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  1. #1
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    746

    Rheem mod t-stat question

    I recently had a rheem prestige modulating furnace, RGFD series, 60k [1500 sqft. very tight and well ins. house], and 400series t- stat installed. Works great but seems to cycle very frequently and short. I realize it's cold out but cylcle seems too short. Changed anticipator setting from FA .6 to SL 1.2, no change. Since the t-stat does not read in tenths it's hard to tell exactly what or when it's going to do something. T stat setpoint will be 70 and room temp 70 and furnace kicks on. Turns off short time later, room temp still 70. Now I'm not complaining about that, it is the most comfy the house has ever been, but with a 1.2 diff shouldn't it at least go to 69? Just a little concerned that some eff. is being lost, and am not that fussy about 1 deg or so off setpoint.

    Thanks

  2. #2
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    Looking in your blower door, what do you see H or h?

  3. #3
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    746
    Cap H

  4. #4
    Join Date
    Dec 2002
    Location
    Rochester, MN
    Posts
    5,304
    You are running in the Mod mode then.

    What t-stat do you have?

  5. #5
    Join Date
    Oct 2006
    Location
    So. NH
    Posts
    746
    RCH-TST401MDMS, I also put the fan in the program mode to help mix things up a little, it rarely activate unless a setback occurs cause the funace always cycles more than once an hour.

  6. #6
    Join Date
    Jan 2007
    Posts
    20
    I have a 2400 sqft house (with 12 skylights in it) and a 75,000 btu Rheem mod. With the inside setpoint at 72 degF and outdoor temperature of 28 degF, the furnace runs continuously for hours on end between cycles.

    I bet if you change your set your temperature adjustment offset in the t-stat to "0", it will run for much longer between cycles. When I had a temp offset of +2 on my system, it behaved exactly like you describe on cold weather-- constant cycling despite the LED reading capital "H".

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