Question about dampers

[anynyg]

Hi, I am new to this site but have used wood stoves for several years. Living in rural areas, complaints about smoke was not an issue, and since the chimney sweeper comes by twice annually i Denmark, I figured he would tell me if anything was wrong.

I have recently moved to a new house, with close-by neighbors. No complaints yet, but I am more careful now and spend a lot of time looking at the chimney. Denmark just got new laws regarding wood stoves, and there are a lot of public interest in the pollution issues. The laws looks like they have been inspired by the US laws.

I recently replaced an old smoke dragon that came with the house, with a Bullerjan type 01 stove. The stove is connected to an huge old masonry chimney in the middle of the house. This stove has a pipe-damper attached to the flue collar, and I have just left it completely open at all times. A couple of days ago, I noticed that the oven burned a lot longer on the same amount of wood, and with normal temperatures in the flue (between 300 and 400 F).

I noticed that the pipe-damper was half-closed. The primary air intake full open. I have read all the warnings about using dampers, but is it possible that the huge chimney generate too much draft, and that it helps to close the damper a little to control it? I know this could also be done by limiting the primary air intake on the front, but it seems more logical to not restrict air inflow.

Am I completely wrong, and should I be careful to use the Damper?

Smile

/Anders

 

[jebatty]

Welcome -- I know nothing about a Bullerjan type 01, so I looked at it on the web, and it is very interesting. It appears to be firebrick lined and surrounded by convection tubes/perforated shielding to maximize heat output. I suspect it has an air mechanism to achieve secondary burn against the super heated firebrick.

My knowledge of chimney comes from personal experience, I am not a professional.

First, a manometer can measure actual chimney draft, if available to you check this against the specs for your stove, and if the draft in w.c. is within the range the stove specifies, you should be ok.

Second, a chimney with too large of a diameter, too small of a diameter, too short or too long, all can affect achieving the proper draft. As can height about your roof, winds, temperature. As can construction material of chimney, masonry vs steel, for example.

Third, a damper can increase or decrease draft, so if without the damper your chimney produces too much draft, the damper can restrict draft to help achieve the desirable draft. But if your chimney without the damper does not produce enough draft, the damper won't help. But it also is an obstruction and a location where creosote can accumulate.

Fourth, for me the ideal would be a chimney without a damper that produces the proper draft, and then using the stove air controls to achieve the appropriate burn.

I have a wood stove of a different design, 18 years old, firebrick lined with secondary air. When it is up to heat (300F at 18" above the stove top, stove pipe surface thermometer), it produces very little to no smoke, although when it is cold you will see steam from combustion. Also, even without smoke there is a light odor of burned wood, depending on winds, which is gentle and I find rather pleasant.

Good luck with your stove and chimeny.

 

[anynyg]

Welcome -- I know nothing about a Bullerjan type 01, so I looked at it on the web, and it is very interesting. It appears to be firebrick lined and surrounded by convection tubes/perforated shielding to maximize heat output. I suspect it has an air mechanism to achieve secondary burn against the super heated firebrick.

Thanks! No firebricks on mine. Ordinary baffle design. The first tube on each side contains a nozzle into the chamber just in front of the baffle. The tubes actually has most of their surface inside the chamber. Heats a large room very quickly.

First, a manometer can measure actual chimney draft, if available to you check this against the specs for your stove, and if the draft in w.c. is within the range the stove specifies, you should be ok.

Great idea. I will try to find a manometer. I do have the specs for the oven.

Third, a damper can increase or decrease draft, so if without the damper your chimney produces too much draft, the damper can restrict draft to help achieve the desirable draft. But if your chimney without the damper does not produce enough draft, the damper won't help. But it also is an obstruction and a location where creosote can accumulate.

I do not know anything about chimneys, but I guess that the larger the chimney, the greater the draft. My chimney was originally used for a cook stove in the kitchen, and is large. If there is the slightest wind, the draft can be so high that the fire blows out when I am trying to start it up. Never experienced this before.

Fourth, for me the ideal would be a chimney without a damper that produces the proper draft, and then using the stove air controls to achieve the appropriate burn.

It has been suggested to lower some elements down into the chimney, that will make it smaller and isolate it better, but the price tag of this operation puts it into the future.

I have a wood stove of a different design, 18 years old, firebrick lined with secondary air. When it is up to heat (300F at 18" above the stove top, stove pipe surface thermometer), it produces very little to no smoke, although when it is cold you will see steam from combustion. Also, even without smoke there is a light odor of burned wood, depending on winds, which is gentle and I find rather pleasant.

I experience exactly the same. Very small amount, if any, of white smoke. A little more just after I put more wood on. Also the smell of burned wood. Quite nice, but maybe not to everyone.

One more question. I mostly use biobricks and they seem to produce a lot of ash. With the draft involved this ash is taken into the flue pipe and deposited there. Is this a problem? Last I checked the chimney there were no signs of this deposit, only in the flue pipe. I normally do not look into my pipes, so this may be perfectly normal.

Smile

/Anders

 

[jebatty]

One more question. I mostly use biobricks and they seem to produce a lot of ash. With the draft involved this ash is taken into the flue pipe and deposited there. Is this a problem? Last I checked the chimney there were no signs of this deposit, only in the flue pipe. I normally do not look into my pipes, so this may be perfectly normal./Anders

Glad my comments are helpful. I have no experience with biobricks but I do have experience with some woods that leave lots of ash compared to other woods, and I do have experience both with the wood stove example in my prior comments and a wood gassification boiler (Tarm).

I have not found that ash necessarily bears any relationship to creosote. The wood stove burns mostly aspen which produces lots of ash compared to oak or birch. Yet, if I burn aspen in the gassification boiler, there is very little ash. So, my conclusion is that the boiler, which burns at close to 2000F, is achieving a much higher level of combustion that does the wood stove. But even in the case of the wood stove, combustion and flue temperatures are high enough to burn off the creosote gases.

Your biobricks may be similar to aspen in their manufacture. You may wish to experiment with different brands, as you may find that some are of higher quality/btu output than are others, and if prices are comparable, the higher btu output should deliver more heat for the money.