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New AC unit, house still hot

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  • New AC unit, house still hot

    Originally posted 7-27-2017 4:57 PM
    By: Wademcolvinjr

    I have a single story ranch type home with a full basement where my new Rudd Furnace is located. I also have a brand new unit outside. I have added extra soffit venting to aid in venting heat in the attic and I am thinking I need to replace the 2 whirlybird vents on the roof as they are at least 50 years old. They do not spin much unless I get a fair amount of wind. Could it be that I need more insulation in the attic as well? I am planning on adding more as what is up there is old and some had to be replaced when we did some demo work in the kitchen. I am thinking I need to do both. Thoughts?
    Last edited by suemarkp; 04-07-2019, 06:23 PM.

  • #2
    Originally posted 7-28-2017 2:06 PM

    There could be so many issues.... is the new unit working properly? Is it sized correctly? Was it installed properly or in a poor place? Are your ducts good? Does you insulation suck? Thermostat issues?

    Some easy things to check:
    Measure the air temp coming from various AC vents when the AC is running. What is that air temperature and what is the return air temp near the return grill?
    What is the outside air temp when the house is too hot, and what temperature are you setting it to?
    Does the air flow seem good out of each vent (is it blowing pretty good)? Check all of them, and make sure most of them are open.
    How long is the outside unit running when the house is too hot -- continuously, or is it cycling at some interval? If cycling, how often?
    How much insulation is in your attic (none, 3.5", 5.5", 7" or more)?
    Are you house windows double pane low E, or older single pane non-low-E?
    Do you know the size of your AC unit in tons? If not, it could be part of the part number. Typically, there is an 024, 036, 048, 060 suffix on the part number indicating the size in thousands of BTU (030 would be 30,000 BTU, 048 would be 48,000 BTU).
    Where is your duct work -- all in the basement ceiling, or some in the attic?
    Kent, WA


    • #3
      Originally posted 7-28-2017 9:28 PM

      Guessing your house is from the 40's or 50's based on your description.

      First, I would make all the above mentioned checks.
      Then I would have the install tech back out and let them see the problem. If it keeps up some days but not others, try to get them out on a "bad" day.

      Does your house stay warm in the winter? Is it drafty?

      If your house has newer windows and is from the era with window weights, the weight cavities are often missed and are huge air leakage spots.. My house has this issue.

      If it gets worse later in the day the evaporator coil could be freezing up. Lots of things can cause this, but you will need to have your tech back out. Should be warranty work if it was all recently done. You will notice much less airflow when this happens. Sometimes you can see the coil if you shut power off and look in through your blower door or where the filter installs, depending on the configuration of your unit.

      If bad assumptions were made on the condition of your house and it's efficiency then it could be a improperly sized unit. Can't easily fix that, but you can fix the problems that lead to the bad assumption.

      Sometimes the fire dept will bring over their thermal imaging camera (if they have a modern one and are permitted to do so) and scan your home for leaks.
      Local organizations may offer you a no cost (or low cost or donation) home energy audit that will find energy wasting issues9


      • #4
        Get yourself a Infrared Thermometer Digital Temperature Gun Non-contact

        The accuracy of these are just so-so but good enough for what you want to do.
        There run about $20.00 and have many uses for a quick read of the temperature ao just about any surface.