29 August 2012

Phoenix (Thermostat) Rising, Part II: The Nest

My trip to Phoenix earlier this summer gave me the unexpected opportunity to test drive the Nest thermostat (the stylish little thermostat that saves energy by learning your habits and only turning on when necessary).

I was there to help a friend who is remodeling the 30-year-old home she recently purchased (with plans to green it up). The kitchen and all of the flooring had already been removed, so it was time to take down some walls.



But midway through all of that, the air conditioner stopped working. After checking the breaker, I began to suspect that the problem might have been the thermostat. (My suspicion was based in part on sheer optimism that it wasn't the AC unit itself, and in part on the fact that the thermostat was original to the house and stopped making the clicking sound it had, until then, made every time we changed the temperature.) Although the whole air conditioning system was going to be replaced at the tail end of the remodel, I suggested that we buy a new thermostat to test my theory, but a Nest was already on hand for the HVAC upgrade, so we went with that. And since I'm the handy one of the two of us, it was all on me to make it work.

Replacing a thermostat was trickier than I expected. There were several different wires, and although they were color-coded, the colors on the old thermostat didn't necessarily correspond with colors on the Nest. Oh, and when I took the old thermostat down, it exploded into about ten different pieces, so there was no turning back.

I followed the Nest instructions to the letter (both in the manual and on the website), attached the face, and...nothing. No numbers, no lights, nothing. Could I have connected the wires wrong? Or could the original problem have been between the air conditioner and the Nest? We needed to figure it out, because if the problem wasn't the original thermostat, we were going to need a usable thermostat before calling an HVAC repair person.

So I held my breath and dialed the customer support number. I cannot say enough good things about Nest customer support. First they talked me through my installation to confirm that I had done everything correctly. (I had.) Then they walked me through the Nest's on-board diagnostics to get to the bottom of the issue. I don't totally understand it, but they determined that, paradoxically, disconnecting one of the wires would get it to work. And it did!

(The blue light at the top of the Nest is one of the motion sensors that help it to learn occupancy habits. The lights are invisible to the naked eye but somehow came through in pictures.)

Although the Nest is still being used with the old air conditioning system, it is already reducing the house's energy use. (Online access to turn it on or off helps with that.) And when the new HVAC system, foam insulation, and upgraded windows are in, things will be very efficient indeed.


  1. That's so cool! This new house has 2 ac units and I try to keep one of them off at all times (or close to it). And the one that is on is run as little as possible (except at night- I'll go all day without ac if it means I can be cold at night). I've thought about programable thermostats, but maybe I'll have to look into one of these.

    1. Good for you! We have three zones and keep two of them at about 80 during the summer, so they rarely come on. We keep the zone with the master bedroom and the bunny room down around 78, which is very comfortable.

      The Nest is really impressive. If they didn't cost $250 (and if we didn't need one for each of our three zones), we'd probably make the switch.