Flue damper for controlling an out of control stove?

John_M · Jan 24, 2009

Follow-up to this thread https://www.hearth.com/econtent/index.php/forums/viewthread/33356/

What would happen if the fire in a wood stove begins to run out of control and you were to close the flue damper? The fire might diminish somewhat but the extreme heat would still be in the stove with nowhere to go. Would the stove "explode" if there was no way for the heat to escape up the chimney? If the stove has an Outside Air Kit would the heat be forced back through the uninsulated OAK to the outside of the house? If the OAK draws from a ventilated crawl space would the dangerous heat be forced into the crawl space?

The reason for this question is that I am now doing all the preparation work for a new wood stove installation and am considering a flue damper just above the stove. The stove should have excellent draw so I want to be be able to control it, I think. None of the stove's literature mentions a flue damper.

I'd like opinions from the many stove users here who have tons of experience.

Best wishes,

John_M

Backwoods Savage · Jan 24, 2009

As soon as the air is cut off the fire should calm down. However, on the newer stoves you cannot cut the air off completely. Still the fire should not get any hotter and should cool gradually. If there is a flue damper, that can also be closed.

The big key is with any fire, if there is not air supply, it will die. As for the stove exploding, I've never heard of that happening but have heard about some terrible warping.

We do not have a damper in the flue nor would I consider one. It really is rare to need one and they are a pain when it comes time to clean the flue.

atvdave · Jan 24, 2009

remember the fire triangle..

FUEL, OXYGEN , HEAT.. remove one of the 3 things and the fire will go out.

The heat will not get any hotter if you remove the air.

blacktop37 · Jan 24, 2009

How come we dont put a shutoff on the OAK. I have a pre epa BlazeKK airtight with no dampener and I can have a wall melter going, Turn the air off and Off- The fire shuts down immediatly I am going to try this on my Hearth EQ new install before I try a chimney dapener.

Zzyk · Jan 25, 2009

blacktop37 said:
How come we dont put a shutoff on the OAK.

I like this idea as it would allow for a bit more range of control over all the incoming air, not just the primary.

Todd · Jan 25, 2009

Zzyk said:
blacktop37 said:

How come we dont put a shutoff on the OAK.

Click to expand...

I like this idea as it would allow for a bit more range of control over all the incoming air, not just the primary.

Unless your stove has two seperate intakes, one for primary and one for secondary, many non cats do.

BrotherBart · Jan 25, 2009

Todd said:
Unless your stove has two seperate intakes, one for primary and one for secondary, many non cats do.

Or three. One for primary, one for secondary and one for boost air for the "doghouse". I wonder why we even worry about a niggling little door gasket leak.

blacktop37 · Jan 25, 2009

Im going to be a little disappointed if My EQ OAK is not a total unit. I saw the kit at the dealer and it is a small round flange to hook a 3" hose on that they charge $65 dollars for. I dont like burning my heated and humidified air. Also my house is tight and wife runs the dryer a lot.

Zzyk · Jan 25, 2009

blacktop37 said:
Im going to be a little disappointed if My EQ OAK is not a total unit. I saw the kit at the dealer and it is a small round flange to hook a 3" hose on that they charge $65 dollars for. I dont like burning my heated and humidified air. Also my house is tight and wife runs the dryer a lot.

Wow $65... I didn't know they were so expensive. I used a piece of old 4 inch vent pipe straight from the back of the stove through the outside wall. Needs a bit of cleanup, but it works. My wife claims (and I concur) that the kit helped even though we have a very old drafty house.

relax · Jan 25, 2009

you will find a lot of people can not give the advise you seek on this fourm.. well anyway does anyone have any idea how far above a wood stove a damper should be installed..you know any guess between the floor and roof would do......... ;-) have a crown... :roll: ..ZZZim

rustynut · Jan 25, 2009

how about it savage,
you hit a point that i have been thinking bout
just put in this 5700 quad
been running for about a month
did put a damper in above the stove just because i had one on my last stove
do have OAK
looked this stove over good and noticed that the controls "DO NOT" fully shut down the air intake
you make it sound as though the manufacturers do not allow for complete air shutdown on current stoves
any idea why this is ?
i went ahead and hard piped most of the OAK durring the install
was thinking about building a shut off that would completely shut down the intake air
i am curious as to why they dont allow full shut down of the intake air using the stove controls ?
i'm thinking complete OAK air shutdown in case of emergency
wouldnt be that much more work and i'm wondering...............
rustynut

blacktop37 · Jan 25, 2009

rustynut said:
how about it savage,

i'm thinking complete OAK air shutdown in case of emergency
wouldnt be that much more work and i'm wondering...............
rustynut

That is the reason Im putting shutoff on my OAK in case of overfire. Im hopeful it will now not need a dampner. If draft is too high, Ill ease the air feed.

Todd · Jan 25, 2009

The reason they don't allow total shut off is the EPA. Stoves have to meet a certain clean burn on lowest setting in order for the stove to be sold. I think it's less than 7 gph for non cats and 4 gph for cats. If the air is shut off completely the stove will smolder into a belching smoke dragon.

John_M · Jan 25, 2009

I started this thread wondering about installing a flue damper within 12" of the outlet on my new stove. The conversation has evolved into ways to totally shut down stove air intake so the flue does not need a damper to control the draft. But, if the air intake is totally shut down with a valve in the 4" OAK willl the pedestal version of my stove then revert back to drawing air from inside the house? If so, the shut down valve in the OAK is meaningless.

