Yes, this YoLink Thermostat needs C wire.
We are going to release new version of thermostat for 4 wires installation wich doesn’t require C wire next year.
YoLink thermostat only support regular 5 wires thermostat, it doesn’t support A/C system with heat pump or 2 stages cooling and heating system.
We will develop and release the new generation of thermostat support the heat pump system in next year.
If you do not have 24V AC, you can use the 24 Volt Transformer C Wire Adapter to power the thermostat. You can find the adapter at the following link.
You can try to upgrading from a 4 Wire Thermostat to a 5 Wire Thermostat, the following videos might be helpful.
We haven’t taken a video for the YoLink Thermostat yet, below is the diagram from one of our customers.
We have a YouTube video for our first-generation Thermostat which involves the same installation. https://www.youtube.com/watch?v=RvneubBlk7k
Please kindly read the following user guide before installation. http://www.yosmart.com/support/YS4002-UC/docs/instruction
Any question, please kindly contact us.