Zigbee In Air Conditioning

Zigbee is a standard wireless communication protocol which is based on IEEE 802.15.4 specifications that can be used for communication between devices without needing a physical wire connection similar to the WI-FI or Bluetooth technology.

Comparatively, it has the following characteristics suitable for HVAC applications:

Simpler
Lower data rate
Lower power consumption
Lower bandwidth
Lower implementation cost
MESH topology that enables large network communication
Suitable for wireless personal area networks (WPAN)
Communication distance of 10m-100m line of sight between each devices.

Many manufacturers have implemented this protocol simply because of the ease of design, lower cost and interoperability with other Zigbee-compliant building management systems. It is also highly secure as the encryption for communication between each devices is using AES 128 bits technology.

On top of that, if designed properly, the batteries of wireless sensors such as thermostats can last for many years.

Take note that your products need to be certified by Zigbee.org before you can use the logo in your products. It is estimated that there will be 8 billion such devices that will be in used by the year 2020.

A Zigbee Thermostat

Zigbee Frequency Assignments

This protocol uses unlicensed frequency bands for its operation. That means that you do not have to pay to use the frequency spectrum unlike mobile phones operators such as 3G or LTE which require approval from the licensing authorities of the countries to operate.

The frequencies being assigned differ from each region of the world. Therefore, when you design or purchase your products, you will have to determine where your products will be marketed.

Country	Frequency
North America	902-928 MHz
Europe	868-868.6 MHz
Rest of The World	2.4-2.4835 GHz

HVAC industry has been around for a long time and the prices of equipment have been dropping every year in particular ductless split units and window air conditioners. In the past, many of these units are not equipped to be able to communicate with building management systems or control through smart phones and computers.

However, these are changing and many models of these air conditioners and heat pumps have been equipped with these optional IoT(Internet of Things) devices that enable them to be control through smart phones and tablets. Wireless capability with encryption for secure communication has increasingly being built-in to enable them to take advantage of the advancement in information technology.

Design Consideration

In designing your products to be compliance to this protocol, the best way to do it is to get the chips that have built-in radio transceivers, central processing unit and flash memory. Currently the maximum flash memory size available is 250kB. Besides that, the encryption in the form of AES 128 bits key is necessary.

Here are some examples of chips that are designed with this in mind of which you can consider using in your design.

1) Texas Instruments CC2630 2.4GHz Chip Set