Controlling minisplit air conditioners


Active Member
For our new home (2-storey, heated slab-on-grade) we are looking at using a ductless minisplit system instead of installing central air.

We don't otherwise need forced air ductwork in the house, and being in eastern Ontario cooling is a very nice to have rather than an absolute necessity so we don't need a gazillion tons of it!

We also like the idea of being able to control each zone independently ... what's the point of all the temperature sensors and HA stuff if the HVAC system only has an on/off switch anyway?

Does anyone have any feedback on using these types of systems? In particular, any comments on how to intergrate the control with an ELK M1? There would be 4 zones upstairs and 2 or 3 downstairs (which is very open plan).


I have an LG mini split as described for my office in my outbuilding (and will likely be adding one to my shop). Installed by my A/C contractor father in law...

I've wondered the same thing (turning on the heat before i go out in the morning, etc) - but haven't dug deep enough.

I will look and see if there's a way to hook into the on board thermostat. Main issue i might see is the handheld remote generally seems to be required to be in sync with the unit. So you might have to leave that on all the time and let the temp displays, fan speeds, etc (and even the mode if you get a heat pump) get out of sync?

I installed a Mini split in my new shop last year. The shop is 24' x 24' square with a cathedral ceiling that peaks at around 11'. I went with a 18,000 BTU heat pump with AC and Heat.

I love this mini split, it has been awesome so far. Only paid $600 bucks from the main BonAire dealer in the miami area. He has an Ebay store.

Not sure I understand your temp sensor question, but I think any sensors you are talking about have to do with the mini splits abilitly to defrost the coils.

My mini split goes into a defrost mode in the winter, which is bascially the AC mode without the inside unit blowing any air. The coils get frosted up pretty heavily and need to be heated up to melt the frost.

Basically how it works is the inside blower unit stops blowing air, the vents close to let you know it's going into defrost mode, the outside units reverses the flow of coolant and goes into the AC mode, it also shuts down the outside unit fan. After about 15 minutes the frost is all melted and the mini split goes back into the regular heat pump mode.

I think there are two temp sensors in the unit that decide when to go into a defrost mode.

Not sure if this helps.
Well i looked at the manual, took off the front panel, got my dad on the phone, and sorry to say i don't have a good answer. My father in law thought it would be possible but isn't 100%.

There is a terminal block inside, but it's not lable with the Y/G/R, etc standard naming used on hard-wired thermostats. And if the schematic in the manual is any indication, that block only ties the indoor unit to the outdoor condensor unit anyway. The circuit board to which the button/led connect to is recessed too much to determine if it could be rewired or hooked into with out me taking it apart more to see.

Apologies - was hoping i could get you a firm answer...

I still think it's possible, just not be as easy as running thermostat wire to an onbaord terminal block (at least on this LG unit)...

Probably the easiest way is to control it by sending the controlling commands by IR. You could have an Elk temperature sensor in the room (not a thermostat), and send the IR commands via an Ocelot as appropriate.

One option is to turn the COOL option at a very low temperature on when the temperature is a few degrees above your set point (custom value in the M1) and then switch to FAN when the temperature reaches a few degrees below the set point.

You could even control the fan speed (save energy, etc.) or even turn the fan off.

This would certainly be a little project.
Mini splits are also far more popular here compared to central aircos

I would choose an Ocelot too as ELCANO mentioned.

However, I did my small apartment (2 fedders and an LG) on the cheap using a USBUIRT with 3 zones and Eventghost (great free app) so that all 3 split units are independently controlled. Total cost $60 (not counting the PC of course). Works great.

The furthest controlled split unit is >100' of copper away from the USBUIRT unit.
Thanks for all the input, especially for digging around inside yours, shenandoah75. We won't be using these for heating -- it gets cold enough here that air source heat pumps quickly stop working -- so they will only see 3-4 months of service a year.

The temperature sensors I was thinking of are not connected to the mini-split directly, but are part of the wiring plan for every room during construction (a 1-wire network).

I hadn't thought of using IR to control them ... I've typically not been a big fan of it due to the lack of feedback and robustness, but it would certainly be a good low cost option that doesn't require dismantling any of the units up front!
This is an old thread but I am looking to purchase ductlass mini-split for my house (6 zones) and would like to know if these can be centrally controlled? This thread is from 2007, so I am hoping for any new ways to control this.
Typically mini splits are controlled with an IR remote. Unless you can find one with wired inputs you're stuck with IR.
I hate to necro-post, but I’m in the same boat myself. I’m planning on using several mini-splits for AC, and home automation control would be a must.

It’s off grid, so every watt counts... hence the need for automation controls.
This is the control that I built for my Mitsubishi mini split.   This is an inexpensive after market IR controller that uses a 12v solenoid to push the power button.   It is pretty basic control, but it works for me.   
This mini split is highly efficient, with a variable speed motor.   The fan motor will slow down but never completely shut off.   I use logic in my OmniPro to shut it off completely when it is not needed.   
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