Results 1 to 13 of 13
  1. #1
    We have a blower, coil and venting in attic

    Our 2 1/2 ton Carrier system is not cooling our two floor, 1900 square foot house in Toronto Ontario below 79 degrees, even if it runs for 5 days continuously. Installer came back and changed two of the 5" ducts to the main floor wtih 8" at a cost of an additional $1000. We have had the filters changed and the unit checked by the installer. So far we have spent $8,000 and have no air conditioning on hot humid days!

    Help!

    We have had conflicting advice from other professionals about venting and insulation and we do not want to continue to spend money with no results.

    We have taped all the ducts in the attic with metal tape and insulated the large metal duct with the aluminum fibreglass insulation. Still not getting the house cool.

    Another vendor has suggested soffit venting to creat cooler attic so that a/c components are not in such high heat. Will this work? We have an 80 year old house with no vents in the aluminum soffits which cover the old wooden soffits. We do have 4 vents in the roof. It will be very expensive to replace the eavestrough,soffit and facia just to get soffit venting. Will this provide the necessary cooling to the attic? Will this enable the air conditoner to cool the house?

  2. #2
    Join Date
    Jul 2005
    Posts
    171
    Katharine, you need to give a more complete description of the situation. Is your AC in the attic because heating is not forced-air? What kind of supply and return ducting is there to the first and second floors other than the 2 8" ducts mentioned?

    Did the installer do a load calculation? How did he come up with 2 1/2 tons? How much insulation is in the attic? In the outside walls of the house? How many windows and how good? Double pane? What was the outside temperature when you couldn't cool below 79? What was the temperature in the attic at 4PM on those days?

    It is easily conceivable that 2 1/2 tons may me insufficient for your house on real hot days.

    Your roof vents will exhaust hot air only if fresh outside air is allowed to come into the attic somewhere. Where is that? Do you have gable vents? If no gable or soffit vents, then no air will come into the attic. You may not need to replace the soffits. You may be able to install a whole bunch of 4" (or bigger, if there is room) round soffit vents, by cutting appropriate size holes in the soffits. I have just done this on a house. It's not cheap, but cheaper than replacing the soffits.

  3. #3

    Hmm

    I think your air conditioning is under size. For 1900sqf house you need at least a 5 ton unit. you better look for a different installer. a real one this time

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323
    Originally posted by katharine
    We have a blower, coil and venting in attic

    Our 2 1/2 ton Carrier system is not cooling our two floor, 1900 square foot house in Toronto Ontario below 79 degrees, even if it runs for 5 days continuously.
    Toronto must be having
    some VERY HOT nights.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Jul 2005
    Posts
    171
    Southpole, did you do a load calc on her house? If not, how do you know what size she needs?

  6. #6
    Join Date
    Sep 2004
    Posts
    3,157
    For 1900sqf house you need at least a 5 ton unit. In Toronto?

    The ice hasnt even melted yet

  7. #7
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323

    Design versus Actual Conditions

    Originally posted by south pole
    I think your air conditioning is under size. For 1900 sq ft house you need at least a 5 ton unit. you better look for a different installer. a real one this time
    Obviously a comment from an amateur to say "at least
    a 5-ton unit" which implies that a 5-ton may not be adequate.

    Outside air Design temperature for Toronto may
    only be 86' to 89'F.

    So on a day when it is 94' F, a properly sized
    A/C unit will really struggle
    to maintain inside design temperature.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  8. #8
    Join Date
    Jul 2005
    Posts
    171
    Designer Dan, Toronto has 347 cooling degree-days and a summer outdoor design temperature of 31C or 88F. Took about 15 seconds to look it up. No need to guess like that other amateur.

    Although I understand this summer they had quite a few days with temperatures higher than Ft. Myers...

