I have a friend who just bought a Buck 91 like mine. He has asked me some question's on the operation.
Over-fire out of control:
One thing I'd be concerned with if throwing the door wide open, would be overheating the flue if the flames got big. What is happening in his "over-fire," too much flame or high cat temps (1800)? You don't want the cat probe going over 1800 for an extended period. I like to run it 1300-1500. To get the burn you want, you have to know your wood. Softer woods and smaller splits will gas more rapidly, and could lead to an over-heated cat. Next, you have to establish the new load so that you get the right amount of wood gassing. If you just load up, then run huge flames trying to get up to temp to close the bypass and light off the cat, you may get too much wood gassing and the cat will go high. If I'm re-loading on coals and the stove is at, say, 250, probe 450, I'll pull the coals way forward and open the air wash (right slider) to burn some of the coals down and get the cat probe up to 600-700, then I'll load. Since my wood is cut to 16" for my other stoves, I have the luxury of being able to shove excess coals in the back and still fit in the 16" splits. If I have a bunch of soft Maple, Cherry or some other faster-gassing wood, I'll put the coals in the middle N-S (front to back) and just get the middle of the load burning with the shotgun air (left slider.) That way, I don't get the whole load burning and gassing too much. With Oak or Hickory, I may spread the coals a little wider and try to get a little more wood burning since those dense woods gas in a slower, more controlled fashion and take more time to get burning well when re-loading. Whatever wood I load, I'll run flame with the bypass open and blower off until the cat probe is around 700, then close the bypass and keep some medium flame going in the box. Within 5-10 min, I'll see the cat probe start to rise at a pretty good clip. I'll keep flame going until the cat probe gets to about 1100-1200. If the cat starts to glow strongly, or the surface meter I have on the front, next to the bypass rod, gets to 325-350, I'll start the blower on low. When the stove is hot enough and the cat is glowing, turning on the blower will drop the cat probe temp by maybe 100, but the cat will keep glowing, although maybe more dimly. If you have enough wood gassing, the cat will hold, you can start cutting the air a little and probe temp will begin to rise again at some point. When everything looks good, I'll have the shotgun air closed and the air wash slider out about 1/4". That's my usual cruise setting. If it's very cold or very warm out, draft will be stronger or weaker and you factor that into your cruise air setting. I'll also use less cruise air if I'm burning soft Maple or other faster-gassing wood. If you don't have enough wood gassing or the stove isn't hot enough, the cat can crash. Won't happen once you get familiar with ramping up the stove. In a crash, probe will fall under 1000 and keep dropping. Time to open the bypass and run more flame to get the stove temp up and more wood gassing. I know it sounds terribly complicated, but you'll get the hang of it fairly quickly. I was at a disadvantage because the Buck is at my MIL's house and I would usually load, cruise and leave. I didn't get the feedback of watching the full burn cycle.
Here's a piece of tin foil I use to tell me where the cat probe went when I was gone.
Da meters.
