I've heard too that Orlan manufacturs equipment for a major German boiler mfg. and Viessman sounds right. I also noticed the other day that the blowers on my EKO 60 are made in Germany, which surprised me. This discussion is way over my head, but could you modulate a wood gasifier by changing the size of the nozzle openings, like what some of us have done with a firebrick over one of the nozzles? Maybe some sliding ceramic valve activated by a bimetal device or motor? I think Zenon knows what he's talking about, at least where wood gasification boilers are concerned.