But this raises another question: My new stove will most likely be the pedestal version of the Pacific Energy Spectrum. The outside air will be plumbed into the chamber of the pedestal but will not be connected directly to the stove. I assume that sucking this air through the unrestricted OAK has less resistance than trying to suck air from under the pedestal, right? The only "full shut down" solutions then would be: 1) Hard connect OAk directly to the stove using procedures outlined in the stove assembly instructions. Then the 4" shut off valve could be installed in the air intake between the stove and the outside wall. I was hoping I could avoid this potentially unattractive 4" pipe suspended behind the stove; 2) Have the EPA allow/require stove companies to install an emergency air shut-down in every stove to be used in emergencies only. This shut-down valve could be spring loaded with a very strong spring and its only two positions are "full open" and "full closed". A simple lever at the side of the stove could be used to release and reset this spring. This emergency air shut down would be located in the primary air supply line in front of the primary air control to the stove. It would be located so as to be very easily accessible if repairs or replacement are necessary.

Solution #2 would be the surest, safest, fastest, no-brainer solution to an out of control burn. I'll even go one step further: Stove manufacturers here and in Canada should put pressure on the EPA in the USA, Canada and Norway to require this safety feature in all stoves.

How about an answer to my question in parageaph #1 and additional opinions about my comments in paragraph #2. I really enjoy all the knowledge I gain at this forum.

My ceiling support box has now been installed and painted and I have already made arrangements with a roofer to cut a hole in the roof. I will build the chimney chase above the roof. He will do the finish flashing and shingle replacement. Things are looking good.

Best wishes and good health,

John_M

downeast · Jan 25, 2009

Todd said:
The reason they don't allow total shut off is the EPA. Stoves have to meet a certain clean burn on lowest setting in order for the stove to be sold. I think it's less than 7 gph for non cats and 4 gph for cats. If the air is shut off completely the stove will smolder into a belching smoke dragon.

Only partly true for non cat EPA's. Those EPA particulate levels are tested with extra dry hardwood in a closed facility. Nothing like what the normal 24/7 woodburner has for firewood.

EPA cat stoves ( e.g. Woodstock, Jotul Firelight, VC Defiant ) can be shut to near NO primary air with secondary air partially drawing along with a "lit" catalytic combustor for a clean , very low particulate burn. The cat "reburns" the exhaust gases. Later non cat EPA stoves do have a narrow range of air control---the "mommie" stoves--that don't allow the user to shut the stove completely down, or way up. Now, IF you have a good bed of glowing coals in a pre-EPA stove and then shut the air down ( it never can be completely shut off due to the inevitable leaks in any stove ) you'll get a clean burn no matter what the stove.

EPA mandated particulate levels, and manufacturers developed non cats because users either would not operate the cats correctly
( giving the cat time to light off ), or users of pre-EPA stoves ( what some incorrectly call "smoke dragons" ) would throw a load into the firebox and let the splits smoulder producing the smoke and creosote from incomplete burns.

Basically, it is user control. We still use pre-EPA stoves -- workshop Tempwood and aluminum Snorkel Hot Tub stove, and a recently sold Jotul 602 for a now unused sauna --by getting the loads burning to coals BEFORE shutting the air down. Not a big deal. Sometimes put green wood in onto a hot bed. Just some care with the burn cycle. Friends and neighbor here also use kitchen cook woodstoves for heat and cooking year-round that are non EPA.

blacktop37 · Jan 25, 2009

The reason I want to try to shut off at the OAK and resist the dampener is my set up will be a lot more tuff to clean with a dampener installed. If my new Eq will not shut down with my plan I will feel the need for a dampener. I have burned stoves for 30 years and have gotten into situtations several times.

snowtime · Jan 25, 2009

ccokstoves are exempt from EPA. Yes you can burn cleanin a pre EPA stove if you want to stay on top of it. But the truth of the matter is most of us load on a coal bed and leave it until we can get to it or when its almost out. I can not imagine anyone not having less smoke with an EPA compared to old smoke dragon. I know here that when we come back from cross country skiing we can see the house for about an hour before we get home. In the old days we would see the smoke and remark the heaters going good. Now when we return the stove in the greenhouse is smoking but the main house is clear of any smoke so we do not have a clue if its going good or not. At first it was disconcerting but now we are use to it. The T6 is very reliable and will not leave anywood unburned, not like the old stoves.

I am against changing the air for more control. My reasons are not just air quality even though we all know it will be abused if altered. I think people will start to have more creosote and more fires with the altered system. I also think an insurance claim will not be honored if its found that the stove was altered. If they are forced to burn correctly with dry wood then they will be alright. I would install a damper and a damper should be installed 6" above the stove outlet. This will not shut the stove down completely but will give you enough control for those unforeseen incidents. For those who are worried about chimney fires the new regs for installation will protect you from that first fire. You will have to check your system but it will probably be alright. It will be up to you to remedy the practices that led to the fire. I think a lot of us old time burners [40 years here] are guilty of leaving things until theres a problem. If someone is not willing to be vigilant and do proper maintenance they should not be burning.

As for a damper getting in the way of cleaning just install a section of telescoping chimney. Get one of those short 1' or less section of double wall with a damper pre installed. They make them to bridge between the stove and your normal pipe. Easy as pie to take out and clean.

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Flue damper for controlling an out of control stove?

John_M

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blacktop37

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Todd

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