Hello all,
I am a total newbie. I am so new that I thought I sent this thread yesterday and it didn't go through. I am building an OWB in my backyard out of concrete for my 2 zone heating in my 4,000 foot home with full basement in Virginia. I'd like to build my boiler as efficiently as possible. I have been in construction for 35 years and am handy but I am a terrible welder. I will have an air gap between the firebricked concrete wall housing the boiler and a second concrete wall which is the outside of the building, which I see being about 8' by 10' and 8' high.
Because I cut and load my logs with a bobcat they will be 6' long, so I hope an efficient firebox could be narrow (20"h x 20"w) and long (96"), with preheated combustion air entering near the front door and mixing with coals for 8 feet before passing up to a secondary combustion chamber for the wood gases at 1100F. In the upper chamber I will plumb 200' of 1" glavanized pipe running at 33 gpm (less pressure loss) for heat recovery. I will try to stick some water pipes up the flue too. I bought several books on stove design by Jay W. Shelton which will arrive next week. Once I find out how hot my flue needs to be I will try to run the exhaust horizontally or with enough water jacket to absorb heat down to this temperature but not so low that it presents a creosote hazard.
Any ideas how big the secondary upper chamber should be? An easy length for me would be 96" and an easy width of 20" because it sits on top of the firebox but the height isn't set yet. How high should this area be and how should it be designed? Should I baffle it? I could probably plumb the pipes to act as baffles or (poorly) weld something.
I may also put heat exchangers at the ceiling of the concrete room for heat recovery. The water would pass through the cooler ceiling heat exchangers before going through the hotter water and flue jackets. Inside my home I will have about 300,000 BTUs of heat exchangers and 500' of radiant pipes. I will first plumb the hot water through a 120,000 BTU heat exchanger on each of my two plenums, then through a water to water heat exchanger for my domestic hot water, then through basement radiators, then through a greenhouse before cycling through the OWB again. I am using a Taco 0010 circulating pump at 33 gpm and a 1" line in a close loop system. I also will drape EPDM rubber in two used 275 gallon fuel oil tanks as heat sinks.
What am I doing right or wrong? I really enjoy criticism because I know it will save me manyhours of construction time. I promise to send at least one joke to everyone that helps out. Be forewarned, my joke repertoire is limited and dirty!
Thanks for any help you can give.
I am a total newbie. I am so new that I thought I sent this thread yesterday and it didn't go through. I am building an OWB in my backyard out of concrete for my 2 zone heating in my 4,000 foot home with full basement in Virginia. I'd like to build my boiler as efficiently as possible. I have been in construction for 35 years and am handy but I am a terrible welder. I will have an air gap between the firebricked concrete wall housing the boiler and a second concrete wall which is the outside of the building, which I see being about 8' by 10' and 8' high.
Because I cut and load my logs with a bobcat they will be 6' long, so I hope an efficient firebox could be narrow (20"h x 20"w) and long (96"), with preheated combustion air entering near the front door and mixing with coals for 8 feet before passing up to a secondary combustion chamber for the wood gases at 1100F. In the upper chamber I will plumb 200' of 1" glavanized pipe running at 33 gpm (less pressure loss) for heat recovery. I will try to stick some water pipes up the flue too. I bought several books on stove design by Jay W. Shelton which will arrive next week. Once I find out how hot my flue needs to be I will try to run the exhaust horizontally or with enough water jacket to absorb heat down to this temperature but not so low that it presents a creosote hazard.
Any ideas how big the secondary upper chamber should be? An easy length for me would be 96" and an easy width of 20" because it sits on top of the firebox but the height isn't set yet. How high should this area be and how should it be designed? Should I baffle it? I could probably plumb the pipes to act as baffles or (poorly) weld something.
I may also put heat exchangers at the ceiling of the concrete room for heat recovery. The water would pass through the cooler ceiling heat exchangers before going through the hotter water and flue jackets. Inside my home I will have about 300,000 BTUs of heat exchangers and 500' of radiant pipes. I will first plumb the hot water through a 120,000 BTU heat exchanger on each of my two plenums, then through a water to water heat exchanger for my domestic hot water, then through basement radiators, then through a greenhouse before cycling through the OWB again. I am using a Taco 0010 circulating pump at 33 gpm and a 1" line in a close loop system. I also will drape EPDM rubber in two used 275 gallon fuel oil tanks as heat sinks.
What am I doing right or wrong? I really enjoy criticism because I know it will save me manyhours of construction time. I promise to send at least one joke to everyone that helps out. Be forewarned, my joke repertoire is limited and dirty!
Thanks for any help you can give.