To Damper...Or Not To Damper...

[Rob From Wisconsin]

Our stove performs really well - perhaps too good.
Draft is perhaps a bit too strong, even with it turned-down
all the way, resulting in short, hot burns. I would like to
lengthen the burns a bit, and perhaps keep some of the heat
around a bit, instead of up the flue.
Is there anyone out there who uses a stovepipe damper to assist
in this?? Good?? Bad?? What did it do for you??

Thanks for your input...

Rob

 

[begreen]

I've have had a damper on both of our installs. It was almost impossible to run the 602 without the damper. Depending on how strong the draft is, wood consumption can be reduced considerably. If the draft is too strong, it is hard to regulate the stove. Adding the damper makes the air control much better. I would say if you damper down all the way and it still has a really hot stack temp, add a damper.

 

[Rob From Wisconsin]

I've have had a damper on both of our installs. It was almost impossible to run the 602 without the damper. Depending on how strong the draft is, wood consumption can be reduced considerably. If the draft is too strong, it is hard to regulate the stove. Adding the damper makes the air control much better. I would say if you damper down all the way and it still has a really hot stack temp, add a damper.

Are you still able to keep your flue nearly as clean as before??

Rob

 

[Eric Johnson]

keeping the damper clean has never been a problem for me, Rob. It's close enough to the stove outlet that it rarely gets cool enough to attract any creosote. The main buildup you get is fly ash. It should clean right up during your annual stove cleaning routine.

I usually put in a damper whether I think I'll need it or not, simply because they don't cost very much and can be really useful. Like BG says, it gives you another way to moderate your burn and cut wood consumption, especially on very cold nights. I had one installation that probably could have benefited from having two of them.

And bottom line, it's yet another line of defense if you have a chimney fire.

 

[begreen]

With the Jotul 602, after yearly inspections I stopped worrying about it. The flue when we took it down, was still clean after 10 years of burning in it. Barely a handful of creosote came out. I'll know pretty soon with the new install, it's due for it's first cleaning. But as long as one is able to maintain a hot flue of say 400 degrees and sticks with good burning practices, it shouldn't be much of an issue with an interior chimney.

 

[pistonslap]

I have an older wood furnace without very good air control and my chimney drafts extremely well. If I don't use my flue damper the wood burns up quickly. If I chop the air to the stove by my air controls, it has a tendency to start to smolder. If I leave my air control fairly open and almost close my flue damper, I get better burn times and hotter burns.

 

[jpl1nh]

I have an older wood furnace without very good air control and my chimney drafts extremely well. If I don't use my flue damper the wood burns up quickly. If I chop the air to the stove by my air controls, it has a tendency to start to smolder. If I leave my air control fairly open and almost close my flue damper, I get better burn times and hotter burns.

exactly my experience too.

 

[Gooserider]

A chimney damper can be useful but there are a few things to be aware of...

1. Many modern manufacturers advise against using them.

2. We have had situations in the past where a damper was thought to be needed, but it was subsequently found that there were other problems with the install that were contributing to what looked like an excess draft problem, and when those were fixed the need for the damper went away.

Look for leaks in the stack pipes, make sure all joints are tight and well sealed.

Particularly check the junction between the stove exit and the chimney pipe. You should NOT see any corrugations, the pipe should fit in far enough so that the ridge above the corrugations is touching the flange on the stove exit or close to it, and the joint should be sealed with stove cement. On many stoves the collar is not as deep as the corrugations on the standard pipe, so the pipe will bottom out before it is properly seated UNLESS you either use a special "stove connector" pipe that has short corrugations, or trim a normal pipe so that it is about 1/8" shorter from the end of the pipe to the ridge than the depth of the flue collar on the stove. Air entering via a leak at this junction can cause short, hot burns that look like an overdraft situation.

Also verify that any bypass dampers (such as are used for startups or reloading) are fully closing and sealing properly, that your air controls are working properly, etc.

Verify that all doors are properly seating against the gaskets (dollar bill test) and that the glass is tight. If you have an older cast iron or soapstone stove especially, but for all stoves make sure that there are no leaks or cracks in the joints or other parts of the body.

The key idea is to make sure that the ONLY way air is getting into the stove is through the manufacturer designed passages and air controls!

The hazard of adding a chimney damper is that if you have one of the problems mentioned above, the damper will mask the symptom so that it looks like a cure, but is really hiding the root cause real problem.

