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  1. #1
    Jon mackay's Avatar
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    Default 3 Ton A/C in 2,000 Sq. Ft. House

    A 3 Ton Air Conditioning unit was installed at a 2,000 Sq. Ft. house I inspected. The system was less than a year old and there were problems with the duct work and electrical. When I got outside, I couldn't believe the size of this a/c unit.
    I was not able to run the unit due to cold outside temperatures.

    I am thinking that there is no way this will work but wanted to get some facts about what some of the issues would be.

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  2. #2
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    I live in middle Geeorgia and have a 4 ton unit (12 years old) and 2400 sq ft (28 years old). Works fine untill we have 98+ days.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  3. #3
    Jon mackay's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    I am just afraid that the unit will drop the temperature too fast to actually be able to remove the moisture from the air. It seems like the temperatures will fluctuate way too much and create a humid/ cold environment but I was looking for some good data before reporting. The temperatures and humidity here in New York are quite a bit different than in Georgia, we are typically in the mid to upper 80s during peak summer months.


  4. #4
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    In NC if the system was replaced under the 2009 code the HVAC contractor who did the installation is required to do a load calculation to determine the size of the system. These calculations have to be available if asked for. You might be able to use that code reference if you are concerned the system is not the right size. Like I said this is in NC.



    SECTION 312
    HEATING AND COOLING LOAD CALCULATIONS
    312.1 Load calculations.
    Heating and cooling system design
    loads for the purpose of sizing systems, appliances and equipment
    shall be determined in accordance with the procedures
    described in the ASHRAE
    Handbook ofFundamentals. Heating
    and cooling loads shall be adjusted to account for load
    reductions that are achieved when energy recovery systems are
    utilized in the HVAC system in accordance with the
    ASHRAE
    Handbook-HVAC Systems and Equipment.
    Alternatively,
    design loads shall be determined by an approved equivalent
    computation procedure, using the design parameters specified
    in Chapter
    3 of the International Energy Conservation Code.

    For one- and two-family dwellings and townhouses heating
    and cooling equipment shall be sized based on building loads
    calculated in accQrdance with ACCA Manual T



  5. #5
    Ted Menelly's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Jon mackay View Post
    I am just afraid that the unit will drop the temperature too fast to actually be able to remove the moisture from the air. It seems like the temperatures will fluctuate way too much and create a humid/ cold environment but I was looking for some good data before reporting. The temperatures and humidity here in New York are quite a bit different than in Georgia, we are typically in the mid to upper 80s during peak summer months.
    3 ton

    2000 sq ft

    I thought your were going to say it was to small, not to big. You are afraid it will cool to quick and not take out enough moisture. I was thinking it was about a 1/2 to small and would run for extended periods of time in those humid New York summer days. With a lot of high ceilings bringing total cubic feet up, maybe ten foot ceilings, even 3 and a half would not be big enough. Obviously it depends on the entire build of the home.

    Ted Menelly, Castle Home Inspection Services
    www.inspectmycastle.com
    Fort Worth, Keller, Southlake, Plano, Flower Mound, DFW, TX

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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Here in southeastern PA, 1 ton will handle approximately 700 sq ft of interior living space. A 3 ton unit here might be slightly oversized based on square footage alone.......but.........square footage is only one of many other factors that go into the sizing of a system. Orientation to the sun, age of house, method of construction, insulation levels in house and maybe some other things will also play a role in sizing a system.


  7. #7
    David Bell's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Too many variables to say if it is sized exactly right. But I'd be willing to bet it's within a half ton, and that extra 200 cfm, or lack of 200 cfm might only make a difference on a 95 degree day. What were the duct problems?


  8. #8
    Jon mackay's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Interesting,
    Maybe the unusually large size of the unit is throwing me off here.

    The duct problem is a return air duct that has been left open pulling in basement air (approx 8" x 10")and improperly connected ducts right at the unit leaving gaps that were just unacceptable.


