Well, the way it worked out i had an old fuel tank, 4'x11' 3/16" steel so thats my tank, i had an old propane tank that was 30" dia i cut off one end and ended up with a firebox 36" long, 3/8 " thick. refractory comes from ISA inc. got two pieces 12" long and found a 10 1/2 " pipe 24" long and thats my secondary chamber. i had a whole pile of 4" sch 40 pipe and thats my exhaust. there's around 58' of 4" in the 5 pass system. the intake is 5" sch 40 12' long going to the air coller in front. 1/2 hp jet pump motor from ebay that turns 3450 rpm 10" blower wheel 3 1/2 " wide with 5" opening pulls the air through the front coller and pushes out the last pass. exhaust temp at front of unit 400-475* 150-175* outside. smokes for about 15-20 min on startup then cleans up real good no smoke. very effecient burn. runs on a timer, 3 hr burn is normal every other day. i run it up to 200-210* small learning curve on when to burn and for how long, but actually very simple. takes about 12, 24"long splits to go from say 110*- 200* in around 2 1/2 hours. 500 gal propane tank vertical beside it for storage. it's an open system, i use the top of the propane tank for expansion. two pumps one top and one bottom of storage, they run on the same timer as the boiler. when the boiler shuts of all the water is the same temp. i pull load off of the top of storage and return to bottom of boiler,there fore pushing hot water from the boiler up to storage. i have run it with the pumps unpluged and it will actualy thermo siphon. cost around 1k to build, and alot of welding.but it was enjoyable work. I'm a welder by trade, so just another project. if i were to build another it would be bigger, prolly 5-6000 gal. then no need for extra storage. 6000 gal whould run me about 4-5 days, but would prolly be a 5-6 hour burn. i have the next burn load in it now but won't lite it till tomorrow afternoon, but it will be nice and warm and lite very easy, i put a 3"x4" window in front so i can watch it burn, looks like a jet engine burning with the refractory chamber glowing red. you can open the door anytime you want and no smoke whatsoever, but dont get your hat to close it might suck it right on in. thats all for now.
Larry