Mitsubishi SEZ not turning off

[Steve B]

Last summer the wife 'encouraged' me to have air conditioning put in. We got a Mitsubishi 3-head variable speed outdoor unit, two room wall-mounted units on the 2nd floor and an SEZ in the attic with outlets into the 3rd floor. The wall units are controlled by wireless remotes while the SEZ has a wired Mitsubishi thermostat.

The problem is the SEZ (um, that is, if you don't count the fact that the installer was totally out of his depth as a "problem"). Even when the room temperature is below the set temperature, the SEZ keeps blowing and cooling. As far as I can tell it never shuts off unless you do it manually.

I went in and set mode 02 (indoor temperature detecting) to 3 (main remote controller). There was another mode that I set as well, I don't have the numnber here but it was to turn up the static pressure setting. I tried the other possible settings for mode 02 and nothing seemed to work.

My question is, is this just a bad thermostat or is there something more subtle at play as relates to the various units and how they interact with the outdoor unit and/or how the SEZ is or could be configured?

Steve

[dan sw fl]

Mitsubish SEZS ... call Your Local Mechanical Contractor

[skippedover]

Is the controller showing any error codes on the display? This could be either a flashing P-() code or an E-() code. () = some number. It sounds like you've got a programming issue in the main control. I'd be concerned that the addresses of the remote thermostats are either not correct (wrong stat controlling the wrong indoor unit) or the remote controls are not set for individual indoor units and the signals are mixing or there could be a wiring issue where the main controller isn't communicating (generally generates an error code).

[Steve B]

Nope, no error codes. As for the thermostats, the only ones I'm aware of are (1) in the SEZ, (2) in the wired controller and (3) inside the wall units. The problem occurs even if the wall units are off, which rules out (3), and the mode set using the wired controller is to use (2) instead of (1). Also I think I saw the installer initialize the remotes for each of the indoor wall units.