Barometric Damper

[rockettmantoo]

This discussion was moved from key damper question thread.

Already have a damper installed and it was fully closed during the test.

A barometric damper is a whole other animal. Google it to see. Commonly used on furnaces and coal stoves

 

[bholler]

Maybe a barometric damper?

Not on a wood stove ever.

 

[Highbeam]

Not on a wood stove ever.

Yet, for some reason, totally acceptable and even required on high efficiency wood furnaces which are simply a woodstove with a box around it. I think it would look dumb above a stove.

 

[bholler]

Yet, for some reason, totally acceptable and even required on high efficiency wood furnaces which are simply a woodstove with a box around it. I think it would look dumb above a stove.

I don't think they are acceptable on any woodburning appliance honestly. They cause massive amounts of creosote buildup and very intense fires if that catches. But yes many furnaces call for them

 

[Highbeam]

I don't think they are acceptable on any woodburning appliance honestly. They cause massive amounts of creosote buildup and very intense fires if that catches. But yes many furnaces call for them

That's what I meant. Even the high efficiency wood burning furnaces require or allow barometric dampers. Yet we have all read that they are taboo on woodstoves for some reason.

 

[jetsam]

That's what I meant. Even the high efficiency wood burning furnaces require or allow barometric dampers. Yet we have all read that they are taboo on woodstoves for some reason.

Because they let room temperature air into the flue, and most of the installs out there are already struggling with uninsulated liners and stove operators who have to call "the guy" to look up a pipe for them to see if there's any creosote.

 

[Highbeam]

Because they let room temperature air into the flue, and most of the installs out there are already struggling with uninsulated liners and stove operators who have to call "the guy" to look up a pipe for them to see if there's any creosote.

I think you miss the point. It’s not that baro dampers should be allowed on wood stoves, it’s why are they only allowed on wood furnaces that also have creosote, low flue temps, inexperienced operators, etc.

Why do you suppose that is?

 

[kennyp2339]

Why do you suppose that is?

Some have mechanical combustion others like regular stoves only relies on the natural vacuum created from the burning fire?

 

[brenndatomu]

I don't think they are acceptable on any woodburning appliance honestly. They cause massive amounts of creosote buildup and very intense fires if that catches. But yes many furnaces call for them

I'm sure this is true on a dirty burner, but in my experience if you are burning clean, there is no creosote...gotta have smoke to make creosote, and if you are doing it right (especially with a Kuuma) there is no smoke after the initial lighting...and at that point the BD is not open much, if any, to be cooling the flue anyways.
And not only do many furnaces call for them, they come with them. Heck, my old Yukon furnace called for -0.02" draft! -0.03" max!
It was interesting with that machine, it made some creosote, but it was almost worse before the BD (heat exchanger) than it was after!

 

[jetsam]

I think you miss the point. It’s not that baro dampers should be allowed on wood stoves, it’s why are they only allowed on wood furnaces that also have creosote, low flue temps, inexperienced operators, etc.

Why do you suppose that is?

...anyway, on the furnace side, I guess that it is considered an allowable evil on furnaces because they are typically in basements on long flues? Still sounds like a bad idea to me, get a manometer and a key damper.

 

[bholler]

I'm sure this is true on a dirty burner, but in my experience if you are burning clean, there is no creosote...gotta have smoke to make creosote, and if you are doing it right (especially with a Kuuma) there is no smoke after the initial lighting...and at that point the BD is not open much, if any, to be cooling the flue anyways.
And not only do many furnaces call for them, they come with them. Heck, my old Yukon furnace called for -0.02" draft! -0.03" max!
It was interesting with that machine, it made some creosote, but it was almost worse before the BD (heat exchanger) than it was after!

No woodburning appliance burns completely. So the only way to avoid creosote buildup is by keeping the exhaust above the condensation point untill it exits the chimney. That is much harder to do with a big hole in the side of the connector pipe. Now yes modern stoves and furnaces absolutely burn more completely than older stuff so even if you drop below the condensation point less material will be deposited. But it still in my opinion is not the best solution.

