My curiosity has got the better of me so I have a couple simple questions. Which OWB's are lambda controlled? Which OWB 's are EPA II certified?
HeatMaster G series is the only one I can think of. Not sure what you mean my "EPA II"? EPA 2020? HeatMaster G series, Central boiler has a couple I believe, and possibly Crown and Polar/Portage & Main have some that meet USA current regs...no lambda to my knowledge though, other than HM...
Woodstove Database | Burnwise | US EPA the list is sorted by name. Click efficiency if you want to sort from highest -> lowest.