Central Boiler here...
If we had to do it all over again (not that we have to), I would do exactly what we did and buy a CB (again).
Personally after a lot of reaserch on OWBs, looking around, and asking for references from plumbing and heating and energy companies here, we bought a Central Boiler. Woodmaster, Taylor and Central Boiler are the best OWBs overall I think. We have a good CB dealer here in Oregon but I did not have to rely on him for much. CB has excellent online support at the factory if your local dealer is a dolt. They speak real live English (what a change from everything else that I call for tech support!), and they know what they are selling and how to install various systems. CB has the best 25 year warantee out there. They have also been around (certaily avoid any new companies selling OWBs, they seem to fold fast). CB also has nice THICK steel and good qulity materials. I chose them mainly for the overkill aspect. I poured a 4" concrete slab for it; why mess with anything else? Insulation will never go bad on a CB... it rains here constantly and there is no problem with the CB insulation. We had a problem with the control readout after a year (it was working, just did not state the temp) and CB replaced it, no problem.
I would not bother with a forced air draft system. More parts to fail over time, and natural convection is more than adequate to keep air on the fire and bring it up to temp. Our boiler will overshoot and undershoot about 5 degrees from setting. We set it at 165 F, where the unit will shut the damper. It opens at 155 F. So overall it swings from 150 F to 170 F. The speed of flame recovery is not really an issue for the draft system. As for the design of the firebox, round or square or whatever is not going to be a real difference. Nether is the baffle system from what I have seen. Most are adequate. I would avoid auger or grated firebox floor systems though. More stuff to clog up and deal with. The CB has a large deep ash pan and it needs ash cleaning depending on the type of wood burned. You want a good ash layer for coals to burn in though, so you do not want the bed of the firebox to be too clean. I clean our boiler ashes about once a month in winter when the ashes get up to the lower level of the door. I use them on the gardens as fertylizer.
We burn mostly Doug for, alder, oak and madrone, and some maple and willow. We also burn wet, bug eaten and dry rot wood, green wood, and old lumber scraps. Anything but treated wood. I also avoid burning plywood and strandboard becasue it has a lot of resin in it. The amount of wood burned will be directly porportional to the outside temerature, heat demand and heat losses in your house. You want to avoid heat loss in the PEX lines to the boiler from the house, and you want to bury them 2 ft deep where you live. Ground water is the biggest casue of heat loss in the PEX lines. To avoid that make sure that your lines are water tight and insulated. You can buy the expensive stuff, or make your own. They sell the stuff that I designed on Ebay now. I took 4 inch corrugated black drain pipe and stuffed them with a pair of (one red and one blue) foam sleeved insulated pex lines. Maybe R-4 at best, but the ground will insulate your pipes more than anything else.
The access panel for the plumbing and electrical in the CB usit is more than adequate for the job. CB has a second pair of intake and outlet ports drilled and tapped so that you can expand the system if you want to upgrade with a second heating loop. There is also more than enough room in the panel for Taco pumps and fittings, as well as bypass valves and hose bibbs. I designed and added a lot more stuff in there than they call for. One way check-valves, drain and fill valves, return temp gauge, etc. Also we bought a plain steel box. CB has a stainless option, but stainless does not conduct heat as well, and it is a grand more. Not worth it or needed from what I have seen. Our system has zero rust after a season and a half of use.
Basically, after the system was installed, all we have had to do is keep it filled with wood. I did the entire design and install myself. I am a degreed engineer and I was a plumber and part time electrician for several years, so this was not that hard for me. Our design was somewhat complicated with an existing solar water heater to tap into, and a pressurized electric hydronic floor heating system. I used 2 flat plate heat exchanges to heat the hot water and house floor loop with. Sizing the heat exchangers was an issue, and CB phone support not only helped me size them, but they got it perfectly matched. Flat plate is more expensive, but they recover heat faster than side arm units. The colored PEX was a pain to get through our local HW store, and the PEX to brass fittings are rediculously expensive.
Anyway, good luck with your decision process. Also keep in mind that there is a lot of anti-OWB laws being passed lately, especially in the Atlantic and New England states. You can also look over on the Mother Earth News Forum for a LOT of posted information and debates about different OWB manufactures and OWB vs indoor wood stoves, etc. Similar to AS, but more flame wars and passion about OWB brand loyalty.
