I have two issues/complaints that I detail below, and one recommendation:
๐๐๐๐๐ฒ ๐ญ: ๐ก๐ฒ๐๐ ๐๐ฒ๐ฎ๐ฟ๐ป๐ถ๐ป๐ด ๐ง๐ต๐ฒ๐ฟ๐บ๐ผ๐๐๐ฎ๐ ๐๐ฒ๐ป ๐ฏ ๐๐ณ๐ฐ ๐ฐ๐ผ๐ฑ๐ฒ, ๐ป๐ผ ๐ป๐ผ๐๐ถ๐ณ๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป ๐ฏ๐ ๐ก๐ฒ๐๐ ๐ผ๐ฟ ๐๐ผ๐ผ๐ด๐น๐ฒ ๐๐ผ๐บ๐ฒ
Why did multiple E74 error codes appear on the face of the Nest thermostat but not appear in my Nest App nor Google Home App "Activity" tab? I finally saw the error while walking by the thermostat yesterday. I then saw several more of these E74 errors as I was diagnosing this problem.
I found that the problem occurred for the previous two (2) days, as evidenced by multiple short-cycle furnace heating periods of only 5-12 minutes in the Google Home App "Activity" tab. I finally diagnosed the root cause of the problem when I measured the furnace's hot air discharge temperature: it was 145F! (Note: it was normally about 120-125F hot air discharge temperature.)
I solved the problem yesterday afternoon by replacing the prematurely dirty furnace air filter (I had changed it last month; it normally is changed every 3 months).
The actual fault involved the high hot air exit temperature tripping the high air temperature safety relay. The burner turned off, and the hot air fan kept running until the furnace cooled off; then the burner restarted after a time-out.
๐๐๐๐๐ฒ ๐ฎ: ๐๐ฎ๐๐ฒ ๐๐ผ๐ผ๐ด๐น๐ฒ/๐ก๐ฒ๐๐ ๐ณ๐๐ฟ๐ป๐ฎ๐ฐ๐ฒ ๐ป๐ผ๐๐ถ๐ณ๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป๐ ๐ฎ๐ณ๐๐ฒ๐ฟ ๐ ๐ณ๐ถ๐
๐ฒ๐ฑ ๐๐ต๐ฒ ๐ฝ๐ฟ๐ผ๐ฏ๐น๐ฒ๐บ
Issue 2.1: Last night (1 or 2 hours after I changed the filters) the Nest App FINALLY gave me a "Heads-Up: Check your Furnace" notification, suggesting I change the furnace air filter.
Issue 2.2: Why did I FINALLY get a "Furnace repeatedly shut down" notification in the Google Home App "Activity" tab this morning after the furnace successfully ran non-stop for 3 hours 13 minutes? And at the same time the thermostat showed this error:
"Your furnace keeps shutting down within 15 minutes of heating. g.co/nest/m6"
What would have been really helpful would have been to mirror the E74 codes to the Nest App AND the Google Home App "Activity" tab. This way I could have minimized thermal cycling of my furnace, which is a slight safety issue. Also, if I had been on a trip away from home and was not able to fix this issue in time, the short cycle time might have led to a furnace failure, and ultimately freezing my water pipes!
๐ฅ๐ฒ๐ฐ๐ผ๐บ๐บ๐ฒ๐ป๐ฑ๐ฎ๐๐ถ๐ผ๐ป:
Please mirror all Nest Thermostat Error Codes to the Nest App AND the Google Home App "Activity" tab, to help catch problems early and prevent small problems from becoming large, expensive problems.
Moderator edit: Subject updated for clarity and findability.