  9. #9
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Jon,

    The old method of using square feet to determine tonnage should not be used. The only accurate way to determine A/C size is by doing the proper Manual J calculations. In addition, a smaller unit will do a better job of removing moisture than a unit that is too large.


  10. #10
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Jon mackay View Post
    I am just afraid that the unit will drop the temperature too fast to actually be able to remove the moisture from the air. It seems like the temperatures will fluctuate way too much and create a humid/ cold environment but I was looking for some good data before reporting. The temperatures and humidity here in New York are quite a bit different than in Georgia, we are typically in the mid to upper 80s during peak summer months.
    3 Tons for a 2,000 sf home, sounds about right. Unless the home has killer insulation and is tight as a drum, I just do not see the size of the unit being an issue. My home is right at 2100 sf and I have a 3.5 ton unit. Middle TN on an average August day might hit the upper 80's to low 90's. RH in the morning and night will be in the 70% to 80% range and drops to around 30% to 40% in the day.

    I kind of agree that using the 1 ton per X number of square feet might not be the most accurate method but it is about all we can expect a home inspector feller to do. Home inspectors just do not perform Manual J calculations as a normal part of an inspection.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  11. #11
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Scott, Exactly right! That is why home inspectors (been one for 12 years) should not comment on the adequacy of the size of the A/C unit. Reporting the size is fine but I do not believe we can do enough to comment on the size of the A/C.


  12. #12
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Bob Spermo View Post
    Scott, Exactly right! That is why home inspectors (been one for 12 years) should not comment on the adequacy of the size of the A/C unit. Reporting the size is fine but I do not believe we can do enough to comment on the size of the A/C.
    Based on experience in what we see in the home....all said and done....can give us a very reasonable idea of what that particular home should have....give or take of course. As far as commenting one way or another it would be our job if we saw something totally out of logic's hands as far as size such as a 2 1/2 ton unit in the average five year old 2100 square foot home. If we think it can vary a bit one way or another by a half ton then let it be.

    I commented on one the other day. High volume ceiling and 2600 sq ft with a 3 ton in it in , of course, north TX and this home had nothing out of the ordinary for a build, windows, insulation, reflective barriers, outside wall etc etc etc etc. I wrote it up to have a HVAC company do some calculations because as far as I was concerned it was far to small for that particular home. To not have done so would have been foolish.

    Ted Menelly, Castle Home Inspection Services
    www.inspectmycastle.com
    Fort Worth, Keller, Southlake, Plano, Flower Mound, DFW, TX

  13. #13
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    I agree on commenting on the adequacy of the cooling power on a residential HVAC system is not the job of a home inspector, but...........

    If as a home inspector, if you find a 4-ton A/C unit in a 1500sf home you better say something about it! A home that is "super" cooled will have major moisture problems.

    I honestly feel that if you use the 500sf to 700sf per ton rule that for most homes in the vast majority of the country that you will be fairly safe when determining if an A/C unit is too big or too small for a home. A/C is a big thing in the South and home inspectors are always asked about the A/C on the home.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Scott Patterson View Post
    I agree on commenting on the adequacy of the cooling power on a residential HVAC system is not the job of a home inspector, but...........

    If as a home inspector, if you find a 4-ton A/C unit in a 1500sf home you better say something about it! A home that is "super" cooled will have major moisture problems.

    I honestly feel that if you use the 500sf to 700sf per ton rule that for most homes in the vast majority of the country that you will be fairly safe when determining if an A/C unit is too big or too small for a home. A/C is a big thing in the South and home inspectors are always asked about the A/C on the home.
    I saw this exact configuration this morning Scott.


  15. #15
    Jon mackay's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    ok, just to check myself, this tag is 3 ton correct? It's a carrier.

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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Jon mackay View Post
    ok, just to check myself, this tag is 3 ton correct? It's a carrier.
    I'm reading it as a 3 ton unit. ......36A311 "36" = 3 tons

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  17. #17
    Jon mackay's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    OK, that's what I thought. Thanks.


