Well, so far no real noticable difference in opening the secondary air screws in terms of smoke. This morning, my stack temp was up a bit, more like 225. Still not bad. Just opened them to 5 turns when I started the fire tonight. Tomorrow morning I'll go to 6 and see how that goes.
I really don't want to have to replace the whole refractory. I thought there was some steel structural support in there? Does the full weight of the wood in the fire box rest solely on the lower refractory? Now I'm scared
!
Eric,
I hear what you are saying about modifying the gas path. But, I'm not sure that it is that dangerous of a thing to do. Basically, all I did was put higher sides on the U shaped pieces and block off the direct path to the rear. All of this at Zenon's recommendation. Having worked for OEMs in the past, I'm going to guess that they keep the refractory simple for manufacturing and maintenance reasons. Not because there isn't a better way.
Same with the controls. We just did a job retrofitting the controls on an industrial wood boiler. The two primary control points are water temp and O2 in the stack. The O2 reading is the sole calculation for efficiency in their setup. And, the fan maintains the air pressure, but a damper controls the air flow. The instrumentation and actuators required to really do the controls right would cost half (or more) of what the boiler costs. (The O2 analyzer on that job cost more than my boiler, tank, pex, copper, and shed all together, and then some.) Knowing the theory, if I could get the parts cheap, I'd take a shot at it. But, for the little gain that is available by doing all of this, I really can't see it paying back.
Barnartist,
At first, I had pipe insulation only on the first 6 feet of pipe up to the pumps. Only the flanges were exposed. I left that in place, and wrapped 6 inch fiberglass insulation around the whole thing, up to the pumps. And that made a huge difference.
My shed is insulated to at least R19, all sides and roof. The tank has R38 all the way around, and on top. This fall, I re-insulated the area over my kitchen in the house. Any insulation that was usable went into the boiler shed. Basically, I used it to stack on top of the boiler, along the front edge, and on each side out to the walls, to form a sort of wall. This way when I open the door, not all of the warm air around the tank is able to quickly escape. I also took some and just wrapped it around the pipes at the return manifold. Seems to have really helped.
If you are going to insulate around the boiler, foam boards are probably better. Glass can hold moisture and dampness. Really, the ideal thing would be to take the covers off and have it sprayed. But, I'm sure you'd never get the covers back on. I'm sure you are losing some heat with that area not being insulated, but how much is the question?
For reasons I don't fully understand, I use more wood when I lose secondary combustion. My only guess, is that the secondary cumbustion creates back pressure on the primary chamber from the rapid expansion of the gasses, and slows the primary air flow, which slows the burn rate. So cutting back too far, and losing that secondary burn later in the cycle, could end up hurting you. And it doesn't take long with the fan dampers open to get good secondary combustion. I had secondary burning in about 30 seconds tonight. Let it go for about 10 minutes (stack temps were already up to almost 300) and closed it down.
Leaddog,
That's a good indications that insulating the boiler is of some value. But, I'm not sure that foil/bubble/foil is the right stuff. After I used a bunch of this, and plain foil, in a few areas around my house, I read a lot of things that made me regret having used it. I know it's a lot cheaper than foam, and easier to work with, but I really think foam is better suited for this application.