  9. #9
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,323

    Design Conditions

    TORONTO Bin Data
    _______ Hours
    _____ Annual July
    ____95+ _ 1 __
    90- 94'_ 12 ___ 5
    85- 89'_ 90 __ 39
    80- 84' 274 _ 106
    75- 79' 491 _ 163
    70- 74' 661 _ 174
    65- 69' 711 _ 129

    ASHRAE DB/WB
    .4% _ 87/71'
    1.0% _ 84/70' (1% of 8,760 = 88 Hours)
    2.0% _ 81/68'

    Based on this bin data, one would
    expect only 17- 22 days (103 hours) to be >85'F.
    Design temperature of 84'F (1% ASHRAE) with inside temperature of ~73'F
    yields only 11'F differential temperature.
    That seems to be ~27 to 35% of AZ conditions.

    I am sure Summer '05 is exceeding normal temperatures.

    So, equipment sizing generalizations will NOT work.
    It's all about:
    Location Location Location
    _Windows _Windows _Windows
    Orientation

    We all have to put up with Windows everyday.
    MS Windows, that is. Have a pleasant day.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  10. #10
    Join Date
    Apr 2004
    Posts
    34
    I am just a few hours west of Toronto and lived there for 5 years. The weather here this summer has been very humid. We haven't seen weather like this in a long time. I run 9 commercial buildings and it has been hell with this weather. I do believe that 2.5 ton a/c unit for a 1900 sq foot home is a bit small. I would have at least went with 3 or 3.5 ton. I would also try to find a way to bring in more fresh air threw the sofit. Also why didn't the installing contractor insulate the duct work to begin with. If installing in an atic I would have inuslated the duct work twice. Just my 2 cents.

  11. #11

    Help! Air Conditioner in attic not cooling home

    Hello
    Thank you for all your suggestions!
    The air conditoner is in the attic because the house is heated with hot water radiators.
    The air conditoner installer said he did a load calculation and our home should be a 2 1/2 ton. I do not know how he calculated this, but again this year, when I called to question I was told that 2 1/2 ton is sufficient for my size of home.
    My home is 80 years old. There is no insulation in the first and second floor walls. The basement is well insulated to code. Most windows are double pane, the newest on the main floor west facing wall are low e argon gas windows. There are four old windows left to replace.
    The attic has about 6" of cellulose fiber insulation. I want to get more insulation in the attic, but was told by the 'Energy saver' that I need to seal all the holes around the plumbing stack, electrical wires and light fixtures first.

    The air conditoner has a large metal vent about 4' long which leads to another long metal vent about 30' long which goes almost the length of the house. From this there are 4 drops of 5" black plastic and insulated bendable duct work to the bedrooms on the second floor. There are two 5" and two 8" ducts to the main floor. The basement receives no air conditioning.

    The outside temperatures in July were almost all at or over 30 degrees Celsius. The days were also very humid.

    How do I check what the correct size of air condioner should be?
    What is the most economical way to improve the air condioning efficiency?
    What type of contractor would install soffit vents? The eavestrough firms I called will install vented soffits, but I do not have any soffit holes in the wooden soffits underneath. They also do not seem to be aware of the proper amount of ventilation required (one square foot per 300 sq feet of attic with half in roof vents and half in the soffits)

  12. #12
    Join Date
    Jul 2005
    Posts
    171
    Based on that information, and with the additional insulation and attic ventilation you are contemplating, it is possible that the 2.5 ton will be adequate once you replace the rest of the windows. Clearly you want to make those improvements.

    To properly calculate the cooling load, you need to do a Manual J calculation, which you can do yourself. Click on the bullseye at the top right of this page. the homeowners version is only $50. You can play with it and see the effects of the extra insulation and good windows.

  13. #13
    Join Date
    Jul 2005
    Posts
    171
    Katharine, if you don't want to tear out and replace soffits, use these:
    http://www.bestlouver.com/product_in...products_id=44
    or similar.
    Any carpenter or reasonably skilled handiman can install them by drilling appropriate size holes in the soffit with a hole saw. You will need to calculate the number and size of louvers to use, based on the available room at the soffit. If the soffit is narrow, you use more vents of a smaller size. Don't forget that the calculated area needed is free air area, meaning any mesh or louver has less actual free area than its overall size, due to the obstruction by the mesh or louvers.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event