Exactly right. Biomass pays big dividends vs all fossil fuels provided there is local, dependable supply. Transportation costs are always a key factor. Plus, using locally supplied pellet biomass provides jobs for local families and supports the local economy, a win-win on all fronts.
A few calculations to help me understand the operation. 400 gal of water, 3x/day, 170F: 400 x 8.34 x 225
![DeltaT ::DT ::DT](/talk/styles/default/xenforo/smileys/deltat.png)
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
x 3 = 2,251,800 btu/day = 93,825 btu/hr to heat the dhw. I'm assuming the water is supplied from a well at about 45F. I think the 260 is rated at 25.9 kWatt = 88,000 btuH max output, so using two boilers allows each to operate continuously at around 55-60% rated capacity (after considering radiation losses), which to me seems a pretty good sweet spot with good excess capacity if needed, and in a crunch one boiler can just about meet the need if the other is down for maintenance. Use of pellets from a hopper can be a substitute for a higher rated boiler with adequate storage, drawing from storage between boiler fuelings. For the pellet boiler the pellets are the storage.
I understand the practical difficulties that existed with the Garn, which is an excellent boiler when used in a batch burn operation and when continuous very hot water (170F in this application) is not needed, and the difficulties that arise when the Garn is operated by a variable staff not well trained in proper fueling and maintenance. The staff issues likely would exist with any cordwood fueled boiler, but they can be overcome with proper staff training.
I like the automated ash removal and normal cleaning with the 260's, and I agree that automating these jobs is a big plus. The Wood Gun with its ash collection system comes close to this outcome because it can be operated for quite a long period of time between the times when more complete cleaning is needed.
This has been an interesting thread to follow. It also will be interesting to see how the 260's fair over the long term and what issues, if any, may arise after a couple of years in operation. Keep up the good work, Heaterman.