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Thread: Hot Weather

  1. #1
    I was last here a year ago with this thread.

    http://hvac-talk.com/vbb/showthread.php?threadid=80695

    Now for the first time since installation of that system we are having a bona fide heat wave. It has been 100 to 110 degrees here for the past eight days straight with dewpoints in the 60s and 70s and overnight "lows" in the 80s.

    I have seen my indoor temperatures slip to 77, 78 and 79 a lot as it struggles to keep it below 80. Sometimes it fails and one day it was 82 in here for a time. It is controlling the humidity though keeping it high 40s and through the 50s.

    I decided to check the db temp of my supply air just for the heck of it. It is high 50s from about 2am to Noon but then it starts slipping through the 60s to finally hold about 69 or 70 through the hottest part of the day.

    One day though (and I have noticed this before but thought it was just my imagination probably) it seemed like the air wasn't as cool to me so I checked and it was sitting at 80 I don't think that 80 degree supply air can do a whole lot of good. It was there for five or ten minutes and then it came back to 69. Meanwhile though the house got two degrees warmer and it was of course unable to recover that until hours later.

    My question is it that normal? Or is there something wrong?


  2. #2
    Join Date
    Jun 2004
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    Time to call your installing contractor back.

  3. #3
    Join Date
    Aug 2003
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    I read your other thread...interesting that you started it a year and a day ago.

    The other thread mentioned you were seeing return air temps of 66 degrees. It made me wonder if there's a supply nearby (you mentioned counterflow furnace, so I'm assuming floor supply registers that discharge airflow up toward ceiling) blowing air up into the return. Also, does your house have a crawl space or is the ductwork cast into the slab?

    How well is the return air ductwork in the attic sealed and insulated? Are you seeing a temperature difference between where the air enters the return at the return grill and where it enters the furnace?

    On the day your supply air temp reached 80, could be the compressor went off on overload briefly. Have the condenser coils been cleaned recently? They should be done yearly, especially if you live near cottonwood trees or experience a lot of other airborne stuff, or mow when the unit is running, etc.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Originally posted by shophound
    I read your other thread...interesting that you started it a year and a day ago.

    The other thread mentioned you were seeing return air temps of 66 degrees. It made me wonder if there's a supply nearby (you mentioned counterflow furnace, so I'm assuming floor supply registers that discharge airflow up toward ceiling) blowing air up into the return. Also, does your house have a crawl space or is the ductwork cast into the slab?


    The ductwork is cast into the slab. The closest supply to the return is 9 feet away but when you stand under the return you can see it.

    Last year I ran the system at a 69 thermostat setting always. The 66 degree return was early in the morning when the house was 69 degrees. This year I have been using either 72 or 73 for my thermostat setting.


    How well is the return air ductwork in the attic sealed and insulated? Are you seeing a temperature difference between where the air enters the return at the return grill and where it enters the furnace?

    I have not been up there personally to see but the installer said that it was in good shape. The way he put it was "you sure don't want to suck up any hot attic air". It is difficult to measure the return at the furnace since it is sealed off so well. I have wondered though when the garage gets to be 105 degrees and you can only imagine how hot the attic is if that is causing a lot of the problem.

    On the day your supply air temp reached 80, could be the compressor went off on overload briefly. Have the condenser coils been cleaned recently? They should be done yearly, especially if you live near cottonwood trees or experience a lot of other airborne stuff, or mow when the unit is running, etc.

    I clean them twice and sometimes three times per year.
    [Edited by ms7168 on 07-22-2006 at 09:18 AM]

  5. #5
    Join Date
    Jul 2002
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    Zelienople, Pa
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    110 outside and maintaining 80 inside is pretty damn good.

  6. #6
    I know

    I have noticed that nobodies air conditioning seems to be very cool actually. Get above "design" temperatures and you're on your own pretty much.

    I realize also that having a system which could cruise under these conditions would be way too much for the rest of the time. Something that a lot of people don't seem to understand.

    You will notice though that in my thread last year several people told me they thought my system was oversized. I feel this refutes that notion.


  7. #7
    Join Date
    Jan 2004
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    Lancaster PA
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    Originally posted by ms7168
    I know

    I have noticed that nobodies air conditioning seems to be very cool actually. Get above "design" temperatures and you're on your own pretty much.

    I realize also that having a system which could cruise under these conditions would be way too much for the rest of the time. Something that a lot of people don't seem to understand.

    You will notice though that in my thread last year several people told me they thought my system was oversized. I feel this refutes that notion.


    Is 110° a normal temp every summer.

    If it is, then the systems not over sized, if it isn't then its over sized.
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  8. #8
    Join Date
    Dec 2002
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    Houston,Tx.
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    Originally posted by BSCHVAC
    110 outside and maintaining 80 inside is pretty damn good.
    Amen! Brother Ben shot at the fox and killed the hen.
    __________________________________________________ _______________________
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  9. #9
    [/B][/QUOTE]


    Is 110° a normal temp every summer.

    If it is, then the systems not over sized, if it isn't then its over sized. [/B][/QUOTE]

    No, it's not. Normal for right now is 94 high and 71 low.
    But this is Oklahoma. We seldom have "normal" weather.
    We may go without any 100 degree days in a Summer but we will usually see some of them. Sometimes (the last time was in 1998) we have them for months. Let me just say that when we do I am happy I have what I have


  10. #10
    Join Date
    Jan 2004
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    Lancaster PA
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    What you have is plenty for your area and then some.

    You wounldn't like the electric bill if you had a unit that could do 70 at 110 outdoor temp.
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