Have been looking for in the US a ductless mini split heat pump system something like the Mitsubishi Electric Mr. Slim that uses a non proprietary wiring scheme for its wall mounted thermostats. Ideally it would be the standard 24VAC wiring scheme something like (R,G,W,Y,C) that would allow the system to be controlled by a internet connected thermostat such as the Nest, EcoBee, etc...

Most of the ductless mini split systems I have observed come with either fairly complex non internet connected programmable wall thermostat or come with a dumb to complex remote control to mange its operation.

Does anyone know of any ductless systems that offer standardized HVAC controls, remote internet management or other smart home automation capabilities?

  • Mitsubishi now (Dec 2020) has an add on interface (PAC-US444CN-1) that supports the Nest and others on some of their units.
    – dlu
    Dec 6, 2020 at 20:18
  • 1
    Another current (2020) option is "Sensibo" which I know about solely because my utility offers them for free (but with a long messy contact that might make me decline after all - plus I'm not really a fan of internet controlled thermostats) so they can do load-shedding by adjusting the temperature slightly.
    – Ecnerwal
    Dec 6, 2020 at 21:55

3 Answers 3


Found some Mini Split units that can use standard 24VAC thermostat controls and it is made by EMI - Enviromaster International LLC - USA. After much searching the only standard 24VAC controllable units found were a handful of EMI's fixed capacity commercial mini split units.

  1. R-410A - WLCG/WLHG Wall Air Handler , Model: R-410A - WLCG/WLHG. The working proof for wiring a standard 24VAC wall thermostat starts on page 11 in the Installation & Operation Manual.

    Additionally they provide two other form factors both offering standard 24VAC control options.

  2. R-410A - CACG/CAHG & CACH/CAHH Cassette Air Handlers , Model: R-410A CACG/CAHG & CACH/CAHH

  3. R-410A - UNCG/UNHG Universal Ceiling/Floor Mount Air Handlers , Model: R-410A - UNCG/UNHG

Again pay attention to the model of EMI unit, some don't support 24VAC controls such as their entire E-verter series. Additionally not sure what kind of prices these units carry, as well as what sacrifices in efficiency are lost due to non smart inverter control, still should be better than central forced air systems, right?


There is an adapter that allows the Nest Thermostat, (or any other 24v thermostat), to control most brands of Mini Split A/C's and Heat Pumps. It is cheap and easy to install. It is made by "JP Manufacturing" and they can be found at NestMiniSplitAdapters.com (December 2020, that site appears to be taken over by malware). I have also seen them on Ebay lately.

We retrofitted 26 mini splits at a hotel in Palm Springs, half Samsung half Mitsubishi, half inverter half non inverter. They all ran without a problem.


If you go with the Mitsubishi line of ductless minisplits you can add the MHK1 wireless remote receiver kit that provides a wall-mounted thermostat that can be located anywhere within the wireless range and also connect via RedLINK to the Honeywell Redlink Internet Gateway (THM6000R1002) which provides control and monitoring via the free totalconnectcomfort site as well iPhone/iPad and Android apps.

  • Seems expensive
    – MrDaniel
    Jun 17, 2015 at 22:33

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