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  1. #14
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39
    How much ice would form on the evaporator without the AH running? I suspect that when the thermostat again called for heat within 20 minutes, the condensing unit and AH would have synchronized. It's working fine. Electronics?

  2. #15
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    If it doesn't have a safety, a lot of ice, if it has a safety, a fair amount.

    I'd have it checked. You don't want it to go the opposite direction, and not run at all.
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  3. #16
    Join Date
    Jan 2008
    Location
    Florida
    Posts
    39
    The system continues to cycle normally. I doubt that a technician could find anything unless I can repeat problem. I guess it's possible that the condensor contactor hung up, but odd that it only happened once and only when I raised the t-stat a few degrees, which I will try again to see if it happens again. If it does then the problem would have to be in the t-stat, which be very odd. I thought that it was impossible for the compressor run without turning on the AH fan and that the delayed fan shutdown was controlled from a board on the condensor unit. Of its there a board for that in the air handler.

    You would think that if the thermostat hung up, it would keep both the AH fan and compressor on? Unless it controls the AH fan sepearately, meaning the fan shutdown board is in the air handler.

    The circuits that I have seen in general seem so show that a T-stat controls a contactor that turns on both the compressor contactor and a contactor for the fan control. Since the fan shutdown normally and the compressor did not, that contactor worked and the compressor contactor stuck, it would seem. But what could be the connection to raising the T-stat temperature. That's what puzzles me. Unless the t-stat controls the fan and compressor separately and it was temporarily scambled so that it turned off the fan but not the compressor.

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    They are controlled seperately.
    Other wise, if you turned your fan to on, the compressor would run.
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  5. #18
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,289
    If the FocusPro is similar to the VisionPro, it has two triacs/relays, one for cycling the compressor and the other for the indoor blower. The VisionPro makes a distinctive "click-click" when activating both compressor and indoor blower, and the same for when they are de-energized, unless the thermostat itself is programmed to perform the blower off-delay. You'd then hear just one "click", followed a minute or so later by the other "click".

    So, listen to your thermostat when it calls for cooling...does it go "click-click"? Same for when it is satisfied and is switching off the equipment? If you want to repeat the increase in temperature scenario which coincided with the problem stated in the OP, listen to the thermostat when you do. If it normally goes "click-click" when shutting the system down, but you now hear only one "click", and the compressor is still running, but the blower stops, the thermostat relay for the compressor could be hanging up. I notice at times my VisionPro "click-click" seems a bit more spread out than usual, but it's the second "click" that is delayed, which is for the indoor blower. The compressor always shuts off on the first "click".

    Worst thing that can happen with indoor blower shutting off but compressor continuing to run is the evap coil ices up, which at best only means no airflow, at worst could mean water damage to the structure and/or damaged compressor.

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