Gas Furnance Turned on without Electricity

[Armoloy]

Yesterday I lost electricity to the house.  I ran to HD and rented a generator.  I shutoff the HVAC circuit breaker on the panel and wired the generator to the heater.   Started the generator up and the furnace along with its fan turned on. At night I shutoff the generator  still with the HVAC breaker in the off position.  The gas furnance completely turned off.  In the middle of the night I hear the furnance going on without the fan blowing.  I saw the Nest was lit up.  With no electric going to the furnance how in heck was a spark produced to ignite the furnance.  I called the HVAC tech who installed it and he had no idea.  Could the Nest thermostat being doing this or is my gas furnace possed?

[CBFox]

I was just about to write in with almost the same question.  Does Safety Temperature somehow work even during a power outage? 

My heating is forced hot water on a gas boiler.  The power went out for 30 hours.  Not only did the pipes not freeze, but once the power came back on, the Nest reported that the indoor temperature was 43.  The Safety Temperature was set at 42.  The outdoor temperature had been below 15 for many hours so how is this possible?  (I'm in Florida right now so was observing this all remotely.)

[Ryan_G]

Hey folks,

Thanks for visiting the Google Nest Community. 

Since this thread hasn't had activity in a while, we're going to close it to keep content fresh.

If you have additional questions, feel free to submit another post and provide as many details as possible so that others can lend a hand. 

Hope this helps!

Kind regards,

Ryan