<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 12 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Hi Rueben, <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>There is some good math hidden in online conventional water heater calculations, including some great averages for how much water typical tasks like dish washing etc takes. You may want to download one of those and see if the setup you're thinking of hits the right sorts of numbers. The other part of this is the heat transfer. I'm guessing that that's a coil around the flue transfer system, there are other heat exchangers out there. The pricey ones are pancake style and do a beautiful job of transferring heat, but are not usually used residentially. The other part of this is making sure that you don't have too much heat loss between the firebox and the point of use. <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>kind regards,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Erin Rasmussen<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>erin@trmiles.com <o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Greenbuilding [mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Reuben Deumling<br><b>Sent:</b> Tuesday, December 31, 2013 12:40 PM<br><b>To:</b> Greenbuilding<br><b>Subject:</b> [Greenbuilding] stealing heat from a woodstove for water heating<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><div><div><div><div><div><div><p class=MsoNormal>The further from the firebox one chooses to steal the heat the fewer<o:p></o:p></p></div><p class=MsoNormal>+ negative repercussions for the combustion process, and<o:p></o:p></p></div><p class=MsoNormal style='margin-bottom:12.0pt'>+ BTUs per hr transfer into the water<o:p></o:p></p></div><div><p class=MsoNormal>But are there nonlinear solutions? Methods for stealing heat close to the firebox that do not negatively effect the combustion process?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'>My ideal scenario relies on (1) below. <a href="http://www.axeman-fireflue.com/">http://www.axeman-fireflue.com/</a> My reason for looking beyond that solution is that the average length of time I burn a fire/day is a little over 2 hrs. The fellow who is advising me on the flue water jacket (at link above) thinks this may not yield very much hot water. My inclination is to have him make the water jacket taller (more surface area), and find a smaller tank (less cold water volume to dilute the heat), but in the absence of some empirical work, or others' experiences, this would be somewhat of a crap shoot . If moving things closer to the firebox increases the rate at which heat transfers into the water, then laying the 'water jacket' right on top of the stove (2) seems almost too easy. Frank Tettemer has spoken up the most on this subject in the past. Anyone else have thoughts on this? <br><br>(1) external stainless flue water jacket<br>(2) external 'water jacket' laid on top of stove<o:p></o:p></p></div><div><p class=MsoNormal>Obviously the more effective this system is at robbing heat from the stove for DHW purposes, the less heat goes into the room, which leads (dynamically) to incrementally longer burn times to reach the same desired air temperatures. This is not a bad thing. <o:p></o:p></p></div></div></div></div></div></div></div></body></html>