Wednesday, February 11, 2015

Nest Thermostat Malfunction

We had our first problem with the Nest Thermostat.

The house felt cold yesterday, although the Nest said it was 75F.

At 4AM this morning, Link woke me up. While I was calming him down, I noticed that cold air was coming out of the air vent, even after I turned the thermostat off via the phone app.

Once I got Link snoring again, I headed down to the furnace to check things out (hey, it seemed like a brilliant idea at the time...of 4AM).

The blower fan was running whether or not the heat was on. A few web searches showed other people had had this problem as well - the most likely root cause was the thermostat baseplate. Relays in the baseplate that control the blower fan and furnace are controlled by the "smart" display that snaps onto the baseplate. The most common complaint (in my limited searching) on Nest's forums are the relays themselves going bad. That's what happened in our case - the relay that controls the blower fan was stuck "on".

I called up Nest's support line, and talked through the issue with a very helpful rep, who was patient with my sleep-deprived self. The temporary fix is to just unplug the wire that controls the blower fan. It turns out the furnace is smart enough to turn on the blower all by itself when the furnace turns on.

However, this means we can't turn the blower on without the furnace being on at the same time. During sunny winter days the house can hit 75F or higher just from the sunshine in the afternoon, so we will turn on the blower to circulate cool air from the basement to the rest of the house. I requested a new baseplate and Nest is shipping one to us, at no charge.

In retrospect, a couple of things stand out:

1) The Nest Thermostat in our house is positioned above the air-return duct (in fact, the builders ran the thermostat wiring through the duct between the furnace and thermostat). This probably accounts for why the thermostat thought the house was warmer than it felt: all the warm air in the house was being sucked down the return duct, keeping the thermostat warm in the process.

2) We got a really high electricity bill last month, well over 60% higher than we got in the summer (our heating system is natural gas). I previously blamed this on the freaking chickens, with their heat lamp and need to drink liquid water, but perhaps having this fan running continuously was part of the problem. I don't think this has been going on for more than a couple days, but I have no way of proving that.

3) This would have been a much bigger problem if one of the other connections had gone bad, leaving us without heat. So I picked up a $15 dumb thermostat from Home Depot as a backup in case something like this happens with the next backplate.

Anyway, that's the adventure in the lives of the Colorado Medemas this week.

***Update Feb 15***

Received the new baseplate from Nest on Saturday, and installed it today (Sunday). The fan is back online, and everything seems to be working optimally! I'll ship the old baseplate back to Nest tomorrow (they included a prepaid shipping label, so I just have to put the old baseplate in the same box in which the new one was delivered, and drop it off at a Fedex location).

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