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  1. #1

    Cycling Questions

    Are there are any rules of thumb regarding how long a system (HP/AC) should run before it turns itself off (t-stat controlled) in a properly designed system? How about how long it should be off before it turns itself back on? Is there any type of test that can be done to measure the force of the air coming out of a supply to confirm it is flowing properly (not to little, not to much), assuming a fully opened damper?

    Thanks.

  2. #2
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,586
    This is kinda a wide open question with a lot of possible answers all depending on what is going on. If it is 100 outside and 90 inside and you want it 70, probably quite a while. Same as if it is 15 outside, 50 inside and you want it 70. How about how tight the house is and how much insulation? It will gain heat when hot outside and lose it when cold, if you have a poorly insulated house that is drafty, it is going to run a lot. I hope you're getting the idea, you need to be a little more specific as to the problem. There is no general rule of thumb, most situations are going to be different.

  3. #3
    It is about 32 degrees outside. T-stat is set at 70. System runs for about 11-13 mins, shuts itself off, sits idle for about 11 mins and then repeats. I'm not sure if this what one would normally expect or not.

  4. #4
    Join Date
    Dec 2007
    Location
    Southern, CA
    Posts
    520
    The airflow can be measured but requires instruments that aren't cheap, but you could have a contractor with air balance equipment check it if it concerns you.

    If it cycles faster than 10 mins on 10 mins off more than once in a while you might have them look at it when they bring the air balance stuff.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,308
    Sounds like your at about 3 CPH, which is normal for a digital thermostat.

    The whole system can be tested for efficiency and capacity.
    Just you won't find many contractors that can do it.
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  6. #6
    Quote Originally Posted by beenthere View Post
    Sounds like your at about 3 CPH, which is normal for a digital thermostat.

    The whole system can be tested for efficiency and capacity.
    Just you won't find many contractors that can do it.
    Thank you.

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