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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Dear Darren<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Based on the hopper size, and presuming you have about 4 metres of chimney, that size is probably going to be enough air to heat a home. Do you have a kW rating in mind? I think you should be able to get 40 kW from it. Do you want that much?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>>></span></b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>The area of the hole should be about 30 x 120mm.</span><o:p></o:p></p><p class=MsoNormal><br>The primary air hole should be 30x120mm? With a valve so its adjustable?<br><br><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Yeah, a sliding plate should be OK. It doesn’t have to fit perfectly. The point about the location of the air inlet is that the air should be able to pass up into the lower portion of the fuel and then cross the bottom of the hopper, and exit the left side (is the drawing you sent) into the flaming area. At that point the passage should be constricted to about 20,000 mm^2 then the secondary air can be admitted above the constriction. Not much, because some of the air passing through the slot will be secondary air. The hopper should have no air leaks into it at all. I hope you saw the stove from Eastern Canada that Kevin passed around. That top was good – it had a woven seal.</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>>></span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Lastly, constrain the entrance into the combustion area (where the secondary air enters) to about 1/3 of the area of the hopper. Keep it square-ish, definitely not long and thin as is often seen in furnaces. </span><o:p></o:p></p><p class=MsoNormal><br><span style='color:#1F497D'>></span>You mean the 'throat' from hopper (A) to combustion area (B). Third of the hopper width <span style='color:#1F497D'>></span>would be about 7cm. 7x7 then?<br><br><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>No, a third of the area, not a third of the dimension. If you have 20 x 30 cm = 600 cm^2 then 1/3 = 200 cm^2 = about 140 x 140. My little model says 14.5 x 14.5 but that is a bit big, just looking at it (subjective opinion). If you only want 20 kW, meaning a max of 20 and sometimes 4, make the constriction smaller, say 100 x 100mm. That constriction is perhaps 100 to 125mm above the lower end of the grate, just as you drew it.<br><br></span><o:p></o:p></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif"'>Put the secondary air entrances where it starts to expand (because there is additional draft there). <br><br></span><o:p></o:p></p><p class=MsoNormal>you mean straight away after the 'throat'?<br><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><br>Your drawing is correct. Just bring all gases and flames into a smaller space than the surface area of the grate. It is by no means the gas flow constriction on the whole system. It is a permanent method of getting the combustion efficiency up. In the GTZ 7 series I put ceramic plates on each of the 4 sides tapering open to about 230 x 100. The height is about 220 or so – not all that important because it is regulated a bit by the oiliness of the fuel. More oil, longer flame, so a longer space to burn in.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>About the bricks, you can use any bricks. Go for the hardest, strongest bricks you can find, if you can’t get genuine low thermal expansion materials. Put them in a way so that when they crack they don’t fall out of place.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Oh yeah, put a damper on the chimney that can cut the cross-section by 75% max.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Regards<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Crispin<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p></div></body></html>