Furnace Failure Or Nest Nuisance?

I bought the first version of the Nest Thermostat back in 2012. After installation, the thermostat worked flawlessly with my now 19-year old Rheem gas furnace for almost four years.

Last week, the furnace stopped heating. I’d recently read about problems with Nest Thermostats tapping power from furnace circuits which lack a common wire, which pretty much describes my installation. Some furnaces would eventually fail due to constant startup signals sent by the Nest.  Apparently, a recent software update could drain the built-in, rechargeable battery, causing the whole system to shut down. I didn’t think the startup signal issue described my problem, since my system had worked flawlessly for almost four years.

Nest version 1 base plate (click on image for larger version)

I called Nest tech support, which proved to be the best tech support experience I had in years. We walked through a variety of different tests. The furnace wouldn’t fire up, but the central air conditioner and fan worked fine. The thermostat would show the furnace heating, but neither the furnace nor the fan would fire up. We removed the Nest dial, uncovering the underlying wiring base. I detached, then reattached each wire. Jiggling the Rh wire (which managed furnace power-on) sometimes caused the furnace to fire up, but it never remained on. The Nest tech suggested replacing the base plate, and initiated a replacement.

The built-in diagnostics and setup information displayed by the Nest made figuring out connection problems pretty simple. The problem was that the diagnostic showed the Rh wire as connected. Disconnecting the wire would clearly show up as being disconnected. But the furnace refused to fire up, even when the wire seemed to be properly connected.

Nest wiring diagnostic display (click on image for larger version)

That seemed amazing — a replacement part for a nearly four year old part, practically unheard of in today’s world of seemingly ephemeral tech products. Four days later, a package arrived, containing not only a new base plate, but and entirely new version 2 thermostat. Color me impressed.

Well, I was impressed until I opened up the box and looked at the new base plate. My admiration for Nest engineering diminished a bit when I noticed the mounting holes were vertically aligned instead of horizontally aligned. My old base plate’s horizontally aligned mounting screws meant one of the screws actually attached to a stud, which seemed be pretty solid after attaching all the screws. I needed to use drywall adapters to screw the new base plate into the wall. While the newly installed thermostat doesn’t wiggle, it seems just a bit less securely mounted. On the other hand, attaching wiring is easier; the push-lock connectors seem to be a bit more robust than the older versions.

However, prior to installing the new thermostat, the furnace automagically started working properly, heating the house as it should. So I’ve also scheduled a furnace diagnostic, just in case the thermostat really isn’t the problem. After working flawlessly for nearly two decades, I suppose the furnace could be ready for retirement.

Version 1 base plate on the right. Note the different location of the mounting holes.

The bottom line, however, is that Nest tech support rocks. Nest could just as easily have washed their hands of the whole matter, telling me my Nest’s warranty had expired. Instead, they went the extra mile, which will likely keep me using Nest products more than any shiny bells or whistles.