One of the few mfgrs that actually talks much about dampers is Hearthstone, who IIRC reccomends that one install a damper ONLY if one has a MEASURED draft in excess of 0.30" WC, which is pretty high. I think that's a reasonable rule of thumb for most stoves - typically to get that much draft requires an unusually tall, well insulated chimney. So unless you fit that category I'd check for other issues before putting in a damper.

Gooserider

 

[Rob From Wisconsin]

A chimney damper can be useful but there are a few things to be aware of...

2. We have had situations in the past where a damper was thought to be needed, but it was subsequently found that there were other problems with the install that were contributing to what looked like an excess draft problem, and when those were fixed the need for the damper went away.

Look for leaks in the stack pipes, make sure all joints are tight and well sealed.

Particularly check the junction between the stove exit and the chimney pipe. You should NOT see any corrugations, the pipe should fit in far enough so that the ridge above the corrugations is touching the flange on the stove exit or close to it, and the joint should be sealed with stove cement. On many stoves the collar is not as deep as the corrugations on the standard pipe, so the pipe will bottom out before it is properly seated UNLESS you either use a special "stove connector" pipe that has short corrugations, or trim a normal pipe so that it is about 1/8" shorter from the end of the pipe to the ridge than the depth of the flue collar on the stove. Air entering via a leak at this junction can cause short, hot burns that look like an overdraft situation.

I had the above problems w/ our current stove, and it was actually stealing from the draft
instead of adding. When I went through & sealed it up properly, the draft improved quite a
bit. The leaks were kinda acting like a "barometric damper", and slowing down the draft.

Rob

 

[Michael6268]

Leaks/holes in the chimney pipe is going to lessen the draft in the stove. So if you seel any gaps, and you already have too much draft through the stove, you are just going to make things worse. On the other hand, leaks in the stove itself or the door/s are going to increase draft through the fire, and fixing those will help.

 

[BrotherBart]

Leaks/holes in the chimney pipe is going to lessen the draft in the stove. So if you seel any gaps, and you already have too much draft through the stove, you are just going to make things worse. On the other hand, leaks in the stove itself or the door/s are going to increase draft through the fire, and fixing those will help.

If you don't seal those flue leaks you are going to have cooler air mixing with the flue gases and cooling the flue. Otherwise known as a creosote factory.

- BroBart (who has had to chisel creosote out of a flue after a season with a flue leak)

 

[Michael6268]

Leaks/holes in the chimney pipe is going to lessen the draft in the stove. So if you seel any gaps, and you already have too much draft through the stove, you are just going to make things worse. On the other hand, leaks in the stove itself or the door/s are going to increase draft through the fire, and fixing those will help.

If you don't seal those flue leaks you are going to have cooler air mixing with the flue gases and cooling the flue. Otherwise known as a creosote factory.

- BroBart (who has had to chisel creosote out of a flue after a season with a flue leak)

Absolutely, but they were asking about draft. But...... that does open up that can of worms again about barometric dampers on woodstoves. I still think they are creosote machines but others disagree.

 

[Rob From Wisconsin]

Leaks/holes in the chimney pipe is going to lessen the draft in the stove. So if you seel any gaps, and you already have too much draft through the stove, you are just going to make things worse. On the other hand, leaks in the stove itself or the door/s are going to increase draft through the fire, and fixing those will help.

If you don't seal those flue leaks you are going to have cooler air mixing with the flue gases and cooling the flue. Otherwise known as a creosote factory.

- BroBart (who has had to chisel creosote out of a flue after a season with a flue leak)

Absolutely, but they were asking about draft. But...... that does open up that can of worms again about barometric dampers on woodstoves. I still think they are creosote machines but others disagree.

I was considering putting one on our stove several years ago, until I received some education
on them. Their main use is intended for wood furnaces that tend to over-fire when they
"kick-in". In that case, with so much wood fuel present, an overfire could be a real big problem.
Not really intended for your regular stove......

Rob

 

[Rob From Wisconsin]

So the way I understand it, adding a damper to my application would be
a positive thing....if I.....

1.) Keep the damper as close to the firebox as possible

2.) Open-up the air controls & let the damper acts as my air-flow control

Anything else I missed from this thread????