  18. #18
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Scott Patterson View Post
    ...

    If as a home inspector, if you find a 4-ton A/C unit in a 1500sf home you better say something about it! A home that is "super" cooled will have major moisture problems.
    Recently I had a 1 bedroom condo with a 5 ton system, which I made a big deal out of, telling the client that it appeared to be grossly oversized and would likely result in a meat-locker feeling in the living space.
    A month or so later I ran into her agent and asked if they'd gotten that resolved. He laughed and said no, they didn't want to get into that.
    Maybe I'll invite myself over this summer when it's 90 F and 90% humidity and see how she's holding up.

    "There is no exception to the rule that every rule has an exception." -James Thurber, writer and cartoonist (1894-1961)
    www.ArnoldHomeInspections.com

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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    The Carrier 24ana7 air conditioner is a 2-stage air conditioner unit. I would think that it would work great in this house. It will not ramp up to full capacity unless demand calls for it. Read the installation manual.

    http://www.docs.hvacpartners.com/idc.../24ana-6si.pdf

    Jeff Euriech
    Peoria Arizona


  20. #20
    Jon mackay's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Great info, Thank you Jeff.


  21. #21
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Scott referenced a Manual J. Until you do one of those, more specifically a Manual J Revised, you're just going to be guesstimating. I've only had one of those done during one of my inspections. The contractor that did it spent as much time in the home as I did for the inspection - that was without running the numbers and creating a report.

    Eric Barker, ACI
    Lake Barrington, IL

  22. #22
    David Bell's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Being a 17 SEER unit might throw you off if you were to just look quick, the larger coil area gives the illusion of a larger capacity unit.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    I did one yesterday that was 4 tons (3100 sq ft) in deep south Texas where we are already hitting mid 90's. I recommended an independent HVAC technician to perform a Manual J Calculation. The seller called his Builder (DR Horton) who claims that they have the calculation, but I am willing to bet that it was done for some other part of the country and they are using it to save some $.
    PS the unit could not get any colder than 70 and it was 80 inside the home.

    Richard Flores
    Professional Inspector TREC # 8139
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  24. #24
    Scott Phillips's Avatar
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    Smile Re: 3 Ton A/C in 2,000 Sq. Ft. House

    3 ton unit, 2000 sq. ft. house near Philadelphia. Works great in my house but the installer took about 1 hour taking measurements and about another 1/2 hour asking me questions.


  25. #25
    Darrell Udelhoven's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Jon mackay View Post
    A 3 Ton Air Conditioning unit was installed at a 2,000 Sq. Ft. house I inspected. The system was less than a year old and there were problems with the duct work and electrical. When I got outside, I couldn't believe the size of this a/c unit.
    I was not able to run the unit due to cold outside temperatures.

    I am thinking that there is no way this will work but wanted to get some facts about what some of the issues would be.
    Endicott, NY is near Binghamton, NY.
    Winter design is 99% -2-F, 97.5% 1-F. (This is correct.)


    EDIT: Wrong, that is for Birmingham, AL - Summer design is 94-dry bulb 75-wet bulb, or around 42% Relative Humidity. Wind turned page; I knew that appeared - too high a temp!

    Syracuse, NY; 87-dry bulb 71-wet bulb or around 46% RH.
    Summer Design is 88-F 73-wet bulb or around 49% RH here in SW WI, - a higher heat load.


    One of the problems that exists in cold climates with moderate summer temps is that an evaporator coil is rated for a certain amount of airflow without going above a usable static pressure drop.

    If you try to push a couple hundred CFM above a coils top rating, the static skyrockets beyond the blower's capabilities.

    Therefore, if they go to a 2.5-ton condenser they would need to use an oversized tonnage evaporator so the TESP (static pressure) would be in the usable range of the furnace blower's graph or chart.

    You always start with a manual J load calc & look at the home's options to reduce both heating & cooling loads.

    I have no doubt that the home could be retro-ed so a 2.5-ton condenser could handle the cooling load & also reduce the heating load.

