Thermostatic Air Control (TAC) for Vermont Castings Encore FlexBurn 2040

  • Active since 1995, is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.


New Member
Jan 26, 2021
Andover, MA, USA
Bought and moved into a new house in 11/2020, and one particularly bright spot was/is an Encore 2040 sitting in an open dining/living/kitchen space (installed by prior owner in 2014). For context, burned when I was a kid, though that was pre-catalytic. Anyway, narrowing down on a few questions in order to get into the zone on hot, overnight burns, which generally seems just out of reach so far, which brings me to my first ever post focusing on the Thermostatic Air Control (TAC).

First, observations. When the stove was cold, I tucked my head to the back and both visually and by touch confirmed the flapper is closed when the air control lever is in the closed position, i.e. when I tap the flapper it makes a 'ding' sound when it falls back into the closed position. When progressively opening the air control lever the flap progressively rises, too. This is all when the stove was cold.

So, I then fire the stove, leaving the air control lever in the downward/mid/6PM position and, using my cell phone, take regular photos of the flapper position during different phases of a burn. Those phases range from lit to steady burn to catalytic-engaged with stove top temperatures ranging from cold into the 400-600 range.

What I see brings me to asking my very first question on this forum, are you supposed to see a discernible adjustment of the flapper by the thermostatic air control, i.e. as the temp rises and falls, should a careful observer be able to see the flapper change position (when the air control lever) is kept in the same, exact position?

Hint: Comparing photos, the flapper doesn't seem to adjust, at least as far as I can tell. Because extended burns are so dependent on regulated air flow, this prompts my first question here.

Thoughts, suggestions, and anything/everything else appreciated!

FYI for anyone else, found this thread tremendously valuable in confirming how the TAC works: