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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear DD<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>></span><span lang=EN-US style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> </span><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>As hot secondary combustion takes place, the stove pipe expands from 6" to 8" diameter five feet up. This expansion causes additional suction. By allowing additional room at this key point, the expanding gasses do not have to create back pressure on the draft.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>That seems <i>really</i> unlikely, unless there are flames burning in the chimney at that point. If it slows the gas speed and allows additional heat to come off the larger diameter tube into the greenhouse, it is actually reducing the total draft.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Do you know, even at a guess, at the power level in kW? <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Draft is related to the average temperature in the chimney and to a lesser extent, the diameter. I think if you have a large enough chimney (6” seems overly large unless the fire is huge) you will ‘win’ by reducing the average diameter to keep the hottest gases restrained in a taller, narrower space with a higher average temperature. That gives more buoyancy which = more draft, automatically.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Have you tried different version of this? Be interesting to hear the results.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></body></html>