    How many days & hours is it 94-F there, I'm betting the vast majority of A/C hours represent a load that will result in shorter runtime cycles than is desirable for efficient operation.

    Everything has to work together so the proper airflows at normal static pressures are obtained in both heating & cooling modes; in cold climates that can be a tough problem that must be properly resolved.

    In SW WI, I have a mere half-ton window unit cooling perfectly to 76-F 55% RH, even in 104-F Heat Index, around 850-sf - first floor of my 1937 farm home, it's not well insulated & has a lot of windows.
    That is 1700-sf per ton of cooling.


    I tested my setup & the rated 6,000-BTUH was delivering over 7,000-BTUH at that particular time & conditions.

    View my Internet pages on it & all other aspects... - udarrell - Retired HVAC/R since mid-1970s

    Last edited by Darrell Udelhoven; 05-03-2010 at 11:04 AM. Reason: EDIT: Syracuse, NY; 87-dry bulb 71-wet bulb or around 46% RH.

  26. #26
    John Sullivan's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    It all depends on what part of the country your in. In southern Nevada our engineers rate tthe A/C at between 400 and 500 sq feet per ton and that will vary depending on type of insulation, ceiling height, number & type of windows ect. Humidity is not a big concern for us. High humidity is 25%. The attic mounted furnace air handler and coils are matched for cooling since we don't don't use that much heat. Summer temps 100 to 115 winter 35 to 50.
    However unless your an HVAC tech, a plumber, an electrician or an engineer its beyound the scope of most property inspectors to determine adiquicy of components weather a A/C unit, heater, water heater, main electrical panels or any other item, so if you do mention adiquicy, how you write it up is going to be your primary concern for your liability.


  27. #27
    Darrell Udelhoven's Avatar
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    Exclamation Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by John Sullivan View Post
    It all depends on what part of the country your in. In southern Nevada our engineers rate the A/C at between 400 and 500 sq feet per ton and that will vary depending on type of insulation, ceiling height, number & type of windows ect. Humidity is not a big concern for us. High humidity is 25%. The attic mounted furnace air handler and coils are matched for cooling since we don't don't use that much heat. Summer temps 100 to 115 winter 35 to 50.
    However unless you're an HVAC tech, a plumber, an electrician or an engineer its beyound the scope of most property inspectors to determine adiquicy of components weather a A/C unit, heater, water heater, main electrical panels or any other item, so if you do mention adiquicy, how you write it up is going to be your primary concern for your liability.
    Additionally, in that dry climate we can use 500-CFM per ton of cooling because there is very little latent load, & therefore we can put a higher sensible heatload through the evaporator & bring the temp down faster.

    Yes, it's how you write it up... udarrell


  28. #28
    Mark Hall's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Scott Patterson View Post
    I agree on commenting on the adequacy of the cooling power on a residential HVAC system is not the job of a home inspector, but...........

    If as a home inspector, if you find a 4-ton A/C unit in a 1500sf home you better say something about it! A home that is "super" cooled will have major moisture problems.

    I honestly feel that if you use the 500sf to 700sf per ton rule that for most homes in the vast majority of the country that you will be fairly safe when determining if an A/C unit is too big or too small for a home. A/C is a big thing in the South and home inspectors are always asked about the A/C on the home.
    Funny - the key statement here is "most of the country" - I've got a 4 ton for 1500 square feet - the wrinkle is, it's two-stage and peak power rates here approach 22 cents a kw/hr, vs a nickel for "off" peak.

    By tightening the envelope (R50 in the ceiling) and letting the house heat up during the day when no one is home we have more comfort and savings. Pulling 1500 square feet down 10 degrees is not "efficient" electrically, and it wouldn't even be possible with a "proper" sized heat pump.

    Having two stages makes up for a multitude of "sins"...

    Weekend power is "off peak" so we leave the house @ 76 - and the HP hasn't kicked into "stage 2" at all so far this year, despite temps approaching 110.

