I bought a Gen 2 when it was first released because it has a feature that lets you control the use of Aux heat on a heatpump, which I have. After using Nest's compatibility test and talking to their tech support to make sure that it was compatible with my Trane heatpump I bought one. Worked great for about 2 months. Then I noticed on the first warm day when I had the windows open I could hear the outside compressor running. I thought, that's funny I don't hear the air handler running. Went to the nest and it said, "heating." So I shut the system off with the nest. Compressor still running. Not good, so I kill the whole system with the breaker.
Talked to Nest tech support. After checking several things they determined that one of the FETs on the device had fused and that they would replace the unit no charge. When I asked them why it had failed they said I must have had a power surge or something to cause the component to fail. I asked why this would not happen to the new unit and they said that it simply would not fail. I also asked them why any of my other dumb digital setback thermostats had not failed. No answer provided. You see, I was concerend that without any real reason for an improvement in the design of the replacement, I could have the same problem. I travel alot. So what happens if I have a similar failure while I am gone for a week or more. Compressor running with no air circulation can't be good for the life of my HVAC system.
New unit arrives and I install it. Again it works great for about 2 months. Now middle of summer and my house is awful hot when we come back from shopping. Nest says "cooling" but no air handler running. Gee, compressor is running. NOT GOOD. Same problem. Interesting, I pop the nest of the wall plate and guess what? Compressor is still running. As before, I kill the whole system and call tech support. Same deal. Seems I've had another surge and the FET has failed yet again. This time they offer a refund and say the Nest is not compatible with my system. Now I have a 2007 vintage Trane XR 13 heatpump which according to all of their tests IS compatible with the Nest. I also have a whole house surge suppression system.
So unlike everyone else in this thread, my experience with this product has not been good. I replaced it with a Trane, Wi-Fi enabled device. No problem in more than two years. And I should also say that I had no problem with the original dumb t-stat installed with the original equipment. It was digital but it had no energy saving features. Since this is a heatpump, the setback for the heat is not really an option regardless of the t-stat used but the home and away sensing function while in cool mode, about six months here in costal NC, would have been a been a benefit.
Given my experience, my personal opinion is that the electronics are too sensitive for typical 24 VAC heatpump applications for the Nest. If you ever look at the relays used in, "traditional", t-stats there must be a reason they are the size they are. I have read about others having the same problem as I have had so I don't think I am unique. Nest customer support was very good throughout the whole problem. All I lost was the $14 in sales taxes paid. I bought the unit at Lowes and since the first unit was replaced by Nest and by the time the second unit failed I was past Lowes return period. I would be afraid to have the Nest in my house given my experiences.
