After a whole saga with a Nest my basic issue is with the company itlesf. We discovered a incompatibility in the power stealing feature on our 4 wire system.The internal fan and air handler ran normally but it turned out that unknown to us the outdoor compressor and exhuast fan was being cycled on and off. We happened to be outside one night and heard the start and stopping. We observed it for a few days and called our highly qualified AC company to check. They did two visits and eventually eliminated every possible before determining that the Nest’s power stealing a real problem, and that the Nest solution of hooking up the C wire would not eliminate the problem. Having done all that and spending $400 with the AC guys I wrote Nest to request a return and refund. After a day they decided that since it was beyond the initial 30 days since the purchase they would not take it back. Such arrogance for a company barely 180 days old. For my good faith honest effort all I got was a brush off. Basically these guys cannot be trusted if they hide behind one sided written disclaimers. So be aware that the Nest product may not work. I just checked the website today and my system is still showing as compatible.