    As someone else mentioned, moisture/humidity isn't a factor.

    And if you think my HP is oversized you should see my little bro's HP -

    2.5 tons for 768 sq ft.

    That said, a northerner (like me) would lay an egg when they saw the windows in these houses. Ma and Pa ripped out their double-pane aluminum windows in the early 1980's - these folks were putting in single-pane aluminum windows until the mid 90's.

    And insulation? ... fuggidaboudit!


  29. #29
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    One ton will handle about 700 square feet of living space around here in SE Pennsylvania.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Around here 3 ton is about right for 2000 sqft
    HOWEVER, my guess is that what is throwing you off is the physical size of the condenser. Notice on the tag, it is an R410a condenser. This typically means it is a 16 SEER unit.
    An R410a 3 ton unit, physically LOOKS like a standard 3 ton unit.
    R410a has different component requirements.
    Gotta go ...

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  31. #31
    David Bell's Avatar
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    It is a 17 seer unit, the manufacturers typically don't double wrap the condenser coils on higher seer units so the condensers are considerably larger.


  32. #32
    Darrell Udelhoven's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    If there is an indoor humidity problem & lack of runtime per cycle, the airflow could be dropped as low as 350 even 325-cfm per/ton, or 975-cfm with a 3-ton condenser using a TEV indoor coil refrigerant metering device. (Which it has.)

    The lower airflow reduces BTUH capacity resulting in lower dehumidification runtime cycles.

    Also, a room t-stat could be used with a wide on/off differential setting. Especially when you're not home, a wide or fewer cycles per hour settings - will get the humidity down & raise the SEER performance of your unit. - udarrell

    Last edited by Darrell Udelhoven; 06-26-2010 at 03:05 PM. Reason: lower airflow reduces BTUH capacity...

  33. #33
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Richard Flores View Post
    I did one yesterday that was 4 tons (3100 sq ft) in deep south Texas where we are already hitting mid 90's. I recommended an independent HVAC technician to perform a Manual J Calculation. The seller called his Builder (DR Horton) who claims that they have the calculation, but I am willing to bet that it was done for some other part of the country and they are using it to save some $.
    PS the unit could not get any colder than 70 and it was 80 inside the home.
    If the return air was 80 inside and the discharge air was 70 then the system may not have been working properly. The size of the house should not affect the discharge air temperature.


  34. #34
    Darrell Udelhoven's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by James Duffin View Post
    'If' the return air was 80 inside and the discharge air was 70 then the system may not have been working properly. (TRUE) The size of the house should not affect the discharge air temperature. (TRUE)
    The actual temp-split was probably considerably more than 10-F.

    The larger cubic foot of possibly high humidity air to have its heat removed, including a lot more air infiltration areas, would affect, -depending on many other factors - how much below 80-F it could pull-down the sensible temp.

    Under specific conditions, many factors affect how low a system will pull the temp.

    The temp-split will be less as the indoor humidity goes above 50%, & the split will be higher as it goes below 50%

    The home's rate of air infiltration is a big factor, as are too many other things to mention here. - udarrell

    Last edited by Darrell Udelhoven; 06-26-2010 at 05:44 PM. Reason: Misplaced word, plus clarifications...

  35. #35
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    From a personal view, owning a 1400 sq ft home in SoCal that was built in 1971 with a 2.5 ton AC, added on 500 sq ft, but didn't install a new system, I can attest that in our climate, 2.5 tons is not nearly enough for 1900 sq ft. After 39 years of almost trouble-free service, we decided to upgrade to a high efficiency (Fed tax credit made it worthwhile) 4-ton system starting from the ground up. We completely redid the distribution system, adding three new outlets, new ducting throughout, installed the new system in the attic--and we couldn't be happier.

    The old system had trouble keeping the temp below 78 and couldn't if the outside was over 95*--ran all day if we didn't set the thermostat higher. The new system, with its variable speed fan and adjustable orifice just coasts along and has no problem whatsoever keeping things at 75. And, it is SO QUIET.

