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  1. #1
    Join Date
    Mar 2008
    Location
    Jackson, NJ
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    176

    Question Tech coming to investigate short cycling - what should he be doing?

    Hey Gang,

    I have a call into my HVAC installer to check out my system. I have a 1 zone system w/ the stat downstairs. It keeps my upstairs and downstairs at the same temperature (good), but the most it will stay on during a 95+ degree day is 9-10 minutes and the most it will stay on when its 80 or so is 7-8 minutes (not so good). Given what i have learned on this forum I suspect it is short cycling, and after discussing w/ my installer he agreed it warranted a look.

    He's coming out early next week. Anything I should know about the visit? What should he be checking? What should I be asking?

    Thanks in advance !

  2. #2
    Join Date
    Dec 2007
    Location
    Afton, VA / Khorat, Thailand
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    2,468
    If the house is the same temp. up and down, what's the problem? How long between cycles? The less it runs, the less YOU pay.......
    Tough times don't last...Tough people do.

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  3. #3
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    1,986
    The question he should be asking you is: Is the system maintaining a comfortable humidity level in your home?
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  4. #4
    Join Date
    Nov 2004
    Location
    NJ
    Posts
    1,195
    Quote Originally Posted by Jopopsy View Post
    , but the most it will stay on during a 95+ degree day is 9-10 minutes
    It's over sized.

    In PA @ 95 it should be running almost if not non-stop.
    Ed J

  5. #5
    Join Date
    Dec 2006
    Location
    Dallas
    Posts
    189
    but the most it will stay on during a 95+ degree day is 9-10 minutes and the most it will stay on when its 80 or so is 7-8 minutes (not so good).
    on a 95F day, 9-10 minutes ON, how long is it OFF? At what temp is the Thermostat set to? On an 80F day, 7-8 minutes ON, how long is it OFF?

    In one full cycle, What is the highest point and lowest point your thermostat reads? And yes... how is the humidity indoors?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,763
    He should be checking the humidity.
    Also the air flow. He may be able to slow the blower if your humidity is higher then it should be.
    He should be checking the CPH setting of your stat. Shouldn't be set higher then 3 CPH.

    When we had our 98* outdoor temps, my unit ran 6 hours with out shutting off.
    When its 90 outside it runs around ½ an hour.
    And its a little over sized.
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  7. #7
    Join Date
    Mar 2008
    Location
    Jackson, NJ
    Posts
    176
    My system doesn't even run a hour to bring the temperature down 2 degrees.

    My humidity upstairs is around 55% when my stat is set to 74. Is that normal?

    My stat is set to 3CPH. It seems like my system runs for 8-10 mins then idles for 10 mins. I THINK that would be 3 CPH performance right? I haven't paid enough attention to how it behaves when its only 80 outside however.

    Since my system is a heat pump too, I just want to make sure its not going to prematurely konk out on me.

    Also, I'm a little concerned b/c once it gets cold and the system calls for my backup propane furrnace, I have a feeling its going to get real hot real quick given its easier to heat then it is to cool. If I can maintain 74 degrees when its almost 100 out while running for only 10 minutes, I almost think I'm going to have a blast furnace when its 30 degrees !!!!

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,763
    Sounds a bite over sized for cooling.
    If you have a VS blower, he can set it to 350 CFM per ton, that should help some.
    Depending on which stat you have. He can set it to a more aggressive coolings algorthym.
    That will make it over shoot set temp, and cause longer off cycles.

    A larger HP allows you to have a lower balance point temp. So you may end up with better heating bills then anticipated.

    You got the 2 stage LP furnace right?
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  9. #9
    Join Date
    Mar 2008
    Location
    Jackson, NJ
    Posts
    176
    Quote Originally Posted by beenthere View Post
    Sounds a bite over sized for cooling.
    If you have a VS blower, he can set it to 350 CFM per ton, that should help some.
    Depending on which stat you have. He can set it to a more aggressive coolings algorthym.
    That will make it over shoot set temp, and cause longer off cycles.

    A larger HP allows you to have a lower balance point temp. So you may end up with better heating bills then anticipated.

    You got the 2 stage LP furnace right?
    I don't have a variable speed blower, but maybe he can lower the speed of the single stage? I don't know of course, just speculating.

    My furnace is a UGRA. The heatpump is a UPNL.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,763
    He can probably slow the blower.
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  11. #11
    Join Date
    Mar 2008
    Location
    Jackson, NJ
    Posts
    176
    Quote Originally Posted by beenthere View Post
    He can probably slow the blower.
    That's what he did this morning. I'll have to watch it now and see if I gain any additional minutes of run time.

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