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Community and Q&A

Temperature adjustment / offset on Mitsubishi minisplit

Adam Emter - Zone 7a | Posted in Mechanicals on

I installed my MSZ-FH12NA two months ago and the unit is performing very well and I am not experiencing the short-cycling issue that others have, but the unit seems to consistently cool (haven’t used heating mode yet) past the set temp on the remote by 4-5 degrees. (If I want it to cool to 70, I have to set the remote at ~74.) Does anyone know if there is a way to offset/adjust the remote control temperature to accurately reflect the actual room temperature?

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Replies

  1. leighadickens | | #1

    This may be too simple, but in full disclosure that I at least was baffled by this until I figured it out and smacked myself on the head... I noticed that the remote and the unit can get out of sync. Just because the remote says it's on a setpoint temperature or a particular mode does not mean the unit is. When you change the temperature or mode on the remote, you have to point the remote at the unit while you are doing it and and hear the unit beep in response to your change. Otherwise the remote didn't actually communicate the setting change to the unit. So maybe the unit never registered a set temperature adjustment that you made on the remote at one point?

  2. Dana1 | | #2

    The head senses the room temperature by the temperture of the incoming air, not the average room temp. The air near the ceiling will always be warmer than the room temperature, so the manufacturers build in a bit of offset to compensate, but some rooms will have less stratification, others more, and in a given room it varies with the season, solar gain, outdoor temp, etc. So, some amount of offset is the norm.

    If the offset is excessive, which can be the case with a tall room with cathedralized ceiling, with the mini-split mounte 8' or more from the floor, sometimes the offset can be tweaked in the control electronics inside the head. (I don't know if that is possible with the FH12), or a wired wall thermostat can be installed (they're not cheap.) Most people just bump the temp up or down a degree or two with the remote until they're comfortable, then adjust as- needed when the weather changes, without looking too hard at what the displayed setpoint is relative to an independent thermometer.

  3. ceggleston | | #3

    After coming back from vacation, I started having this same issue in heating mode—I need to set the remote up to 84F to get the room to 70F. Leigha, I noticed the same thing and tried to reset the remote control (using the "reset" button), but it did not seem to help. Did you figure out a way to reset this accidental offset?

    1. NaturalEngineer | | #4

      This is so easy that a lot of folks miss it. As previously noted, if one is not pointing the remote at the unit, sometimes it does not register the change in set point. So use that to re-calibrate the offset. As an example - the room is actually 70 degrees but the remote is set at 75. Simply point the remote at the floor, away from the unit. Decrease the set point to 70, listening to be sure you get no acknowledgement beep from the unit. Now point the remote at the unit. Raise the set point to 75, listening to be sure you get the beep with each degree. Now you should be good to go. -- A retired engineer

      1. joshdurston | | #5

        I've found there is a pretty wide band were the unit continues to run at a low capacity (might be up to 4degF). I'm running off the remote MHK1 room sensor though.

        I don't think it works that way. I think the remote sends the absolute setpoint each time (and all the other settings as well). I know this because I have the MHK1 wireless wall mount controller that is updated with any change the happens from the IR.
        I can set the fan speed and vane angle on the MHK1, then if I bump the setpoint with the IR remote, it reverts all the settings to whatever is on the MHK1, not just the setpoint (it's two way data). And the setpoint matches even if they were far apart initially.
        But if I set the MHK1 setpoint, the IR won't update (it's one way).
        The MHK1 always updates to match the IR if any change is made from the IR.
        You need to listen for the confirmation beep after making an IR change.

        1. NaturalEngineer | | #6

          I have the regular IR remote that came with the system. Calibration as previously described works for both heat and cool on my system and has for about 3 years.

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