    We are obviously very satisfied and wonder why we didn't do this years ago--oh yea! Tax credits.

    Have a cool one on me.
    Jack


  36. #36
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    In high humidity areas it is actually better to be slightly under sized to eliminate excessive humidity. The rule of thumb in central Florida is 500 Sq. ft. per ton. I have inspected homes where the homeowner says he has over sized his condenser (and proud of it) thats when I start to look for moisture problems. The oversized unit cools so fast and shuts down it never has time to take out moisture from the air. You might have seen signs of droplets on the interior walls this can indicate an over sized system. Unfortunately the fix can be expensive.

    Thomas W. McKay
    ASHI Certified Home Inspector


  37. #37
    Darrell Udelhoven's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    [QUOTE=jackt0402;139024]From a personal view, owning a 1400 sq ft home in SoCal that was built in 1971 with a 2.5 ton AC, added on 500 sq ft, but didn't install a new system, I can attest that in our climate, 2.5 tons is not nearly enough for 1900 sq ft. After 39 years of almost trouble-free service, we decided to upgrade to a high efficiency (Fed tax credit made it worthwhile) 4-ton system starting from the ground up.
    We completely redid the distribution system, adding three new outlets, new ducting throughout, installed the new system in the attic--and we couldn't be happier.
    IMHO, the old 2.5-Ton system due to the duct system, airflow, & other critical factors, - it was NOT Delivering its nominal tonnage to the conditions areas!

    The new duct system is probably properly sized & well insulated. Additionally that 2.5-T install might have been far from performed properly.

    That original install could have been actually delivering between 1.5 & 2-Ton of cooling to the conditioned areas.

    I cool a 1937 farm home loaded with windows & NO special retro work first floor at over 800-sf with a mere 6,000-BTUH Half-Ton window unit & 20" vertically adjustable fan to move the air through the rooms. That 20" 3-speed fan is critical to its cooling performance!

    It will cool that first floor when it's 90-F with heat Indexes above 106-
    F. We had 113-F Heat Index in Prairie du Chien, WI recently I wrote it down, hope they got it right!. At 800-sf, that's 1600-sf per/ton. Therefore, why would I need 4-Ton for 1900-sf, or a Ton of cooling for a mere 475-sf, at 95-F?

    I have a web page on my first floor window unit, - & can prove my statements. Call it 1600-sf per-ton of cooling, that is miles from 475-sf per ton; go figure.

    A lot of split system installs are terribly compromised due to a host of factors that weren't done right.

    The old system had trouble keeping the temp below 78 and couldn't if the outside was over 95*--ran all day if we didn't set the thermostat higher. The new system, with its variable speed fan and adjustable orifice just coasts along and has no problem whatsoever keeping things at 75. And, it is SO QUIET.
    We are obviously very satisfied and wonder why we didn't do this years ago--oh yea! Tax credits.
    Have a cool one on me.
    Jack
    I will bet I could have started with a manual J room by room heat-gain calc, with the HTM multipliers, on the home, then a manual D on the ductwork & airflow, & with a proper install & a verification of its Nominal 2.5-Ton being delivered to the conditioned areas, - it would control perfectly to 75-F with long enough runtime cycles to deliver 50%, or considerably less, humidity levels.

    I am glad you are happy with the 4-Ton, - that's what counts; I am simply indicating what could have been accomplished. - udarrell

    Last edited by Darrell Udelhoven; 07-26-2010 at 09:22 AM. Reason: Typo & sf...

  38. #38
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    We (other AHJ's) had a discussion about Manual J and D with HVAC contractors. Mostly when there is a complete change out of the system. The HVAC contractor stated that if the mechanical contractor wanted too they could munipulate the Manual J calculations to fit any scenario they needed. There is so much guess work on infiltration, duct size/leakage that they (the HVAC company) could upsell any unit just by plugging in numbers to match what they want to sell. House only requires a 2.5 ton unit but the company would make more on a 3.5.

