Secondary Combustion Best Practices in a VC Resolute Acclaim 0041

[DarrenC]

Scored a secondhand unused 1988 Vermont Castings Resolute Acclaim (A steal at $350 Cdn). Has a secondary combustion (non-cat) which is new to me. Have been studying up on the forum and reading the manual but Im left with a few unanswered questions.

Basic info for those not familiar with the model. Secondary combustion is behind main the firebox at back of stove, intake is back bottom of firebox. With damper open, the firebox routes directly to flue. With damper closed, firebox routes down low into secondary and then up thru baffles and then up flue. secondary air is non-adjustable and the interior air holes are visible at that bottom hole between firebox and secondary chamber.

1. What happens if I run the secondary combustion at too low a temperature? I know the secondary combustion package is $$$ to replace so Im trying to be cautious. Id like the option of going to bed w secondary burn engaged but with the primary air turned down and i know eventually itll cool too much to be achieving secondary combustion. Is temporary creosote build up a problem? Do the secondary air holes have a tendency to clog?

2. How do I know that secondary combustion is happening? My understanding is that it starts at a certain temp and gets better at higher temps. A post on this forum made it sound like a higher temp on the back of the stove (i assume not in the middle because the secondary combustion baffles are closer to the edge) than on the griddle indicates secondary combustion is happening, but I just wanted to fact check that.

3. Are there any other tips for secondary combustion on this model that I should be aware of?

 

[blades]

I do not know the model per say. Secondary combustion occurs at around 1000? deg F burning the gases coming off the wood. In a perfect world there might not be any flames visible off the wood proper. If things get to cool the secondary burn will cease. The area will carbon up but generally a proper burn will clear that. Very important to have wood that is no more than 18% moisture content internally at room temperature. Vaporized moisture will kill the secondary burns as it cools thing down below the threshold of ignition. Back in the day some of the stoves had controls for combustion air on the secondaries. I have a small ( rated for 900 sq ft) forget the box size but I could get almost 8 Hours of burn from that unit in total. 2000 EPA regs killed secondary air controls. There are times when it really helps prolong the burn , like excessive draft from high winds, or extreme off gassing. So I manually variably block the secondary port . Even with that port completely blocked there is enough aux combustion air, generally from air wash ( unregulated also), to keep them going and extend burn time.

 

[coal and wood man]

Let me say this - Great find!

I have a pre 1990 Resolute also and it is a great stove.

It has a lever on the left that when down forces the exhaust gases to route through the right side of the stove from the bottom up to the flue. This forces the fire to burn from the top down and not the bottom up. Routing the gases this way restricts the path so the gases get hotter and the secondary combustion occurs. This allows the gases to burn. This only occurs at a high temperature. The trick is to have a good fire with a good bed of coals. Putting the lever down into downdraft mode before the fire is ready will make it smoke since there will not be enough draft to sustain the burn. The advantage with downdraft is a more complete burn and a longer burn. When loaded up I have no problem going through the night. Even if the fire is gone in the morning there are usually enough coals so restarting the fire is just a matter of putting some wood in.
Some important items here: 1. Dry wood and preferably hardwood. I am in PA so I have no experience with any wood other than oaks, hickory, beech, maple and other hardwoods. 2. The gaskets must be in good shape or putting the stove in downdraft mode can smoke you out. 3. Take it out of downdraft before reloading the wood box.
Also attaching a manual for pre 1990 VC

 

[DarrenC]

Sorry for the delay. I had login issues.

1.If what im hearing is correct, running stovestoce in downdraft mode when its too cool for secondary combustion isnt a problem, provided you have a hotter fire sometimes to burn off rhe carbon. Is that correct? I like downdraft for multiple reasons, one of which is that without it, my single wall pipes can get too hot ( i try to keep them below 600F) so it means less monitoring.

2.Its funny, lately with this stove, even tho my wood is drier, it seems harder to get secondary combustion (as evidenced by method mentioned in my OP). I keep an eye on the secondary air ports inside the firebox to make sure they aren't clogged. Could anything else be making it harder? I still get secondary combustion sometimes, just seems harder to achieve.

3. I imagine im getting secondary combustion even if the back of the top of the stove isnt hotter than the grill, right? If its only slightly lower (like 30°), thats still less of a temp spread than when there is definitely not secondary happening. Thats my reasoning but im guessing

 

[coal and wood man]

If you are putting the stove in downdraft and it is not going out then I would say you are achieving secondary burn. Even though the stove creates more heat it burns the wood slower since the gasses and by products are burned at the higher temperature and more efficiently. With the stove in updraft mode there is a 6" flue from the firebox to the roof and more of your heat is going up the chimney. In downdraft that space is much smaller at least in the side of the stove so the process is taking place in a more confined area and the stove itself is radiating heat from a larger surface area than just the griddle and top. Look at the right side of the stove and the bulges are actually the tubes used to route the gases up.

Do you have glass panes? Watch how the fire changes and the flames curl more in downdraft mode towards the bottom right of the stove.

I like to keep a bed of ash in the stove but not too much. Make sure you do not have too much ash in the bottom of the stove that is restricting the airway when in downdraft. The channel is on the bottom right and should be free and clear.

Found this on the Hearth WIKI:

Downdraft Stove Operation

Burning the newer Downdraft (base burning) - Type Wood Stoves Definition: A wood stove which draws the smoke and exhaust DOWN through the burning load and embers in an attempt to extract as much heat as possible from the gases in the wood. Also sometimes called downdraft, cross draft and base...

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