Flue damper

[steve ashby-p]

Any advantage to flue damper in small Jotul wood stove?

 

[stoveliker]

That depends. Others will be able to answer better but their question will certainly include: how tall is the flue from stove top to the chimney cap?
Lined, insulated, internal or external? Any elbows, length of horizontal run?

And what stove exactly?

If it burns well, controllable without them there is no need...

 

[30WCF]

If the stove is under control no matter how full it is, then the only thing it will help you do is slow the fire a little for a slightly longer burn, but that comes at the expense of lower heat output too.

 

[St. Coemgen]

Any advantage to flue damper in small Jotul wood stove?

If your chimney flue is a miss match to your stove specs (your stove should include required flue information), then it may be something to consider.

 

[St. Coemgen]

If the stove is under control no matter how full it is, then the only thing it will help you do is slow the fire a little for a slightly longer burn, but that comes at the expense of lower heat output too.

Wood contains a fixed amount of recoverable energy. The capture of that energy into the house as heat can vary. A slower burn might actually capture more heat into the house than a fast burn that sends most heat up the chimney. Or not. It is complicated.

 

[Pinesmoke]

For the incredibly low cost of one, 12 bucks this fall when I changed my setup, it can be handy. My stove is very well behaved but as recently as 2 days back I used it to calm the girl down after hot loading oak for the night. The load would have been fine I'm sure but would have burned much faster than normal. 10 minutes with the damper and air down and it was set for overnight burn.

 

[30WCF]

Wood contains a fixed amount of recoverable energy. The capture of that energy into the house as heat can vary. A slower burn might actually capture more heat into the house than a fast burn that sends most heat up the chimney. Or not. It is complicated.

I agree, that a slower burn will put heat into the steel and iron for a longer time, and possibly more efficiently, but, is the intensity enough to meet one’s needs at a lower output rate? That will vary from house to house, location to location and set up to set up.

In a drafty old uninsulated 1950s house like mine, sometimes I need to waste some heat up the flue to get the stove hot enough to throw enough heat to be beneficial, other days I close the air down a little more so I don’t get cooked out and try to just simmer on some coals till evening.

So you are right. Day time burns in warmer climates, or more efficient houses probably benefit most people most of the time to be turned down some, and get more BTUs into the house over a longer period of time. This is an efficient use of the energy potential, but I still think it comes at the expense of lower heat output as I stated earlier.

Correct me if I’m looking at this wrong, but we are likely saying the same thing, but want to frame the information differently because individually, our brains need to hear it the way we need to hear it for it to click.

I’m also trying to think about other stoves than what I have experience with and imagine if they would behave differently than what I am used to, so maybe there is a difference in the appliance?

 

[stoveliker]

You appear to forget that burning high indeed puts more BTUs up the flue *per hour* but also more in the room per hour. Burning low puts less BTUs up the flue per hour (and less into the room per hour), but burning low does out BTUs up the flue for longer... What matters is the ratio.

I don't know how this is for tube stoves, but the mfg of BKs has started on here that the efficiency (i.e. the ratio of BTUs into the room over BTUs up the flue) doesn't change significantly between the two burning modes.

 

[30WCF]

You appear to forget that burning high indeed puts more BTUs up the flue *per hour* but also more in the room per hour. Burning low puts less BTUs up the flue per hour (and less into the room per hour), but burning low does out BTUs up the flue for longer... What matters is the ratio.

I don’t think this is different than what I was saying at all except I may have misused the word “efficient”, but the theories seem to be aligned.

I don't know how this is for tube stoves, but the mfg of BKs has started on here that the efficiency (i.e. the ratio of BTUs into the room over BTUs up the flue) doesn't change significantly between the two burning modes.

I can’t imagine that the result changes from one model to the other, or even tube vs cat. Some stoves are more efficient than others.
I don’t think that you can reverse the rule that more air flow is hotter than less airflow, as long as we are not going to the extreme measures of opening the door to saturate the stove with air and cool the chimney in an over fire.

