocking the boat. Installing a second unit might be something we will consider for next year if the wife insists.
     
  19. Rich

    Rich DBSTalk Club DBSTalk Club

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    I'd like to know what temps are at the registers. That's what really matters. If you're getting 55-65 degrees, something's wrong. I just had a capacitor blow on me in the condensing unit a couple of weeks ago and I found out that the new coolants and AC units should run about the same as with the good old freon.

    Don't know if this is still true, but Lennox systems used to use copper tubing up to the condenser and the coils in the condenser were aluminum. Dissimilar metals cause troubles when joined if not joined correctly or even if joined correctly. Witness what we went thru with aluminum wiring in houses years ago.

    I see your point. Your house should have had at least a three and a half ton unit in the first place, it's just a tad larger than mine in square feet, altho mine has vaulted ceilings and that makes a big difference, harder to cool. That's why houses are scoped out using cubic square feet.

    Rich
     
  20. trh

    trh This Space for Sale

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    You can't compare your two houses based on square footage (or volume). Your house is in Climate Zone 4 (maybe 5 if you're in the very northern part of NJ) and his house is in Zone 3. He has a higher AC requirement than you do and you have a higher heating requirement. The volume of the house has a small part in calculating the size of the AC. You have to calculate the loads on the walls, ceilings, floors, doors and windows. That is how the size of the AC is calculated.

    As the ACCA says this in a section on reasons for oversized equipment:
    You have to take into account the construction of the actual house.
     

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