 

[SpaceBus]

I think the real reason they use baro dampers is that most stove operators can't be trusted with an air tight stove. MFG's would rather see a hotter fire with a diluted flue than creating an appliance capable of closing the air enough to reduce draft to acceptable parameters. Such a stove would be capable of letting a fire smolder indefinitely.

 

[kennyp2339]

I think the real reason they use baro dampers is that most stove operators can't be trusted with an air tight stove. MFG's would rather see a hotter fire with a diluted flue than creating an appliance capable of closing the air enough to reduce draft to acceptable parameters. Such a stove would be capable of letting a fire smolder indefinitely.

Kind of, but not, and more of a default benefit from epa testing, when stoves get tested to be certified part of the epa process is to mimic conditions of worst case scenario and still achieve a clean burn under the emissions standards, the test includes a warm lab to mimic a mild wood burning day and draft at .005 (considered minimum to the epa lab)
Since the majority of wood burners operate there stoves under colder conditions, drafts a much better and stoves tend to burn hotter (and cleaner) then the minimum environment set up in the test lab, now lets go back to the Alaska issue and you have to wonder why I was adamant about nit picking from the state side of things.

 

[brenndatomu]

I think the real reason they use baro dampers is that most stove operators can't be trusted with an air tight stove. MFG's would rather see a hotter fire with a diluted flue than creating an appliance capable of closing the air enough to reduce draft to acceptable parameters. Such a stove would be capable of letting a fire smolder indefinitely.

So why do they still do it on computer controlled wood furnaces then?

 

[vwmike]

I had the same problem and added a damper in my double wall stove pipe. It still didn’t give me enough. I took it out and welded a plate over the lower moon shape opening and that gave me enough to get it down to .05” during cold weather.

 

[bholler]

So why do they still do it on computer controlled wood furnaces then?

Because the furnace manufacturer is doesn't care enough to make the furnace able to compensate for varying draft conditions. Which wouldn't be that hard on a computer controlled furnace

 

[SpaceBus]

So why do they still do it on computer controlled wood furnaces then?

Because the computer cannot close the stove to the point that the draft would slow down enough. If the power goes out during such a scenario the fire will end up smoldering indefinitely. Obviously these are like, worst case scenarios, but that's what you have to design for. Also, computer controlled things are ultimately controlled by the end user. You could easily set the thermostat low, light a fire, and then cause a complete smoldering situation if the computer could completely close off the air. Easier to dilute the flue in a litigious society.

 

[brenndatomu]

Because the computer cannot close the stove to the point that the draft would slow down enough...if the power goes out during such a scenario the fire will end up smoldering indefinitely.

Exactly.

Also, computer controlled things are ultimately controlled by the end user. You could easily set the thermostat low, light a fire, and then cause a complete smoldering situation if the computer could completely close off the air.

Not without making changes to the controls...and that's not the OEM's problem then.`
On the Kuuma the tstat doesn't even need to be hooked up.
And it doesn't have the ability to let the fire smolder, because it is looking at firebox temps only.
To me, there is almost zero risk using a BD on a unit like this...about the same level as with a oil burner.

 

[kennyp2339]

Exactly.

Not without making changes to the controls...and that's not the OEM's problem then.`
On the Kuuma the tstat doesn't even need to be hooked up.
And it doesn't have the ability to let the fire smolder, because it is looking at firebox temps only.
To me, there is almost zero risk using a BD on a unit like this...about the same level as with a oil burner.

It a whole different technology & design though, Kuma is a great example of new tech for the woodfired furnace market, those guys out in Minnesota were the first to have the clean burn approved before the new epa regs went into effect.
Traditional woodstove that are essentially driven by a static draft are way different, as far as path of the fire, preheated combustion air, and amount of default air coming into the unit after the draft control is closed off 100%.

 

[brenndatomu]

It a whole different technology & design though, Kuma is a great example of new tech for the woodfired furnace market, those guys out in Minnesota were the first to have the clean burn approved before the new epa regs went into effect.

