Mini-split heat pumps, also referred to as ductless heat pumps, have become an energy efficient alternative to standard HVAC systems. The system consists of two parts, an outdoor compressor unit and an indoor air handler. The two components of the system are connected by refrigerant lines. During the summer, heat is removed from inside the home and it is released outside. In the winter, the process is reversed. The outside unit absorbs heat and releases it through the inside air handler.

There are significant advantages to a mini-split heat pump compared to other types of heating/cooling systems in a home.

However, before you throw away your old forced air heating/cooling system and replace it with a mini-split heat pump, there are a few things to be aware of:

There is a great deal to be gained by integrating an HVAC (heating, ventilation, and air conditioning) system with a smart home processor/hub.

The challenge of implementing the above use cases with a mini-split system is that there isn’t a single, centralized, thermostat that can easily be replaced with a smart thermostat. Instead, each zone of the mini-split system has its own built-in thermostat that is fully integrated into the room unit and cannot be replaced with one that is compatible with your smart home processor/hub. Fortunately, third-party companies have come up with a solution to this problem.

Sensibo and Ambi Climate both offer products that allow smart home processors/hubs to integrate with a wide variety of mini-split systems. In addition, they also allow integration with a wide range of heat pumps, in-room air conditioners, and window units. Throughout the remainder of the article I will simply refer to mini-split systems, but it is important to remember that Sensibo and Ambi Climate devices can control many other types of air conditioners and heat pumps besides just mini-splits.

Sensibo also offers both Sensibo Sky and Sensibo Air for controlling mini-split, heat pump, and air conditioning systems that are operated by a remote control. Both products allow you, using your smart phone, to control your mini-split system from anywhere, can automatically turn the connected mini-split system on/off through geo-location, offer smart temperature settings, and seven-day scheduling.

The Sensibo Air also offers compatibility with Apple HomeKit, is slightly smaller (approximately 2-5/8” wide x 2-5/8” long x 3/4” high) and is compatible with their optional Room Sensor that can be used to determine if a room is occupied, or not. Finally, according to Sensibo, the Sensibo Air includes a more advanced chipset.

Both products are small and would easily fit into a contemporary décor with their white plastic cases and dark plastic IR windows. Like the Ambi Climate Mini and Ambi Climate 2, the Sensibo Air and Sky control mini-split, heat pump, and air conditioning systems by sending IR commands to the device.

Sensibo provided me with a Sensibo Air and a Sensibo Room Sensor to test for this article. Throughout the remainder of the article I will simply refer to the Sensibo Air, instead of both the Sensibo Air and Sky as the products are primarily the same, other than the differences I’ve already pointed out, and all my testing was done with the Sensibo Air.

Sensibo appears to be compatible with a broader range of mini-split, heat pump, and air conditioning systems than Ambi Climate. I base this on the fact that the Ambi Climate Mini and Ambi Climate 2 will only work with mini-split systems that have discrete power on and power off IR commands. Also, the Sensibo Air will work with mini-split systems that have either discrete power on/off commands or power toggle commands.

I don’t have a way to validate whether or not Sensibo truly has a larger compatibility list than Ambi Climate. However, another Crestron programmer helped me test the Crestron driver I wrote for the Sensibo Air. He has a Mr. Cool mini-split system and only Sensibo is compatible with it. Like Ambi Climate, Sensibo offers a tool for checking compatibility on their website.

Included with the Sensibo Air are a power cord, plug-in power supply, and a small double-sided adhesive pad for wall mounting the Sensibo Air. The Sensibo Air also has a keyhole slot in the underside of the case for mounting the device to a wall using a screw. Printed on the packaging are the basic instructions for downloading the Sensibo app and for contacting Sensibo support if you need assistance.

After the very simple Sensibo app installation process on an iPhone or Android device, The Sensibo Air provides complete control of a connected mini-split system including the ability to:

Sensibo also offers an advanced operating mode called “Climate React.” Climate React offers the ability to, for example, setup dual set points so the system will automatically change the mode to air conditioning when it is too warm and change the mode to heat when it is too cold. Climate React can turn the system on/off, change the operating mode, change the fan level, and change the set point in response to a change in the actual temperature, the “feels like” temperature, or the humidity. So, for example, during a family vacation the mini-split system could be placed into dry mode when the humidity gets too high to avoid the possible growth of mold in a home.

Sensibo offers an optional, battery operated, Room Sensor that is used as an occupancy sensor in the room where the mini-split system being controlled by the Sensibo Air is located. The Room Sensor is easily installed by choosing the Sensibo Air that it will be paired with, scanning the QR Code on the bottom of the device, and pulling the small plastic tab which will allow the replaceable, internal battery to begin powering the device.

