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

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QualityGig

New Member
Jan 26, 2021
7
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: https://www.hearth.com/talk/threads...-air-control-work-in-my-vc-encore-2n1.116194/
 

PatrickWR

New Member
Apr 14, 2021
23
Oregon
I'm following this topics, as I'd like to learn more about how to get the most out of the TAC on my VC Dauntless.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
The flapper should close once the stove is hot and the room temp is warm. Try the opposite experiment. Once the stove is warmed up and the room is at a comfortable temp of say 72º, move the air control until the flap just closes. Then see if the flap opens as the room cools down.
 

gthomas785

Minister of Fire
Feb 8, 2020
714
Central MA
The thermostat should respond to the stove temperature, but probably not much to the room temperature. I have never watched the flap, but once it's settled in mine keeps the stove temperature pretty constant (+/- 50 deg) until it runs out of fuel.
 
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gthomas785

Minister of Fire
Feb 8, 2020
714
Central MA
However I should add that the total heat output does seem to fluctuate somewhat as the cat ramps up and down. It's not a perfect system.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
Yes, admittedly my only VC stove was a new Resolute I. I watched the flapper a lot just because I was fascinated by it and how well it worked. I don't have experience running the cat version VC stove, but here is a thread on all things VC for the season.
 

QualityGig

New Member
Jan 26, 2021
7
Andover, MA, USA
Hello, everyone! Looking to get ahead of the game with a follow-up question: Is there any way to determine whether your Thermostatic Air Control (TAC) has failed and/or something in between the air control lever and flapper isn't working right?

There's no real update on my original post -- I got on my hands and knees at different points of burns to take snapshots of the flapper and just couldn't see any discernible change in flapper condition. Being new to the house and area, still also looking for quality wood (dealing with a few variables here).
 

stoveliker

Minister of Fire
Nov 17, 2019
6,313
Long Island NY
If you can hear it close, (just) close it while the stove and room is hot and see if it opens up when the room cools down.
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,455
South Puget Sound, WA
There should be a visible change from the opening for a cold stove vs a hot one. On our old Resolute this could be a 1/4" swing open. Try this: the next time the stove is taken up to a high temp, move the air control lever until the air intake flap is just closed. Let the fire go out and let the stove go stone cold. Now check the air control flap. Is it slightly open?
 

QualityGig

New Member
Jan 26, 2021
7
Andover, MA, USA
There should be a visible change from the opening for a cold stove vs a hot one. On our old Resolute this could be a 1/4" swing open. Try this: the next time the stove is taken up to a high temp, move the air control lever until the air intake flap is just closed. Let the fire go out and let the stove go stone cold. Now check the air control flap. Is it slightly open?

Great suggestion! Will try that when I do our first burn, though that certainly isn't today in the nearly 100-degree weather!
 

t0asty

New Member
Oct 12, 2021
64
NJ
@QualityGig hope all is well. If you don't mind reporting back your findings when you test this? I just bought a new VC Encore and should be getting it in about 4-5 weeks. I have an old VC Defiant 1975 now and unfortunately my heat spring broke years ago so I would manually adjust a lot since the flapper was on the back exterior, so this will be sort of new for me. I live in NJ so you'll have slightly cooler weather than me earlier or about the same time, anxious for the cooler weather.

Additionally, I plan on having it burn overnight but this will be my first experience with a cat. Are there any issues with letting it burn until the fire potentially diminishes while leaving the damper closed and it hurting the cat? The TAC should adjust but at a certain point will run out of fuel and start to cool, with an overnight burn I won't be there to tend to the fire. My old Defiant I never really gave it a second thought but with this being an expensive investment just don't want to make a dumb mistake here. Thanks!
 

QualityGig

New Member
Jan 26, 2021
7
Andover, MA, USA
@QualityGig hope all is well. If you don't mind reporting back your findings when you test this? I just bought a new VC Encore and should be getting it in about 4-5 weeks. I have an old VC Defiant 1975 now and unfortunately my heat spring broke years ago so I would manually adjust a lot since the flapper was on the back exterior, so this will be sort of new for me. I live in NJ so you'll have slightly cooler weather than me earlier or about the same time, anxious for the cooler weather.

Additionally, I plan on having it burn overnight but this will be my first experience with a cat. Are there any issues with letting it burn until the fire potentially diminishes while leaving the damper closed and it hurting the cat? The TAC should adjust but at a certain point will run out of fuel and start to cool, with an overnight burn I won't be there to tend to the fire. My old Defiant I never really gave it a second thought but with this being an expensive investment just don't want to make a dumb mistake here. Thanks!

Don't have much specifically on-point information or data to share, but will share a couple of related tidbits. First and for context, bought and moved into a new place a couple of years ago, inheriting the Encore we have. My folks had an Encore at their place, and between that and an old model when I was growing up, have a fair amount of wood burning experience. We've burned at this place now for two winters, and neither has met expectations. We've had wood quality issues, in particular, and between that and not having complete perspective on the stove itself (use, care, and performance under prior ownership), just still trying to get a handle on the situation.

One concern related to your question is that I'm not clear on the performance cycle on overnight catalytic burns, specifically their duration and what happens at the transition point on the backend. I've generally found people saying a true overnight burn is (slightly) out of reach for the Encore. We had better wood this past winter but clearly didn't burn as clean as I'd like. Suspicions are: something wrong with TAC (maybe it's not adjusting properly), cleaning the catalytic a few times during the season (no evidence it's plugged or not working right), not understanding temperature targets quite right, needing a cat thermometer (stove doesn't have one and about to start researching if/how to add one), and air supply (the original setup draws from the room, but my folks had their Encore draw from outside via the basement), among other possible issues. Of course these can also overlap.

My understanding on how this stove should behave over the course of an overnight burn is, simply put, a steady-state output . . until it runs out of fuel. Standard recommendations are a good bed of coals, filling the stove with large seasoned pieces, then giving it a few to get back to catalytic temperature at which time you switch to catalytic, sent the air control lever at just more than closed . . . and let the TAC take it from there. The TAC will then adjust air flow automatically and -- I think -- open more as fuel runs out. The temperature at some point will fall below the threshold for cat operation, and at that point it just becomes and updraft >> downdraft >> updraft >> flue situation. When opening the back to check the cat there's generally just very fine, light gray soot on (but not plugging) the cat and down in the lower chamber below the cat. Of course at that point you're not burning clean, and figuring out that transition point for our Encore has been a bear. Stovetop temperatures have typically run around 450-550 and stovepipe around 350 at a foot above where the pipe and stove join.

Don't know if this offers much immediate help, but I'd sure like to keep this thread active in the hopes we (and others) get the most out of our Encores.
 
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