Questions on draft requierments for gasifiers

Yes performance would be hurt. Most require 12' - 15' of chiminey.

If you use a barometric damper you can maintain the mfg min draft and not hurt the performance.

Rob

I would agree that you need to comply with the requirements of the manufacturer.

That was one of the reasons that I picked my boiler, is that it has a very low draft requirement, and I was worried about my chimney height.

Taxidermist, I was under the impression that a barometric damper only helped make sure you didnt have too much draft. I honestly dont know, as I havent ever put one in.

Clarkbug said:

I would agree that you need to comply with the requirements of the manufacturer.

That was one of the reasons that I picked my boiler, is that it has a very low draft requirement, and I was worried about my chimney height.

Taxidermist, I was under the impression that a barometric damper only helped make sure you didnt have too much draft. I honestly dont know, as I havent ever put one in.

Click to expand...

Yes you are right..... if to much draft use a baro... if not enough add a length of pipe.

In a shed with a short roof as long as you meet the 3' 10' i would think you would be fine. If too much add a baro.

Rob

I have my Tarm 40 in an outdoor shed with 9ft of insulated and ~2ft of non insulated 6"dia chimney. The eaves on my shed are only 8 ft, even with only 3 sections of insulated pipe, I have almost 6' above the roof. I originally thought I would not have enough draft, so I left off the chimney cap. Eventually I bought a gauge and measured the draft, I was surprised to find I had way too much. My unit calls for .02 to .05 in water and I was always over .05, sometimes over .1. I put a chimney cap on thinking that would reduce the draft a bit, but it made no difference to a slight increase depending on the wind. I put in a key damper, but having it set in one position would not keep the draft at a stable number during operation. Put in a barometric damper and all is now operating per the requirements. I noticed a slight reduction in flue temperature and perhaps a slight increase in efficiency.

I believe (but don't have any experience to verify) having a longer shiomney will provide a more stable draft. I remember reading another post on this site where someone had too much draft from a short chimney. That prompted me to measure my draft and make to corrections.

Also worth noting, I have very little draft until the boiler is running and the chimney heats up. This is what eventually drove me away from the key damper - I could not set it to a fixed position and walk away for the entire firing cycle.