With the Room Sensor installed, the Presence React function can be configured in the Sensibo app to turn the mini-split system on/off and enable/disable Climate React when someone enters or exits the room. The amount of time after motion is last detected, before the Room Sensor triggers that the room is unoccupied, is also adjustable. Finally, the scheduler can be used to, for example, disable Presence React at night so the mini-split system in a bedroom can’t be turned off by a lack of motion when people are sleeping.

Sensibo also offers a subscription based “Sensibo Plus” program. Sensibo Plus costs $4.99 per month or $2.99 per month when purchased on an annual basis. Sensibo Plus offers:

Sensibo supports integrations with Amazon Alexa, Google Assistant, IFTTT, Siri (Sensibo Air Only), and an open API so programmers can create their own integrations. The Sensibo Air acts as a thermostat within the Amazon Alexa ecosystem. This allows a homeowner to use simple commands including “Alexa, turn on the <room name> air conditioner” or “Alexa, increase the temperature in the <Room Name> by X degrees”.

IFTTT can also be used to control the Sensibo Air. IFTTT provides the ability to turn the connected mini-split system on/off, set the operating mode, adjust the set point, and set the fan level.

Using the Sensibo open API I created a Crestron driver to allow a Sensibo Air to be controlled from a Crestron smart home 3-Series or 4-Series processor. The driver can be downloaded from my GitHub here.

Unlike the Ambi Climate, the Sensibo API doesn’t implement OAuth2 security but that doesn’t mean that the API isn’t secure. To use the API you begin by obtaining an API Key. To accomplish this, you will need to use your username/password and login to the Sensibo website. There is a login link in the menu at the bottom of the main page of the website. You will then be presented with a screen that shows you your Sensibo devices. In the upper left-hand corner of the screen is a menu icon and selecting it will present you with an option to create an API Key. The API Key is then included in a parameter field of the Crestron driver module and limits the driver’s access to only those Sensibo devices associated with the account used to create the API Key.

Next, you will need to obtain the ID of your Sensibo Air. In the lower right corner of the square that represents your Sensibo Air, when you are logged in on the Sensibo website, is a three-dot menu icon. Pressing this displays a drop-down menu. Press the “Advanced” option on the menu and then choose “Advanced Info.” The UID is the device ID of the Sensibo Air. The Sensibo Air’s device ID is then included in a parameter field of the Crestron module.

The driver provides full control of mini-split system connected to the Sensibo Air including:

It is important to understand that not every mini-split system, heat pump, or air conditioner that will be controlled by a Sensibo includes every option in the module. It is up to the programmer who is including the driver in a Crestron program to only expose the options available for the homeowner’s mini-split system in the Crestron system’s UI.

Overall, the Sensibo Air is a well-designed and easy-to-use product that can optimize the operation of a mini-split system. The API allows the products to be integrated with an overall smart home platform. However, there is one way, I think, the product could be improved. Climate React needs a third set point that can be programmed to change the operation of a mini-split system. In this way, the first set point can control when it is too cold, and the mini-split system should change to heat mode. The second set point can control when it is too warm, and the mini-split system should change to cool mode. The third set point would sit between the original two and provide the ability to turn on the mini-split system’s fan to improve the comfort of the people in the room but save money by not changing to cool mode.

Ambi Climate offers Ambi Climate Mini and Ambi Climate 2 for controlling mini-split systems, which are operated by a remote control. Ambi Climate provided me with both to evaluate for this article.

The two models offer the same functionality. The primary difference between them is size. While the Ambi Climate 2 is not very large (approximately 4-1/4” wide x 3-1/8” high x 1-5/8”deep), the Ambi Climate Mini is a fraction of that size. In addition, while the Ambi Climate 2 is designed to be placed on a table or shelf, the Ambi Climate Mini can, in addition, be mounted on a wall.

One other important difference between the Ambi Climate Mini and the Ambi Climate 2 is the lifetime operating cost of the two models. While the Ambi Climate Mini is slightly less expensive than the Ambi Climate 2, the Ambi Climate Mini requires a subscription to access Ambi Climate’s smart AI features after an initial two-month trial period. A lifetime subscription is included with the Ambi Climate 2. The subscription is not expensive, at $2.99 per month, and I understand that companies need a continuing income stream to support the cost of their back-end cloud platform. But it is important to understand that this fee exists and including it as part of a purchasing decision.

