The manual I'm looking at shows 3 AAA cells. So, they should last a while..
But, maybe the 24VAC line provides power when the stat isn't calling for heat.?.
No need to open up the bubble-pack, I'm not going to look a gift horse in the mouth..
Hey, I guess that means it's impolite to inspect the teeth of a horse you just got as a gift..
![Smile](images/smilies/smile.gif)