DIY Smart HVAC for Smart Homes

Automate a HVAC split system using a Z-Wave smart thermostat

Bonus: automate your Audio / Visual equipment as well

Heating and cooling systems are one of the most integral parts of any home; they largely dictate our comfort indoors. Yet they’re also one of the biggest power draws and, ergo, one of the biggest contributors to our electricity bills. Intelligently automating them via smart home systems can not only improve the accuracy and your control over HVAC split-systems, but can also severely reduce the costs of running them. And yet connecting heating and cooling systems to an automation controller is no easy task, particularly for DIYers.

That’s true of all split-systems, whether a mini split or any other ductless AC with an IR remote control, which end up one of the least commonly automated devices in a home despite how common they are; tackling their automation is often seen as too much of a challenge. Owners typically face 4 challenges:

  1. Compatibility: automating split-systems is often deemed impossible because few offer smart home automation standards, such as Z-Wave, Zigbee or Matter, built in. Fewer still offer APIs or the ability to even achieve complex WiFi integration.
  2. Installation: intelligent thermostats for HVAC systems can be complex and may require see some owners seek out professional installation.
  3. Control: limited control over a HVAC split system as remote-control functionality is limited or property managers have reduced the system’s functionality.
  4. Cost: native integration of a HVAC into a smart home system typically means more expensive indoor units. 

Yet all 4 challenges can be overcome when it comes to making split-systems smart.


The best option for making a HVAC split-system smart is to use a wireless smart thermostat, such as the IR2900 from MCO Home or the ZXT-800 IR Extender from Remotec with a Z-Wave controller such as a Z-Stick with Home Assistant or a SmartThings hub. You can increase the accuracy and intelligence of the thermostat's automations by integrating further Z-Wave sensors. Read on for more detail on each element, including tips on how to also automate your audio / visual equipment with Z-Wave.

What you’ll need

To automate your split-system cooling and heating, your automation system will need at least the following components:

  1. smart home controller which supports Z-Wave and, optionally, other standards. If you don’t already have one, you can compare between commercial options such as Samsung SmartThings or locally-hosted and open-source software such as Home Assistant with a Z-Stick.
  2. A smart thermostat designed for controlling HVACs.

Smart thermostat options

Smart Z-Wave thermostats for split-system ACs and heaters fall into 2 categories;

  1. Wireless: these require no wiring, and often offer battery or USB powering. They don’t replace an existing thermostat in your home, which split-systems typically don’t have anyway, but are instead remote controls designed to look like thermostats or set top boxes.
  2. Wired: these do require wiring, are a more complex installation, and do replace existing thermostats. These won’t be necessary for most homes: it’s a rare made-for-the-home split-system to have centralised thermostats. These are the type of thermostats people purchase from the likes of Ecobee, Honeywell, and Sensi.

Given the ease, ZWaveProducts recommends the wireless type of smart thermostat for integrating split-systems with a Z-Wave gateway such as Home Assistant or SmartThings. Installation is simple, compatibility is broad, and responsive automation routines easy to achieve.

There are two key smart thermostat brands to consider:

  1. The IR2900 from MCO Home is built with 800 series Z-Wave, InfraRed over Z-Wave Plus, and an InfraRed blaster / repeater. You can control it directly via the buttons on the thermostat itself or via your Z-Wave gateway’s app. It then converts the instruction (e.g., increase the temperature) into IR and sends an IR command exactly like the remote control for your split system would. It is battery powered and can be wall-mounted using screws or tape or can be left free floating. 
  2. Like the IR2900, the ZXT-800 IR Extender from Remotec is also built with 800 series Z-Wave, InfraRed over Z-Wave Plus, and an InfraRed blaster / repeater. It's key advantages include an inbuilt temperature and humidity sensor and the fact that it's compatible with both ACs and Audio/Visual equipment. One disadvantage is that it isn't style like a thermostat so isn't suited to every installation. It's an upgrade to the ZXT-600, a 500 series IR blaster from Remotec, which has bee the most popular Z-Wave to IR device to date. 

Both models offer internet connectivity for downloading IR commands from a global database of remote-control signals, manufacturers, and models of split-system air conditioners.

What you’ll gain

  1. Responsive automation: you can have heating and cooling turn on or off based on the use of a room or a home. For instance, a holiday mode could be set up so that heaters to only operate when the temperature drops below freezing during such a period. 
  2. Scheduling: you can schedule the on-and-off times of any heating or AC and use a time schedule in parallel with other data available through your Z-Wave controller. For instance, you can have an air conditioner turn on at 12 noon, but only if the interior temperature is above a chosen temperature and it is similarly warm outdoors. 
  3. Really remote control: you’ll be able to control your HVAC systems remotely via apps on a smart device. Most commonly, people use their apps to remotely adjust room temperatures when they’re coming back from a holiday or have encountered another change to the home’s typical routine. Remote control via an app is also extremely popular amongst property managers, particularly those managing short term rental / AirBNB type properties
  4. Zoning: zoning systems can be installed to allow for customized temperature settings in different areas of the home. This can help to maximize energy efficiency and ensure that each room is comfortable.
  5. Additional control: along with your Z-Wave app, you’ll be able to control your smart thermostat from a variety of compatible voice controllers such as Amazon Alexa, Google Home, and Apple’s Siri.

Overall, Z-Wave automation provides greater flexibility and control over split system HVAC systems, allowing for customized temperature settings, energy and cost-efficient optimization, and remote control from anywhere in the world.

Making it smarter still

You can make any responsive or schedule automation smarter by syncing your smart thermostat with other Z-Wave sensors. In this way, you can use additional data to refine automations. Humidity, temperature, dew point, and UV data points are most commonly used. They’re available in sensors such as these:

  • aerQ temperature and humidity sensor, which also provides data on a room’s dew point and the potential for mould to grow in a room. Given their small size, users sometimes install multiple per room so that an average of a room’s temperature can be used to refine temperature control.
  • MultiSensor 7, which offers 6 different data points including temperature and humidity, and also the ability to use its motion detection to better automate around the presence of people in a home. 

These sensors can be used to adjust temperature settings automatically based on the readings.

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