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Thread: Bad thermostat?

  1. #1

    Hmm

    I have a strange thing going on and wonder if some of you can help me out. Honeywell programmable thermostat.
    With the thermostat on "auto", both the fan and condenser will shut off before set temperature is reached (today's case within three degrees of set). I can turn the fan back on immediately by switching to "on", but the compressor waits a couple of minutes before turning back on.
    Could this be a sign of a bad thermostat? Motor thermal overload?

    Thanks

  2. #2
    Join Date
    Mar 2004
    Location
    Illinois
    Posts
    6,959
    Thermostat has time delay built in, if it's shutting off system before it's satisfied you need to call a pro.

  3. #3
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Time for a service call. It might be a safety shutting it down, not the t-stat. The t-stat's time delay is so you don't damage your compressor.
    If everything was always done "by the book"....the book would never change.

  4. #4
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,019
    Safety wouldn't be securing the fan, too.

    Stat shouldn't be securing the equipment before setpoint. Time to have the stat checked.
    Perhaps you should have read the instructions before calling.

  5. #5
    Well, I got home tonight and although the thermostat had reached set temperature, it didn't shut off. Turned the stat off and then back to cool and it stayed off. One extreme to another.
    ?????

  6. #6
    Join Date
    Nov 2001
    Posts
    105
    I had a similar issue with my Honeywell (CT3300). When I called Honeywell about this, they said that when there is a substantial change in setting (i.e., from a setback point, like when you're gone all day and have it set several degrees different from where you keep it while you're home), it is normal for the stat to shut off a degree or two prior to reaching its set point so that it does not overshoot the set point. It will then come back on around 5 minutes later. Once it reaches the set temperature, this should settle down. That's what they told me, for what it's worth. I guess that's just how they programmed their anticipation.

  7. #7
    Join Date
    Mar 2004
    Location
    Chester County PA
    Posts
    371
    Since it's programmable check the setting for your temp differential.
    Sounds like the t-stat is set at 3 degrees over/under to compensate.
    This can be changed within the program menu.

    nn
    "That motor's done, he let the factory smoke charge out!"

  8. #8
    Join Date
    Aug 2006
    Location
    Phoenix, AZ.
    Posts
    38
    Some programmable T-stats have whats called adaptive recovery which cycles the system until it reaches set point. Saves energy $$. This can be dis-abled. Check the manual or Honeywell.com
    Some newer stats have max run times which are adjustable through the stat programming.
    Hopes this helps.

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