Not new tech really...they have been doing this for well over 30 years (40?) but yes, they were clean burn before clean burn was cool.

Traditional woodstove that are essentially driven by a static draft are way different, as far as path of the fire, preheated combustion air, and amount of default air coming into the unit after the draft control is closed off 100%.

I am not arguing that they should be put on stoves...although I wouldn't be afraid to put one on mine, if it was a reliable clean burner (I know I have dry wood, a well mannered stove/chimney, and proper burning habits (including maintenance) my argument was with when @bholler said they should not be used on any wood burner.
Key damper is a better solution on a manual stove though...even if you had to block some of the factory holes to get the draft under control (as verified by a manometer)

 

[bholler]

Not new tech really...they have been doing this for well over 30 years (40?) but yes, they were clean burn before clean burn was cool.

I am not arguing that they should be put on stoves...although I wouldn't be afraid to put one on mine, if it was a reliable clean burner (I know I have dry wood, a well mannered stove/chimney, and proper burning habits (including maintenance) my argument was with when @bholler said they should not be used on any wood burner.
Key damper is a better solution on a manual stove though...even if you had to block some of the factory holes to get the draft under control (as verified by a manometer)

I stand by my statement. Introducing cool dilution air into the smoke stream is not a good idea with any wood burning appliance. Just because furnace manufacturers don't care to address variations in draft properly doesn't make a barometric damper a good idea.

 

[brenndatomu]

Still sounds like a bad idea to me, get a manometer and a key damper.

Specifically forbidden by many manufacturers on a wood furnace...when the intake control damper (automatically) changes, the negative pressure on the firebox drops due to the key damper blocking the flue...bad idea.

 

[Highbeam]

With all of the crazy computers, thermocouples, and intake motors on the furnaces I wonder why they don’t put a motorized key damper in the furnace too. Simple little vacuum switch to control it like the pellet stoves use. Then they can control combustion.

My theory is that, in a dramatic flip in history, the technology currently being used in 2020 wood furnaces will find its way into stoves. Just like my dash mounted choke knob went away when computerized controls made cars run cleaner.

My stove needs a key damper I think. No computers on this stove so I don’t want a baro damper.

Does the baro damper’s injection of such a small amount of room air really cool the flue that much? It doesn’t take much of a “leak” to really spoil the draft. Properly adjusted, are we talking about 100 degree drop, 10 degrees?

 

[bholler]

With all of the crazy computers, thermocouples, and intake motors on the furnaces I wonder why they don’t put a motorized key damper in the furnace too. Simple little vacuum switch to control it like the pellet stoves use. Then they can control combustion.

My theory is that, in a dramatic flip in history, the technology currently being used in 2020 wood furnaces will find its way into stoves. Just like my dash mounted choke knob went away when computerized controls made cars run cleaner.

My stove needs a key damper I think. No computers on this stove so I don’t want a baro damper.

Does the baro damper’s injection of such a small amount of room air really cool the flue that much? It doesn’t take much of a “leak” to really spoil the draft. Properly adjusted, are we talking about 100 degree drop, 10 degrees?

It depends on the draft of the chimney really. If it is high you basically have a 6" hole in the side of your pipe. Even closed most barometric dampers are pretty leaky

 

[Highbeam]

It depends on the draft of the chimney really. If it is high you basically have a 6" hole in the side of your pipe. Even closed most barometric dampers are pretty leaky

The ones I’ve seen on oil furnaces have a pretty tight fitting “plug” that just barely cracks open. Then I read stories here of dramatic draft increases by simply sealing the flue to the stove better. Leaving out the extreme cases where the chimney is 49 feet tall, and considering a guy trying to drop from line .1 to 0.05, I can’t imagine a whole lot of dilution air being necessary.

Still, why not accomplish this with a key damper. Motorized if necessary. Maybe that’s why furnaces use baro dampers, because they’re automatic and cheaper.