    It all depends on how honest the HVAC company is. Manual J's don't mean anything if the contractor is not honest!


  39. #39
    Darrell Udelhoven's Avatar
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    Arrow Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Wayne Carlisle View Post
    We (other AHJ's) had a discussion about Manual J and D with HVAC contractors. Mostly when there is a complete change out of the system. The HVAC contractor stated that if the mechanical contractor wanted too they could munipulate the Manual J calculations to fit any scenario they needed. There is so much guess work on infiltration, duct size/leakage that they (the HVAC company) could upsell any unit just by plugging in numbers to match what they want to sell. House only requires a 2.5 ton unit but the company would make more on a 3.5.

    It all depends on how honest the HVAC company is. Manual J's don't mean anything if the contractor is not honest!
    That is another reason we need independent auditors to do Energy Audits, & Manual J room by room heat-gain calcs.

    We don't have a fraction of the CERTIFIED Energy Auditors & BTUH System Performance auditors we need for the Bill in congress...

    I.E., an 18-SEER unit may only be delivering 9-SEER, etc.
    The install, set-up, duct system & airflow can half the delivered BTUH.

    Last edited by Darrell Udelhoven; 07-27-2010 at 02:56 PM. Reason: typo... Bill in congress...

  40. #40
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Nick Ostrowski View Post
    One ton will handle about 700 square feet of living space around here in SE Pennsylvania.
    that's about right here in arkansas too.


  41. #41
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Jon mackay View Post
    A 3 Ton Air Conditioning unit was installed at a 2,000 Sq. Ft. house I inspected. The system was less than a year old and there were problems with the duct work and electrical. When I got outside, I couldn't believe the size of this a/c unit.
    I was not able to run the unit due to cold outside temperatures.

    I am thinking that there is no way this will work but wanted to get some facts about what some of the issues would be.

    Jon, it would help everyone here if you put location information in your bio. Then when you ask a question here, such as this one, folks can offer comments without wondering where you are in the workd, and be forced to ask.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Wayne Carlisle View Post
    We (other AHJ's) had a discussion about Manual J and D with HVAC contractors.
    ...It all depends on how honest the HVAC company is. Manual J's don't mean anything if the contractor is not honest!
    Wayne, I think this applies to all trades and overseers. They have (need) to be trusted for their experience and integrity. I'm not saying there isn't a bad apple here and there, or a mistake is made with the load, but overall they are all honest and try to do a good job.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Jon,
    Here is a link to a site that will help to ascertain the age of the Units as well. The production date is usually found in the serial number and the tonnage in the model number. HVAC -PRODUCTION DATE/AGE | Building Intelligence Center


  44. #44
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Rich Goeken View Post
    Jon, it would help everyone here if you put location information in your bio. Then when you ask a question here, such as this one, folks can offer comments without wondering where you are in the workd, and be forced to ask.
    The original poster is no longer on Inspection News, this thread is from 2010.

    This is a good example of why you should look at the date of the post before you post a comment to the threads.

    Start a new thread if you want to talk about the topic you will get a better response.....

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  45. #45
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Scott Patterson View Post
    The original poster is no longer on Inspection News, this thread is from 2010.

    This is a good example of why you should look at the date of the post before you post a comment to the threads.
    Start a new thread if you want to talk about the topic you will get a better response.....
    Scott, Thanks, didn't notice as it poped up on the weekly digest, and usually whatever is there is current and has current postings. Will check from now on. However, it was interesting reading the replies. I stand by my comment that a location should be there to assist in replies.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    When I worked in sales for an HVAC/R wholesaler, I used to have an old Montgomery Wards Air Conditioner sizing chart that they supplied to their outside salesmen back in the '60s and '70s when most homes were not well insulated. Back then they recommended the old timers to sell 1 ton per 400 square feet for a brick or frame structure without insulated walls.