Rob

 

[begreen]

#2 - This will take a bit of finessing depending on the draft and stove. You may find the sweet spot is with the stack damper half-closed. So I would say start the fire with all dampers wide open. Then, once the stove is getting hot, (over 400?- your setting may vary), find the sweet spot at which setting the stack damper allows full regulation with the stove air controls. In our old installation with the 602, this meant shutting the stack damper closed, though it never really closes all the way. With the Castine, this is with the stack damper about half-closed.

#3 - If you don't have one already, invest in a stack thermometer. It helps one regulate the stove better and avoid running the stove in the opposite condition where the stack is always too cool.

 

[Rob From Wisconsin]

#2 - This will take a bit of finessing depending on the draft and stove. You may find the sweet spot is with the stack damper half-closed. So I would say start the fire with all dampers wide open. Then, once the stove is getting hot, (over 400?- your setting may vary), find the sweet spot at which setting the stack damper allows full regulation with the stove air controls. In our old installation with the 602, this meant shutting the stack damper closed, though it never really closes all the way. With the Castine, this is with the stack damper about half-closed.

#3 - If you don't have one already, invest in a stack thermometer. It helps one regulate the stove better and avoid running the stove in the opposite condition where the stack is always too cool.

Yes, I do indeed have a stack thermometer. It is located at about the same height as yours.
What temps. do you typically read there??
Being that our stove is small, just like the 602, I may be able to fully close the damper.

Thanks for the advice...

Rob

 

[Gooserider]

So the way I understand it, adding a damper to my application would be
a positive thing....if I.....

1.) Keep the damper as close to the firebox as possible

2.) Open-up the air controls & let the damper acts as my air-flow control

Anything else I missed from this thread????

Rob

Key thing is that with a modern stove, the bulk of the control should be done using the air controls built into the stove itself, not with the stack damper (which wouldn't be needed on a "normal draft" chimney)

If you are having trouble controlling the burn with the stove controls because the draft is overpowering them, you would use a stack damper closed to the minimum amount needed to give full control back to the on-stove controls. Once that sweet-spot is found, you probably shouldn't touch the stack damper, other than possibly to open it during startup and refueling, then return it to the "sweet spot" setting.

On a smoke dragon the stack damper is one of the actively used controls, but it is not on the modern stoves.

Gooserider

 

[begreen]

The 602 was on a different stack which didn't have the stack thermometer, so I had to use the surface one (it was single wall). The 602 liked to burn hot. I'd damper down fully when the stack surface temp reached about 500 degrees. With the Castine, I damper down around 400 degrees on the probe thermometer (double-wall pipe) or 500 stove top temp. Each stove and stack combo is different. You'll have to experiment a bit to find the right temp, but generally you don't want to do is too early, like when the kindling is firing off. Better to wait until a good bed of coals is established.

 

[rdrcr56]

Last winter I played around with the stack damper and found over night burns could be one, sometimes two hours longer. I found on my homestead two thirds closed on the damper and one quarter open on the air control worked good.

 

[precaud]

Adding a secondary air control is a more precise way to control combustion air. And it gives you the ability to completely close down the stove. I think this is an important safety feature and every stove should have it. It also extends the "burn time" of any stove to 8-12 hours. See:
https://www.hearth.com/econtent/index.php/wiki/Add_secondary_air_control_to_stove_Morso_2110/

 

[begreen]

Adding a stack damper when there is high draft would be done to make the stove able to regulate as the manufacturer intended. It does not void the warranty. Adding a secondary air control is not the same thing and does have the potential to void the warranty.

 

[precaud]

Adding a secondary air control is not the same thing and does have the potential to void the warranty.

I'm glad you edited your sentence to state it this way BG, because it would be petty and baseless for any manufacturer to void a warranty on the basis of adding a secondary air control. It wouldn't stand up in court, that's for sure.

Oh, and with primary AND secondary controls, you CAN properly meter air under any condition you'll normally encounter. The same can't be said for a damper.

 

[begreen]

You're probably right, and with a stove as well built as the Morso, it's pretty unlikely that you would be sending back on warranty. Though Morsoe warranty specifically mentions that they do not cover: 7. Damage caused by unauthorized modifications, use or repair.

But my advice is more in the general sense. Not every stove is as easy to modify without permanent evidence. And most folks are not as hands on capable as you are and prolly should not be modifying a new stove.