Both models are aesthetically pleasing with an IR window on top, a white plastic body, and a wooden base. Both Ambi Climate models control mini-split systems by sending IR commands to the device in the same way the mini-split system’s remote control does. Because of this Ambi Climate devices can only work with mini-split systems that include discrete commands for different functions; such as power on/off.

Included with each product is a power cord, plug-in power supply, and a brief getting start guide (a full user manual is available here). The Ambi Climate Mini also includes a wall mounting bracket.

Set up of the Ambi Climate app very simple. The most important thing to remember is to make sure you have the manufacturer/model of your mini-split system along with the model number of the system’s remote control. The model number of the remote control can typically be found on the underside of the remote.

Ambi Climate provides a wide range of options for controlling your mini-split system:

The Ambi Climate app offers a number of other additional features:

Ambi Climate supports integrations with Amazon Alexa, Google Assistant, IFTTT, and an open API so programmers can create their own integrations. For example, the Ambi Climate Alexa skill supports commands for providing comfort feedback to the Ambi Climate AI system by saying “Alexa, tell Ambi Climate it’s too warm in <room name>” or “Alexa, tell Ambi Climate it’s a bit cold in <room name>”.

Similarly, through IFTTT you can select the operating mode of the Ambi Climate device, provide comfort mode feedback, and more. For convenience Ambi Climate has provided a wide selection of pre-made IFTTT applets.

Using the Ambi Climate, open API I created a Crestron driver to allow the Ambi Climate to be controlled from a Crestron smart home 3-Series or 4-Series processor. The driver can be downloaded from my GitHub here.

The Ambi Climate open API requires OAuth2 authentication. Normally this is a showstopper when writing a Crestron driver because a full OAuth2 implementation requires a port forward on the homeowner’s router to the Crestron processor; a significant security risk in itself. Fortunately, Ambi Climate allows a user to create their OAuth2 access token through a website form instead of having to programmatically support callbacks by adding port forwards to the router on the homeowner’s network. The form for creating the access token can be found here.

Ambi Climate has not completely removed the complexity of implementing the OAuth2 protocol. Their access token expires after 40 hours and the driver software needs to implement a token refresh process, or it will lose the ability to communicate with the Ambi Climate device. I chose to simply implement a timer that refreshes the token any time the processor is restarted and after every 24 hours of operation. I hope that this will prove reliable.

The Ambi Climate API includes rate limiting that limits the number of API calls 20 during any 10-minute period. A programmer using the Crestron driver I wrote, or any other driver based on the API, needs to keep this in mind. For example, a basic up/down arrow interface to adjust the temperature set point that sent a new set point to the Ambi Climate on each button press could fairly easily exceed the API call limit. In writing the Crestron driver for the Ambi Climate I limited the functionality I provided in the driver because of this.

Overall the Ambi Climate Mini and Ambi Climate 2 are well designed and easy to use products that can optimize the operation of a mini-split system. However, there are a couple of ways I believe the product could be improved.

It is a pet peeve of mine that when you run an app on a table it should be able to operate in landscape mode. Many people, including myself, have keyboards attached to their tablets and an app that is locked in portrait mode is a pain to use.

While this won’t impact most users the Ambi Climate API needs improvement. First, the API documentation is incomplete and doesn’t fully document the protocol. Without support from Ambi Climate it would have been exceedingly challenging to develop the Crestron-Ambi Climate driver I wrote. Second, none of the API calls return feedback on the new state of the Ambi Climate after a command has been acted on. To implement a driver properly would require a second command to obtain the Ambi Climate’s status after any command is sent. This cuts in half the number of commands that can be sent before the rate limit is exceeded. As mentioned above, implementing a temperature set point using up/down arrow buttons on a touch panel could also exceed the rate limit. I understand the desire to limit API calls, so the Ambi Climate cloud server doesn’t become overloaded. But, given the current state of the API the limit is very restrictive.

Both the Sensibo and Ambi Climate provide a way for a homeowner to better control their mini-split system. Ambi Climate offers more intelligent control but this feature comes at the price of a subscription with the Ambi Climate Mini. Sensibo offers an optional subscription. But, unlike the Ambi Climate subscription, it is optional; and no “must have” features are lost if the subscription isn’t purchased.

For the integrator, the Sensibo API offers much simpler, and complete, control of the customer’s mini-split system.

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Jay Basen has been a home automation hobbyist for over 30 years and has worked professionally in the industry for almost 20 years. His professional background is electrical engineering and software development. He has a master's degree in engineering and has been writing software professionally for over 40 years. To read more of Jay's articles, visit his blog http://topicsinhomeautomation.blogspot.com/