    In the early '80s, when I would perform a Manual J load calculation on an older home, the unit size was usually a half ton lighter than using the old Montgomery Wards method. I was selling 7, 8, 9 and 10 SEER units at the time. 10 SEER was considered high efficiency and the manufacturers were just starting to develop 12 and 13 SEER due to pending congressional legislation.

    On January 1, 1987, 10 SEER became the minimum manufactured rating allowed. That minimum was raised to 13 SEER on January 1, 2006.


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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Its hard to use rule of thumbs anymore though they might tell you if a unit is grossly oversized. Some of the new heat pumps and higher effieceny units look huge. Adding even a little rigid foam insulation under vinyl siding can have a noticable effect. Shading, replacement window with a low shgc, etc really has an effect on ac needs.

    Some very energy efficienct homes with high efficiency units have a hard time controlling latent heat loads.


  48. #48
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Nick Ostrowski View Post
    Here in southeastern PA, 1 ton will handle approximately 700 sq ft of interior living space. A 3 ton unit here might be slightly oversized based on square footage alone.......but.........square footage is only one of many other factors that go into the sizing of a system. Orientation to the sun, age of house, method of construction, insulation levels in house and maybe some other things will also play a role in sizing a system.
    That is basically a rule of thumb on this issue and supported by most.
    Since he has said it is a certain size I see no problem as not all rooms will need to be cooled evenly and some rooms not at all.
    This would equate to a 2100 sq ft home.


  49. #49
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Rich Goeken View Post
    Scott, Thanks, didn't notice as it poped up on the weekly digest, and usually whatever is there is current and has current postings. Will check from now on. However, it was interesting reading the replies. I stand by my comment that a location should be there to assist in replies.
    Rich Goeken,

    When Jon MacKay was active on the forum, his profile location was clearly filled out. His location denoted New York State. If memory is correct it was far beyond the greater NYC area, may have been near Buffalo.

    Here is another of his post threads, where location made a tremendous difference:

    Deck structure questions


  50. #50
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Rich Goeken,

    When Jon MacKay was active on the forum, his profile location was clearly filled out. His location denoted New York State. If memory is correct it was far beyond the greater NYC area, may have been near Buffalo.

    Here is another of his post threads, where location made a tremendous difference:

    Deck structure questions
    I see what you mean, location is important. That deck is scary... Don't think I would want to walk on it!!! EVER!!


  51. #51
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Bob Spermo View Post
    Scott, Exactly right! That is why home inspectors (been one for 12 years) should not comment on the adequacy of the size of the A/C unit. Reporting the size is fine but I do not believe we can do enough to comment on the size of the A/C.
    +1. We are not energy auditors. (Unless of course you're doing that business too, in which case there should be no doubts - whatever the load calculates.)


  52. #52
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    Default Re: 3 Ton A/C in 2,000 Sq. Ft. House

    Quote Originally Posted by Darrell Udelhoven View Post
    If there is an indoor humidity problem & lack of runtime per cycle, the airflow could be dropped as low as 350 even 325-cfm per/ton, or 975-cfm with a 3-ton condenser using a TEV indoor coil refrigerant metering device. (Which it has.)

    The lower airflow reduces BTUH capacity resulting in lower dehumidification runtime cycles.

    Also, a room t-stat could be used with a wide on/off differential setting. Especially when you're not home, a wide or fewer cycles per hour settings - will get the humidity down & raise the SEER performance of your unit. - udarrell
    It might be easier to just say the lower airflow creates a colder coil, which condenses more moisture from the air. If your on the east coast 350 would be good, but since all the new stuff is so much more computer controlled you really need to look close. The t-stat could be measuring the humidity and adjusting the air flow to get comfort just right. The HVAC stuff has changed a lot. Sure you can still get the plain Jane, on or off system, but a lot of the new ones are not that way. Especially if they bought one with the 2010 tax credit. Those systems will be variable speed fans at the least

    Jon you need to take pic's of the indoor unit and t-stat to get a better informed response, and location like posted above. Otherwise we are making assumptions.



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