 

[stoveliker]

You said "waste some heat up the flue" (in a drafty home) running high.
I think that is a common misconception.
My point is that that is not generally true as the ratio doesn't necessarily change. (At least one known counter example.)

 

[30WCF]

You said "waste some heat up the flue" (in a drafty home) running high.
I think that is a common misconception.
My point is that that is not generally true as the ratio doesn't necessarily change. (At least one known counter example.)

Agreed. The ratio that a stove was designed to operate with doesn’t change, but I do have to send more heat out to get more heat in.

And this is where I think we are hung up on the nuances and nomenclature that one can interpret differently based off their environment and culture, and I’ll try not to get too deep into the weeds.

Even if I’m technically incorrect if we pick apart a word’s meaning, I think we are in agreement of what is happening.
-More air is more intense but a shorter duration of BTUs both in the room and in the flue.
-Less air is a lower intensity if BTUs spread over a longer duration.

The word meaning can change with context. Meanings and truths change over time due to context, culture, the way individuals perceive things and with new information.

Once upon a time, you couldn’t eat pork med-rare, but now with the commercial practices in place, you can. But go out and kill a wild boar and you better cook that thing all the way through.

Gay used to be a happy joyous descriptor used in everyday language and Christmas carols, then it became an insult, and now to many it’s a badge of honor. Time, context and culture shape an individual’s perceptions, and we almost live in a time where all three are still understood interpretations.

One can feel like if they are not getting to keep part of what they invested in, put work and resources into as a waste of part of the result. Others may view it as the taxes they had to pay to get the heat that they were able to collect. We can all feel how we want to feel about the taxes. Taxes can be used effectively or squandered, but figuratively that’s what this is. They are probably being used largely effectively and some percentage squandered at the same time. Based off the current technology that we have, we have to send X up the flue to get Y into the room.

Until we build a better mousetrap, some may try to grab some of the “wasted” heat with an exchanger or reclaimer, or pick single wall over double wall to try to add to their return on investment, and we can debate the efficacy of those. Others may view sending more heat up the pipe with double wall as an investment in increasing their draft and keeping the pipes cleaner.

Some will say this is just the way a thing is, and that is the cost of doing business. Others will say it’s wasted energy. The ones that say it’s wasted may bang their heads against the wall for nothing and never produce a better result. Perhaps one of them may discover a better mousetrap.

I wasn’t even thinking this deeply into the conversation on nuances and which words I was articulating with earlier. But even still, after that rant, I think what I actually intended with my earlier statements on efficiency was not to suggest that I’m manipulating what a stove is capable in doing or can I change the ratio of the stove’s designed efficiency, but rather was the user being efficient with when the BTUs were being released. Blowing through 2-3 loads mid day with the widows open is a waste of resources and energy when we can slow it down and not waste that heat, and save those splits until needed, for the times we need to send extra heat up to get more heat off the stove. Perhaps that that explains away the need for all my gibberish above.

I suppose I could have used the like button instead to suffice.🤣

 

[BillBurns]

I hardly notice any change with the damper part closed, or open. I keep it at 45 degrees just so my mind thinks its right.

 

[bigealta]

You have to consider if you slow a tube stove down to much where the secondaries don't fire, you will be wasting unburnt smoke which reduces total btu's from the fuel load.

 

[CanFireman]

And unburned smoke will condense within flue & chimney to form creosote.

 

[30WCF]

You have to consider if you slow a tube stove down to much where the secondaries don't fire, you will be wasting unburnt smoke which reduces total btu's from the fuel load.

You bring up a good point. I said in reference to a damper, I can’t change how a stove runs outside of how it was designed to run, but, as you said, you can slow it down enough to kill the secondaries. I suspect you can choke out a cat too.

I was having a similar thought later after my last post, but it got late and I didn’t get back to it. Some of the folks here also need 2-3 dampers to slow down a stoves draft from the basement to the top of a 2 story house.